Trismus And Restricted Mouth Opening

Causes

Common triggers are post-radiotherapy fibrosis in head and neck cancers (oral and salivary tumours), TMJ issues, infections (peritonsillar abscesses), trauma, tetanus, or myofascial pain. Masticatory muscle spasm (masseter, pterygoids) is the most common type of muscle spasm. Oral submucous fibrosis is common in South Asia because of betel quid.

Signs and symptoms

Patients report a maximum interincisal openness of less than 35mm (normal is 40–55mm), as well as jaw pain, stiffness, trouble chewing and swallowing, speech problems, and poor dental hygiene that puts them at risk for cavities. Acute cases exhibit oedema and fever, but chronic cases result in ankylosis and malnutrition.
Diagnosis
Check how wide the mouth can open (passive/active) and feel the muscles and TMJ for pain. Imaging (MRI/CT/panoramic) finds fibrosis and tumours; a biopsy can rule out cancer. The Therabite® gauge measures how far you've come.
Care
Conservative: NSAIDs, muscle relaxants, jaw exercises, and heat. Advanced: injections of botulinum toxin, coronoidectomy, and physiotherapy devices like Therabite®. Pentoxifylline helps with fibrosis after radiation, and surgery is needed for ankylosis. A multidisciplinary approach leads to a 70–90% improvement.