A painful condition that restricts normal mandibular movement and function as a result of masticatory muscle spasms. Patients are unable to open their mouth within the normal range (35 to 55 mm [average is 40 mm]; 3-finger wide).
Several factors cause trismus, ranging from motor disturbance of trigeminal nerve to potentially life-threatening conditions, like tetanus. In general, all conditions for which there is an impaired ability to open the mouth within a normal range are addressed as trismus.
More likely to develop in:
- Young adults (age 18-25), secondary to an associated pericoronitis with an impacted wisdom tooth
- Head and neck cancer patients who received radiation treatments (radiation-associated fibrosis)
- Those with a temporomandibular disorder (TMD); it is then classified as a myospasm (tonic contraction myalgia). (Author Note: recent studies indicate that myospasms are not a common source of muscle pain in TMD patients. Factors that likely promote myospasms in TMD patients include local muscle conditions, deep pain input, and systemic conditions.)
- Limited mouth-opening ability
- Deviation of the jaw toward the affected side (muscles not functioning properly because of spasms)
- Diffuse facial swelling and fever (only if associated with infections)
- Pain severity: severe pain in acute condition (if there are trigger points in muscles); dull, aching pain if muscle spasms persist for a long time.
- Pain at rest
- Difficulty to open the mouth wide and attain full-range motion
- Inability to chew or bite on solid foods
- Discomfort when yawning
- Difficulty to brush teeth and follow routine oral hygiene care, which can lead to bad breath and a high risk of caries
- Pain in one or more masticatory muscles
- Sensation of muscle tightness, cramping, or stiffness
Difficulty with respect to speech; inability to receive proper dental care
Rule Out Other Pathologies
- Thoroughly review the patient's dental and medical history
- Ask about the onset, nature, progression, aggravation, radiation of pain, and relieving factors
- Ask about any dental treatment, joint clicking and locking, trauma, infections, medical conditions, radiotherapy, or drug intake
- Inquire about pain in neck, shoulder, and back muscles
- Inquire about sleep bruxism (clenching/grinding/tooth tapping) or daytime parafunction (clenching, gum chewing, fingernail biting)
- Perform a complete extraoral and intraoral examination
- Check for visible muscle fasciculation, pathognomonic for myospasm/trismus diagnosis
- Check for facial asymmetry
- Measure maximum mouth opening (check for interincisal distance) and lateral range of jaw motion
- Palpate the masticatory muscles in the jaw and check for tenderness (some areas may be extremely tender due to deep pain input from myofascial trigger points)
- Palpate the neck muscles (especially sternocleidomastoid muscle) and upper shoulder muscles (trapezius)
- Examine the temperomandibular joint (TMJ) (check for any tenderness, uncoordinated movement, clicking sounds, and crepitus)
- Look for partially erupting third molars and gingival inflammation
- Check teeth for any wear facets and/or occlusal disharmony
- Perform a radiographic investigation.
- Panoramic radiographs may be advisable to look for any associated abnormalities with TMJs.
- Oral medicine specialists may advice CT (cone beam or conventional) and MRI scans. They may be required to rule out pathologies in structures such as TMJs, ears, etc.
Based on the clinical history and signs, a diagnosis of trismus is determined.
- Facial trauma with or without bone fracture
- Nonodontogenic infections (tonsillitis, meningitis, tetanus, parotid abscess): trismus is a hallmark of masticatory-space infections and may also occur along with pericoronitis
- Needle stick injury to the medial pterygoid muscle
- Fibrosis (when masticatory muscles are involved in field of radiation)
- Prolonged mouth opening (following any dental procedure like dental extraction or high points after dental restoration)
Treatment (including patient education, self-care management, rest, and analgesics) should be directed towards the underlying causes.
- Partially impacted tooth: extraction of offending tooth may be required
- Infection: antibiotherapy
- Trauma: referral to an oral and maxillofacial surgeon
Common Initial Treatments
- Advise the patient to follow a soft diet and avoid solid foods.
- Suggest heat therapy (placing moist hot towels on the affected area for 15-20 minutes every 1 hr).
- Suggest taking analgesics: ASA or acetamiophen 325 mg, 1-2 tablets every 4-6 hrs; or ibuprofen 200 mg, 1-2 tablets every 4 hrs.
- Muscle relaxants may be used in combination with analgesics or alone. Benzodiazepines may also be used, such as diazepam (2-5 mg, 3 times/day).
- Physiotherapy treatments may be required to establish normal function (exercises will include neck stretching, chin tuck, massaging of masticatory muscles, and other jaw stretching).
- Mandibular opening devices might be considered in some cases, but most likely provided by a physiotherapist or dental specialist.
- Avoid any daytime jaw parafunction (gum chewing, finger nail biting, tooth clenching, etc.)
- Work with a physiotherapist to strengthen their jaw muscles, if needed (in acute conditions)