Ashdin PublishingJournal of Case Reports in MedicineVol. 2 (2013), Article ID 235749, 4 pagesdoi:10.4303/jcrm/235749

ASHDINpublishing

Case Report

A Rare Case of an Acoustic Tumor Diagnosed in an Elderly Patient withAtypical Nystagmus

Hidetake Matsuyoshi and Hidenori Goto

Matsubase Otolaryngology and Internal Medicine Clinic, Kirara 2-2-15, Matsubase, Uki city, Kumamoto Prefecture 869-0503, JapanAddress correspondence to Hidetake Matsuyoshi, lymphotactin@yahoo.co.jp

Received 4 May 2013; Accepted 3 June 2013

Copyright © 2013 Hidetake Matsuyoshi and Hidenori Goto. This is an open access article distributed under the terms of the Creative CommonsAttribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract We describe a rare case of an acoustic tumor diagnosed in a69-year-old female who presented with a history of persistent rotatoryvertigo on shifting her head position since several weeks, whichwas accompanied by mixed upper eyelid-oriented counterclockwiserotation on standing. Pure-tone audiometry and auditory brainstemresponses were symmetrical, and thermal stimulus test results werenormal. These symptoms ruled out Meniere’s disease and acutevestibular neuronitis; therefore, benign paroxysmal positional vertigo(BPPV) of the right posterior canal was considered the most probablecause. However, no improvement was observed with the Epleymaneuver. Furthermore, the eye-tracking test indicated ataxia, andoptokinetic nystagmus was also abnormal, which warranted furtherexamination using magnetic resonance imaging (MRI). T2-weightedimages revealed a 5-mm tumor within the internal acoustic meatus.This case strongly suggests that MRI should be considered for allpatients presenting with atypical nystagmus, even when BPPV is themost probable cause.

Keywords acoustic tumor; nystagmus; benign paroxysmal positionalvertigo

1. Introduction

Vertigo is defined as the sensation of tilting within astable environment. It accounts for > 50% of all dizzinesscases reported in the primary care setting [6]. The mostcommon causes of vertigo are Meniere’s disease, acutevestibular neuronitis, and benign paroxysmal positionalvertigo (BPPV), which account for > 90% of all cases [4].The incidence of acoustic tumors during the course of BPPVis approximately 30% [7]. Moreover, vertigo is reportedlyan important symptom of tumor growth when hearing isnormal, or when there is no bilateral difference in hearingability [8]. Therefore, physicians should consider othercauses, including stroke, migraine, or acoustic neuroma,when symptoms persist for several hours [5]. We report therelatively rare case of a 69-year-old female who presentedwith symptoms of an acoustic tumor that manifested asrotatory vertigo and nausea on shifting of her head position,with nystagmus findings similar to those observed in BPPV.

2. Case report

2.1. Clinical history

A 69-year-old female with a history of hypertensionwas receiving treatment at our internal medicine clinic.The patient experienced rotatory vertigo and nausea onawakening on the morning of March 26, 2009. She visitedthe emergency department and underwent head computedtomography, but no abnormal findings were detected.The symptoms were initially relieved with intravenoustreatment. She revisited our clinic on the same day for amore detailed examination. Our initial analysis indicated noabnormal neurological findings or cochlear symptoms otherthan rotatory vertigo on shifting of the head position.

During our initial evaluation, we considered the threemost common causes of vertigo: Meniere’s disease, acutevestibular neuronitis, and BPPV. Initially, Meniere’s diseasewas ruled out because pure-tone audiometry only revealedsymptoms at the initial visit, and a > 10-dB differencebetween the right and left ear was only detected at an 8-kHzfrequency (Figure 1). The symptom of rotatory vertigoon shifting of the head position was consistent with acutevestibular neuronitis and BPPV, which can be differentiatedon the basis of vertigo type. Acute vestibular neuronitis isgenerally characterized by nystagmus with central horizon-tal vertigo [7]; however, our patient exhibited a mixed uppereyelid-oriented component and a counterclockwise rotatingcomponent when turning from the sitting position to thesuspended head position, as shown in Figure 2. Moreover,counterclockwise rotatory nystagmus was also observedwhen turning from the suspended head position to the sittingposition. Therefore, the rotational and vertical vertigo didnot support a diagnosis of acute vestibular neuronitis butindicated right posterior canal-type BPPV. We tested ourhypothesis by performing the Epley maneuver [3] thrice,but the nystagmus and rotatory vertigo symptoms persisted.

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Figure 1: Audiogram of pure-tone audiometry. A differenceof > 10 dB between the right (◦) and left ear (×) wasdetected at an 8-kHz frequency at (a) the initial visit (March26, 2009) (b) but not at a follow-up visit, when the acoustictumor was no longer visible on MRI (May 12, 2012).

Figure 2: Initial nystagmus findings. Nystagmus at theinitial visit was characterized by a combination of an uppereyelid-oriented component and a counterclockwise rotatingcomponent when turning from the sitting position to thesuspended head position.

Together, these findings were inconsistent with the threemost common causes of vertigo.

