Studies on the human spontaneous electromyelogram (EMyeloG). II. Patients with peripheral nerve, root and spinal cord disorders.

Using an intrathecal recording technique the spontaneous electromyelogram (EMyeloG) was recorded in 44 patients having peripheral nerve, spinal root and lower motor neurone disorders (17 cases), suprasegmental spinal cord disorders (18 cases) and diffuse involvement of the posterolateral funiculus or spinal ganglia (9 cases). In the first 17 cases, labelled as 'afferent group,' the spontaneous EMyeloG was significantly reduced, parallelling the paucity of afferent signals entering the spinal cord. However, the spontaneous EMyeloG was found to be normal in cases with the diffuse anterior horn cell involvement and motor polyneuropathy. In the second 18 cases labelled as 'efferent group,' the spontaneous EMyeloG was more prominent and the amplitude and frequency of the spontaneous cord potentials were significantly increased. Especially in patients with spastic paraparesis various peripheral afferent stimuli could produce more significant facilitation of the EMyeloG in the 'efferent group' than in normal subjects. In the third group labelled as 'mixed group' a different type of abnormal spontaneous action potentials was observed in addition to increase of the spontaneous EMyeloG. These potentials were positive or mainly positive and their duration was long, being 10-25 msec. It was concluded that the human spontaneous EMyeloG recorded from an intrathecal electrode probably originates from the interneurones of the posterior horns, facilitated by peripheral afferent inputs and inhibited by suprasegmental descending pathways, especially the pyramidal tract.