Objective: To report a case with hemimasticatory spasm responsive to serial botulinum toxin injections.

Background: Hemimasticatory spasm is a rare neurologic disorder characterized by involuntary paroxysmal contractions of the unilateral masticatory muscles which may be provoked by a voluntary or an automatic movement of the mouth and usually lasts from a few seconds to several minutes. The etiology of this disorder is controversial, it has been widely accepted that the course is neurovascular conflicts. Varied treatments have been used, for example, oral medication of carbamazepine or phenytoin and focal injection of botulinum toxin[1, 2, 3]. Here, we present one case of hemimasticatory spasm with well response to serial botulinum toxin injections.

Method: A 53-year-old male Taiwanese presented with a complaint of insidious onset of intermittent spasm on the right face since 30 years old. The involuntary twitching on right face showed several times one day and mostly lasted 2-3 minutes. The duration and frequency progressively increased over time. Some trigger factors were found, such as eating, talking and laughing. He often felt soreness or pain in the right masticatory muscles. It showed no response to “sensory trick”. The spasm was absent during sleep. Physical examination showed hypertrophy of the right side of the face. Results of the trigeminal motor, sensory and reflex examination were normal.

Results: An EEG were normal. A head MRI showed mild hypertrophy of the right masseter [figure 1] and temporal [figure 2] muscles. No clinical or laboratory evidence was found of connective tissue disease. Because of unsatisfactory response to oral medications, the patient was treated with focal injection of botulinum toxin type A into the right masseter and temporalis muscles. The spasms disappeared almost completely for 3 months. The subsequent serial injections showed similar effect in resolution of the symptoms. Besides, the painful spasm decreased gradually in severity and frequency after long-term treatment with serial botulinum toxin injections which also decrease the size of hypertrophied muscles.

Conclusion: This case is the first one reported in Taiwan which shows well response and prognosis to serial injections of botulinum toxin in masticatory muscles. Our case further illustrates that botulinum toxin injections is a safe and effective management of hemimasticatory spasm.

References: [1] Lagueny A, Deliac MM, Julien J, et al. Jaw closing spasm–a form of focal dystonia? An electrophysiological study. J Neurol Neurosurg Psychiatry 1989;52:652-655 [2] Ebersbach G, Kabus C, Schelosky L, et al. Hemimasticatory spasm in hemifacial atrophy: diagnostic and therapeutic aspects in two patients. Mov Disord 1995;10:504-507 [3] Auger RG, Litchy WJ, Ahlskog JE, et al. Hemimasticatory spasm: clinical and electrophysiologic observations. Neurology 1992 Dec;42(12):2263-6

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-case-of-hemimasticatory-spasm-with-well-therapeutic-response-to-serial-injections-of-botulinum-toxin/