Electrophysiological determination of the site involved in generating abnormal muscle responses in hemifacial spasm.
In patients with hemifacial spasm (HFS), abnormal muscle responses due to abnormal cross-transmission are observed in facial muscles. However, the site in the facial nerve responsible for the cross-transmission remains a matter of controversy. We have developed a model in which by considering the electrophysiological parameters involved in producing the abnormal muscle response, we can determine the site of the abnormal cross-transmission within the facial nerve. This model was applied to HFS patients with three different etiologies: idiopathic, post-Bell's palsy, and post-XII-VII anastomosis. Our data show that: in idiopathic HFS, the cross-transmission may occur in the facial nerve at the level of the pontocerebellar angle; in post-Bell's palsy, it is inside the petrous bone; and in XII-VII anastomosis, it must be in the extracranial part of the facial nerve. The possible mechanisms for this cross talk are discussed in terms of ephaptic transmission or of a central hyperexcitability in the facial motor nucleus.
Tankéré
F
F
Department of Otorhinolaringology, Hôpital Pitié-Salpêtrière, Paris, France.
Maisonobe
T
T
Lamas
G
G
Soudant
J
J
Bouche
P
P
Fournier
E
E
Willer
J C
JC
D000328:Adult; D000368:Aged; D004594:Electrophysiology; D005152:Facial Muscles / Q000294:innervation / Q000502:physiology*; D005154:Facial Nerve / Q000503:physiopathology*; D020220:Facial Nerve Injuries; D005158:Facial Paralysis / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D019569:Hemifacial Spasm / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D007002:Hypoglossal Nerve / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology