Maturational Effects of the Vestibular System: A Study of Rotary

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J Am Acad Audiol 18:461–481 (2007)

*Program in Audiology and Communication Sciences, Washington University School of Medicine

Maureen Valente, Director of Audiology Studies, Assistant Professor of Otolaryngology, Program in Audiology andCommunication Sciences, Washington University School of Medicine, 660 W. Euclid Avenue, Campus Box 8042, St. Louis,MO 63110; Phone: 314-747-0107; Fax: 314-747-0105; E-mail: [email protected]

Maturational Effects of the Vestibular System:A Study of Rotary Chair, Computerized DynamicPosturography, and Vestibular Evoked MyogenicPotentials with Children

Maureen Valente*

Abstract

Maturational effects were investigated in two age groups (N = 30 per group)of children with normal hearing sensitivity, using rotary chair (RC), computerizeddynamic posturography (CDP), and vestibular evoked myogenic potential(VEMP) measures. Children recruited within the younger group were threethrough six years of age, and children within the older group were nine througheleven years of age. Data obtained for each pediatric group were comparedwith clinic and/or published adult normative data for each measure. Significantage effects were seen on many CDP subtests (sensory organization test andmotor control test); VEMP latencies; and RC gain, phase, and step velocitymeasures. The results of this study demonstrate significant maturationaleffects from preschool age through adulthood and suggest that adult normativedata may not be appropriate when interpreting pediatric test results. Since adulttechniques should oftentimes not be utilized, a proposed test battery isdescribed that may be efficiently utilized with pediatric patients.

Key Words: Computerized dynamic posturography, pediatric vestibularevaluation, rotary chair, vestibular evoked myogenic potentials

Abbreviations: CCW = counterclockwise; CDP = computerized dynamicposturography; CW = clockwise; EOG = electrooculography; MCT = motorcontrol test; RC = rotary chair; SCC = semicircular canal(s); SCM =sternocleidomastoid muscle; SOT = sensory organization test; SV = stepvelocity; TC = time constant; VEMP = vestibular evoked myogenic potentials;VOG = video-oculography; VOR = vestibulo-ocular reflex

Sumario

Se investigaron los efectos de la maduración en niños con sensibilidad auditivanormal en dos grupos de edad (n = 30 por grupo), utilizando la silla rotatoria(RC), la posturografía dinámica computarizada (CDP) y mediciones depotenciales evocados miogénicos vestibulares (VEMP). Los niños reclutadosdentro del grupo más joven tenían de tres a seis años de edad, y los niñosen el grupo más viejo tenían de nueve a once años de edad. Los datosobtenidos de cada grupo pediátrico se compararon con datos normativos deadultos, clínicos y/o publicados, para cada una de las mediciones. Seencontraron efectos significativos de la edad en muchas sub-pruebas de laCDP (pruebas de organización sensorial y pruebas de control motor), en laslatencias del VEMP, las medidas de ganancia, fase y velocidad de paso de laRC. Los resultados de este estudio demuestran efectos significativos de

Journal of the American Academy of Audiology/Volume 18, Number 6, 2007

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The importance of vestibular evalua-tion with the pediatric populationcannot be overestimated, especially

when hearing impairment and/or vestibu-lar symptoms exist. Vestibular impair-ment may occur comorbidly with numer-ous childhood disorders. Examples ofthese disorders are sensorineural hearingimpairment (Brookhouser et al, 1982; Cyret al, 1986; Huygen et al, 1993; Rine et al,2000), childhood benign paroxysmal ver-tigo (Mira et al, 1984a; Mira et al, 1984b;Ansink et al, 1985), and a myriad of child-hood syndromes (Wang et al, 1981; Younget al, 1996; Wiener-Vacher et al, 1998;Guyot and Vibert, 1999; Abadie et al,2000). Erbek et al (2006) studied vertigoin 50 children, finding migraine syn-drome to be the most frequent cause.Wiener-Vacher (2004) stressed the impor-tance of recognizing common clinicalsigns, with vestibular dysfunction mostcommonly arising from migraine equiva-lent, ophthalmologic disorder, benign ver-tigo, and temporal bone fractures.Although vestibular techniques have notbeen readily available when testingyoung children, it is crucial that methodsbe developed to more accurately measurethese young systems. This is especiallytrue in view of challenges experiencedwhen attempting standard electrooculog-raphy (EOG) with this population. Someinvestigators have described modificationof adult vestibular evaluation techniques(Cyr, 1980; Cyr, 1983), but these have notbeen widely used on either a research or

clinical basis. More recently, Weiss andPhillips (2006) described identification ofvestibular dysfunction with five pediatricsubjects through use of sinusoidal rota-tion, step velocity, dynamic visual acuity,observation of post headshake nystag-mus, computerized dynamic posturogra-phy, and relevant case history details.

In addition to establishing pediatrictechniques, it is important to collect pedi-atric normative data so that accurateinterpretation of pediatric test resultsmay occur. Purposes of the current inves-tigation are to (1) describe a vestibulartest battery that may efficiently be uti-lized with children from three througheleven years of age, (2) study this testbattery with normal-hearing childrenprior to evaluating its use with childrendemonstrating disorders, and (3) evalu-ate age-related effects on vestibular func-tion tests. In addition, this study com-pares pediatric results with adult norma-tive data, augmenting existing pediatricnormative data.

It is the author’s experience that posi-tional testing and bithermal caloric irri-gation subtests of EOG have proven chal-lenging when attempted with young chil-dren. A number of researchers haveinvestigated maturation effects of nystag-mic response during rotation (per-rotary)in young children (Eviatar et al, 1974;Eviatar et al, 1978). Although prematureinfants demonstrate weaker nystagmicresponse than full-term cohorts, thevestibular systems of premature babies

maduración en niños pre-escolares hasta la edad adulta, y sugiere que los datosnormativos de adultos pueden no ser apropiados cuando se interpretanresultados pediátricos. Dado que las técnicas para adultos a menudo nodeben ser utilizadas, se describe una batería propuesta de pruebas quepuede ser eficientemente usada en pacientes pediátricos.

Palabras Clave: Posturografía dinámica computarizada, evaluación vestibularpediátrica, silla de rotación, potenciales evocados miogénicos vestibulares

Abreviaturas: CCW = contra las manecillas del reloj; CDP = posturografíadinámica computarizada; CW = con las manecillas del reloj; EOG = electro-oculografía; MCT = prueba de control motor; RC = silla rotatoria; SCC =canales semicirculares; SCM = músculo esternocleidomastoideo; SOT =prueba de organización sensorial; SV = velocidad de paso; TC = constantede tiempo; VEMP = potenciales evocados miogénicos vestibulares; VOG =video-oculografía; VOR = reflejo óculo-vestibular

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seem to “catch up” by nine months of age.Early researchers studying effects ofdevelopmental age on the vestibulo-ocularreflex (VOR) following caloric irrigationhave found varying results. Van der Laanand Oosterveld (1974) found low nystag-mus frequency and large amplitudes withchildren, as compared with adults.Andrieu-Guitrancourt et al (1981) discov-ered that nystagmic beat frequencyincreases and maximum eye speeddecreases as children mature. Strongerresponses have been reported in one-month-old versus eleven-year-old chil-dren with respect to amplitude and veloc-ity (Ornitz et al, 1979) while other inves-tigators noted more intense response inmiddle to late middle age (Mulch andPeterman, 1979). Donat et al (1980) con-cluded that the VOR goes through sever-al developmental stages, with a healthyresponse developing by several monthsbeyond full term. Fife et al (2000) report-ed that absence of the VOR by the age often months should be considered anabnormal finding. Krejcova et al (1975)reported significant differences betweencaloric responses of children and adults,with children demonstrating higher fre-quency of nystagmic beats. These andother investigators stressed the impor-tance of considering these differenceswhen interpreting pediatric versus adulttest results (Kenyon, 1988; Levens, 1988).

