Case Report Gravity-dependent Nystagmus and Inner-Ear Dysfunction Suggest Anterior and Posterior Inferior Cerebellar Artery Infarct Aasef G. Shaikh, MD, PhD, Benjamin R. Miller, MD, Sophia Sundararajan, MD, PhD, and Bashar Katirji, MD Cerebellar lesions may present with gravity-dependent nystagmus, where the direction and velocity of the drifts change with alterations in head position. Two patients had acute onset of hearing loss, vertigo, oscillopsia, nausea, and vomiting. Examination revealed gravity-dependent nystagmus, unilateral hypoactive vestibulo-ocular reflex (VOR), and hearing loss ipsilateral to the VOR hypofunction. Traditionally, the hypoactive VOR and hearing loss suggest inner-ear dysfunction. Vertigo, nausea, vomiting, and nystagmus may suggest peripheral or central vestibulopathy. The gravity-dependent modulation of nystagmus, however, localizes to the posterior cerebellar vermis. Magnetic resonance imaging in our patients revealed acute cerebellar infarct affecting posterior cerebellar vermis, in the vascular distribution of the posterior inferior cerebellar artery (PICA). This lesion explains the gravitydependent nystagmus, nausea, and vomiting. Acute onset of unilateral hearing loss and VOR hypofunction could be the manifestation of inner-ear ischemic injury secondary to the anterior inferior cerebellar artery (AICA) compromise. In cases of combined AICA and PICA infarction, the symptoms of peripheral vestibulopathy might masquerade the central vestibular syndrome and harbor a cerebellar stroke. However, the gravity-dependent nystagmus allows prompt identification of acute cerebellar infarct. Key Words: Stroke—posterior circulation—posterior fossa— dizziness—vertigo—embolic stroke. Ó 2014 by National Stroke Association Introduction Acute inner-ear dysfunction and cerebellar stroke in the vascular distribution of posterior inferior cerebellar artery (PICA) can have identical clinical presentation—the vestibular syndrome—featuring vertigo, nausea, vomiting, From the Department of Neurology, Case Western Reserve University, Cleveland, Ohio. Received March 23, 2013; revision received May 10, 2013; accepted May 13, 2013. Grant support: None. Address correspondence to Aasef G. Shaikh, MD, PhD, Department of Neurology, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106-5040. E-mail: aasefshaikh@gmail.com. 1052-3057/$ - see front matter Ó 2014 by National Stroke Association http://dx.doi.org/10.1016/j.jstrokecerebrovasdis.2013.05.020 788 and nystagmus.1-5 Reactivity of the vestibulo-ocular reflex (VOR) is often used to differentiate peripheral from central vestibulopathy. VOR can be normal in central vestibular syndrome, but it is hypoactive in acute inner-ear or vestibulo-cochlear nerve dysfunction due to neuritis, labyrinthitis, or in rare occasions anterior inferior cerebellar artery (AICA) infarct.6,7 Neuritis affecting the superior division of the vestibular nerve typically spares hearing, but deafness is reported when neuritis affects the inferior division of the vestibular nerve or in cases of cochlear–labyrinthine infarct due to AICA compromise.6,8 Combined AICA and PICA infarct could prominently manifest as peripheral vestibulopathy and potentially masquerade cerebellar ischemia. In two such patients, presence of gravity-dependent nystagmus unmasked cerebellar infarct. Journal of Stroke and Cerebrovascular Diseases, Vol. 23, No. 4 (April), 2014: pp 788-790 ‘‘THE DOUBLE HIT’’—AICA AND PICA INFARCT Cases 789 Discussion Two patients had acute onset of hearing loss, oscillopsia, vertigo, nausea, and vomiting. The oscillopsia was present during locomotion. Supine (patient 1) or left-ear down (patient 2) provoked gravity-dependent nystagmus. Both patients had unilateral VOR hypofunction and hearing loss on the same side. Table 1 summarizes the clinical presentation and treatment outcome. This constellation of symptoms suggested combined central and peripheral vestibular syndrome. Unilateral hearing loss and hypoactive VOR favored peripheral vestibulopathy; however, the gravity-dependent nystagmus identified the central etiology. In both patients, the magnetic resonance imaging revealed ischemia affecting posterior cerebellar vermis (Fig 1). Simultaneous ischemia in the vascular distribution of AICA and PICA could lead to the combination of central and peripheral vestibulopathy. These cases can be a conundrum because the peripheral vestibulopathy could masquerade its central counterpart. In such instances, gravity-dependent nystagmus can clinically identify the central vestibulopathy. The gravity-dependent nystagmus was described in degenerative cerebellar disease, but it was reported only once in a patient with an acute cerebellar stroke.5,9-11 We propose that gravitydependent nystagmus is due to the combination of impaired central representation of the gravity and disinhibition of the deep cerebellar and vestibular nuclei.12-14 Table 1. Summary of clinical features in 2 patients with combined AICA and PICA distribution infarct Age/gender Oscillopsia Characteristics of nystagmus VOR Hearing Remaining neurological examination Time frame: symptom onset to examination ABCD-2 scores MRI findings Time frame: symptom onset to MRI Subsequent course of hospitalization Patient 1 Patient 2 52 year-old man During locomotion Sustained right-beating nystagmus in straight-ahead gaze. Worsening of right-beat nystagmus on rightward eccentric gaze. No nystagmus on leftward gaze Downward and rightward beating nystagmus on upward gaze. No change in characteristics of nystagmus during supine or