[Investigations of peripheral and central somatosensory pathways in peroneal muscular atrophy and Friedreich's heredoataxia (author's transl)].

Twenty-eight patients with peroneal muscular atrophy (PMA) have been investigated. Eighteen of them were affected by the Charcot-Marie-Tooth disease and three by Dejerine-Sottas disease. In these 21 cases the nerve conduction velocity (NCV) was decreased. Four patients presented the neuronal type of PMA, two cases showed sensory neuropathy of the neuronal type with ophthalmoplegia, and one case, PMA with ataxia, i.e., a myatrophic ataxia. In the neuronal type of PMA, including both cases with ophthalmophegia, the amplitudes of the sensory nerve action potentials were decreased, and the NCV was normal to slightly subnormal. In myatrophic ataxia NCV was decreased. In all cases with reduced NCV, the latencies of the spinal-evoked potentials (spinEP) and somatosensory-evoked potentials (ssEP) were prolonged. In the neuronal type of PMA, these latencies were normal. The central latencies (from thoracic and cervical level) were normal in all 28 patients with PMA of different types. Seventeen patients with Friedreich's heredoatazia have been investigated. In all except two cases, NCV was normal. The sensory nerve-action potentials markedly decreased or disappeared in all cases. The peripheral neurographic picture, accordingly, corresponds to that of patients with the neuronal type of PMA. The latencies of spinEP were normal. All patients with Friedreich's heredoatazia, however, showed prolonged latencies of ssEP. Calculating the central latencies as the difference between ssEP and spinEP latencies (cervical and thoracic) confirms that this is due to a slowing of the conduction velocity via the spinobulbar tracts.