Current technologies and testing tech-niques allow expanded evaluation ofvestibular function with youngerpatients, particularly crucial since manychildren do not tolerate bithermal caloricirrigations. Rotary chair (RC) subtestsinvolve harmonic acceleration of variousvelocities and durations, primarily forassessment of horizontal semicircularcanal (SCC) function. The sensory organ-ization test (SOT), a CDP (computerizeddynamic posturography) subtest, assistswith evaluation of functional balance andrelative contributions of proprioceptive,visual, and vestibular inputs. The motorcontrol test (MCT), another CDP subtest,measures reactions to unexpected distur-bances with various-sized perturbationsof the support surface in forward andbackward directions. Vestibular evokedmyogenic potentials (VEMPs), recordedfrom the contracted sternocleidomastoid

muscle (SCM) in response to auditorystimuli, lend valuable information relat-ed to saccular function. The followingmay also be useful tools within the pedi-atric audiovestibular diagnostic battery:audiologic evaluation, otoneurologic eval-uation, thorough case history, and video-oculography (VOG) when the child is ableto tolerate goggles. Ideally, pediatric eval-uation should thoroughly assess SCC andotolith function and should differentiallydiagnose between peripheral and centralnervous system lesions. In addition tohelping to determine site of lesion, theideal battery should provide functionalinformation and help suggest directionfor remediation.

Cyr et al (1980, 1983) were at the fore-front in modifying adult vestibular tech-niques for use with children. They filledthe visual field for optokinetic (OKN)testing with rotating cartoon charactersand used similar cartoon characters forEOG calibration and smooth pursuit test-ing. Their RC enclosure was decorated toresemble a spaceship, and tasking wasaccomplished by piping in familiar chil-dren’s songs and nursery rhymes. Cyr etal (1985) successfully performed RCscreening at .08 Hz with premature andfull-term infants as young as threemonths of age. In this study, childrenwere seated on a parent’s lap, and aninfrared camera was situated within thedarkened enclosure for observation of theVOR. Staller et al (1986) also described RCtesting with children, although theseinvestigators tested from .01 to 16 Hz.They found that nystagmus was not pres-ent in very young children at .01 Hz butwas elicited by the age of 10 months. Phasedifferences found in subjects younger thanfour years of age indicated that the VORwas still developing at this age. A number of studies have also described

successful performance of CDP subtestswith children, primarily involving theSOT. These subtests measure functionalbalance and organization of the followingcues for regaining and maintaining bal-ance: visual, vestibular, and somatosen-sory. Six SOT conditions may bedescribed as follows:Condition #1: Eyes open, platform and

visual surround stableCondition #2: Eyes closed, platform stable

Condition #3: Eyes open, platform stable, and visual surround referenced to one’sown sway pattern (sway-referenced)

Condition #4: Eyes open, platform sway-referenced, and visual surround stable

Condition #5: Eyes closed, platform sway-referenced

Condition #6: Eyes open, platform and visual surround sway-referenced

DiFabio and Foudriat (1996) reportedthat a child as young as three years of agemay be tested through use of CDP tech-niques. Even a child this young will uti-lize shear forces for balance while ignor-ing misleading inputs, although theseinvestigators reported that these skillswill develop further as the patient ages.Hirabayashi and Iwasaki (1995) foundthat somatosensory function in childrenreaches adult levels by three to four yearsof age, and the visual system develops toadult acuity by 15 years of age. Theyfound that the vestibular system is thelast system to develop, that postural sta-bility increases with age, and many chil-dren have not reached adult developmen-tal levels by 15 years. Shimizu et al(1994) studied SOT subtests with chil-dren from six to thirteen years of age,finding that pediatric scores significantlydiffered from adult scores in many sub-test conditions. Male scores increasedwith age while female scores remainedrelatively constant after seven years.Ionescu et al (2006) compared BalanceQuest results of 12-year-old children withadult normative data. Mean stabilizingpercentages for children were significant-ly poorer than for young adults, especial-ly when visual information was compro-mised. The authors described their find-ings as supporting findings reported inexisting CDP literature. According to Cyret al (1988), CDP testing is indicated witha history of imbalance, when childrenexhibit “clumsiness,” neurological impair-ment, and suspected organic disease.Rine et al (2000) conducted CDP studieswith three- to seven-year-old children,finding that the SOT provides stable anduseful measures of the sensory systemsand of maturational changes with thispopulation.

VEMPs have recently been reportedwith the adult population, adding anobjective measure of otolith function.

Colebatch and Halmagyi (1992) recordedthe VEMP from the SCM and demon-strated that the response is of vestibularorigin. The VEMP is seen in response toan auditory stimulus presented via insertearphone to the ipsilateral side. The trac-ing reveals a positive peak (P1) and anegative peak (N1). The important testparameters are the P1 and N1 latenciesand the difference in amplitude betweenP1-N1.

Various investigators have researchedthe origin of these evoked responses andhave traced them to saccular function(Colebatch and Halmagyi, 1992;Halmagyi and Colebatch, 1995). Theresponse is not cochlear in origin, in thatthe VEMP has been effectively recordedin patients with profound, sensorineuralhearing impairment. Sheykholeslami etal (2005) successfully recorded VEMPswith 12 normal neonates and 12 with var-ious clinical findings. They concludedthat the pediatric VEMP morphology issimilar to that of adults, although theyfound a shorter latency of the N peak andwider amplitude variability. Kelsch et al(2006) also successfully recorded theVEMP in children from 3 to 11 years ofage. Mean latency data in this study alsosuggested a shorter initial negative peak,consistent with prolongation effects ofaging. They concluded that VEMP is awell-tolerated test for screening vestibu-lar function in young children.

It is important to consider a time-efficient,noninvasive, accurate, and comfortabletest battery for vestibular assessmentwith all ages of children. The earlier avestibular disorder is identified, the soon-er remediation strategies can be imple-mented. Consideration of the abovepoints has given rise to the current study,where various adult techniques havebeen successfully adapted for use withnormal-hearing children. Specifically, theauthor has compiled a comprehensivevestibular evaluation battery for chil-dren, including RC subtests, CDP sub-tests (SOT and MCT), and VEMPs.

