Evoked potentials in patients with Huntington's disease and their offspring. I. Somatosensory evoked potentials.

Spinal and cortical somatosensory evoked potentials (SEPs) were recorded in a large sample of patients with Huntington's disease (n = 37) and subjects at risk (first order offspring, n = 43). The SEPs were elicited by stimulation of the median and tibial nerves and recorded at Erb's point, the cervical level (C2) and at the corresponding scalp areas. The most striking finding in patients with Huntington's disease was a drastic diminution of the amplitude of the early cortical components, especially N20/P25 for the median nerve and N33/P40 for the tibial nerve. The latencies (Erb's point, C2, cortical) were only slightly prolonged in comparison to the normal values. Forty-three per cent of the persons at risk exhibited pathological results with a clear reduction in amplitude of the early cortical responses or with a pathological side difference between the amplitudes. Fifty-three per cent of the persons at risk exhibited a normal result. Two persons at risk (= 6%) could not be classified unambiguously. Some patients with benign and symptomatic chorea were investigated. These showed normal results with one exception. The diagnostic and predictive value of the investigation of SEPs in Huntington's disease is discussed.