An autopsy case of atypical infantile motor neuron disease with hyaline intraneuronal inclusions.

We describe a 5-year-old boy who had had a progressive motor weakness with bulbar palsy and spasticity of the lower extremities since age 3 years and who died of bronchopneumonia after about two and a half years of the illness. Neuropathologic examination revealed combined degenerative processes in the upper and lower motor neurons, the spinocerebellar and olivocerebellar systems, and the ventral thalamic nuclei. Lewy body-like intraneuronal hyaline inclusions, which ultrastructurally showed irregular accumulations of trilaminar membranous profiles, were detected in the spinal anterior horn, Clarke's dorsal nucleus, facial nerve nucleus, inferior olivary nucleus, and substantia nigra. This case could be considered as a unique form in the group of the infantile motor neuron diseases associated with multi-systemic degenerations in the central nervous system.