Study of evoked potentials in human African trypanosomiasis

Human African trypanosomiasis or sleeping sickness has a stage of neurological involvement characterized by the onset of diffuse meningoencephalitis with sleep disturbances and decreased wakefulness. The pathogenesis of this disease is not well understood. We studied auditory, visual, sensory, and motor evoked potentials in 16 patients with trypanosomiasis in the early stage of meningoencephalitis. In all patients, the brain-stem auditory evoked response (BAER) and the pattern-reversal visual evoked response (PVER) were normal. On the other hand, abnormalities of the somatosensory evoked response (SSER) or the motor evoked response (MER) were found in only five cases; however, their relationship to the illness could not be definitely confirmed. The study results indicate that the evaluated pathways were essentially intact, in particular at the level of the brain-stem in the early stage of the disease. Sleep disturbances and decreased wakefulness noted at this stage were thus linked more closely to functional involvement at the level of the sleep centres than to any detectable specific anatomic lesion.