Cortical somatosensory magnetic responses in multiple sclerosis

Somatosenosor evoked magnetic fields (SEFs) to contralateral medium and ulnnar nerve stimulation were analyzed in 10 patients with multiple sclerosis and in 8 healthy controls. SEFs were recorded with a 24-channel SQUID gradiometer over both hemispheres. Seven patients' showed abnormally large-amplitude SEF deflections at 60–80 msec; 5 of them had multiple lesions around lateral ventricles in magnetic resonance imaging. In 2 patients with plaques at the level of 3rd and 4th ventricles and medulla, the 30 msce response were enlarged. The equivalent sources of 20 msec and 30–80 msec responses were in the primary hand sensorimotor cortex both in patients and in control subjects. The results suggest that early and middle-latency SEFs reflect parallel processing of somatosensory input. Recording of middle-latency evoekd responses, electric or magnetic, may give additional information about the somatosensory function in multiple sclerosis.