Since the vestibular system continuesto mature through adolescence, the inves-tigator has examined differences betweentwo age groups of children. The first is apreschool/early school-aged sample fromthree through six years of age (N = 30),


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meeting the minimum weight of 40pounds recommended for CDP research.The second sample of children (N = 30)fell within the preadolescent age range of9 through 11 years. In addition to study-ing age effects between groups of chil-dren, the investigator also performedcomparisons of pediatric results withclinically attained and published adultnormative data. Since vestibular dysfunc-tion is more common in hearing-impairedchildren and evaluation is crucial withthis population, results of this studycould provide important implications forapplication with at-risk populations.

The research questions for this studyare as follows:

1. How efficiently may this test battery(RC, CDP, and VEMP) be utilizedwith the two groups of children, andwhat adaptations of adult techniquesare necessary?

2. What implications might these find-ings with typically developing chil-dren have toward testing at-risk pop-ulations?

3. What maturational effects areobserved with all measures betweenthe two age groups of children?

4. What maturational effects areobserved when comparing pediatricresults with adult normative data?

METHODS

Two groups of normal-hearing subjectswere utilized in this study. The first

group was of preschool/early school age(three through six years), and the secondgroup was preadolescent (9 through 11years). With the younger group, theauthor insured that children met theminimum weight limit of 40 pounds rec-ommended for CDP research. Thirty sub-jects were included within each agegroup, recruited via local preschools andpublic and private schools. Within theyounger group were 16 females and 14males, with a mean age of 5.5 years (SD =.9; range = 3.9–6.9 years). The oldergroup consisted of 9 females and 21males, with a mean age of 10.1 years (SD= .8; range = 9.0–11.8 years). Subjectshad no history of vestibular disease andwere not tested if suspected of middle earor other otologic pathology via history or

tympanometry. All subjects were asked torefrain from caffeinated beverages,aspirin, and over-the-counter cough andcold medications for 48 hours prior totesting, since these substances may affectvestibular test results. Subjects wereasked to eat lightly prior to the testingsession, in the event of queasiness ormotion sickness.

Prior to undergoing the vestibularevaluation test battery, all subjectspassed a pure-tone hearing screening at.5, 1, 2, and 4 kHz at 20 dB HL. ASHAGuidelines for Audiometric Screening(American Speech-Language-HearingAssociation, 1992) were modified toinclude 500 Hz since screening was con-ducted within a double-walled IAC(Industrial Acoustics Co., Niederkruchten,Germany) sound suite. This screeningwas performed using a GSI-16, two-channeldiagnostic audiometer (Grason-StadlerInc., Madison, WI). Children also under-went and passed an immittance screen-ing, utilizing the GSI-33 otoadmittanceaudiometer, to rule out the presence ofmiddle ear dysfunction.

The following vestibular measureswere utilized to compare the two groups’performance. Counter-balancing wasimplemented with respect to the order inwhich tests (RC, CDP, and VEMP) wereperformed, and all testing was performedby the author.

Rotary Chair (RC) Testing

All children were tested with theMicromedical 2000 Computerized RotaryChair (RC) equipment (MicromedicalTechnologies, Chatham, IL), encapsulat-ed within a darkened enclosure. Eitheradult or pediatric-sized goggles were uti-lized for VOG, depending upon headsize/comfort. The child was seated on aparent’s lap if she or he could not be test-ed alone. Rotary chair subtests were com-pleted at .08 and .50 Hz. The examinerrepeated subtests at .08 and .5 Hz duringthe same testing session and wheneverattention span allowed, to collect dataabout test-retest reliability.

Step velocity (SV) measures wereattained under clockwise (CW) and coun-terclockwise (CCW) conditions. With thistest, the chair rotates at 100°/sec in one


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direction. As the chair begins to move,nystagmus is induced. A per-rotary timeconstant (TC) measure in seconds isobtained as the original slow componentvelocity (SCV) decays to 37% of its origi-nal strength. Nystagmus accelerates inthe opposite direction as the chair sud-denly stops (post-rotary condition).Computerized measures of the responsedecay, again in the form of a TC, areattained. With adults, the TC in return-ing the vestibular system to 37% of itsoriginal strength is approximately 13–14sec and represents central prolongation ofthe peripheral signal (Goebel and Hanson,1997).

Extensive tasking and mental alertingexercises, appropriate for the child’s age,were implemented during all RC sub-tests, to minimize suppression of nystag-mus. Nystagmic activity was recordedvia the infrared VOG camera andobserved on a television screen duringall subtests. Measures of gain, phase (indegrees), and symmetry (in percent)were established per child for each VORsubtest, and TC measures (in seconds)were obtained for each SV subtest (twoTC measures for CCW and two for CWrotation).

Computerized DynamicPosturography (CDP)

The previously described six subtestsof the SOT were performed, utilizing aNeurocom CDP System (NeurocomInternational, Clackamas, OR). Duringtesting, the subject was secured via thesmallest harness to prevent falling. Three20 sec trials of the six subtests were com-pleted whenever attention span and com-fort would allow. Each child was exten-sively coached to maintain balance andpositively reinforced throughout eachsubtest. The six SOT subtest scores wereautomatically calculated via computer foreach subject.

The MCT subtest of CDP was per-formed with each subject. For MCT sub-tests, right and left latency scores wereobtained for small, medium, and largeplatform translations in forward andbackward directions. Latency is the timedelay in milliseconds between the start ofsurface translation and the onset of

active force exerted by the feet (Nashner,2001). For all subjects, three trials wereincluded with each of the subtests: smalltranslation backward (baseline), mediumtranslation backward, large translationbackward, small translation forward(baseline), medium translation forward,and large translation forward. Theamount of platform movement is directlyproportional to subject height, accordingto standard CDP protocol. A latency relia-bility score from 0 to 4 is provided for theright and left side of the body with each ofthe six subtests, with “4” indicating themost reliable, “1” indicating the least, and“0” indicating no reportable/interpretabledata. In accordance with WashingtonUniversity’s clinical protocol, data wereincluded in this study only if the subtestreliability rating was 2 or higher.

Vestibular Evoked MyogenicPotentials (VEMP)

VEMP testing was performed for bothright and left ears. Disposable electrodes(Nicolet, Inc., Madison, WI) were placedat specified locations on the head andneck: noninverting electrodes on eachcontracted SCM, inverting electrodes ateach sterno-clavicular junction, andground on the forehead. With adults,research has shown that the P1-N1amplitude of the VEMP tracing is direct-ly proportional to tonic level of neck musclecontraction (Lim et al, 1995; Murofushi etal, 1999). One method to standardizethis level of contraction among patientshas been to utilize commercially avail-able EMG electrodes (also applied to theneck) and monitoring software. Adultpatients have successfully been able tomonitor level of neck contraction bymaintaining a visual laptop target at aspecified microvolt level (30–50). Resultsof a pilot study indicated that it was notfeasible with children to utilize addition-al EMG electrodes on the SCM, for mon-itoring of tonic EMG activity. This wasbecause of a child’s limited attentionspan, limited space on a pediatric neck,weight of the EMG electrodes, and achild’s difficulty in monitoring neck con-traction to a desired target level.

