Continuing Education Activity

Trismus is commonly referred to as lockjaw and is usually due to sustained tetanic spasms of the muscles of mastication. Although it was initially described in the setting of tetanus, it is now used to refer to a bilateral restriction in mouth opening from any cause. This activity reviews the evaluation and management of trismus and highlights the role of interprofessional team members in collaborating to provide well-coordinated care and enhance patient outcomes.

Objectives:

• Review the etiology of trismus.
• Outline the presentation of a patient with trismus.
• Summarize the treatment options for trismus.
• Outline the importance of enhancing care coordination among the interprofessional team to ensure proper evaluation and management of trismus.

Introduction

Trismus refers to the restriction of the range of motion of the jaw. Initially described in the setting of tetanus, it currently refers to restricted mouth opening due to any etiology. It is usually temporary and typically resolves in less than two weeks, but permanent trismus may also occur, interfering with everyday activities such as speaking, eating, and swallowing and complicating oral hygiene and the delivery of dental procedures.[1][2]

Etiology

Multiple conditions can result in trismus. Acute trismus may be caused by facial, mandibular, or iatrogenic trauma. Examples of iatrogenic trauma include third molar extraction and intramuscular administration of anesthesia.[3] Acute trismus from iatrogenic causes tends to be self-limiting.[3] Severe trauma usually causes chronic trismus.[3]

Chronic trismus may arise from temporomandibular disorders, neoplasia, surgery, radiotherapy in the head and neck for managing cancer, local infections, and connective tissue disorders like lupus erythematosus.[3]

Trismus As a Complication of Local Anesthesia

Trismus is a possible complication of the inferior alveolar nerve block (IANB). During the administration of this block, the masticatory muscles can be accidentally penetrated, mainly the medial pterygoid muscle, resulting in pain-related trismus. When the affected muscle stretches, it triggers pain, causing its immediate reflex contraction and mandibular opening limitation.[4] Trismus may also arise when an intramuscular hematoma occurs.[4] Injury to the inferior alveolar artery or vein may lead to hematoma in the pterygomandibular space, resulting in trismus.[4] Trismus after two to three days of the injection is most likely caused by a needle track infection.[4]

Trismus As a Complication of Dental Extractions

Pain, trismus, and swelling are common complications of the surgical extraction of mandibular third molars.[5] Such complications result from the inflammatory response to surgical trauma and are classically short-term.[5][6][5]

Trismus As a complication of Trauma to the Face and Mandible

Fractures, mainly mandibular, may result in limited mouth opening.[1] Although rare, fractures of the zygomatic arch and zygomaticomaxillary complex have the potential to cause trismus as they impede the movement of the coronoid process.[1]

Trismus As a sign Of Temporomandibular Disorders (TMD)

Temporomandibular disorders refer to the dysfunction and pain of the temporomandibular joint (TMJ) and muscles of the mastication.[7] TMDs typically cause facial and preauricular pain, functional noises in the TMJ, and limitation in mandibular movement.[7] Therefore, many patients reporting limited mouth opening are likely to have a TMD. Myofascial pain and disc displacement without reduction are two common types of TMD that may cause trismus.[8]

Trismus As a Complication of Dental Infection

Dental infection must be suspected in patients presenting with acute trismus, as severe dental infections involving the masticatory muscles often cause trismus.[9] These infections can extend into the head and neck spaces and result in life-threatening complications, like mediastinitis and cervical cellulitis.[1] From the infections of dental origin, pericoronitis is more associated with trismus.[1] Examples of infections from non-odontogenic sources that may trigger trismus include tonsillitis, parotid abscess, tetanus, meningitis, and brain abscess.[1]

Trismus as a Sign of Malignancy

Patients presenting with limited mouth opening and pain in the pre-auricular area are likely to be diagnosed as having a TMD.[10] However, although less common, trismus may also be caused by malignancy.

Trismus rarely presents as the primary sign of malignancy, but it should not be ruled out. Cases of misdiagnosis of trismus as TMD leading to delayed diagnosis of malignancy have been described in the literature. For example, a case of a 62-year-old patient presenting with severe trismus and TMJ pain who was misdiagnosed as having a TMD and underwent treatment but was found to have adenocarcinoma of the temporal region a year later.[10] For this reason, a specialist TMD clinic has developed a checklist to identify trismus cases with atypical features.[8] If a patient presents with any of the following five signs and symptoms, radiographs and referral to a senior clinician must be considered.[8]

1. Opening less than 15 mm
2. No history of clicking
3. Pain of non-myofascial origin (e.g., neuralgia)
4. Lymphadenopathy
5. Suspicious intra-oral soft tissue lesion

