[Familial olivo-ponto-cerebellar atrophy with myoclonus. Limits of cerebellar myoclonic dyssynergia (Ramsay-Hunt syndrome)].

The case is described of a woman of 26 suffering (like her mother, a brother and a sister) from a progressively degenerating cerebellar syndrome, at first considered to be hereditary cerebellar ataxia, but which, after action myoclonus appeared, was diagnosed as dyssynergia cerebellaris myoclonica (D.C.M.). Anatomical verification however revealed a syndrome of olivo-ponto-cerebellar atrophy comprising massive demyelinisation of the white matter of the cerebellum and of the cerebellopontine fibres; atrophy of the pontine nuclei; the cerebellar cortex itself was severely affected; moderate nigral lesions; marked spinal lesions of the cerebellospinal fasciculi and of the posterior columns; lesions of the anterior horns and of the bulbar nuclei; cortical chromatolysis. The fact that the dentate system remained unaffected, also noted in some cases of olivo-ponto-cerebellar atrophy with myoclonus, whilst in a number of other cases the lesion remains clinically silent, emphasises the difficulty in establishing an accurate correlation between myoclonus and dentate nucleus. Discussion of the nosological limits of D.C.M.: confirmed cases generally displayed lesions of the dentate system and hereditary degenerative spino-cerebellar lesions. The same clinical symptoms can be observed in cases which do not come under this classification--or even under that of degenerative conditions of the cerebellar system--and D.C.M. appears to be only a syndrome, the Ramsay-Hunt syndrome.