[The central action of botulinum toxin type A assessed by brain auditory and somatosensory evoked potentials].
OBJECTIVE
Botulinum toxin type A (BTX-A) acts as a neuromuscular blocker in the release of acetylcholine. Nevertheless, some clinical effects and side effects are difficult to explain only due to the peripheral mode of action. The aim of the study was to assess the central effects of BTX-A by measuring the two modalities of evoked potentials (somatosensory and brain-stem auditory).


METHODS
In 23 patients (13 females, 10 males, mean age of 46, range of 25-71) with idiopathic cervical dystonia (never treated with BTX-A) brainstem auditory evoked responses (BAER) and somatosensory evoked potentials from upper extremities (SEP) were performed before and 4-6 weeks after BTX-A administration. BTX-A (Botox in 14 patients, Dysport in 9 patients) was injected into neck muscles: sternocleidomastoideus, splenius capitis, trapezius and levator scapulae.


RESULTS
The authors did not find any statistically significant differences in basic parameters (latency and interlatency of I, III, V in BAER and N9, N13, N20 and P25 responses in SEP) before and after BTX-A administration.


CONCLUSIONS
It seems that BTX-A does not have any direct central effect or the methods are not sensitive enough to detect them. Remote (anatomically distant) clinical effects seen by other authors or side effects may be explained by indirect mechanism due to deafferentation of stimuli from muscle spindles after BTX-A injection and thus modifying the central loops of reflexes or due to unpredictable hematogenous spread of BTX-A to distant muscles.
Sławek
Jarosław
J
Oddział Neurochirurgii Czynnościowej i Chorób Układu Pozapiramidowego, Klinika Neurochirurgii, Akademia Medyczna w Gdańsku. jaroslawek@amg.gda.pl
Recławowicz
Daniel
D
D000328:Adult; D000368:Aged; D019274:Botulinum Toxins, Type A / Q000494:pharmacology* / Q000627:therapeutic use; D016057:Evoked Potentials, Auditory, Brain Stem / Q000187:drug effects*; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009465:Neuromuscular Agents / Q000494:pharmacology* / Q000627:therapeutic use; D013997:Time Factors; D014103:Torticollis / Q000188:drug therapy* / Q000503:physiopathology*; D016896:Treatment Outcome
D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A