[Eye movement disturbance in multiple system atrophy: chronological study of 50 patients]

To clarify the features of the eye movement disturbance in the patients with multiple system atrophy (MSA), we retrospectively examined chronological changes of 9 oculomotor parameters as described below in 50 MSA patients including 12 autopsied cases. Patients with MSA were consisted of 35 patients with cerebellar ataxia-preceding type and 15 patients with parkinsonism-preceding type. Nine parameters include saccade test, eye tracking test, positioning/positional/gaze/caloric nystagmus tests, and visual suppression test. Each parameter was evaluated by three categories; normal and the two abnormal findings according to their characteristic features. In all of the 9 parameters, no significant differences were found between the cerebellar ataxia- and the parkinsonism-preceding types of MSA both in the early (disease duration less than 3 years) and in the advanced stages (duration between 8 to 11 years). From the chronological analysis, 9 oculomotor parameters could be divided into three groups: the first group with the higher frequency of the abnormality from the early stage, the second with gradual increase of the frequency, and the third with less increased frequency even in the advanced stage. We here focused on the three representatives corresponding with the above-described each group; positioning nystagmus test mainly showing downbeat nystagmus as a first group, visual suppression test showing a qualitative change from depressed into increased response as the second, and the caloric nystagmus test showing decreased response as the third. Based on these chronological changes of the oculomotor parameters, we supposed that in MSA the dorsal vermis is involved at first, followed by the flocculus in the cerebellum, and then the degenerative lesions might expand to the vestibular nucleus, and the cerebral cortex including the vestibular cortex.