Isolated Tuberculous Myositis of the Temporalis Muscle Mimicking Temporomandibular Joint Internal Derangement: A Case Report

Tuberculous myositis is a rare manifestation of extrapulmonary tuberculosis (TB), and isolated involvement of the temporalis muscle without adjacent osseous or temporomandibular joint (TMJ) disease is exceedingly uncommon. Clinical presentation may mimic TMJ disorders, leading to diagnostic delay. We report a case of a 32-year-old female presenting with progressive trismus and facial swelling. Magnetic resonance imaging (MRI) revealed a well-defined intramuscular lesion within the left temporalis muscle exhibiting central necrosis and surrounding edema, without mandibular cortical erosion or joint involvement. Cartridge-based nucleic acid amplification testing (CBNAAT) of aspirated material confirmed Mycobacterium tuberculosis, with rifampicin sensitivity. Standard anti-tubercular therapy resulted in marked clinical improvement. A follow-up MRI at three months demonstrated a significant reduction in lesion size, with resolution of necrotic and inflammatory changes. To our knowledge, this is the first reported case demonstrating MRI-documented treatment response in isolated temporalis muscle tuberculosis. This report highlights a rare presentation of isolated temporalis muscle tuberculosis, its diagnostic challenge due to clinical mimicry of TMJ internal derangement, and the role of MRI in documenting treatment response.