[Electrophysiological investigation s in diagnosis and evaluation of ALS progress]

In diagnostics of ALS the electrophysiologic investigation should be able to evaluate two fundamental processes: the primary process of the loss of some motoneuros--denervation, and secondary process of reinnervation. The most important diagnostic methods include the quantitative electromyography (EMG) evaluating several parameters of the motor unit potential (MUP) and of the maximal effort pattern. The earliest features are the signs of spontaneous activity (denervation) and the elevation of MUP amplitude and area (reinnervation). Finding of spontaneous activity in the tongue muscles as well as in the paraspinal muscles is of great diagnostic value. SFEMG may early detect increased density of muscle fibres (FD) and jitter elongation as signs of recent reinnervation. Electroneurography is critical in differentiation against the multifocal motor neuropathy with conduction block and other polyneuropathies. The aim of the electrophysiological investigations is also the evaluation of the intensity of lesion in the muscle investigated and, indirectly, the evaluation of the progress of the disease in serial studies. It might play a great role in prognosing and in monitoring of therapeutical trials. The abnormalities in the maximal effort pattern presenting as decrease of recording density and amplitude as well as of bioelectric activity indicate in the quantitative EMG a high degree of lesion. Those signs are accompanied by altered MUP parameters: decrease of MUP amplitude and area as compared with the former stages of reinnervation. Those signs express decompensation and denervation predominating over reinnervation. In SFEMG they present as FD decrease and in Macro-EMG as decrease of amplitude as compared to the reinnervation period. Serial investigations of amplitude of the potential resulting from supermaximal stimulation (CMAP), quantitative evaluation of the maximal voluntary isometric contraction (MVIC) and the assessment of the number of motor units (MUNE) are further valuable methods in monitoring of ALS progress.