Pathology · patient case question
Which procedure would best CONFIRM a myofascial rather than an intracapsular origin?
Patient case: Painless mandibular deviation on opening with limited range
Patient: Female, 36 years old
Chief Complaint: “When I open, my jaw pulls over to the left side.”
Background: Reports daytime clenching under work stress. No trauma, no prior TMJ treatment. No systemic disease.
Vital Signs: BP 118/74 mmHg · HR 72 bpm
Findings: On opening, the mandible DEVIATES TO THE LEFT and remains deviated at maximum opening. Maximum interincisal opening 32 mm. NO PAIN reported on opening or on joint loading. No clicking or crepitus. Tenderness on palpation of the masticatory muscles on the left.
Show answer and explanation
Correct answer: D. Diagnostic local anaesthetic injection into the tender trigger point
- A. Electromyography is a research tool in this setting. It is not validated for routine clinical diagnosis of temporomandibular disorders and is not part of standard assessment.
- B. A panoramic film screens for gross bony change and for growth or fracture, but it images the condyles obliquely and superimposed. It tells you nothing about muscle, and nothing about the disc.
- C. Arthrocentesis is a therapeutic lavage for a joint that has already been identified as the problem. Performing it to establish the diagnosis is invasive and backwards.
- D. CORRECT. A DIAGNOSTIC TRIGGER POINT INJECTION of local anaesthetic is both a test and a treatment. If infiltrating the tender band abolishes the pain and improves the opening range, the source is MUSCULAR — the anaesthetic has interrupted the pain-spasm-pain cycle. If the restriction persists unchanged, the problem lies within the joint. It also confirms REFERRED pain patterns, since myofascial trigger points refer to predictable distant sites, masseter trigger points to the teeth and ear among them.
Note: The Diagnostic Criteria for TMD separate MYALGIA — local, myofascial, or myofascial with referral — from the INTRA-ARTICULAR disorders: disc displacement with or without reduction, degenerative joint disease, and subluxation. The clinical discriminator is whether palpation of the muscle REPRODUCES the patient's familiar pain.