Abstract
Convergence nystagmus, which is a main finding in Sylvian aqueduct syndrome is not common. We examined two patients of convergence nystagmus associated with infarction of the thalamus. The patients, aged 21 and 64-years, visited our clinic because of sudden dizziness. There was no cochlear sign in either case. Neurotological examinations, including electronystagmography (ENG), were carried out. Both patients had up-beat nystagmus, convergence nystagmus and abnormal vertical eye movements; however, no upward gaze palsy was observed. One patient showed a normal response to caloric testing, but the other showed rt-canal paresis (41%). On computerized tomography (CT scan), no lesion could be identified in the midbrain or thalamus of either patient. However, in one patient, T2-weighted MRI revealed a high signal region and Ti-weighted MRI demonstrated a low signal region in the lt-medial part of the thalamus. In the second patient, T2-weighted MRI revealed multiple bilateral lacunar high signal lesions in the thalamus, the putamen and in the region of the deep white matter. The etiology of abnormal vertical eye movements and convergence nystagmus is discussed with emphasis on the neurotological examinations and MRI.
Convergence nystagmus may be associated with lesions of the posterior commisure and nucleus in the medial part of the thalamus, and abnormal vertical eye movements may be attributed to a lesion in the tract from ri-MLF to the posterior commisure.
