□ CASE REPORT □ Unilateral Hearing Disturbance could be an Isolated Manifestation Prior to Ipsilateral Anterior Inferior Cerebellar Artery Infarction Hisashi Ito 1, Makoto Hibino 1,2, Mitsuharu Iino 1, Kosyo Matsuura 2 and Tetsumasa Kamei 1 Abstract A 50-year-old man presented with a sudden onset of right-sided hearing disturbance. His hearing disturbance improved gradually, however, dysarthria, right-sided facial weakness and dysesthesia, and gait disturbance was developed 11 days after the onset of hearing disturbance. MR imaging revealed fresh infarctions of the right dorsolateral pons and middle cerebellar peduncle localized in the territory of anterior inferior cerebellar artery. Unilateral hearing disturbance could be an isolated manifestation prior to ipsilateral anterior inferior cerebellar artery infarction. Key words: hearing disturbance, preceding manifestation, anterior inferior cerebellar artery, infarction (Inter Med 47: 795-796, 2008) (DOI: 10.2169/internalmedicine.47.0739) Introduction Infarction in the distribution of the anterior inferior cerebellar artery (AICA) is known to be associated with hearing disturbance, vertigo, cerebellar ataxia, facial weakness, and hypalgesia. Characteristically, sudden hearing disturbance due to AICA infarction is associated with multiple brainstem or cerebellar symptoms (1). Here, we describe a patient of AICA infarction with preceding transient hearing disturbance. right-sided peripheral facial nerve palsy, right-sided trigeminal nerve palsy, right-sided limb ataxia and gait ataxia, however, hearing disturbance was not observed. The Weber test was not lateralized. T2-weighted MR imaging of the brain demonstrated high-intensities involving the right dorsolateral pons and middle cerebellar peduncle (Fig. 1). Right AICA was shown in MR angiography and neither stenosis nor dis- Case Report A 50-year-old man with untreated hypertension and hyperlipidemia suddenly developed right-sided hearing disturbance. Other symptoms such as tinnitus and vertigo were not observed. Although hearing disturbance disappeared gradually in a week without any treatment, dysarthria, rightsided facial weakness and dysesthesia, and gait disturbance developed 11 days after the onset of hearing disturbance. The patient admitted to Naze Tokushukai Hospital. On admission, the patient presented ataxic dysarthria, 1 Fi g ur e1 . Br a i nMRi ma g i ng( T2 we i g ht e di ma g e ) :Hi g hi nt e ns i t yl e s i o nswe r ei nt her i g htdo r s o l a t e r a lpo nsa ndmi ddl e c e r e be l l a rpe dunc l e( a r r o w) . Department of Neurology, Chigasaki Tokushukai Medical Center, Chigasaki and 2Department of Internal Medicine, Naze Tokushukai Hospital, Amami Received for publication November 14, 2007; Accepted for publication January 9, 2008 Correspondence to Dr. Hisashi Ito, hisashi.ito@tokushukai.jp 795 Inter Med 47: 795-796, 2008 DOI: 10.2169/internalmedicine.47.0739 Fi g ur e2 . Thec l i ni c a lc o ur s e . section was observed. Ultrasonography showed mild intimal thickening in the right common carotid artery. On brainstem auditory evoked potentials (ABR), the right sided latency of wave I and the interwave latencies between III and V were mildly delayed. Regarding blink reflex, there were no rightsided R1 and R2 components evoked on right stimulation and no right-sided R2 component on left stimulation. Antithrombin agent followed with anti-platelet agent was administered. During the course, diplopia due to right-sided abducent nerve palsy developed transiently; however, the clinical symptoms were improved (Fig. 2). Discussion AICA supplies the anterior inferior cerebellum, middle cerebellar peduncle, dorsolateral pons, inner ear, and vestibulocochlear nerve (2). Accordingly, AICA infarction presented ipsilateral cerebellar ataxia, peripheral facial nerve palsy, facial sensory disturbance, Horner sign, hearing disturbance, and vertigo. Among these symptoms, the combination of hearing disturbance and cerebellar ataxia or hearing disturbance and vertigo were considered important for the diagnosis of AICA infarction (1, 3) and the reported incidence of hearing loss ranged from 30% (4) to 100% (5). Recently, preceding symptoms of AICA infarction have been noted. Sudden deafness and vertigo could precede other neurological symptoms in AICA infarction (4, 6). The characteristic of this patient was that hearing disturbance developed suddenly and improved spontaneously before the onset of ipsilateral AICA infarction. The result of ABR indicated the existence of subclinical disturbance in the cochlear nerve. Therefore, the preceding hearing disturbance could have resulted from transient ischemia of the internal auditory artery, which had originated from the AICA. As the preceding ischemia was limited to the cochlear nerve, vertigo might be absent. AICA was identified on MR angiography, however, vascular risk factors and the stepwise development of a stroke with a prodromal episode indicated that the pathomechanism of this patient was atherothrombosis. In general, transient unilateral hearing disturbance with or without vertigo has been considered to indicate a benign inner ear lesion involving an obstacle of semicircular canals. However, brain MR imaging and ABR should be considered to exclude an ischemic lesion of the brainstem when hearing disturbance occurs in a patient with vascular risk factors, even when brainstem or cerebellar signs are absent. Acknowledgement The authors are grateful to Sonomi Katsuyama and Masafumi Miyata for electrophysiological examinations. References 1. Lee H, Sohn SI, Jung DK, et al. Sudden deafness and anterior inferior cerebellar artery infarction. Stroke 33: 2807-2812, 2002. 2. Oas JG, Baloh RW. Vertigo and the anterior inferior cerebellar artery syndrome. Neurology 42: 2274-2279, 1992. 3. Takamatsu K, Ohta T. A study of infarction in the resion of the anterior inferior cerebellar artery. Rinsho Shinkeigaku (Clin Neurol) 35: 621-625, 1995 (in Japanese, Abstract in English). 4. Amarenco P, Hauw JJ. Cerebellar infarction in the territory of the anterior and inferior cerebellar artery. A clinicopathological study of 20 cases. Brain 113: 139-155, 1990. 5. Matsushita K, Naritomi H, Kazui S, et al. Infarction in the anterior inferior cerebellar artery territory: magnetic resonance imaging and auditory brain stem responses. Cerebrovasc Dis 3: 206212, 1993. 6. Lee H, Ahn BH, Baloh RW. Sudden deafness with vertigo as a sole manifestation of anterior inferior cerebellar artery infarction. J Neurol Sci 222: 105-107, 2004. Ⓒ 2008 The Japanese Society of Internal Medicine http://www.naika.or.jp/imindex.html 796