Quantitative eye movement recordings in a patient with spinocerebellar degeneration who had macrosquare wave jerks and macrosaccadic oscillations showed the mechanism of macrosaccadic oscillations. Macrosquare wave jerks show square waves, but macrosaccadic oscillations show spindlelike waves on recording papers. Both saccadic eye movements had intersaccadic intervals. The relationships of amplitude-maximum velocity of saccades, macrosquare jerks and macrosaccadic oscillations were normal. Macrosaccadic oscillations on fixation and saccadic pursuit were the same in intersaccadic intervals and errors-amplitude of corrective saccade relationships. Observation of the intersaccadic intervals of macrosaccadic oscillations showed that the saccade following the first interval was a corrective saccade.
Since the corrective saccade is hypermetric, however, the eyes oscillate. Finally the eyes catch the target by visual inputs. Neuro-otological examinations showed that this patient had disturbances of the cerebellar vermis, which controls saccadic eye movement. Thus, it was shown that macrosaccadic oscillations are caused by disturbances of the cerebellar vermis.
