This study applied both ocular vestibular-evoked myogenic potential (oVEMP) and cervical VEMP (cVEMP) tests in patients with cerebellar disorders to determine whether VEMP test can differentiate between cerebellar and brainstem lesions. A total of 12 patients with cerebellar disorder, including extended cerebellar lesion (involving the brainstem) in 8 and localized cerebellar lesion (excluding the brainstem) in 4, were enrolled in this study. All patients underwent caloric, visual suppression, and oVEMP and cVEMP tests via bone-conducted vibration stimuli. The abnormal rates for the caloric, visual suppression, and oVEMP and cVEMP tests were 62, 83, 88 and 75% in patients with extended cerebellar lesion and 0, 25, 0 and 0% in those with localized cerebellar lesion, respectively. The rate of abnormal oVEMP results significantly differed between the two groups, but caloric, visual suppression and cVEMP test results did not differ. In another ten healthy subjects, characteristic parameters of oVEMPs obtained under light and dark conditions did not significantly differ. In conclusion, ocular VEMP test can differentiate between cerebellar and brainstem lesions. Abnormal oVEMPs in patients with cerebellar disorder may indicate adjacent brainstem involvement.

When a vertiginous patient displayed ataxia, persistent vomiting, and persistent nystagmus, lesion affecting the fourth ventricle should be kept in mind because its prognosis is poor. Abnormal results in electronystagmography and in ocular and cervical vestibular-evoked myogenic potentials may serve as a supplementary to magnetic resonance imaging to delineate the involvement of the lesion.

Of the 70 patients, 22 (31%) demonstrated pathological eye movements including persistent (>24 h) unilateral gaze nystagmus in 12 patients, and multi-directional gaze nystagmus in 10 patients. Conjugate eyes movements were identified in 18 patients, and disconjugate eye movements were shown in 4 patients including medial longitudinal fasciculus syndrome in 1, paramedian pontine reticular formation syndrome in 1, and one and a half syndrome in 2. The vestibular test battery revealed abnormal responses for >85% of the patients in each test. MRI demonstrated infarction or hemorrhage involving the brainstem in 12 patients, cerebellum in 8 patients, and both in 2 patients.