A case of primary lateral sclerosis taking a prolonged clinical course with dementia and having an unusual dendritic ballooning.

Motor neuron disease associated with dementia has provided unique opportunities for studying the pathomechanisms of both disorders. In most instances, the former is amyotrophic lateral sclerosis (ALS). In this paper, we report a case of primary lateral sclerosis (PLS) with dementia. An adult female developed slowly progressive spastic paraparesis and dementia over a period of 17 years and died at the age of 55. Autopsy disclosed neuronal loss of the motor cortex and prominent degeneration of the pyramidal tract. Cranial and spinal motor neurons were well preserved. Neither Bunina bodies nor ubiquitin-positive inclusions were detected. The findings were compatible with PLS. Diffuse cerebral atrophy, and marked atrophy of the striatum and the thalamus was observed. Senile plaques and Alzheimer's neurofibrillary tangles were absent, but an unusual clear ballooning of dendrites was observed in the molecular and Purkinje cell layers of the cerebellum, and the anterior horn of the spinal cord. Together with reports of two similar cases, it is suggested that this case should be categorized as a rare disease entity of PLS with dementia.