The child was placed within a double-walled sound suite and asked to sit quietly,


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turning only the head to either the rightor left for contraction of the neck muscles.The right ear was stimulated/ testedwhile the child turned the head to the leftand vice versa. The child was asked tofocus on a wall-placed cartoon characterduring testing to create the necessarymuscle contraction. This designated spotwas predetermined so that all childrenwere seated at the same place with thehead turned the same degree, toward thesame cartoon character.

A Nicolet Bravo Evoked Potential unit(Nicolet, Inc., Madison, WI) was utilizedfor VEMP testing, using software version3.00, and two-channel recording wasattained. The VEMP procedure thorough-ly described by Akin and Murnane (2000)was utilized in this study. The responsewas amplified (5000) and band-pass fil-tered from 20 to 1500 Hz with a 12dB/octave slope. The epochs were 100msec, including a 25 msec pre-stimulusbaseline, and were digitized at 5 kHz.Stimulus levels for clicks (100 µsec, rar-efaction) and 500 Hz tonebursts were cal-ibrated in dB nHL by establishing theaverage behavioral thresholds for eachstimulus using a group of normal-hearing

adults. For 500 Hz tonebursts, stimuluspresentation level was calibrated in dBpeak SPL (120 dB SPL) using a Quest1900 Precision Sound Pressure LevelMeter with OB-300 1/3–1/1 Octave FilterSet, Quest 4140 �� ” pressure microphone,and a Frye HA-1 2-cc calibrated coupler.ER 3A insert earphones delivered teststimuli.

A VEMP tracing was obtained for eachear, with click (95 dB nHL) and 500 Hztoneburst stimuli. This resulted in fourtracings per child: click stimulus R, clickstimulus L, 500 Hz toneburst R, and 500Hz toneburst L. With toneburst stimuli,the examiner incorporated rarefactiononset phase, Blackman gating function,two cycle rise-fall time with no plateau.One hundred twenty eight sweeps wereaveraged per test. Counterbalancing wasattained with right versus left ears andstimulus presentation (toneburst versusclick). Test repetition to assess test-retestreliability was not always possible, due tolimited attention span and comfort levelof the child. Therefore, VEMP measuresmay approach more of a screening thandiagnostic evaluation. P1 and N1 latencymeasures and P1-N1 amplitude measures


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Figure 1. VEMP tracing for a six-year-old. Note P1 and N1 latencies, as well as P1 –N1 amplitude.

were obtained from all present responses. Figure 1 represents a typical VEMP

waveform, obtained on a six-year-old sub-ject. Attaining an accurate and repeat-able P1-N1 amplitude was challengingsince tonic level of neck contraction couldnot be monitored. Raw (uncorrected)amplitude measures were obtained foreach tracing, with pre-stimulus baselineEMG activity calculated by hand. Thisbaseline amplitude was calculated byaveraging 50 amplitude values thatoccurred within the 25 msec pre-stimulusbaseline period. A procedure was utilizedwhereby a normalized/corrected ampli-tude was obtained for each waveform bydividing the raw (uncorrected) amplitudeby the average baseline measure (Li et al,1999; Welgampola and Colebatch, 2001).It was felt that this procedure reducedvariability and allowed for more accuratecomparison of amplitudes.

DATA ANALYSIS

Prior to the major statistical analyses,all variables were examined to deter-

mine normalcy of distribution. Histograms,boxplots, and measures of skew and kur-tosis were used. Most variables exhibitedreasonably normal distributions, butsome were noticeably skewed. To investi-gate the possible consequence of thisskewness, transformations were per-formed on two different variables thatappeared to demonstrate the greatestdegree of skew: RC asymmetry at .08 Hz(cube root transformation) and a VEMPraw amplitude measure (fourth roottransformation). Data analyses compar-ing age groups conducted on the originaland the transformed data revealed nosubstantial differences in results.Therefore, the following results reportanalyses performed with the original,nontransformed data.

T-tests for independent samples wereperformed for all variables, to determinethe presence of significant gender differ-ences between male and female subjects.No consistent gender differences werenoted, and each subject pool representscombined data for the male and femalesubjects. Where relevant, t-tests were alsoused to compare measures with “right”and “left” versions (e.g., VEMP). These

analyses likewise did not reveal consis-tent differences, and thus right and leftmeasures were averaged to yield morereliable composites.

Analyses of variance (ANOVA) wereperformed to determine age effectsbetween groups of children. One-sample t-tests were implemented to determine sig-nificant differences between pediatricresults and adult normative data. RC test-retest reliability measures were ascer-tained utilizing Pearson correlation coeffi-cients. ANOVA was performed with SOTsubtests with trials 1–3 serving as repeat-ed measures, so that effects of trial and agegroup were seen. Relative generalizabilitycoefficients were calculated for all condi-tions of the SOT test, to determinerequired number of trials for optimum reli-ability. ANOVA on VEMP data determinedeffects of ear-tested, test stimuli, and agedifferences. In the analyses that follow,degrees of freedom vary slightly due tooccasional missing data for some meas-ures. These rare instances arose becausethe test could not be adequately performed.

RESULTS

Rotary Chair Testing

Table 1 reports means and standarddeviations for .08 and .5 Hz gain, asym-metry and phase measurements for thetwo groups. This table also comparesthese pediatric measures with adult nor-mative data. The Washington UniversityDizziness and Balance Center con-tributed adult normative data suppliedby Micromedical Technologies, and thesecontributions are included in softwareutilized for this study.

No significant age effects between thetwo groups of children were seen for gain,asymmetry, or phase measures at eitherfrequency tested. When younger groupdata were compared with adult norms,the following pediatric results were with-in the normal range for adults: asymme-try at .08 Hz; gain, asymmetry, and phaseat .5 Hz. A significantly higher gainmeasure at .08 Hz was seen for children,when compared to the adult upper limitof .65 (t[28] = 2.65; p = .013). A phase leadat .08 Hz was also seen for the youngerage group, when compared with the adult


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upper limit of three degrees (t[28] = .404;p < .01).

When older group data were comparedwith adult norms via one-sample t-tests,

results mirrored those described abovefor younger child-adult comparisons. Thefollowing pediatric measures were withinthe normal range specified for adults:


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Table 2. Pearson Correlation Coefficients for Test-Retest of RC Gain, Asymmetry, and PhaseMeasures

Gain 1-2 Gain 1-3 Asymmetry 1-2 Asymmetry 1-3 Phase 1-2 Phase 1-3

.08 Hz

.893* .783* .315 .372 .696* .501*

.50 Hz

.591* .408** .722* .284 .312 .007

*p < .01 **p < .05

Table 1. Comparisons of Pediatric Means and Adult Normative Ranges (±2 sd) for RC: .08 and.50 Hz, with Standard Deviations Appearing in Parentheses

.08 Hz .50 Hz

Gain Asymmetry Phase Gain Asymmetry Phase(%) (degrees) (%) (degrees)

** *

Young .72 (0.1) 5.41 (7.5) 9.45 (5..4) .80 (0.1) 6.21 (9.5) 5.10 (3.9)

** *

Old .71 (0.1) 7.5 (4.6) 6.28 (5.6) .77 (0.1) 4.86 (3.4) 6.76 (5.3)

Adult .5 to .65 -15 to 15 -13 to 3 .5 to .88 -15 to 15 -5.2 to 15

*p < .01 **p < .05

Figure 2. Means and SDs (in parentheses) for SV time constants with CW and CCW rotation.

asymmetry at .08 Hz; gain, asymmetry,and phase at .5 Hz. A significantly highergain measure at .08 Hz was seen for olderchildren, when compared to the adultupper limit of .65 (t[28] = 2.50; p = .019).A phase lead at .08 Hz was also seen forthe older age group, when compared withthe adult upper limit of three degrees(t[28] = 3.13; p = .004). These results indi-cate greater differences at the lower fre-quency tested and help to suggest thatadult norms should not be utilized whentesting pediatric patients.

