We describe an autopsy case of MM1-type sporadic Creutzfeldt-Jakob disease (CJD), the duration of which was 93 days. The patient was a 59-year-old Japanese man with no family history of prion disease or known iatrogenic exposure to CJD. His first symptom was dysesthesia in the left arm, suggestive of cervical cord involvement, and he showed rapidly progressive neurologic signs, such as dysarthria, dysphagia, lethargy, sleep apnea and respiratory failure, suggestive of brainstem involvement. Progressive mental deterioration combined with episodes of myoclonic seizure and periodic synchronous discharges on the electroencephalogram were observed in the later disease stage. Autopsy showed typical spongiform change to be wide-spread in the cerebral and cerebellar cortices, thalamus and basal ganglia. Synaptic-type PrP deposition was marked in the cerebral cortex, thalamus and basal ganglia. In the cerebellum, although the granular, molecular and Purkinje cell layers were well preserved from neuronal loss and gliosis, PrP deposition was marked in the molecular and granular cell layers. Spongiform degeneration and neuronal loss were not seen in the brainstem and spinal cord, but relatively marked PrP deposition was observed in the quadrigeminal body, substantia nigra, pontine nucleus, inferior olivary nucleus and posterior horn. Immunohistochemical staining for HLA-DR showed proliferation of activated microglia in the cerebral and cerebellar cortices, pontine nucleus, inferior olivary nucleus and posterior horn. The mechanisms underlying the neurologic symptoms and signs were unclear, but we speculate that, in addition to widespread involvement of the cerebral cortex, PrP deposition and microglial activation in the brainstem and spinal cord were responsible.