Zusammenfassung
Background: According to histological studies, axonal sprouting and the return of vesicle turnover are two competitive mechanisms accounting for the recovery of neuromuscular transmission after injection of botulinum toxin type A (BoNT/A). Methods: 12 healthy individuals, 23 to 32 years old, received random injections of 5,15 or 45 MU Dysport(R) in the M. extensor digitorum brevis (24 feet, 8 ...
Zusammenfassung
Background: According to histological studies, axonal sprouting and the return of vesicle turnover are two competitive mechanisms accounting for the recovery of neuromuscular transmission after injection of botulinum toxin type A (BoNT/A). Methods: 12 healthy individuals, 23 to 32 years old, received random injections of 5,15 or 45 MU Dysport(R) in the M. extensor digitorum brevis (24 feet, 8 feet each dose). Automatic quantitative EMG and neurography were done at baseline and 7,19, 46, 92, and 180 days after the injections. Results: The amplitude of compound muscle action potentials (CMAPs) and the amplitude, duration, number of phases and of turns of the motor unit action potentials (MUAPs) were reduced by the injections. Spontaneous activity was only mild to moderate. The EMG changes were most pronounced on day 19 and subsequently return to baseline. The CMAP amplitude, the amplitude and duration of MAP, and the amplitude at maximum voluntary contraction were still reduced after 6 month for all three doses. The dose dependence of the changes were only partly significant. Conclusion: The EMG changes resemble a myopathy-like pattern without evidence of collateral sprouting suggesting that BoNT/A causes a dysfunction of single fibres within the motor units. It appears that collateral sprouting plays a minor role in the functional recovery after intramuscular injections of BoNT/A.
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