Clinical characteristics of lateral pterygoid myospasm: a retrospective study of 18 patients.

The available scientific literature on masticatory myospasm-induced oromandibular dystonia is limited. The objective of this study was to determine the clinical characteristics of lateral pterygoid myosapsm in a series of 18 patients. Clinical and electromyographic (EMG) data of 36 patients diagnosed with masticatory muscle myospasm were reviewed, and data from 18 patients with needle EMG-confirmed lateral pterygoid myospasm were extracted for retrospective study. The study population included 6 men and 12 women with a mean age of 53.2 ± 15.3 years. Patients' chief complaints, severity and frequency of myospasm, clinical observations, video recordings, and surface/needle EMG recordings were analyzed. Despite the variety of manifestations, 3 characteristic signs and symptoms of lateral pterygoid myospasm were observed. These were: 1) jaw function disabilities; 2) difficulty in jaw closing after wide opening; and 3) involuntary jaw movements. A differential diagnosis of lateral pterygoid myospasm should be included when oromandibular dystonia is accompanied by the fore mentioned.