title: Electrophysiological determination of the site involved in generating abnormal muscle responses in hemifacial spasm.
abstract: 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.
authors.affiliation: Department of Otorhinolaringology, Hôpital Pitié-Salpêtrière, Paris, France.
authors.forename: F
authors.initials: F
authors.lastname: Tankéré
authors.forename: T
authors.initials: T
authors.lastname: Maisonobe
authors.forename: G
authors.initials: G
authors.lastname: Lamas
authors.forename: J
authors.initials: J
authors.lastname: Soudant
authors.forename: P
authors.initials: P
authors.lastname: Bouche
authors.forename: E
authors.initials: E
authors.lastname: Fournier
authors.forename: J C
authors.initials: JC
authors.lastname: Willer
mesh_terms: 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