On March 28, 2009, other possible causes of vertigowere investigated using several tests to discriminate betweencentral and peripheral disorders. As shown in Figure 3,auditory brainstem response audiometry showed a latencyperiod between waves I-V, with an extension on the leftside indicating a normal response. In contrast, the eye-tracking test suggested ataxia (Figure 4), the optokineticnystagmus test (maximum velocity, 95 °/s; acceleration,4 °/s2) showed that nystagmus release varied between theright and left eyes (maximum slow phase velocity for theright and left eyes was 40 °/s and 76 °/s, respectively), andthe air caloric test (15 °C, 60-s stimulus) showed no obviousdifference between the right and left ears (maximum slowphase velocity for the right and left ears was 23 and 27 °/s,respectively). The visual suppression test results werenormal for both ears (65.2% and 59.3% for the right andleft ears, respectively). In summary, the presence of severevertigo, the positive caloric test results, and the negativevisual suppression test results indicated that the persistentrotatory vertigo in our patient had a central cause.

The major causes of central vertigo are cerebrovas-cular disease, multiple sclerosis, and neoplasms [7]; and

Figure 3: Auditory brainstem response audiometry. Theauditory brainstem response audiometry analysis showed alatency period between waves I-V, with an extension on theleft side. This indicated a normal result.

Figure 4: Eye-tracking and optokinetic nystagmus tests.Equilibrium testing using the eye-tracking test indicatedataxia, and the optokinetic nystagmus test showed avaried nystagmus release between the right and left eyes(maximum slow phase velocity for the right and left eyeswas 40 °/s and 76 °/s, respectively). The air caloric testindicated no obvious differences between the right and leftears (maximum slow phase velocity of the right and left earsbeing 23 °/s and 27 °/s, respectively). The visual suppressiontest results of both ears were normal.

elderly patients with a clinical history of hypertension areparticularly at risk of the cerebrovascular causes of vertigo.

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Figure 5: Magnetic resonance imaging of the brain. OnMarch 31, 2009, T2-weighted imaging showed a 5-mm lowintensity area within the internal acoustic meatus, whichwas diagnosed as a right acoustic tumor. The mass was alsodetected on June 27, 2009; however, it was no longer visible3 years later.

Therefore, we performed plain magnetic resonance imaging(MRI) on March 31, 2009 to detect potential cerebrallesions. As shown in the T2-weighted image in Figure 5, a5-mm low intensity area was observed within the internalacoustic meatus, indicating a right acoustic tumor. Threemonths later, MRI revealed no increase in tumor size, and3 years since then, no increase in size has been observed(Figure 5). The symptoms of nystagmus and rotatory vertigoon shifting of the head position have gradually improvedsince their onset. Eight months after initial diagnosis, theepisodes of vertigo and nystagmus completely resolved,indicating a central compensatory mechanism.

3. Discussion

We reported a relatively rare case of a right acoustic tumorin a 69-year-old female with symptoms and nystagmus find-ings similar to those observed in right posterior canal-typeBPPV. Including suspected BPPV, BPPV are present at ahigh frequency (approximately 50%) in patients with ver-tigo [9]. However, it is plausible that the present patient wasactually a case of BPPV; furthermore, the acoustic tumorwas incidentally found on diagnostic imaging. Nonetheless,the persistent symptoms after several Epley maneuvers aswell as the abnormal eye-tracking and optokinetic nystag-mus test results suggested that the symptoms of vertigo andnystagmus were due to the acoustic tumor.

First, we examined the cause of nystagmus, which pre-sented symptoms similar to those of BPPV or an acous-tic tumor. Although the vestibular-evoked myogenic poten-tial was not examined in this study, the normal caloric testresults indicated that the tumor was derived from the infe-rior vestibular nerve, which communicates with the poste-rior semicircular canal and saccule. Therefore, we consid-ered that the tumor compressed the inferior vestibular nerve,resulting in nystagmus that appeared as right posterior canal-type BPPV.

Although the tumor in the present case was relativelysmall (5 mm), the eye-tracking and optokinetic nystagmustest results were abnormal; therefore, we considered that

the tumor position in the internal auditory canal mayhave induced the nystagmus by applying pressure to thevestibulocochlear nerve, thereby indirectly impairing innerear blood circulation [1]. The eye-tracking test was affectedin both directions, which may be explained by the patient’sadvanced age. Nonetheless, our results indicated thatneuro-otological tests are useful to differentiate centralvertigo, including acoustic tumors, and that MRI should beperformed if abnormalities are present in these test results.

Dunniway et al. [2] reported five cases (two cerebel-lopontine angle meningiomas, one acoustic tumor, onecerebellopontine angle lipoma, and one thalamic glioma)characterized by BPPV-like symptoms and verified themas intracranial tumors after performing various tests. Thestudy concluded that MRI imaging should be executed forcases that do not show improvement after performing thecanalith repositioning procedure twice. However, in thepresent case, although the canalith repositioning procedurewas performed thrice, the nystagmus and vertigo symptomsdid not improve. The success rate of the Epley maneuverfor the treatment of BPPV is approximately 85% [10].However, even for probable BPPV cases that are refractoryto appropriate treatment, neuro-otological tests and MRIshould be performed to rule out central lesions, includingacoustic tumors.

4. Conclusion

From the results of the caloric test, we suspected that thetumor in the present case was derived from the inferiorvestibular nerve, which communicates with the posteriorsemicircular canal and saccule. The tumor likely appliedpressure to this nerve, thereby causing the nystagmussymptom and the manifestation of right posterior canal-type BPPV. Despite the small tumor size, the eye-trackingand optokinetic nystagmus test results were abnormal,indicating that in addition to MRI, neuro-otological testsshould be performed to differentiate central causes ofvertigo, including acoustic tumors. In cases that demonstrateBPPV-like symptoms and nystagmus findings, MRI imagingshould be performed for further diagnosis if the symptomsdo not improve after the canalith repositioning procedure isperformed twice.

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