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To investigate the frequency and pattern of failure of the fixation suppression (FFS) of spontaneous nystagmus (SN) in unilateral cerebellar infarction, and to identify the structure responsible for FFS, 29 patients with acute, mainly unilateral, isolated cerebellar infarction who had SN with a predominantly horizontal component were enrolled in this study. The ocular fixation index (OFI) was defined as the mean slow phase velocity (SPV) of the horizontal component of SN with fixation divided by the mean SPV of the horizontal component of SN without fixation. The OFI from age- and sex-matched patients with vestibular neuritis was calculated and used as the control data. The FFS of SN was only found in less than half (41 %, 12/29) of the patients. Approximately 65 % (n = 7) of the patients with isolated anterior inferior cerebellar artery territory cerebellar infarction showed FFS, whereas only a quarter (n = 3) of the patients with isolated posterior inferior cerebellar artery (PICA) territory cerebellar infarction showed FFS. The proportion of gaze-evoked nystagmus (6/12 [50 %] vs. 2/17 [12 %], p = 0.04) and deficient gain of ipsilesional pursuit (10/12 [83 %] vs. 6/17 [35 %], p = 0.05) was more frequent in the FFS group than in the group without FFS. Lesion subtraction analysis in isolated PICA territory cerebellar infarction revealed that the nodulus was commonly damaged in patients with FFS, compared to that of patients without FFS. Our study shows that FFS of SN due to acute cerebellar infarction is less common than previously thought and the nodulus may be an important structure for the suppression of SN in humans.

Abstract: Background: Acute ischemic stroke in the distribution of the anterior inferior cerebellar artery (AICA) can cause the vestibular dysfunction in the roll plane of the vestibuloocular reflex with abnormal ocular torsion (OT). There has been no systemic study that carefully investigates the nature of OT that occurs with AICA infarction. Objectives: To investigate the frequency, the characteristic patterns of OT associated with AICA territory infarction, and the crucial site for determining the direction of OT in AICA territory infarction. Methods: We studied 12 consecutive cases of infarction in the territory of the AICA diagnosed by brain MRI. Fundus photography, prism cover test, and subjective visual vertical tilting test were performed to evaluate the function of the otolith system. Pure tone audiogram was also performed to evaluate the function of the auditory system. Results: Nine (75%) of 12 patients exhibited pathological ocular torsion (OT). Two types of pathological OT were found: ipsiversive OT accompanying skew deviation (n =6), and contraversive OT only (n =3). Six patients with ipsiversive OT with skew deviation showed an audiovestibular loss with canal paresis and hearing loss ipsilaterally whereas three patients with contraversive OT without skew deviation had a normal audiovestibular response. In all cases with pathological OT, the direction of the subjective visual vertical tilt corresponded to the direction of the OT. Conclusions: Our findings emphasize that the peripheral vestibular structure with inner ear probably plays a crucial role in determining the direction of OT associated with AICA territory infarction. [Copyright &y& Elsevier]

Sudden deafness without associated neurological signs and symptoms is typically attributed to a viral inflammation of the labyrinth. Sudden deafness as a heralding manifestation of basilar occlusion has rarely been described. A 60-year-old male with hypertension presented with an acute onset of isolated sudden deafness with vertigo. On admission, initial brain MRI, including diffusion-weighted images, was normal. Two days after the onset of symptoms, the patient presented with an exacerbation of vertigo. A follow-up MRI scan revealed new infarcts involving the right middle cerebellar peduncle, right dorsolateral pons and right anterior cerebellum. In this patient, the acute onset of isolated sudden deafness with vertigo may have been a heralding manifestation of the pontocerebellar infarction. [ABSTRACT FROM AUTHOR]

Abstract: Background: There has been no systematic study that carefully investigates the characteristic features of abnormal cervical vestibular-evoked myogenic potential (cVEMP) response associated with the AICA territory infarction. Objectives: To investigate the frequency, the characteristic patterns of abnormal cVEMP associated with AICA territory infarction, and the crucial site for producing abnormal cVEMP response in the AICA territory infarction. Methods: We studied 16 consecutive cases of unilateral AICA territory infarction diagnosed by brain MRI. VEMP was induced by a short click sound and was recorded in contracting sternocleidomastoid muscle. Each patient underwent a quantitative audiovestibular evaluation, including bithermal caloric test and pure tone audiogram. Results: Eight patients (50%) exhibited abnormal cVEMP response on the side of the AICA territory infarction. All patients with abnormal cVEMP showed an absent or decreased response in amplitude but no difference in latency. Patients with abnormal VEMP were significantly more likely to have canal paresis (CP), sensorineural hearing loss, or both compared with patients who had normal cVEMP. Conversely, abnormal cVEMP was more frequently observed among patients with CP than among those without CP. There was no difference in lesion sites according to brain MRI among patients with or without abnormal cVEMP response. Conclusions: Our findings suggest that the peripheral vestibular structure with the inner ear probably plays a crucial role in producing abnormal cVEMP response associated with AICA territory infarction. [Copyright &y& Elsevier]

Abstract: Objectives: To document otolith dysfunction in patients with posterior inferior cerebellar artery (PICA) territory cerebellar infarction. Methods: From March to October 2006, 14 consecutive patients with PICA territory cerebellar infarctions (brainstem spared) diagnosed by brain MRI from the acute stroke registry at the Keimyung University Dongsan Medical Center were enrolled within 12 days of onset (mean 4.0 days). Otolith function tests included ocular torsion (OT), skew deviation, and subjective visual vertical (SVV) were performed. The extent of the cerebellar infarction was determined by previously validated MR anatomical templates. Results: All patients had an abnormal posture as a result of otolithic dysfunction. Eleven patients (79%) had at least one otolith-related test abnormality: abnormal tilt of SVV (79%), abnormal OT (29%), or skew deviation (21%). Two common patterns of otolith dysfunction were identified based on whether or not the nodulus was infarcted: 1) ipsilesional SVV tilt (mean 5.0° at binocular viewing) without accompanying abnormal OT or skew deviation (nodulus spared); 2) contralesional SVV tilt (mean 11.3° at binocular viewing) with concomitant abnormal OT and skew deviation (nodulus infarcted). Patients with type 1 infarcts (i.e., nodulus spared) fell toward the side of lesion while patients with type 2 infarcts (i.e., nodulus infracted) fell toward the opposite side. Conclusion: Isolated PICA territory cerebellar infarction usually produces two distinct patterns of otolith dysfunction — Ipsilesional SVV tilt and falling without accompanying OT or skew deviation if the nodulus is spared and contralesional SVV tilt and falling with OT and skew deviation if nodulus is infarcted. [Copyright &y& Elsevier]