EYE-MOVEMENTS IN CHILDREN WITH OPSOCLONUS-POLYMYOCLONUS

The anatomical localisation of the abnormality underlying opsoclonus-p olymyoclonus - the ''Dancing Eye Syndrome'' - is uncertain and both th e brainstem and cerebellum have been implicated. We used electro-oculo graphic recordings to assess the eye movements in five children with t his syndrome. Overshoot dysmetria was the consistent feature for the s accades of all five cases. One patient was also assessed after the mai n symptoms of ataxia and opsoclonus (saccadic oscillations, without an intersaccadic interval) had resolved and the saccades were found to r emain hypermetric. Smooth pursuit and optokinetic nystagmus were norma l, although the opsoclonus occurred throughout the recording session a nd were superimposed upon the normal eye movement waveforms. The vesti bulo-ocular reflex was normal in four patients, but in one case, the t ime-constant was significantly prolonged: this has only been reported in experimental lesions of the nodulus in monkeys. The presence of sac cadic overshoot dysmetria is highly suggestive of a cerebellar origin for the abnormal eye movements in these children. However, the preserv ation of normal smooth pursuit and the absence of gaze-paretic, reboun d and downbeat nystagmus, implies the sparing of the flocculus and par aflocculus. We propose that the origin of these oculomotor deficits co uld be the cerebellar fastigial nuclei.