127-133 Static Equilibrium and Vestibular Function

7/28/2019 127-133 Static Equilibrium and Vestibular Function.

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STATIC EQUILIBRIUM AND VESTIBULAR FUNCTION *BY JAMES E. BIRREN

Lieutenant


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128 JAMES E. BIRRENposit ion, and that they are able to adjust to slow inclinations inducedby t i l t ing pla t forms (15) . D e N o de m on stra te d th a t loss of muscle' t o n e ' was regained in a few days following labyrinthectomy inexp erim ental anim als (1). Spiegel after a review of th e l i ter atu res ta ted th a t " th e hyp otonia regresses ra th er rap id ly a fter th e op era-t ion, in cats and dogs in a few hours or days, in rabbits and monkeysaf ter several w eek s" (16, p . 1651). I t is ap pa re nt th a t a l though th eampullae of the semicircular canals may exer t a s ta t ic regulatoryeffect on posture, loss of function of this organ is not accompaniedby such changes that body sway could, as Edwards c la ims, be usedto 'facil i tate th e diagnoses of th e ex ten t of ve stib ula r injur y ' (5, p .187). This would be especially true of Edward's subjects since theywere cases of loss of vestibular function of long standing.The other considerat ion, the so cal led dynamic act ion of theam pullae , or response to mo tion, has now to be discussed. T hr es -holds to movement have usual ly been s tudied by using eye or headm ov em en ts as th e cri terion of st im ula tion (2, 14). A n excep tion tothis is the work of Lowenstein and Sand, who recorded action po-tentials directly from a nerve f iber from the ampulla of a ray (9).They reported a threshold value of 3/sec.2 Accelerations as largeas these may be noted in body sway but usual ly occur only a t theend of mu scula r compensa t ion for bod y m ove m ent . H ence , th eampullae would not be expected to be the sense organ init iat ing thecompensat ion s ince i ts threshold would be reached only upon act ivecompensa t ion .Dodge determined thresholds to rota t ion in man, us ing eye move-m en t as th e cri terion (2). H is results are no t given in te rm s ofaccelera t ion bu t as th e ex ten t of m ov em en t a t ' sud den o nse t ' andwere expressed as angu lar veloci ty . H e found t h a t co nsis tentresponses were observed only with movement having a terminalveloc ity of 4/sec. or m ore . Ac ceptin g for th e t im e being the low estvalue 2/sec. for purposes of this discussion, then a five-foot ten-inchman would have to sway the equivalent of 2 .4 inches per second,sta rt in g from r est , to st i m ula te th e lab yr in th (r == no, or 7o ".2 ir / l8 o= 2.4 inches). T his wou ld assum e th e heig ht of th e S as th e ra diu sof a circle, his feet or ank les bein g th e ce nte r of ro ta tio n. W hile itis possible to observe movements equivalent to 2.4 inches per secondin some Ss, th ey a re infreq uen t, and eve n casual ob serv atio n willreveal that most movements associa ted with body sway would besub-threshold as considered in terms of angular velocity.In contras t to the value reported above for thresholds of thelabyrinth to movement , Miles (13) quoted Goldscheider 's work asindicat ing that the thresholds for sensi t iv i ty to movement in largejoin ts were 0.75 to 1.50 degrees. I t ap pe ars th a t recep tors in joi nts


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STATIC EQU ILIBRIUM AND VESTIBULAR FUNCT ION 12 9probably play a more important role in movements associated withbody sway than do end organs in the labyrinth.This brief review of the literature serves to support the view thatthe receptors in the labyrin th are insensitive to fine body m ovem ents,and that functional loss of these receptors would not impair theperception of or response to movements associated with body sway.This is in keeping with Rademaker's findings that human Ss withsuch loss were able to compensate for small displacements but losttheir balance with larger movements for which a normal subjectcould compensate and m aintain balance (15). I t is the problem ofthis paper to demonstrate this thesis with relevant clinical andexperimental data.

PROCEDURETwo experimental procedures were employed to investigate the possible relation betweenvestibular function and body sway, (1) the measurement of body sway and other observationson a male S manifesting complete loss of function of the vestibular apparatus, and (2) observationof vestibular function, B arany C hair tests, and body sway in 45 Ss with intact labyrinths .The measurement of body sway of the Ss reported in this study consisted of kymographicrecords of anterior-posterior sway, feet in V position (6, 13). Two trials with eyes open andtwo trials with eyes closed were made in each case. Each tr ial was two m in. in length with a30-sec. rest period between trials. The graphic records were scored by measuring the length ofthe line with a Dietzgen map measure, and subtracting the horizontal movement due to thekymograph rotation . Scores are reported as millimeters of movement in two min.The rail-walking test used with the patient manifesting loss of vestibular functions wassimilar to that described by Heath (8).Conventional Barany Chair tests were run on the Ss in both right and left directions, withthe head in the 30 degree forward position. A motor-driven 30 R.P.M . Barany chair was usedwith 10 rotations per test. Nystagm us was timed by an observer using a stop watch. Thevalues used in this study represent the mean nystagmus time of the right and left rotations.Duration of the nystagmus in the two directions was correlated to the extent of an r of 0.79(N = 52).

