Electrophysiological diagnosis of motor neuron disease and pure motor neuropathy

Motor neuron disease (MND) is a group of disorders in which there is degene ration of upper and lower motor neurons to a variable degree. Amyotrophic l ateral sclerosis is the most frequent form of the disease, presenting with both upper and lower motor neuron involvement. Frequently, especially in th e early stages of the disease, only lower motor neuron signs are present. I n these conditions, some pure motor neuropathies may resemble MND. The diag nosis is of importance because some of these motor neuropathies are "dysimm une" disorders and may respond to immune therapies. In such diseases the mu ltifocal motor neuropathy with conduction block appears to be the more freq uent. In MND and pure motor neuropathies, the electrophysiological examinat ion is the most decisive test. In MND, it is of diagnostic importance. In a ddition, it is useful in the assessment of disease severity and progression , in the evaluation of therapeutic trials and in the understanding of etiop athogenesis of the disease. Tn pure motor neuropathies, the presence of con duction block leads to immune treatment with good response in more than 50% of the cases.