Test-retest reliability was explored for13 subjects within the younger groupand for 13 subjects within the oldergroup for RC subtests at .08 Hz and .5

Hz. After initial testing, each childunderwent a second and then a thirdtrial of these subtests within the sametwo-hour testing session. Please seeTable 2 for a summary of Pearson corre-lation coefficients for each set of meas-ures. At .08 Hz, correlations were signif-icant and strong for gain 1–gain 2, gain1–gain 3, phase 1–phase 2, and phase1–phase 3 comparisons. Correlationswere not significant for asymmetrymeasures at .08 Hz. At .5 Hz, correlationswere significant (but not strong) for gain1–gain 2, gain 1–gain 3, and asymmetry1–asymmetry 2. Correlations were notsignificant for asymmetry 1–asymmetry3 or for phase measures.

These results indicate that gain meas-ures appeared to be most reliable acrossfrequency. Phase measures were reliableat the lower frequency, at least with thisstudy and within a short time frame.Asymmetry measures appeared to be unre-liable at .08 Hz but more reliable at thehigher frequency, at least between test 1and test 2. Phase measures appeared to bereliable at .08 Hz but not at .5 Hz.

SV testing proved to be a difficult taskfor children, especially within the youngergroup, due to head stabilization and/or


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Figure 4. Mean SOT scores as a function of condition and age group.

Figure 3. Example of displayed scores for six conditionsof the SOT.

EQUILIBRIUM STRATEGYConditions Trial 1 Trial 2 Trial 3 Trial 1 Trial 2 Trial 3

1 89 91 94 99 99 992 93 88 89 99 99 993 93 91 84 99 99 994 47 31 20 88 87 845 67 40 46 89 84 906 7 32 36 40 89 89

Composite = 55

tasking issues. Figure 2 contrasts meanCCW and CW time constants for each ofthe two groups. Within the younger group,data were interpretable from the follow-ing numbers of subjects: CCW per-rotary(moving): N = 16; CCW post-rotary (stop):N = 21; CW per-rotary (moving): N = 18;and CW post-rotary (stop): N = 20.

Within the older group, data were inter-pretable from the following numbers ofsubjects: CCW per-rotary (moving): N =26; CCW post-rotary (stop): N = 29; CWper-rotary (moving): N = 27; and CW post-rotary (stop): N = 26. ANOVA revealed nosignificant differences between dataobtained via clockwise and counterclock-

wise rotations. No significant differenceswere seen between the younger and olderage groups for either decay measure withCCW rotation or for the per-rotary meas-ure obtained via CW rotation. A signifi-cantly shorter TC was noted with theyounger group, however, for the post-rotary measure obtained via CW rotation(F[45] = 4.13; p = .048). With so many sta-tistical comparisons, it is not unusual foran occasional significant difference tooccur by chance alone. This finding is mostprobably not clinically significant since allfour time constant measures for eachgroup fell within the adult normal rangeof 5–25 sec.


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Table 3. T-Scores for Three Trials of Each of the Six SOT Conditions, When Comparing Scoresof Younger Children with Adult Normative Data

Condition 1 Condition 2 Condition 3

Trials 1 2 3 1 2 3 1 2 3

t-score -7.89 -6.73 -8.40 -5.21 -6.43 -7.19 -8.75 -6.66 -6.18

df 29 29 26 29 29 26 29 29 25


Trials 1 2 3 1 2 3 1 2 3

t-scores -8.52 -8.92 -8.85 -9.44 -10.68 -9.18 -9.12 -7.55 -7.04

df 29 29 26 29 29 23 29 28 24

Note: p < .001 for all trials.

Table 4. T-Scores for Three Trials of Each of the Six SOT Conditions, When Comparing Scoresof Older Children with Adult Normative Data


Trials 1 2 3 1 2 3 1 2 3

t-score -3.58 -2.79 -3.22 -3.11 -3.77 -2.98 -2.38 -2.27 NS

df 30 30 27 29 29 25 29 29

p .001 .009 .003 .004 .001 .006 .024 .031


Trials 1 2 3 1 2 3 1 2 3

t-scores -4.58 -3.15 -2.49 -4.50 -4.18 -2.49 -2.84 -2.05 NS

df 30 30 28 29 29 26 29 29

p <.001 .004 .019 <.001 .001 .019 .008 .028

Table 5. Motor Control Test (MCT) Latencies (msec) for Both Groups of Hearing Children,Contrasted with Adult Normative Data

Small Medium Large Small Medium Large Forward Forward Forward Backward Backward Backward

Younger 156.2 147.6 139.0 133.3 **129.1 *129.8

Older 146.0 140.8 **129.0 133.7 *131.2 120.2

Adult Norms 143 135 124 117

Note: Composites of right and left are represented.*p < .01 **p < .05 when comparing children with adults

Computerized DynamicPosturography

Figure 3 reports an example of scoresrecorded for the six conditions of the SOT.Strategy scores were not studied in thisinvestigation. Mean composite scoreswere 51.0 (SD = 13.8) for the youngergroup and 69.4 (SD = 12.7) for the oldergroup. Mean SOT scores for condition andage group are reported in Figure 4. Notethat three trials are collapsed for each con-dition so that one grand mean is provided.

No significant differences among trialswere seen for conditions 1–4 or for condi-tion 6 with either age group. Significantdifferences were seen among trials forcondition 5, one of the most difficult sub-tests where one relies on vestibular inputalone, with both age groups. Improvementin scores with each age group appeared,possibly reflecting a practice effect. Withmean data averaged across each trial, theANOVA further revealed that the youngergroup of children achieved significantlylower scores than the older group on allsix SOT conditions.

The following reliability coefficientswere seen for the younger group for threetrials each of conditions 1–6, respectively:

.74, .74, .75, .86, .77, and .84. Many sci-entists typically strive toward a coeffi-cient of .8 or higher with group data.These findings indicate that three trialsmay be optimum for conditions 4 and 6,although four trials might be optimal forconditions 1–3 and 5. Four trials maypresent a challenge for the attention spanof such young patients. The following coefficients were seen for

the older group for three trials of condi-tions 1–6, respectively: .66, .72, .78, .89,.84, and .87. These results indicate thatfour or more trials might be optimal forconditions 1–3 (coefficients of .72, .77, and.80 for trials 4–6 of condition 1; .78 and .81for trials 4–5 of condition 2; and .82 fortrial 4 of condition 3), although limitedattention span may also present a chal-lenge with the older children. With regardto conditions 4–6, these findings indicatethat only two trials per condition may pro-vide the examiner with viable test results(coefficients of .84 for trial 2 of condition 4;.78 for trial 2 of condition 5; and .82 fortrial 2 of condition 6).