right-ear-down position. Nystagmus disappeared in left-ear-down position. No change in examination on removal of visual fixation with Frenzel goggles. Hypoactive VOR on leftward head impulses Hearing loss on the left side Normal 74 year-old man During locomotion Rightward and upward beating nystagmus in left-ear-down position. Stable gaze holding in upright and supine positions. Hypoactive VOR on rightward head impulses Hearing loss on the right side Normal 6h 12 h 2 Diffusion restriction with apparent diffusion coefficient correlate in the left cerebellar lobules IX and VIII. 10 h 4 Diffusion restriction with apparent diffusion coefficient correlate in the left cerebellar lobules IX, VIII, and VII 36 h Bilaterally symmetric gaze-evoked nystagmus, but there was no gravity-dependent nystagmus on day-3. Hypoactive VOR and hearing loss persisted. Patient was discharged home with outpatient physical therapy, eye-head vestibular exercises, and warfarin therapy. The nystagmus resolved in 1 day. Hypoactive VOR and hearing loss persisted. Patient was discharge to short-term nursing facility with physical therapy, eye-head vestibular exercises, and antiplatelet therapy with aspirin 81 mg by mouth daily. Abbreviations: ABCD-2 score, age blood pressure, diabetes, and duration score; AICA, anterior inferior cerebellar artery; MRI, magnetic resonance imaging; PICA, posterior inferior cerebellar artery; VOR, vestibulo-ocular reflex. 790 A.G. SHAIKH ET AL. Figure 1. Diffusion-weighted magnetic resonance image showing acute cerebellar infarct affecting posterior cerebellar vermis (lobule VIII, IX in case 1 and 2, and also VII in case 2). Common and putatively peripheral vestibular disorder, benign paroxysmal positional vertigo (BPPV), also features gravity-dependent modulation of nystagmus. Head position dependent change in nystagmus characterizing BPPV, however, follows a specific trend. Posterior semicircular canal BPPV presents with upbeat and torsional nystagmus when the plane of affected posterior canal is aligned parallel to the pull of gravity, but there is reversal of nystagmus (unwinding) on sittingup phase of Dix–Hallpike maneuver.15 Anterior semicircular canal BPPV features downbeat nystagmus during supine position, and it becomes prominent when the head is oriented such that the affected ear faces away from the ground. Lateral semicircular canal BPPV manifests in horizontal nystagmus directed either toward the ground (geotropic) or away from the ground (apogeotropic). In cases with geotropic nystagmus, the affected ear is to the side with stronger nystagmus but vice versa for apogeotropic nystagmus. In BPPV, there is time latency between change in head position and emergence of nystagmus. Furthermore, the nystagmus related to BPPV habituates within several seconds.15 Our patients with central gravity–dependent nystagmus did not follow a specific trend as noted in BPPV. The nystagmus was instanenously modulated by the change in head position, and it did not habituate. To summarize, we identified patients with combined AICA and PICA infarcts with mixed acute peripheral and central vestibulopathy. Peripheral vestibulopathy had a potential to masquerade the cerebellar stroke, but gravity-dependent nystagmus precisely clinched the diagnosis. References 1. Duncan GW, Parker SW, Fisher CM. Acute cerebellar infarction in the PICA territory. Arch Neurol 1975;32: 364-368. 2. Rubenstein RL, Norman DM, Schindler RA, et al. Cerebellar infarction—a presentation of vertigo. Laryngoscope 1980;90:505-514. 3. Amarenco P, Hauw JJ. Cerebellar infarction in the territory of the anterior and inferior cerebellar artery. A clinicopathological study of 20 cases. Brain 1990; 113(Pt 1):139-155. 4. Lee H, Sohn SI, Cho YW, et al. Cerebellar infarction presenting isolated vertigo: frequency and vascular topographical patterns. Neurology 2006;67:1178-1183. 5. Kim HA, Yi HA, Lee H. Apogeotropic central positional nystagmus as a sole sign of nodular infarction. Neurol Sci 2012;33:1189-1191. 6. Aw ST, Fetter M, Cremer PD, et al. Individual semicircular canal function in superior and inferior vestibular neuritis. Neurology 2001;57:768-774. 7. Newman-Toker DE, Kattah JC, et al. Normal head impulse test differentiates acute cerebellar strokes from vestibular neuritis. Neurology 2008;70:2378-2385. 8. Lee H, Sohn SI, Jung DK, et al. Sudden deafness and anterior inferior cerebellar artery infarction. Stroke 2002; 33:2807-2812. 9. Marti S, Palla A, Straumann D. Gravity dependence of ocular drift in patients with cerebellar downbeat nystagmus. Ann Neurol 2002;52:712-721. 10. Shaikh AG, Marti S, Tarnutzer AA, et al. Ataxia telangiectasia: a ‘‘disease model’’ to understand the cerebellar control of vestibular reflexes. J Neurophysiol 2011;105: 3034-3041. 11. Kattah JC, Gujrati M. Familial positional downbeat nystagmus and cerebellar ataxia: clinical and pathologic findings. Ann N Y Acad Sci 2005;1039:540-543. 12. Angelaki DE, Hess BJ. Lesion of the nodulus and ventral uvula abolish steady-state off-vertical axis otolith response. J Neurophysiol 1995;73:1716-1720. 13. Sheliga BM, Yakushin SB, Silvers A, et al. Control of spatial orientation of the angular vestibulo-ocular reflex by the nodulus and uvula of the vestibulocerebellum. Ann N Y Acad Sci 1999;871:94-122. 14. Wearne S, Raphan T, Cohen B. Effects of tilt of the gravitoinertial acceleration vector on the angular vestibuloocular reflex during centrifugation. J Neurophysiol 1999; 81:2175-2190. 15. Leigh RJ, Zee DS. The neurology of eye movements. New York, New York: Oxford Publishers, 2006.