The effects of botulinum toxin A on ephaptic transmission in idiopathic hemifacial spasm.
OBJECTIVE
Lateral spreading and synkinetic responses of blink reflex are a sign of ephaptic transmission in idiopathic hemifacial spasm (HFS). The aim of this study was to evaluate the effect of botulinum toxin A (Btx A) on ephaptic transmission in idiopathic HFS.


METHODS
Thirty-three patients with idiopathic HFS were investigated. Btx A was injected only into the affected orbicularis oculi (OC) muscle. Electrophysiological studies were performed before and three weeks after the Btx A injection.


RESULTS
After Btx A, the latencies of motor response and blink reflexes elicited from the OC muscle were significantly increased. The lateral spreading was not obtained in the OC muscle, while the orbicularis oris muscle response was not changed. There were no significant differences in the synkinetic responses of blink reflex. During needle EMG examination, positive sharp waves and fibrilation potentials were observed due to chemodenervation only in the OC muscle.


CONCLUSIONS
Btx A affects only the neuromuscular junctions of the injected muscle and has no effect upon ephaptic transmission.
Kurt
Tülay
T
Neurology Department, Atatürk Training and Research Hospital, Izmir, Turkey. tkurt2@hotmail.com
Seçil
Yaprak
Y
Gürgör
Nevin
N
Tokuçoğlu
Figen
F
Beckmann
Yeşim
Y
Ertekin
Cumhur
C
D001767:Blinking / Q000187:drug effects* / Q000502:physiology; D019274:Botulinum Toxins, Type A / Q000494:pharmacology*; D003714:Denervation / Q000379:methods; D004576:Electromyography; D005152:Facial Muscles / Q000187:drug effects / Q000294:innervation / Q000503:physiopathology; D005154:Facial Nerve / Q000187:drug effects / Q000503:physiopathology; D005155:Facial Nerve Diseases / Q000188:drug therapy / Q000503:physiopathology; D005260:Female; D017629:Gap Junctions / Q000187:drug effects / Q000502:physiology; D019569:Hemifacial Spasm / Q000188:drug therapy* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009465:Neuromuscular Agents / Q000494:pharmacology; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000503:physiopathology; D017063:Outcome Assessment, Health Care; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D016896:Treatment Outcome
D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A