A comparison of pediatric results withadult normative data was performed for allconditions of the SOT. Figure 4 comparespediatric SOT scores with adult normative


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Figure 5. VEMP latencies as a function of age and stimulus.

data. For the younger group, significantdeviations (lower scores) from adult normswere seen for all trials of all six SOT con-ditions. Table 3 reports t-scores for theyounger group–adult norm comparisons,with each trial of the six SOT conditions.For the older group, significant deviations(lower scores) from adult norms were seenfor all trials of all SOT conditions exceptwith the third trials of conditions 3 and 6.Table 4 reports t-scores for the oldergroup–adult norm comparisons, with eachtrial of the six SOT conditions.

Latency scores for the MCT are reportedfor each group in Table 5. Latency values of200 msec or greater are generally consid-

ered within the abnormal range for adults,from a clinical perspective, and no child’sperformance exceeded this value. No sig-nificant differences were seen betweenage groups for small or medium transla-tions in either a forward or backwarddirection. Latencies for the older group,however, were significantly shorter thanthose for the younger group with largetranslations in both forward and back-ward directions (F[1,56] = 8.81; p = .004;F[1,57] = 5.50; p = .023). While these arestatistically significant differences, theymay not be clinically significant in view ofabove-described normal range for adults.

Table 5 also compares pediatric MCT


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Table 6. T-Scores Demonstrating Significant Differences between Pediatric VEMP Latencies andAdult Normative Data Obtained Utilizing the Same Procedures

Younger children and adult comparisons

Click P1 Click N1 500 Hz P1 500 HzN1

t-score -12.19 -15.86 -10.49 -7.24

df 28 28 28 28

Older children and adult comparisons

t-score -6.29 -9.27 -6.36 -4.16

df 27 27 27 27

Note: All were significant at the p < .001 level.

Figure 6. VEMP amplitude as a function of age and stimulus.

results with adult norms. Adult norma-tive data were available from Neurocom,Inc., for medium and large translations,but not for small translations (consid-ered a baseline). With the youngergroup, significantly longer latencieswere noted for medium (t[28] = 2.08; p =.047) and large (t[28] = 5.26; p < .001)backward translations but not with for-ward translations. With the older group,significantly longer latencies were seenfor medium backward (t[29] = 4.04; p <.001) translations. Interestingly, signifi-cantly shorter latencies were noted forlarge forward (t[29] = -2.37; p = .024)translations.

Vestibular Evoked MyogenicPotentials

Salient features of each VEMP tracingare P1 and N1 latency, uncorrected P1-N1amplitude, and corrected (normalized)P1-N1 amplitude. The corrected ampli-tude is the important amplitude variablewith this study. Figure 5 compares P1and N1 latencies as a function of agegroup, while Figure 6 compares ampli-tudes as a function of age group. Adultnormative data for VEMP were obtainedwith the same evoked potential equip-ment and same procedures previouslydescribed for collecting child data.

Significant stimulus effects were seenbetween click and 500 Hz stimuli withboth age groups, consistent with pub-lished studies utilizing adult subjects(Akin and Murnane, 2000). P1 latenciesappeared later for 500 Hz than click stim-uli for both right and left ears (F[1,50] =155.38; p < .001; F[1,54] = 168.60; p <.001). Similarly, N1 latencies appearedlater for 500 Hz than for click stimuliwith both right and left ears (F[1,50] =128.30; p < .001; F[1,54] = 239.60, p <.001). A significant difference betweenstimulus type was also seen with normal-ized amplitude measures. Tracingsobtained via 500 toneburst stimulidemonstrated a significantly higheramplitude for right and left sides (F[1,50]= 5.13; p = .028; F[1,54] = 7.63; p = .008).

Significant differences were notedbetween child latencies (both groups) andclinic adult normative values. Whenresults obtained from the younger group

were analyzed, latencies of both P1 andN1 appeared earlier than they appearedwith adults, for both click and 500 Hztoneburst stimuli. When results obtainedfrom the older group were analyzed,results mirrored the above, and latenciesof both P1 and N1 appeared sooner thanthey appeared with adults for both typesof stimuli. Table 6 reports t-scores forchild-adult comparisons as a function ofstimulus and latency measures.

These findings suggest that VEMPlatencies may vary as a function of ageand that child latencies appear sooner, atleast with regard to procedures andequipment utilized in this study.Comparisons were made between pedi-atric normalized amplitude measures andadult normative data, utilizing the sameequipment and procedures. No significantdifferences were seen between adults andchildren of either group, with toneburstor click stimuli. Considerable intersub-ject variability was noted with pediatricVEMP testing, in addition to variabilitybetween ears of the same subject. Thisvariability, especially with child subjects,may be partially due to such factors aslevel of tonic neck contraction, movementduring the test session, fatigue, and elec-trode impedance. Because of such exten-sive variability, amplitude ratio values(between right and left ears) were notattained as they sometimes are withadult patients.

DISCUSSION

The results from this study demon-strate that the described, comprehen-

sive vestibular test battery may success-fully be performed with children of theselected age ranges. No significant ageeffects between the two groups of normal-hearing children were noted with gain,asymmetry, or phase measures for eitherRC test frequency. When compared withadult norms, there were no significantdifferences between child and adultasymmetry measures for either frequen-cy, or for gain and phase at .5 Hz. Gainmeasures attained for each group of chil-dren revealed significantly higher meas-ures at .08 Hz, however, than the upperlimit of adult normal range. In addition, asignificant difference was seen with the


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phase measure (child phase lead) at .08Hz for both groups. These findings indi-cate the importance of testing several testfrequencies when performing RC testing(as did Staller et al, 1986) and the impor-tance of utilizing child normative datawith pediatric patients. It has beenimportant to attain further child norma-tive data related to gain, asymmetry,phase, and step velocity measures of RCwith comparisons to adult normativedata.

Test-retest reliability was examined forRC measures at both test frequencies,revealing that the gain measure was veryreliable at both test frequencies. Phasewas reliable at .08 Hz but not as reliableat .5 Hz within this study. Asymmetryappeared reliable between test 1 and test2 for the higher frequency but not for thelower frequency tested.

SV measures were difficult to attain,especially with the younger children.This task may have been too difficult inlight of tasking and/or head controlissues. No significant age effects wereseen between the two groups of normalchildren with respect to either CCW rota-tion or with the per-rotary CW measure.An age effect was seen, however, with theCW post-rotary measure, in that theyounger group demonstrated a signifi-cantly lower time constant than the oldergroup. Wide variability was seen withboth groups, and it is not readily appar-ent why there was a significant differencebetween groups with this one measureonly. This was the last RC measureobtained, and fatigue could have played arole, particularly with the younger chil-dren. With such a large number of signif-icance tests being conducted, it would notbe unusual for a few results to show sig-nificant differences by chance alone. Thiseffect is just below p = .05 and is not con-sidered a strong effect.

