小脳障害例の視運動性眼振異常

抄録

Peculiarities of optokinetic nystagmus (OKN) in patients with cerebellar disturbances were studied by a method which examines the relationship between optokinetic nystagmus and target movement.
An Ohm-type rotating cylinder was rotated electrically with an angular acceleration of 2°/sec² for 90sec. OKN, induced by optokinetic stimulation, and signals. of stripes rotating in front of the subject were sampled at 100Hz for 90sec by a PDP-12 computer through an analog-to-digital converter. The stripe movements were calculated from stripe signals using Lagrange's square interpolation formula. The nystagmus waves and stripe movement were superimposed on a cathode ray tube.
The test was given to 7 patients with late cerebellar cortical atrophy (LCCA), 1 with Holmes type atrophy, 11 with olivo-ponto-cerebellar atrophy (OPCA), 1 with Menzel's atrophy, 6 with cerebellar hemisphere tumors and 8 with vermis tumors.
OKN of patients with LCCA showed a square wave jerk, saccadic pursuit and delay of eye movements in stripe pursuit and ocular dysmetria in target catching. OKN of patients diagnosed as having OPCA showed a deficit of smooth pursuit and delay of eye movements in stripe pursuit and delayed initiation and reduced saccadic velocity in target catching. When the stripe speed was increased, pursuit of stripe movement became virtually impossible, and the number of nystagmus beats decreased markedly. Patients with cerebellar hemisphere tumors showed no abnormality of OKN. Those with vermis tumors showed abnormalities similar to those in patients with LCCA or OPCA.
The difference between OKN abnormalities in LCCA and OPCA is presumably due to the fact that in LCCA degeneration of Purkinje cells in the cerebellar vermis is predominant, whereas in OPCA there is also degeneration of the pontine nuclei.