RESULTSThe S demonstrating complete loss of vestibular functions was a19 year old male convalescing from acute meningococcus meningitiswhose last symptoms occurred within three months of the observa-tions reported in this paper. The loss of vestibular function wasdetermined by complete absence of response to the caloric test andto rotation in the Barany Chair; both tests were repeated on severaloccasions. The S was also suffering from complete bilateral deafnessas a result of the infection.Measurements of body sway were made on this S one monthap ar t. A t the first session the S had a mean sway of 488 mm . witheyes open, and a mean sway of 1901 mm. with eyes closed. Nounusual qualitative features appeared in the S's records with eyesopen. W ith eyes closed, several large movem ents occurred no tusually noted in normal Ss. Th e S appeared to lean gradually


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130 JAMES E. BIRRENforward upsetting his equilibrium to the point where he wouldsuddenly have to stand erect to maintain his balance, in a reactionvery akin to a startle response. H e did not lose his balance to th eextent th a t he had to shift his feet to prevent falling. Th e recordsof these trials were unlike those of normal Ss in that the large totalsway was the result of a few large movements instead of to the usualfine oscillatory type of sway.One month later, just prior to the S's discharge from the hospital,body-sway measurements were again taken . The mean sway at thistime with eyes open was 531 mm. and 1043 mm. with eyes closed.This represents an improvement from the previous session with theeyes closed and was particularly notable in that the S no longerswayed to the point of losing balance momentarily, as he did in thefirst session. Q ualitative observation of the S's performance sup-ported the conclusion that he made a very real improvement in hisability to m aintain stable posture during the mo nth interval. Th erecords for the last session are presented in Fig. 1 and can be comparedwith an S of average sway and with an S having considerable bodysway bu t no detectab le vestibula r defect. N o physical defects ap -peared in the latter S to account for his considerable movement.Other than being quite susceptible to seasickness the S appearednormal in all other observable respects including vestibular functions.It was impossible for the meningitis patient in either test sessionto perform the rail-walking test to any scorable degree. In bothsessions the S could no t place his second foot on the rail in a balancedposition to proceed to walk. During the second observation periodthe S was tried on one-inch, two-inch, and four-inch rails without hisachieving any success. W hether this loss of dynam ic equilibriumwas incurred as a result of vestibular involvement, or occurred as aresult of other lesions, is impossible to determine at this point.Similar observations on other patients might elucidate the generalnature of the phenomenon.In tre ating the data of the 45 norm al Ss correlation coefficientswere determined for the relations between body-sway measurementsand post rota tional nystagm us. Th ree correlation coefficients calcu-lated are shown in the following table: Con-elation with nystagmus (r)N = 4 S

Bod y sw ay, eyes open r = .02Body sway, eyes closed r = .03Body sway, eyes open/eyes closed r


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STATIC EQUILIBRIUM AND VESTIBULAR FUNCTION 131One might expect a low correlation between body sway with eyesopen and nystagmus, since body sway with eyes open is to a greatextent dependent on vision. However, the zero correlation betweenbody sway with eyes closed and nystagmus is indication that vesti-bular function, as measured by nystagmus, is unrelated to body

S U B J E C T WITH INTACTV E S T I B U L A R APPARATUS

SHOWING E X C E S S I V E SWAY

50iANTERIOR - POST ERIOR SWAY ONLY3 0 S E C O N D R E S T P E R I O D S B E T W E E N T R I A L SF E E T IN "V" POSITION

FIG. I . Comparison of ataxiagraph records of an S having no vestibular functionwith records of normal Ss.


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132 JAMES E. BIRRENsway . T h e zero corre la tion betw een nystag m us and th e ra t io ofbody sway eyes open to eyes closed further supports this conclusion.

D I S C U S S I O NThe quest ion as to what the Barany Chair tes t real ly measuresm ay ha ve relevance to the se resu lts . Following th e l ine of reason ingof Dohlman i t appears that the character is t ic of a s low and fas tphased nystagmus is associa ted only wi th vest ibular s t imulat ion (4) .I t i s apparent ly impossible to produce the s low phase throughvo lun ta ry ac t ion . One m ay assume, there fore , th a t whenever th i sty pe of ny stag m us ap pea rs , ves t ibular s t im ulat ion exis ts in some form.The converse need not fol low, that the lack of such nystagmus isind icat iv e of th e lack of ve st ib ula r st im ula t ion . On e has only toreview the history of the Barany Chair test in the period fol lowingthe f i rs t World War to real ize that a shor tened nystagmus may bebr ou gh t abo ut as a result of experience. A m odificat ion of th epos t ro ta t iona l nys tagmus through exper ience , however , can hard lybe a t t r ibuted to any a l tera t ion of the per ipheral sense organ.In na ive Ss the dura t ion of pos t ro ta t iona l nys tagm us m ay thu sbe expected to fol low the durat ion of any vest ibular s t imulat ion.This durat ion, about 20 to 30 sec. in most cases, agrees with thevalue rep or ted for the du rat io n of the p ost ro ta t ion al discharge in ave st ibu lar ne rve fiber of a ra y, 20 to 30 sec. (9) . T he se wo rkers,Lowens te in and Sand, a t t r ibu te the dura t ion of the pos t ro ta t iona ldischarge to the t ime required for the ampullae to regain theiror iginal posi t ion. Th is suggests th a t th e B ara ny Ch air tes ts m easureindirect ly the t ime required for the ampullae to come to rest af ter

