Microvascular Decompression for Hemimasticatory Spasm: A Case Report and Review of the Literature

Hemimasticatory Spasm: The First Case Report of Bilateral Presentation

“…The pathophysiology of HMS is thought to be quite similar to that of hemifacial spasm and classical trigeminal neuralgia, suggesting that involuntary muscle contractions occur due to ectopic firing from damaged trigeminal motor root fibers. Such lesion may originate from trigeminal nerve root compression by the superior cerebellar artery or its entrapment, and this notion is supported by the fact that vascular decompression has been successful for the treatment of HMS in many cases 6,7 . It is also supposed that irritation of the motor root of the trigeminal nerve may cause changes in the excitability of central reflex pathways that are responsible for the physiological characteristics of HMS 8 …”

“…Such lesion may originate from trigeminal nerve root compression by the superior cerebellar artery or its entrapment, and this notion is supported by the fact that vascular decompression has been successful for the treatment of HMS in many cases. 6,7 It is also supposed that irritation of the motor root of the trigeminal nerve may cause changes in the excitability of central reflex pathways that are responsible for the physiological characteristics of HMS. 8 Most of the cases described in the literature were pharmacologically treated for a while.…”

“…3,5,9 Microvascular decompression of the trigeminal motor root from the superior cerebellar artery was beneficial when applicable. 6 According to many reports, botulinum toxin has a dramatic effect on contraction frequency and severity with the mean duration of the effect of 4 months. 8 In line with other reports, our patient was also successfully treated by bilateral botulinum toxin injections of masseter muscles.…”

“…Medications that have been used are carbamazepine, phenytoin, and clonazepam, but they only had a partial effect on the frequency of contractions 3,5,9 . Microvascular decompression of the trigeminal motor root from the superior cerebellar artery was beneficial when applicable 6 . According to many reports, botulinum toxin has a dramatic effect on contraction frequency and severity with the mean duration of the effect of 4 months 8 .…”

Long-Term Outcome of Hemimasticatory Spasm

“…6,12 The presence of a vascular loop around the trigeminal nerve in patients with HMS and subsequent relief of symptoms following microvascular decompression has been reported. [13][14][15][16] Removal of the masseter nerve root attached to the temporomandibular joint has shown favorable outcomes. 7 Debulking of the masseter muscles has also yielded good improvement.…”