Motor evoked potential studies in Creutzfeldt-Jakob disease.

OBJECTIVES: Motor evoked potentials (MEPs) were recorded in 7 cases of Creutzfeldt-Jakob disease (CJD) to asses the involvement of pyramidal motor pathways in these cases. The diagnosis of CJD was confirmed by autopsy in 5 cases and based on clinical data in two cases. METHODS: Transcranial (MEP-cortex), root magnetic (MEP-root) and electrical stimulation of peripheral nerves (F-wave, direct M-response) were performed. The cortical excitability threshold, F-wave frequency, MEP amplitudes, peripheral motor conduction velocity, standardized distal latencies and central, root, and F-wave conduction times were evaluated. RESULTS: The results of MEP testing were markedly abnormal. Cortical excitability thresholds were elevated, MEP amplitudes were reduced while the conduction function was rather preserved. The features of functional disturbances and/or loss of upper and lower motor neurons were revealed. They correlated with the advancement of key clinical CJD symptoms (progressive dementia, extrapyramidal and cerebellar signs, myoclonic jerks, mutism and typical periodic EEG changes), while motor lesion signs might only be slight or absent. CONCLUSIONS: Conduction slowing, if present, seemed to be secondary to axonal lesion.