Pyramidal tract degeneration in sporadic Creutzfeldt-Jakob disease.

We investigated the neuropathologic features of pyramidal tract degeneration in 27 cases of sporadic Creutzfeldt-Jakob disease (sCJD). The present study included 13 cases of subacute spongiform encephalopathy (SSE), 13 cases of panencephalopathic-type (PE-type) sCJD and one case of thalamic-type sCJD. Pyramidal tract degeneration was observed in PE-type sCJD cases with disease duration of more than 13 months. Cases of SSE, PE-type sCJD of relatively short duration and thalamic-type sCJD showed no pyramidal tract degeneration. All cases with pyramidal tract degeneration showed severe cerebral neocortical involvement with widespread cerebral white matter degeneration. The loss of myelin and axons and macrophage infiltration and fibrillary gliosis seen in these pyramidal tract lesions is consistent with secondary tract degeneration due to cerebral neocortical involvement. Interestingly, some cases with pyramidal tract degeneration showed a distal-dominant pathology that we believe indicates retrograde degeneration or a "dying-back" phenomenon of the pyramidal tract. Our results indicate that pyramidal tract degeneration is a late pathologic event in sCJD. Investigation of pyramidal tract degeneration may help clarify the mechanisms underlying the development of sCJD white matter pathology, particularly that of PE-type sCJD.