Increased central motor tract excitability in Creutzfeldt-Jakob disease

Central motor tract excitability was examined in 2 patients with Creutzfeldt-Jakob disease (CJD) and 8 normal subjects by measuring change in the motor evoked potential (MEP) by transcranial magnetic stimulation of the motor cortex after peripheral nerve stimulation. Conditioning stimulation of the median nerve at the wrist greatly increased MEP size (500-1700%) as compared to the size for normal subjects (140-380%) at conditioning-test (C-T) intervals of 30-60 msec for patient 1 and 40-70 msec for patient 2. Moreover, stimulation of the contralateral median nerve at the wrist and of the second and third digits also increased MEP size in the CJD patients; whereas, there was no increase in size in the normals. The time courses of abnormal MEP potentiation were very consistent with the course of the corresponding C reflex. One of the CJD patients had a normal size SEP, and neither patient showed hyperexcitability in SEP-recovery at C-T intervals of 20-60 msec at which there was marked MEP potentiation. These results indicate that there was hyperexcitability of the central motor tract in the CJD patients after the conditioning of muscle and cutaneous peripheral afferents and that it extended to the ipsilateral cortex on the conditioning side as well.