Abnormal somatosensory evoked potentials in amyotrophic lateral sclerosis

The sensory symptoms and the involvement of the sensory tracts in amyotrophic lateral sclerosis (ALS) were much debated by various authors. The SEPs were studied in 10 patients with ALS by percutaneous stimulation of the median and tibial nerves. The SEPs were recorded at: Erb's point, cervical level (CII), lumbar level (L1) and parietal level. The peripheral sensory and motor nerve conduction were normal, excluding the spondylotic origin of altered SEPs found in these patients. There were 9 patients with abnormal parietal SEPs to the tibial nerve stimulation, usually bilateral. Abnormal cervical potential (N13) to the median stimulation was noted in 7 cases of whom 3 had also abnormal parietal SEPs. The most severe abnormalities were obtained in the 5 patients with fast advancing ALS and notably to the tibial nerve stimulation. Our results confirm the findings of other authors and reflect physiological dysfunction in the sensory system in a disease considered so far as restricted to the motor system.