Trismus As a Complication Of Head and Neck Cancer Treatment

Trismus is a common side effect of head and neck cancer and its treatment.[11] According to recent studies, it develops in 38% to 42% of head and neck cancer patients.[12][13]

The temporomandibular joint or the mastication muscles can experience fibrosis because of radiotherapy, leading to trismus.[11] The risk of trismus goes up when the medial pterygoid muscle is in the radiation zone.[14] Furthermore, surgical procedures to treat head and neck cancer can scar the mastication muscles and restrict mandibular opening.[15]

Classification

Multiple conditions can result in trismus. Some authors classify trismus according to the involvement of the temporomandibular junction (TMJ) in intraarticular and extraarticular etiologies.[2] Others have outlined the causes into broad categories, such as infectious, traumatic, and neoplastic sources.[1] Trismus may also be iatrogenic, resulting from prescribed interventions and treatments. Below are some of the conditions associated with trismus:

Traumatic

• Hemarthrosis/hematoma
• Fracture or dislocation of the mandible or zygomatic arch
• Temporomandibular joint (TMJ) contusion
• Intraarticular bone islands/foreign bodies
• Displaced meniscus
• Direct injury to muscles of mastication

Inflammatory

• Osteoarthritis
• Soft tissue fibrosis
• TMJ ankylosis
• Rheumatoid arthritis
• Scleroderma
• Temporal arteritis

Infectious

• Pyogenic arthritis
• Osteomyelitis of the mandible
• Tonsillitis
• Peritonsillar or other pharyngeal abscesses
• Tetanus
• Odontogenic abscess
• Mumps
• Parotid abscess

Congenital Malformations

• Pierre-Robin sequence         
• Trismus-pseudocamptodactyly syndrome

Head and Neck Neoplasms

• Pharyngeal carcinoma
• Parotid gland tumors

Odontogenic

• Impacted third molar (or following extraction thereof)

Iatrogenic

• Perioperative inflammation
• Radiotherapy for head and neck cancer

Neurogenic

• Tetanus
• Status epilepticus
• Parkinsonism
• Strychnine, phenothiazine poisoning
• Medication adverse effect (phenothiazines, metoclopramide, tricyclic antidepressants)
• Hypocalcemia, hypomagnesemia, respiratory alkalosis

Psychogenic (conversion disorder)

Epidemiology

The prevalence of trismus ranges widely, partly because no clear criteria have been established, and depends on the inciting etiology. Importantly, trismus is a common finding in certain patient populations, such as those with congenital micrognathia syndromes or undergoing radiation therapy for head and neck cancers.[16][17] It can also be a relatively rare complication of common conditions, such as pharyngitis.

History and Physical

Normal mouth opening ranges between 40 to 60 cm (two to three finger breadths), and many authors consider a maximum mouth opening of less than 35 mm trismus.[1] However, it varies from individual to individual, and even according to sex, males generally feature a wider mouth opening.[1]

Patients presenting with trismus will note a restricted mouth opening and sometimes pain when attempting to open the mouth. However, patients often have complaints related to the causative condition rather than the resulting trismus. Those with odontogenic etiologies may complain of tooth or gum pain and swelling; patients with traumatic causes may note facial or mandibular pain. A complete clinical examination should be performed to identify systemic causes. Fever may indicate an infectious source; weight loss may be notable among patients with neoplastic causes; carpopedal spasms and paresthesias may accompany trismus in patients with neurogenic or metabolic causes. A history of tobacco use or known cancer could raise suspicion of a neoplastic cause.[1]

Trismus may also be encountered when attempting to visualize the oral and pharyngeal structures during a physical exam. This challenges the examining clinician's attempt to ascertain the cause of trismus. As much as possible, the exam should be targeted to the teeth and gums; facial bones and TMJ; pharyngeal pillars, tonsils, uvula; and the neck.

Assessment of the patient's speech may be necessary; some pharyngeal infections implicated in trismus may also cause changes in the patient's voice; a "hot potato voice" may be associated with tonsillitis or peritonsillar abscess. A directed neurologic exam should be performed to evaluate for neurogenic causes.[2]

Evaluation

The diagnosis of trismus is mainly clinical. Imaging adjuncts may be useful to determine its etiology and the TMJ's articular involvement. Computed tomography can help to identify traumatic etiologies, including hematomas or facial and mandibular fractures. Magnetic resonance imaging may identify space-occupying lesions or abnormalities in the pharyngeal or oral structures.

