Clinical Characteristics of Spontaneous Downbeat Nystagmus in Koreans: Analysis of 218 Cases

ABSTRACT

BACKGROUND: Downbeat nystagmus is the most-common type of central nystagmus. However, no published study has attempted to analyze the etiology and clinical features of downbeat nystagmus in a large sample of Korean patients. METHODS: We analyzed the demographic and clinical features of spontaneous downbeat nystagmus in 218 Korean patients who had been evaluated at the Dizziness Clinic of Seoul National University Bundang Hospital from 2003 to 2014. RESULTS: All patients were aged from 15 to 92 years (mean+/-SD 58.7+/-18.0 years), and they included 117 (53.7%) men. Underlying causes were found in 162 patients (74.3%, secondary group), while no etiology was identified in the remaining patients (idiopathic group). The age and sex distributions did not differ between the idiopathic and secondary groups. The underlying etiology included hereditary disorders (n=48, 22.0%), vascular diseases (n=46, 21.1%), and inflammatory diseases (n=19, 8.7%). Infarctions (n=34, 15.6%) and episodic ataxia (n=32, 14.7%) were the most-frequent underlying disorders. The most-common site of lesions identified by MRI was the cerebellum (68.9%), followed by the brainstem (28.6%). Among the 74 patients with lesions confirmed by MRI, 25 (33.7%) showed an isolated cerebellar involvement, while 35 (47.6%) had lesions in multiple areas. CONCLUSIONS: This study extends the clinical features of spontaneous downbeat nystagmus to Korean patients. Cerebellum is the most-common lesion site, which is consistent with the results of previous studies. The prevalence of Arnold-Chiari malformation is relatively low, which may be a distinct finding relative to those of previous studies involving other ethnic populations.