Trismus

Introduction, Etiology, Classification, Clinical features, Diagnosis, Management and Prognosis

Trismus

Introduction, Etiology, Classification, Clinical features, Diagnosis, Management and Prognosis

Introduction of Trismus

  • Trismus is most commonly known as Lockjaw.
  • It is a medical condition of limited jaw opening, in which the normal motion of the mandible (jaw) is reduced due to sustained tetanic spasm of the masticatory muscles.
  • It is a motor disturbance of the trigeminal nerve. 
  • This limitation has serious health implications, such as:
    Reduced nutrition due to impaired mastication,
    Difficulty in speaking, and
    Compromised oral hygiene.

Normal Mouth Opening

  • The Maximal Interincisal Opening (MIO) or normal range of mouth opening varies from person to person and usually ranges between 40-60mm (some authors, however, insist on a 35 mm). 
  • It is equivalent to two-three finger breadths when inserted sideways with lateral movement of 8-12mm.

Etiology/Causes

Trismus has several potential causes, which are single and range from simple and non-progressive to those are complex and potentially life-threatening.

Congenital Disorders
  • Hypertrophy of the coronoid process causes interference of the coronoid against the anteromedial margin of the zygomatic arch.
  • Pierre-Robin syndrome
  • Trismus-pseudo-camptodactyly syndrome




Infections
  • Trismus is a typical symptom of masticatory space infections.
  • Infections causing Trismus could be odontogenic or non-odontogenic in nature. 
    • Odontogenic infections include pulpal infections, periodontal infections, and pericoronal infections.
    • Non-odontogenic infections include tonsillitis, tetanus, meningitis, parotid abscess, and brain abscess.




Trauma
  • Fracture or dislocation of the zygomatic arch,
  • Hemarthrosis/Hematoma, 
  • Temporomandibular Joint (TMJ) contusion, 
  • Intra-articular bone islands/foreign bodies, 
  • Displaced meniscus, 
  • Injury to muscles of mastication.



Iatrogenic
  • 3rd molar extraction-related inflammation, 
  • Inaccurate nerve block injection procedure, 
  • Puncturing medial pterygoid muscle or vessels,
  • Radiotherapy for head and neck cancer


Neoplasia
  • Malignant tumors involving the mandible, muscles of mastication, and associated structures.
  • Primary tumors or neoplastic diseases occurring in many parts of the body could metastasize to the epipharyngeal region, parotid gland, mandible, or temporomandibular joint.


Radiotherapy
  • Involvement of the medial pterygoid muscles during the radiotherapy around the head and neck region. 
  • When the muscles of mastication are within the field of radiation, fibrosis may lead to Trismus. It is attributed to the ischemia caused by endarteritis obliterans.




Temporomandibular Disorders
  • TMJ disorders are divided into intra-articular or extra-articular. 
    • Intra-articular causes include fibrous ankylosis, anchored disc phenomenon, bilateral anterior disc displacement without reduction, arthritis, and unilateral condylar hypoplasia. 
    • The extra-articular covers all myofascial-related causes.


Drugs
  • Due to secondary effect of some drugs 
    • Succinylcholine, Phenothiazines, Tricyclic Antidepressants, Metaclopramide, Phenothiazines.

Psychogenic
  • Hysteria is a cause of Trismus. Electromyography is a useful test in diagnosing Hysterical Trismus.

Miscellaneous
  • Trismus can be associated with multiple sclerosis, pseudobulbar palsy, lupus erythematoses, scleroderma, acquired deformity e.g. burns, and neck flexion deformity.

Classification of Trismus

Based on Range of Mouth Opening
  • Mild trismus = 30-40mm
  • Moderate trismus = 15-30mm
  • Severe trismus = ≤15


Based on Duration
  • Acute trismus
  • Subacute trismus
  • Chronic trismus
Based on Aetiology
  • Intra-articular
  • Extra-articular

