Abnormalities of somatosensory evoked potentials in konzo--an upper motor neuron disorder.

OBJECTIVE: To determine whether the somatosensory pathways are involved or not in konzo. METHODS: In 1998, 21 konzo subjects (15 females and 6 males; mean age 21 years) underwent a SEP study with a two-channel-equipment (Medtronic Keypoint, Denmark) whereas in 2000, 15 subjects (7 females and 8 males; mean age 21 years) participated in a study with a 4-channel-equipment. RESULTS: Most subjects (19/21 in 1998 and 12/15 in 2000) showed normal median SEPs. The remainders had no median cortical responses. All 21 subjects in 1998 and 9 out of 15 in 2000 showed abnormalities of tibial SEPs mainly consisting of absence of cortical responses, prolonged cortical latencies, and central sensory delay to the lumbar spine. Most subjects showed normal absolute latencies both at peripheral and spinal levels. The SEP findings did not correlate with the severity, neither the duration of konzo, nor the experience or not of sensory symptoms at the onset of the disease. CONCLUSION: Our findings are not specific of konzo. However, they suggest involvement of intracranial somatosensory pathways and point to similarities with other motor neuron diseases.

Analysis of motor pathway involvement in konzo using transcranial electrical and magnetic stimulation.

To elucidate the involvement of motor pathways in konzo, 21 konzo subjects (mean age 22 years) underwent transcranial electrical stimulation (TES) in 1998. Fourteen konzo subjects (mean age 21 years) underwent transcranial magnetic stimulation (TMS) in 2000. Three subjects underwent both TES and TMS. Motor evoked potentials (MEPs) were recorded in the abductor pollicis brevis (APB) muscle with TES, and in the abductor digiti minimi (ADM) and tibialis anterior (TA) muscles with TMS. APB-MEPs were normal in 2 of 21 subjects and absent in 9; central conduction time (CCT) was prolonged in 10. Resting ADM-MEPs were absent in 9 of 14 subjects with clinically preserved upper limbs. Among these nine, seven subjects responded after facilitation. Most subjects (13 of 14) failed to show TA-MEPs. Of the subjects who underwent both types of stimulation, one had normal TES-MEP but abnormal ADM-MEP with TMS. These findings suggest involvement of both corticomotoneurons and motor descending pathways in konzo.