J'ournal ofNeurology, Neurosurgery, and Psychiatry 1994;57:43-50 43 Pathophysiology of hemimasticatory spasm J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.57.1.43 on 1 January 1994. Downloaded from G Cruccu, M Inghilleri, A Berardelli, G Pauletti, C Casali, P Coratti, G Frisardi, P D Thompson, M Manfredi Abstract the trigeminal nerve. We also reviewed pub- Two patients aged 21 and 50 years pre- lished reports of patients literature in whom a sented with facial hemiatrophy and uni- diagnosis of HMS was supported by EMG lateral spasms of the masticatory findings, to examine the presence of a com- muscles. Masticatory muscle biopsy mon pathophysiological mechanism. showed normal findings in both patients and facial skin biospy specimens only showed atrophy, although morphoea Case reports (localised facial scleroderma) had been PATIENT 1 diagnosed nine years previously in the A young man first noticed a hollowing of his second patient. The involuntary move- left cheek at the age of 17. One year later, ments consisted of brief twitches and brief involuntary twitches appeared in his left prolonged contractions clinically and temporalis muscle. Clinical examination dis- electromyographically similar to those of closed dilatation of the left pupil and the hemifacial spasm and cramps. The jaw facial asymmetry; CT and magnetic reso- jerk and the silent periods were absent in nance imaging (MRI) of the brain were nor- the affected muscles. Direct stimulation mal. Left facial hemiatrophy was diagnosed. of the muscle nerve and transcranial At the age of 20 years, when the patient stimulation of the trigeminal root came to our observation, the involuntary demonstrated slowing of conduction and movements were still restricted to the tempo- after-activity due to autoexcitation. ralis muscle. Small twiches alternated with Observations in other reported cases and severe and painful, prolonged contractions these two patients suggest that hemimas- (lasting up to several minutes). Clinical ticatory spasm is produced by ectopic examination showed only marked hypertro- activity secondary to focal demyelination phy of the left temporalis muscle and hollow- of the trigeminal motor nerve fibres. The ing of the cheek. Facial sensation was normal proposed cause of the neuropathy is focal and the patient never complained of paraes- damage to the masticatory nerves caused thesias or neuralgia. by compression, possibly resulting from No clinical or laboratory evidence-includ- University of Rome the deep tissue changes that occur in ing antinuclear antibodies, extractable 'La Sapienza', Rome, facial hemiatrophy. nuclear antigen, native DNA, and mitochon- http://jnnp.bmj.com/ Italy drial antibody titres-was found of connec- Department of (T Neurol Neurosurg Psychiatry 1994;57:43-50) tive tissue disease. Neurosciences G Cruccu The patient has been taking 1200 mg car- M Inghilleri bamazepine daily for six months and reports A Berardelli Hemimasticatory spasm (HMS) is a rare con- moderate benefit. G Pauletti P Coratti dition, characterised by unilateral forceful M Manfredi contractions of one or more masticatory mus- PATIENT 2 on September 29, 2021 by guest. Protected copyright. Institute of Nervous cles. In most patients it is associated with A 50-year-old woman first noticed small and Mental Diseases ipsilateral facial hemiatrophy." The cause of spots of abnormal pigmentation on the right C Casali the spasms is not understood. side of the face at the age of 41 years. On her Department of Kaufman,3 who first studied the elec- admission to a dermatological division, a skin Odontology tromyographic (EMG) characteristics of biopsy was consistent with the diagnosis of G Frisardi hemimasticatory spasm, stressed the close MRC Human localized scleroderma of the face, or Movement and similarity with hemifacial spasm, and pro- morphoea. Corticosteroids were prescribed. Balance Unit and posed that the spontaneous activity was gen- At the age of 44 years she began to have University erated in the trigeminal nerve fibres. involuntary twitches of the Department of right masseter and Clinical Neurology, Thompson and Carroll4 found similar EMG temporalis muscles; the twitches increased in Institute of Neurology, characteristics and also proposed a trigeminal duration and frequency over the years. London, UK neuropathy. Other authors, however, sug- At her first neurological assessment, the P D Thompson gested CNS, sympathetic ganglia, or muscle dyschromia was less apparent, but the face Correspondence to: Dr Giorgio Cruccu, dysfunction.56 Because none of the previously was frankly asymmetrical because of a slight Dipartimento Scienze reported patients underwent masticatory hollowing of the right cheek and marked Neurologiche, Viale Universita' 