Clinical Features

The clinical sign depends on the cause of the Trismus. Some common signs are:
  • Restricted mouth opening: preventing the 2-3 fingers positioned side by side from fitting into the interincisal space.
  • The inability to perform lateral mandible movements.
  • Pain during forced mouth opening.
  • Elicits Pain: Palpation of the masticatory muscles affected in the acute phase.
  • Improper function of muscles due to spasms causes deviation of the mandible.
  • A sensation of muscle tightness, cramping, or stiffness
  • Diffuse facial swelling
  • Fever when associated with infections.
  • Hot Potato Voice: Speech impairments.
  • Weight loss due to impacted oral intake (mastication).
  • Poor oral hygiene
  • Difficulty breathing

Diagnosis

  • History: A detailed history is investigated to establish the cause and duration of the Trismus.
  • Measurement: Active and passive mouth openings are measured from the upper incisor to the lower incisor. Trismus is diagnosed when the mouth opening is less than 35mm.
  • Screening of neck mobility to rule out neck muscle shortening, especially the flexors.
  • Palpate masticatory muscle for tenderness. Also, palpate the TMJ (using index fingre in the patient's ear) to determine the available motion at the TMJ.
  • Imaging to determine its etiology and determine the articular involvement of the TMJ. 
    • Computed tomography may be useful to identify traumatic etiologies including hematomas or facial and mandibular fractures. 
    • Magnetic resonance imaging may also be helpful in identifying space-occupying lesions or abnormalities in the pharyngeal or oral structures.

Management

  • The management/treatment depends upon the aetiological factors.
  • In case of mild pain and dysfunction, Heat therapy, Analgesics, a Soft diet, and Muscle relaxants are usually prescribed to manage the initial phase of muscle spasms.
  • Heat Therapy: It involves using a moist hot towel on the affected area to increase the extensibility of collagen tissue. It increases blood flow, decreases stiffness, relieves pain and spasms, and helps resolve inflammations.
  • Medical Management
    • Aspirin is used to manage pain and inflammation.
    • Narcotic analgesic to manage more intense discomfort.
    • Botulinum treatment injections (a latest treatment modality) to manage the pain. Recommended doses are 25IU into each masseter and 10IU into the temporalis muscle.
    • In the case of Trismus due to a wisdom tooth, administration of local anesthesia may be difficult. A closed-mouth nerve block is used to help the patient open the mouth for appropriate dental treatment.
    • An appropriate antibiotic for infection-associated Trismus.
  • Physiotherapy
    • It is advised, once the acute phase is over.
    • The patient can start with 7-7-7. This involves assisted closing and opening of mouth seven times, followed by holding the maximum open position (that can be sustained without pain) for seven seconds. The patient should repeat the exercise for seven times a day.
    • Chewing sugarless gum help in achieve lateral movement of the TMJ.
  • Surgery
    • Surgical management is rare and directed toward the etiology.
    • Intracapsular TMJ pathosis, bony interferences from styloid or coronoid processes, the presence of a foreign body or restrictive maxillomandibular bands, or dense scar tissues may require surgical intervention.
    • Laser is used for lysis of fibrotic band formation in the submucosa.
  • Trismus Appliances 
    • Various appliances are used in combination with physical therapy.
    • According to their design, they act externally or internally. 
      • Externally Activated Devices
        • Inflatable Bite Opener
        • Dynamic Bite Opener
        • Threaded Tapered Screw
        • Shell Shaped Mouth Opener
        • Screw-Type Mouth Gag
        • Tongue Blades
        • Fingers
        • Therabite Jaw Motion Rehabilitation System.
      • Internally Activated Devices
        • Tongue Blades
        • Plastic Tapered Cylinder

Prognosis

  • Trismus is most commonly self-limited and transient, usually resolving within two weeks. 
  • Patients who develop fibrosis from radiotherapy, the course of trismus may be longer and refractory to conservative treatment. 
  • Successful treatment's critical factors are early detection, correct surgery approach, implementation of an intensive physiotherapy program, and good post-operative conduct.

References

1. Textbook of Oral Medicine by Anil Govindrao Ghom and Savita Anil Ghom
2. Textbook Of Oral Medicine, Oral Diagnosis And Oral Radiology by Ravikiran Ongole and Praveen B N
3. Clinical Manual for Oral Medicine and Radiology by Ongole
4. Dhanrajani PJ, Jonaidel O. Trismus: aetiology, differential diagnosis and treatment.  https://pubmed.ncbi.nlm.nih.gov/11928347/

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