Avtor/Urednik		Khuraibet, AJ
Naslov		Microphysiology of motor end-plates in neuromuscular diseases
Tip		monografija
Kraj izdaje		Ljubljana
Založnik		Faculty of medicine
Leto izdaje		1989
Obseg		str. 92
Jezik		eng
Abstrakt		The aim of this work was to study presynaptic potentiation and depression at individual human motor end-plates in vivo and in situ as a function of activation frequency. SFEMG with axonal microstimulation was used to measure the neuromuscular jitter at a range of stimulation frequencies from 0.5 to 50 Hz. Normal MEPs most often exhibited a net depression manifested as an increase in the jitter as stimulation rate was raised from 0.5 to 5 Hz. This was followed by a decrease of jitter, i.e. net potentiation, at 10 or 20 Hz in some MEPs. Most, however, showed a sharp increase in jitter on further raise in rate to 50 Hz. Myasthenic MEPs showed a similar pattern, however, with more exaggerated jitter changes and changes in incidence of intermittent blocking. It is concluded that the jitter and intermittent blocking in myasthenia gravis reflect the normal variability in presynaptic transmitter release, unmasked due to decreased postsynaptic sensitivity. In Lambert-Eaton myasthenic syndrome, the abnormal jitter and incidence of blocking were most pronounced at lowest stimulation rates but showed dramatic improvement with increasing rates as a result of exaggerated rate dependent presynaptic potentiation. In neurapraxia, the MEPs of blocked axons mainly showed normal jitter, with a minority (3 per cent in 13 patients of Bell's palsy and 20 per cent in two patients with acute radial compression neuropathy), showing increased jitter. On stimulation with varied frequencies, the MEPs of neurapraxic axons showed patterns of depression and potentiation similar to those of normal MEPs. Ho wever, a proportion of MEPs showed unusually low jitter values. The increased stability in some MEPs of neurapraxic motor units may either be due to more uniform presynaptic transmitter release or to increased postsynaptic sensitivity.
Deskriptorji		NEUROMUSCULAR DISEASES MOTOR ENDPLATE ELECTROMYOGRAPHY MICROELECTRODES NEURAL TRANSMISSION NEUROMUSCULAR JUNCTION FACIAL PARALYSIS RADIAL NERVE NERVE COMPRESSION SYNDROMES MYASTHENIA GRAVIS LAMBERT-EATON MYASTHENIC SYNDROME