There appeared to be no significant dif-ferences between pediatric results ofeither group and established adult nor-mative data. That is, all four time con-stants for both groups of childrenappeared within the adult normal range.Because of this, the effect described aboveis most probably not clinically significant. Out of 61 subjects recruited, only one

could not adapt tasks required for RC,

and only two required the testing to beperformed while sitting on a parent’s lap.Most children felt that this test wasenjoyable, resembling an amusementpark ride. Pediatric goggles with videocamera attached efficiently recorded thechildren’s eye movements.

The console talk-back system was uti-lized constantly for encouragement oftasking exercises and for continual posi-tive reinforcement. Oftentimes, it wasnecessary to open the door between sub-tests and to reinstruct and encourage,given the limited attention span of somechildren. In addition to limited attentionspan, challenges involved children keep-ing the eyes open and the head within theproper position.

With respect to SOT subtests of CDP, itwas found that older children performedsignificantly better than younger on allsix subtests. These findings may be con-sistent with a maturational effect of thevestibular system as the child maturesfrom preschool through school age, andare consistent with maturational effectsreported in the literature (Hirabayashiand Iwasaki, 1995). When younger chil-dren’s results were compared with adultnormative data, significantly poorer pedi-atric scores were seen for all trials of allSOT conditions. Significantly poorerscores were also seen when older chil-dren’s results were compared with adultnorms. These findings again might sug-gest maturational effects, from preadoles-cence to adulthood, as also reported byShimizu et al (1994).

Statistical analysis provided furtherinsight as to optimal number of SOT trialsrequired for reliable measurement. Withthe younger group, four seemed to be opti-mal with conditions 1–3, while three tri-als appeared sufficient for conditions 4–6.Four or more appeared optimal with theolder group for conditions 1–3, althoughthe above recommendations may not befeasible when working with the limitedattention span of children. Fortunately,two trials seemed to be sufficient for con-ditions 4–6 when testing the older chil-dren.

With respect to the MCT, older childrendisplayed significantly shorter latenciesthan younger children with large transla-tions in both forward and backward direc-


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tions. Child data in both age groups dif-fered significantly from adult normativedata. The younger group displayed signif-icantly longer latency values than adultswith medium and large backward move-ments but not with forward movements.The older group displayed significantlylonger latency values than adults withmedium backward movements and signif-icantly shorter latencies (better perform-ance) with large forward perturbations.

All SOT and MCT subtests may suc-cessfully be performed with children ofthe age ranges studied in this investiga-tion. The smallest jacket or harness wasutilized for testing subjects, and subjectsreadily adapted to all tasks required.Continual reinforcement and encourage-ment to maintain balance was providedduring each trial of each subtest. The chil-dren were also continually reminded thatthe harness and the examiner’s presencewould keep them from falling.

This study may be viewed as contribut-ing normative child data related to thevarious tests implemented. A few studieshave reported norms for SOT, and one ofthe most notable is Hirabayashi andIwasaki (1995) because of their relativelylarger number of subjects. The currentinvestigation supplements these normsand also contributes normative data forthe MCT.

With regard to VEMP, no significantage effects between the two groups of chil-dren were seen with either P1 or N1latencies. Current research is focusing onlatency differences as a function of age,although most studies have leaned towardstudying advancing age. Child latenciesfound in the present investigation appearto be in close agreement with adult laten-cies appearing in the literature(Colebatch and Halmagyi, 1992; Akin andMurnane, 2000). When comparing childlatencies with adult norms attained onthe Nicolet Bravo unit used for the cur-rent study and utilizing the same proce-dures, child latencies were found toappear significantly sooner. These find-ings are in good agreement with the earli-er pediatric latencies reported by Kelschet al (2006). The adult latencies obtainedwith the Bravo unit may be more delayedthan some published norms appearing inthe literature (Colebatch and Halmagyi,

1992; Halmagyi and Colebatch, 1995;Akin and Murnane, 2000), and the reasonfor this is not known. This underscoresthe importance of obtaining individual nor-mative data within each clinic and replicat-ing, to account for possible equipment andprocedural differences, as well as theimportance of additional research studiesto explore effects of age on the VEMP.VEMP latency and intensity values havenot abundantly appeared in the literaturerelated to pediatric populations, and it isimportant to study these values as a func-tion of age.

The VEMP measure is importantbecause it lends information about saccu-lar function and status of the inferiorbranch of the vestibular nerve. Because ofthe high incidence of vestibular dysfunc-tion with children demonstrating hearingimpairment and other childhood disorders,it may be important to consider perform-ing VEMP along with other vestibularmeasures at the earliest possible age. Asfound with adults (Akin and Murnane,2000), significant stimulus effects wereseen with P1 and N1 latencies. Both P1and N1 latencies appeared later in timewith use of a 500 Hz toneburst stimulusthan with a click stimulus.

Comparisons of normalized amplitudesfor both groups of child subjects revealedno significant age effects between groups,although wide intersubject and interauralvariability was seen. Because of the widevariability, asymmetry ratios (comparingright and left ears, as is oftentimes con-ducted with adults) and other comparativeear measurements were not calculated.The challenges of performing VEMP withchildren lend support toward future relia-bility studies. VEMP normalized ampli-tudes were significantly higher for bothgroups of children with the 500 Hz tonebursts,as opposed to clicks. No significant ageeffects were seen with normalized ampli-tudes when comparisons of child data andadult normative data were made.

VEMPs may easily be performed onchildren within the age groups included inthis study. It is a rapid, objective, and non-invasive measure. Obtaining of eachVEMP tracing was swift, since it onlyrequires 128 or fewer sweeps. Because oflimited attention spans and the exposureto high-intensity stimuli, however, it was


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not always possible to repeat each tracingto insure reliability. This would be a clini-cal recommendation and possible focus forfuture study.

CLINICAL APPLICATIONS ANDSUGGESTIONS FOR FUTURE

RESEARCH

The three vestibular tests used in thisstudy comprise a battery that assess-

es major components of the vestibular sys-tem. One of the author’s purposes was tohelp determine feasible pediatric proto-cols for each individual test.

RC testing should be performed at sev-eral frequencies, especially when low gainis attained with one test frequency. Thecurrent protocol of testing at .08 and .5 Hzwas successful, and child subjects tolerat-ed it well. SV measures were toleratedwell, although results were sometimes dif-ficult to measure and interpret, especiallywith the younger subject group. Testingprocedures might be improved by enhanc-ing measures to stabilize the head andimplementing more childlike taskingtechniques (nursery rhymes and music,for example). As Cyr and colleagues advo-cated (1983), these RC measures may bemore of a screening tool with very youngchildren, and it is crucial to observe pres-ence or absence of nystagmic activity viavideo camera. The gain measure appearsreliable from test to retest, but reliabilityof phase and asymmetry might be ques-tionable. Sitting on a parent lap is a veryviable option for RC testing with youngchildren, with many finding it enjoyable.Measurement of gain, asymmetry, phaseand TC parameters, as well as observingnystagmus on a monitor are viable toolsin assessing VOR function. RC may pro-vide a milder stimulation and informationabout more harmonic acceleration fre-quencies than bithermal caloric irriga-tions. Additional investigations may studyyounger populations, enhanced head sta-bilization techniques, and additional testfrequencies.

