Non-infectious myositis of the lateral pterygoid muscle: a report of four cases

Abstract Non-infectious myositis is a condition characterized by chronic localized myalgia originating from central nervous system effects. It is also known as centrally mediated myalgia associated with neurogenic inflammation. When this condition occurs in the lateral pterygoid muscle, clinical evaluation is difficult due to its inaccessible anatomic location. In order to diagnose this rare condition, careful clinical examination and advanced imaging are necessary. The authors report herein four cases of non-infectious myositis of the lateral pterygoid muscle diagnosed by magnetic resonance or enhanced computed tomography imaging. The patients reported prolonged parafunctional habits and chronic jaw pain. In each case, clinical signs suggested the diagnosis of anterior disc displacement without reduction, but the progressive history of internal derangement did not fit this diagnosis. Limited lateral excursion was observed, and patients reported pain in the temporomandibular joint (TMJ) area without tenderness to palpation of the TMJ. Advanced imaging, including axial views, provided valuable information for accurate diagnosis and appropriate management.