周期性方向交代性眼振の一症例

その臨床所見と薬物の効果

抄録

We analyzed periodic alternating nystagmus (PAN) in a 47-year-old male with spinocerebellar degeneration of three years duration. The neurological examination revealed normal mental status and higher cerebral functions, spontaneous and gaze nystagmus, neck tremor, scanning speech, ataxic gait, mild weakness of the proximal lower extremities, hypotonia, dysmetria and decomposition of limb movements, generalized hyperactive deep tendon reflexes and Babinski's sign.
Neuroophthalmological examination showed gaze nystagmus on both lateral and downward gaze, hypermetria of saccadic eye movements, disturbance of pursuit eye movements, poor optokinetic response and normal caloric response with absent visual suppression.
The effects of fixation, eye position and drugs on the period of oscillation and maximum slow phase velocity of nystagmus were evaluated. Eye movements were recorded by an oculotracker and DC-EOG. The slow phase velocity of PAN was calculated by a computer.
The period of oscillation and maximum slow phase velocity of nystagmus did not differ in forward gaze with and without visual fixation. Maximum velocity of nystagmus tended to increase as the eyes deviate laterally. However, on upward gaze, nystagmus was suppressed. Eye position did not affect the period of oscillation of PAN. Baclofen 30 mg/day did not stop PAN, but tended to decrease the maximum velocity of PAN without changing the period of oscillation. Chlordiazepoxide 30 mg/day or baclofen 15 mg/day had no effect on PAN.
We concluded that the PAN of this patient was probably related to lesions of the brain stem and cerebellum with sparing of the vestibuloocular reflex pathway and that PAN was influenced by eye position. The hypothetical model of PAN proposed by Leigh et al. resembled the findings in this case.