CDP was also efficiently utilized in thisstudy to measure functional balance.Three trials of all six SOT subtests wereemployed, to facilitate comparison withadult norms. Even though each trial last-ed 20 sec, the attention span of even the

older children was taxed with three trials.Since most children performed well onconditions 1 and 2, it might be possible toperform only conditions 3–6 for diagnosticinformation. The clinician might performmore difficult conditions first, adding eas-ier conditions if attention span allows.The order in which tests are performedmight be a topic for further study.Analyses of the data revealed that thethird trial of each subtest optimally wasnecessary for reliability, whenever possi-ble. Two trials per condition would mostprobably suffice with older children whentesting conditions 4–6.

The MCT provides latency values asthe child attempts to regain balance inresponse to small, medium, and largetranslations in backward and forwarddirections. There did not appear to beattention span difficulties, since the testis quite time efficient.

Questions related to the most efficientCDP test battery with younger andyounger populations might be explored inaddition to CDP results with variouschildhood disorders. SOT and MCT werethe only subtests studied with this proj-ect, and additional child studies are rec-ommended, incorporating the adaptationtest and other CDP subtests. It would bean interesting contribution to the litera-ture to compare strategies that childrenuse to maintain balance with strategiesthat adults use.

VEMP may also be a viable diagnosticprocedure for children, specifically forassessment of saccular function. This pro-cedure was found to be time efficient, non-invasive, and objective for use with thestudied age ranges of children. It is rec-ommended that the clinician incorporateat least two repeated measures per stimu-lus per ear. Well-formed, interpretableVEMP tracings were attained via both500 Hz toneburst and click stimuli; there-fore, the utilization of both may be redun-dant. The 500 Hz toneburst stimulusmight be the stimulus of choice, sinceamplitude measures were more robustthan with click stimuli.

It appeared that interpretable VEMPtracings may be obtained with only 64sweeps per tracing, which would diminishconcerns related to attention span withchildren. Although not performed with


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this study, bilateral tracings may also beeffective with children. With this type oftesting, the child would recline and ele-vate the head to contract the neck mus-cles. Inserts would deliver stimuli to bothears simultaneously and potentials wouldbe recorded from both SCMs simultane-ously.

Monitoring of tonic EMG activity wasnot effective with these age groups of chil-dren, as the electrodes were too heavy andthere was insufficient room on each SCMfor three electrodes. Monitoring neck con-traction to reach a certain target level ona laptop computer graph also appearedtoo difficult for the age groups used in thepresent study. Equipment and softwarefor such monitoring could be a recommen-dation for future pediatric VEMP testing.

Future studies may determine feasibil-ity of measuring VEMP thresholds in chil-dren. The procedures outlined in thisstudy may describe more of a screening,as opposed to diagnostic, procedure inyoung children. That is, the clinicianmight be viewing presence or absence ofthe VEMP tracing with latencies also pro-viding valuable information. Moreresearch may be needed related to inter-preting VEMP parameters with respect tovarying degrees of saccular and/or inferiorvestibular nerve damage. Additional stud-ies might explore effects of stimulusparameters on the pediatric VEMP trac-ing: frequency of toneburst, duration ofstimuli, and others. Child studies mightexplore VEMP diagnostic results expect-ed with various childhood disorders.Investigators might study optimum elec-trode placement and whether it indeed isthe SCM in children, the bone-conductedVEMP, and other issues that are beingexplored with adult subjects. CrucialVEMP parameters for interpretationappear to be P1 and N1 latencies, P1-N1amplitudes, and the VEMP thresholds.Additional studies might focus on laten-cies with other age groups and with uti-lization of other stimuli.

Clinical recommendations may also bein order beyond the realm of the describedbattery. As with any patient with balancedisorders, a thorough case history is oneof the most important diagnostic tools.Dizziness questionnaires for children arenot currently prevalent, although their

development would be highly beneficial.Bithermal caloric irrigation and otheraspects of VOG is a highly effective toolwith adults and should also be consideredwith children. In the author’s experience,VOG may be successfully performed onchildren within the older age range andpossibly may be performed on cooperativechildren as young as six to seven years.Oculomotor subtests may be modified forchildren, as previously described, andmay be beneficial in assessment of centralpathology. For the sake of thoroughness,any child who presents with a possiblebalance disorder should undergo compre-hensive otolaryngologic and audiologicevaluations.

There remains a paucity of researchand clinical work related to balance disor-ders in children. Among the primary mes-sages conveyed with this study is thatvestibular function can and should betested with many children. In reviewingthe literature, the professional communi-ty may note that vestibular dysfunctionhas been linked to a myriad of childhooddisorders. Additional studies to explorethese relationships would be beneficial.Further research should explore effectivetesting techniques for use with youngerand younger populations. Multidisciplinaryresearch and clinical work to improve cor-relations among diagnostic tools or todetermine how they complement oneanother would serve to enhance patientcare. Collaboration and sharing of knowl-edge across disciplines should be imple-mented.

A thorough discussion of vestibularevaluation in children leads to the issue ofremediation. Vestibular rehabilitation hasrapidly taken hold within the adult arenaand is certainly an area where moreresearch is needed with children. Adultdizzy patients may be referred for headand neck exercises, learning visual com-pensation strategies, relying more onankle versus hip strategies, or a widerange of other procedures. Just as a mul-tidisciplinary approach may be recom-mended with diagnostics, the involvementof numerous disciplines might also beeffective with treatment. Occupationaland physical therapy colleagues arealready working with children whodemonstrate delayed motor performance,


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balance issues, and difficulty with headand postural control. Additional studiesare warranted with respect to the variouschildhood disorders that accompany bal-ance dysfunction and the most effectiveways to remediate.

The current study has served to high-light the need for additional research andclinical work in the area of vestibular dis-orders in children. Vestibular dysfunctionmay accompany a myriad of childhood dis-orders, when hearing loss is or is not pres-ent. Methodologies must be fine-tuned,particularly with younger and youngerchildren and results related to childhooddisorders. This investigation hasdescribed several tests that may efficient-ly be performed with young children. Thesuggested test battery presented withinthis study appears to successfully evalu-ate major aspects of the balance systemand is well tolerated by pediatric popula-tions. Results obtained with pediatricpatients may not always effectively becompared to adult norms. This study hasserved to demonstrate maturationaleffects and to add to the normative databanks for children. Audiovestibularhealth-care professionals must not losesight of the high incidence of balance dis-orders and of the importance of evaluationwith young children. As professionalswork to develop more efficient diagnostictools and more effective remediationstrategies, it is important to strive towardearlier and earlier identification. The ear-lier a vestibular disorder is identified, thesooner the implementation of remediationstrategies may begin if warranted.

Acknowledgments. The author would like to thankDr. Joel Goebel, Medical Director, and Ms. BelindaSinks, Supervisor, of the Washington UniversitySchool of Medicine Dizziness and Balance Center forexceptional mentoring and support. She would alsolike to thank other members of the Department ofOtolaryngology, her doctoral dissertation committee,and anonymous manuscript reviewers.


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