Plasticity of cortical hand muscle representation in patients with hemifacial spasm Joachim Liepert a, * , Celia Oreja-Guevara b , Leonardo G. Cohen c , Martin Tegenthoff b , Mark Hallett c , Jean-Pierre Malin b a Department of Neurology, Friedrich Schiller University Jena, Germany b Department of Neurology, BG-Kliniken Bergmannsheil, Ruhr University Bochum, Germany c Human Cortical Physiology Section, NIH, USA Received 14 June 1999; received in revised form 7 July 1999; accepted 8 July 1999 Abstract To investigate interactions between face and hand representations in the human motor cortex, we studied patients with a hemifacial spasm before and after treatment with Botulinum toxin. Focal transcranial magnetic stimulation was used to assess the cortical motor output map of the abductor pollicis brevis muscle (APB) on both sides. Prior to therapy the representation of the APB ipsilateral to the facial muscle contractions (iAPB) was signi®cantly smaller than on the contralateral side. Two weeks after successful therapy, the iAPB output area was signi®cantly enlarged and expanded into the direction of the face representation. The results indicate activity dependent interactions between hand and face representations in the adult human motor cortex. q 1999 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Plasticity; Motor cortex; Transcranial magnetic stimulation; Mapping; Hemifacial spasm; Botulinum toxin In somatosensory and motor cortices of adult humans, reorganisations were reported after amputation [12], after stroke [13], following peripheral nerve block [3] and increased or decreased use [14,15]. In most studies plastic changes were observed within the cortical representation of the affected limb. This is easily understandable as fMRI studies have demonstrated that a broad overlap between the cortical representation of proximal and distal muscles and movements exists [18]. Much less is known about inter- actions between different limb representations, for example hand and face. In general these representations are thought to be strictly separated. Only recently it was shown that patients with a facial palsy have an enlarged cortical repre- sentation of the hand ipsilateral to the paretic facial muscles which expands into the neighbouring face representation area [17]. In the present study we examined the cortical hand representation in patients with a hemifacial spasm (HFS). HFS presents with unilateral involuntary phasic or tonic contractions of facial muscles. An aberrant blood vessel irritating the facial nerve close to the brainstem is supposed to be the cause in most patients [11]. The muscle twitching is either due to an ephaptic signal transmission in the facial nerve [19], or a hyperexcitability of the facial nucleus in the brainstem [10], or both. Today, most patients are treated successfully with local, subcutaneous injections of Botulinum toxin which blocks the neuromuscular trans- mission in facial muscles [20]. In terms of plasticity, patients with HFS are of special interest as the facial nerve is not damaged and the treatment of HFS allows study of dynamic changes when comparing pre and post therapy results. Twelve patients (mean age, 58:5 ^ 9:9 years, range, 42± 78 years, 7 male) were included. The mean duration of illness was 8:9 ^ 6:6 years (range, 1±12 years). In 7 patients the HFS was left-sided, in 5 patients right-sided. CT and MRI scans of the brain were normal in all patients; in 1 patient a blood vessel close to the facial nerve was found. Additional neurological symptoms were excluded by clin- ical examination. None of the patients reported a facial palsy and the blink re¯ex was normal. A mean dose of 100 I.U. Botulinum toxin (Dysport) was injected subcuta- neously into the periorbital area. Focal TMS with a ®gure-eight coil (The Magstim Comp, Dyfed, UK) was used to map the motor output area of the abductor pollicis brevis muscle (APB) consecutively on Neuroscience Letters 272 (1999) 33±36 0304-3940/99/$ - see front matter q 1999 Elsevier Science Ireland Ltd. All rights reserved. PII: S0304-3940(99)00574-1 * Corresponding author. Department of Neurology, Friedrich Schiller University, Philosophenweg 3, D-07743 Jena. Fax: 149- 3641-935-399. E-mail address: liepert@neuro.uni-jena.de (J. Liepert)