Treatment / Management

Treatment of trismus is directed at the inciting etiology and is most commonly managed symptomatically. Symptom-directed interventions, including heat therapy, analgesics (NSAIDs), and muscle relaxants, are usually prescribed in the acute phase and are the mainstays for treating uncomplicated transient trismus. Heat therapy includes applying moist hot towels for 15 to 20 min per hour.[1] When it comes to analgesics, aspirin is usually sufficient.[1] When a muscle relaxant is needed, a benzodiazepine, such as diazepam, is recommended with a dose of 2.5 to 5 mg three times per day.[1] The clinician should also encourage a soft diet for the duration of the pathology.[1]

Further dental treatment must be avoided until the trismus resolves,[18] usually within 48 hours of initiating treatment.

Stretching exercises may be indicated after the acute phase or in patients with post-traumatic and post-operative trismus, particularly when persisting longer than one week. The exercises typically consist of repeated attempts to open the mouth against applied resistance, usually divided into multiple sessions per day.[11] Physiotherapy includes opening and closing the mouth and lateral movements for 5 min every 3 to 4 hours.[19] Sugar-free chewing gum can be indicated to stimulate lateral movements.[1]

Physical therapy is performed in an attempt to alleviate edema and fibrosis, restore blood circulation, improve range of motion and muscle strength, and keep the muscle active.[3]

Trismus may become chronic in the setting of fibrosis or ongoing radiotherapy. These cases may benefit from intensive physiotherapy, sometimes utilizing commercially available jaw motion rehabilitation devices or microcurrent therapy, particularly in patients refractory to more conservative approaches. Some authors have also described treatment with xanthine derivatives such as pentoxifylline.[1][20]

If trismus does not improve after 2 to 3 days, or in cases of extreme trismus, referral to an oral and maxillofacial surgeon should be considered.[1]

Extreme trismus cases that are repeatedly refractory to treatment require surgical procedures, like reducing the mandibular height to achieve a larger mouth opening, coronoidectomy, or tissue release and free flap reconstruction.[11]

The treatment of trismus is summarized in the table below.[1][11][1]

Differential Diagnosis

Since trismus has been defined as a restriction in mouth opening regardless of etiology, it does not have a wide differential diagnosis. Some authors have argued that "true trismus" is mediated via the trigeminal nerve, and intraarticular causes of impaired mouth opening, such as TMJ ankylosis or fibrosis, should be considered separately.[1] Others have outlined such intraarticular processes as subclassifications of trismus.[20]

Prognosis

Trismus is most commonly self-limited and transient, typically resolving within two weeks. However, in certain cases, like patients who develop fibrosis from radiotherapy, the course of trismus may be longer and refractory to conservative treatment.[17]

Complications

Trismus interferes with speaking, eating, and swallowing; it has also been associated with aspiration due to impaired swallowing mechanisms. Intubation via the oropharyngeal route may be impossible in patients with significant trismus, necessitating other approaches such as nasopharyngeal intubation or tracheotomy. When its duration is prolonged, it leads to TMJ fibrosis, necessitating directed therapy.[20]

Consultations

Consultation may be considered based on the suspected etiology. Dental or oral surgery care may be enlisted for odontogenic causes, while an otolaryngologist is, at times, consulted for drainage of a peritonsillar abscess. Physiatrists may also be involved in a patient's care when directed therapeutic interventions are necessary to treat refractory trismus.[1]

Deterrence and Patient Education

Patients should receive counsel to rest their jaw, avoid activities like nail-biting and teeth clenching, and work with a physical therapist on jaw muscle strengthening in certain cases.

Pearls and Other Issues

• Trismus most commonly occurs in the setting of uncomplicated common conditions (e.g., wisdom tooth extraction); it may also be a relatively common complication of uncommon diseases (fibrosis following head and neck radiotherapy).
• Trismus is best addressed by identifying the inciting etiology and directing treatment to the underlying cause.
• Most cases of trismus resolve following symptom-directed treatment with heat therapy and NSAIDs.
• Refractory chronic trismus may require physiotherapeutic interventions.
• Implementing a checklist to identify cases of trismus with an atypical presentation may help identify cases of malignancy at early stages.
• Mandibular opening devices are usually prescribed by a specialist or physiotherapist.

Enhancing Healthcare Team Outcomes

Due to the wide variety of trismus etiology, the condition is best managed by an interprofessional team. Consultation may be considered based on the suspected etiology. Dental or oral surgery care may be enlisted for odontogenic causes, while an otolaryngologist is, at times, consulted for drainage of a peritonsillar abscess. Physiatrists may also be involved in a patient's care when directed therapeutic interventions are necessary to treat refractory trismus.[1] The outcomes are good if the primary cause can be treated. However, in patients with severe trauma, scarring, and radiation therapy, trismus may be chronic and lead to poor quality of life.[21][22][23][24] [Level 5]