ELSEVIER Electroencephalography and clinical Neurophysiology 97 (1995) 355-368 Electrophysiological characteristics of lesions in facial palsies of different etiologies. A study using electrical and magnetic stimulation techniques KM. Riisler ay*, M.R. Magi&-is b, F.X. Glocker ‘, A. Kohler b, G. Deuschl ‘, C.W. Hess a a Department of Neurology, University of Beme. Inselspital, CH-3010 Berne, Switzerland b Department of Neurology, University of Geneva, Geneva, Switzerland ’ Department of Neurology, Uniuersity of Freiburg. Freiburg, Germany Accepted for publication: 29 May 1995 Abstract Using magnetic stimulation techniques in addition to conventional electrical stimulation, the entire facial motor pathway can be assessed electrophysiologically. To study the diagnostic yield of these examinations, 174 patients with facial palsies of a variety of etiologies were examined (85 Bell’s palsies, 24 Guillain-Barr6 syndrome (GBS), 19 Lyme borreliosis, 17 zoster oticus, 12 meningeal affections, 10 brain-stem disorders and 7 HIV-related facial palsies). The facial nerve was stimulated electrically at the stylomastoid fossa and magnetically within its canalicular portion. Additionally, the face-associated contralateral motor cortex was stimulated magnetically. Recordings were from the nasalis or mentalis muscle, or both, using surface electrodes. Bell’s palsy patients showed typically a unilateral local hypoexcitability of the facial nerve to canalicular stimulation. In GBS, bilateral latency prolongations were frequent, as expected for a myelinic disorder. In contrast, in zoster, predominant axonotmesis was unilateral, and in HIV infection sometimes bilateral. The method was very sensitive to detect subclinical dysfunctions in meningo-radiculitis and malignant meningeal diseases, either prior to the onset of palsy, or on the contralateral (clinically unaffected) side. It also distinguished reliably between central and peripheral facial motor pathway lesions. In our experience, these inexpensive and non-invasive electrophysio- logical techniques contribute substantially to the differential diagnosis of facial palsies. Keywords: AIDS; Bell’s palsy; Guillain-Bark syndrome; Herpes zoster; Lyme disease; Meningeosis 1. Introduction The clinical differential diagnosis of acute or progres- sive facial palsies is sometimes difficult, and paraclinical tests are required to elucidate their etiology. As yet, these investigations rely mainly on cerebrospinal fluid (CSF) analysis (to search for inflammatory signs, e.g., in Lyme borreliosis) and on neuroradiological investigations (to rule out processes in the posterior fossa or within the temporal bone). Neurophysiological examinations are usually per- formed to characterize the conduction disorder and for prognostic purposes (Zander Olsen, 1975; Mamoli, 1976; * Corresponding author. Tel.: + 41 31 6323098; Fax: + 41 31 6329679: E-mail: kroesle@insel.unibe.ch. Esslen, 1977; Boongird and Vejjajiva, 1978; Thomander and St&erg, 1981). A limitation of the neurophysiological investigation in the diagnostic work-up of facial nerve disorders is the frequent location of facial nerve lesions within the skull, where the nerve is not accessible to conventional electrical stimulation. The introduction of magnetic stimulation tech- niques has changed this situation (Barker et al., 1985). With magnetic transcranial stimulation, the proximal in- tracranial part of the facial nerve and the contralateral hemisphere can be excited (Murray et al., 1987; Benecke et ‘al., 1988; Schriefer et al., 1988; Rasler et al., 1989). Hence, conduction measurements across the entire periph- eral and central facial motor pathways can be performed (RSsler et al., 1989). Theoretically, these methods should allow further localization and characterization of intracra- 0924-980X/9.5/$09.50 0 1995 Elsevier Science Ireland Ltd. All rights reserved SSDI 0013-4694(95)00134-4 EEM 94679