30, I-00185 nerve stimulation, conduction velocity and hypertrophy of the right masseter and tempo- Rome, Italy. after-discharges could not be studied. ralis muscles. The involuntary masticatory Received 12 January 1992 We studied two patients with HMS and muscle contractions consisted of brief and in revised form 13 April 1993. facial hemiatrophy and demonstrated ectopic twitches and prolonged spasms, occurring Accepted 19 April 1993 activity and slowing of motor conduction in many times a day either spontaneously, or 44 Cruccu, Inghilleri, Berardelli, Pauleti, Casali, Coratti, Frisardi, Thompson, Manfredi more often, triggered by chewing, speaking or A J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.57.1.43 on 1 January 1994. Downloaded from other voluntary movements of the mouth and jaw. Tonic contractions could last up to a few minutes; they were most painful and pre- vented the patient from opening her mouth. ,-1i Like patient 1, she had never had sensory sysmptoms other than the pain induced by the muscle spasms. Neurological examination disclosed no abnormal signs apart from the spasms and hypertrophy of the masticatory B muscles. MRI and CT scans showed hyper- I n.l-1-ii- trophy of the right temporalis, lateral ptery- 1111117 goid, and masseter muscles, and dislocation of the right temporomandibular joint. V- Serum tests for speckled and homogeneous antinuclear antibodies, and smooth muscle r if' antibodies gave positive results; circulating immune complexes were increased. Cu Extractable nuclear antigen, native DNA, and mitochondrial antibody titres were negative. No evidence was found of kidney, intestinal, or other systemic manifestations of vasculitis. The painful spasms were attenuated by carbamazepine 600 mg daily and transiently blocked by injection of local anaesthetics into Figure 1 Involuntary EMG activity in patient 1. (A) Highfrequency discharges of a single motor unit the masseter and temporalis muscles. potential. Calibration 10 msll mV. (B) Briefbursts of Diazepam was ineffective. After completion multiple motor unit potentials (corresponding clinically to of all the twitches). Calibration 100 msll mV. (C) Large investigations, injection of botu- compoundpotential ofmultiple synchronised motor units linum A toxin (30-50 U, Oculinum) into the discharging tonically at a 60 Hzfrequency (corresponding affected muscles was repeated three times, clinically to prolonged spasms). Calibration 50 msllO m V. with clinical benefit. The following investigations were approved by the local ethical committee and both and the right masseter and temporalis mus- patients gave their informed consent. cles in patient 2. Involuntary EMG activity was similar in the two patients. Brief trains Investigations (30-100 ms) of two to seven single motor MUSCLE AND SKIN BIOPSY unit potentials reaching a discharge frequency In both patients, an elliptical biopsy speci- of 100 Hz (fig IA), or brief bursts (50-200 men, including skin and underlying tempo- ms) of multiple motor unit potentials ralis muscle, was obtained from the affected occurred spontaneously, irregularly, and side. In patient 2, a further skin biopsy speci- arrhythmically (fig 1 B). The bursts would men was taken from an area of slight dyschro- occasionally become more frequent and mia on the right forehead. intense, with the progressive recruitment and http://jnnp.bmj.com/ In both patients, the muscle was histologi- synchronisation of more and more motor cally normal and skin specimens only showed units, leading to a large (12-15 mV) com- a flattened epidermis and atrophy of dermal pound potential, discharging tonically at a appendages. In particular, no evidence of high frequency (fig 2C). The discharge fre- scleroderma was found in patient 2, in whom quency was always around 60 Hz in patient 1 morphoea had been diagnosed nine years and 70 Hz in patient 2. This activity corre- beforehand. sponded to the painful tonic contractions. on September 29, 2021 by guest. Protected copyright. A masticatory nerve biopsy was excluded The maximum duration of the contractions because of the consequent functional dam- was 2 minutes in patient 1 and 30 s in patient age. 2. In patient 2, the prolonged spasm some- times affected the temporalis muscle alone STANDARD EMG EXAMINATION with complete electrical silence in the mas- The masseter, temporalis, suprahyoid, and seter or vice versa. At other times the spasm facial muscles were bilaterally examined by moved from one muscle to the other (fig 2), concentric needle recordings (filters 50-5000 but never spread to involve the facial muscles Hz). No abnormalities were found in either or contralateral muscles of the jaw. In both patient in the muscles clinically unaffected by patients, these patterns of involuntary