m ov em en t induced by accelerat ion. H ighe r nervous centers pla y aminor role in the mediat ion of this effect in the naive S, but mayexert an important inhibi t ing influence in experienced Ss.S U M M A RY A ND C O N C L U S I O N S

Observat ions of body-sway and ra i l -walking tes ts were made on a19 ye ar old ma le w ho had lost all V I I I n erve functions (vest ibu lar)following an at ta c k of ac ute m eningococcu s m enin git is . T h e exist-ence of the vest ibular defect was established by complete absence ofresponse to the calor ic and Barany Chair tes ts .T his S m anifes ted m arked bod y sway dur ing the f irs t t r ia l per iod.He did, however , mainta in his balance s tanding erect wi th eyes openand w i th eyes c losed. One m on th la ter this S displayed im pro ve m en tin his postural control so that the record would not be categorized aspatho logica l . D ur in g ne ithe r of th e sessions could th e S score abo vezero on the rai l-walking test .


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STATIC EQU ILIBRIUM AND VESTIBULAR FUNCTION 133Postrotational nystagm us time and body-sway m easurements weremade on 45 male Ss. None of th e correlation coefficients obtainedbetween body-sway measurem ents, eyes open or closed, and nystagmustime were significantly greater than zero.The findings of this study are interpreted as indicating that manmay maintain stable posture despite loss of vestibular function, andthat measurements of body sway cannot be used to detect vestibulardefects. Po stural defects may occur following th e loss of vestibu larfunctions, bu t the defect is soon compensated for. The lack ofcorrelation between postrotational nystagmus time and body swayis further indication of the lack of complete dependence of postureon vestibular functions, or at least on those functions reflected innystagmus. Superficially it would seem th a t body-sway measure-ments were indicative of the adequacy of integration by the cere-bellum of sensory cues arriving from many sources, among which thosefrom the labyrinth are not the most important.

(Manuscript received September 18, 1944)BIBLIOGRAPHY1. DE NO, R. L. Ausgewahlte Kap itel aus der vergleichenden Physiologic des Lab yrinthes.Ergebn. Physiol., 1931, 32, 73.2. DODGE, R. Rotation thresholds. / . ixp. psychol., 1923, 6, 107-137.3. DUSSER DE BARENNE, J. G. The labyrinthine and postural mechanisms. Pp. 204246in : A handboo k of general experimental psychology. Carl Murchison, Ed. Worcester ;Clark University Press, 1934.4. DOHLMAN, G. On the mechanism of transformation into nystagmus on stimulation of thesemicircular canals. Ada oto-laryng., 1938, 26, 425442.5. EDWARDS, A. S. The measurement of static ataxia. Amer. J. Psychol., 1942, 55, 171-188.6. FEARING, F. S. The factors influencing static equilibrium. / . comp. P sychol., 1924, 4,

91-121.7. FEARING, F . S. The experimental study of the Romberg sign. / . nerv. men t. Dis., 1925,61, 449-465-8. HEATH, S. R. The military use of the rail walking tes t as an index of locomotor coordination.Psychol. Bull., 1943, 40, 282-284.9. LOWENSTEIN, 0., & SAND, A. Th e mechanism of the semicircular canal. A study of singlefiber preparations to angular accelerations and to ro tation at constan t speeds. Proc.roy. Soc. London, 1940, 129 B, 256-275.10. MAXWELL, S. S. Labyrinth and equilibrium. Philadelphia: Lippincott, 1923.11. MCNALLY, W. J., & TAIT, J. Func tion of the utricular maculae of the frog. Ada oto-laryng., 1934, 20, 73-76.12. MCNALLY, W. J., & STUART, E. A. Physiology of the labyrinth reviewed in relation toseasickness and other forms of motion sickness. War M ed., 1942, 2, 683-771.13. MILES, W . R. Static equilibrium as a useful test of motor control. / . industr. Hyg., 1922,10,316-331.14. MOWRER, O. H . Th e nystagmus response of the pigeon to constant angular accelerationat liminal and supraliminal intensities. / . comp. Psychol., 1935, 19, 177-193.15. RADEMAKER, G. Reactions labyrinthiques. Paris: Masson et Cie., 1935.16. SPIEGEL, E. A., & SOMMER, I. Vestibular mechanisms. Pp. 1638-1653 in: Medical physics.Otto Glasser, Ed . Chicago: Yearbook Publishers, 1944.

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127-133 Static Equilibrium and Vestibular Function