Lockjaw or trismus is defined as the decreased ability to open the mouth fully (jaw hypomobility) . Trismus has also been described as a sustained contraction of the chewing (masticatory) muscles . An individual with trismus usually cannot open the mouth by more than 35-40 mm (3 fingers wide) [1,6].
The jaw can be locked in a closed position with the limited ability to open the mouth (closed lock) or in an open position with inability to close the mouth completely (open lock).
The medical term trismus originates from the Greek trismos, which means grating, grinding or rasping .
Trismus may or may not be associated with jaw pain.
Symptoms and Signs
Trismus can develop suddenly or gradually and can include [1,3]:
- Decreased range of motion in the temporomandibular joint (TMJ)
- Decreased ability to chew, talk, sing, yawn and brush the teeth
- Difficulty swallowing or choking
- Stiffness, severe or dull aching pain, tenderness or swelling in the chewing muscles
- Grating, cracking, clicking or popping sounds during the movements of the lower jaw
- Deviation of the jaw toward the affected side
- Earache, headache
- Fever (in infections)
The distance between the front upper and lower teeth (incisors) when the mouth is fully open is used for the trismus grading :
- Mild: >30 mm
- Moderate: 15-30 mm
- Severe: <15 mm
Causes of lockjaw include:
- TEETH problems:
- Dental work that includes prolonged mouth opening or an injection of the local anesthetic
- Wisdom tooth impaction or removal
- MOUTH and THROAT problems:
- Pericoronitis (inflammation of the gum around the tooth crown)
- Oral submucous fibrosis (due to areca nut chewing)
- Removal of the tonsils
- Strep throat
- Cancer in the mouth, throat, parotid or other salivary glands
- BRUXISM: teeth grinding at night with jaw stiffness in the morning
- TEMPOROMANDIBULAR DISORDER (TMD)
- Psychological causes: stress, anxiety, depression, hysteria, malingering (the fabricating of symptoms)
- Disorders of the temporomandibular joint (TMJ): arthritis in the temporomandibular joint (osteoarthritis, rheumatoid arthritis, gout), TMJ disc displacement
- Ankylosis (abnormal bone adhesion) of the temporomandibular joint due to trauma, infection, rheumatoid arthritis or ankylosing spondylitis
- TRAUMA: contusion, fracture of the lower jaw (mandible), needlestick injury, burns, prolonged jaw immobilization after trauma (which leads to muscle wasting – atrophy), scars
- ELECTROLYTE imbalance: hypocalcemia (tetany)
- Lyme disease (spread by ticks) 
- Mumps (viral infection of the parotid glands)
- Meningitis (infection of the soft brain membrane)
- Trichinosis (a parasitic infection)
- Tetanus (a rare infection that can develop in deep wounds)
- Osteomyelitis (infection of the lower jaw bone)
- INFLAMMATORY diseases:
- Giant cell or temporal arteritis
- Systemic lupus erythematosus (SLE)
- Myositis (polymyositis)
- NEUROLOGICAL disorders:
- Damage of the trigeminal or glossopharyngeal nerve
- Multiple sclerosis
- Parkinson’s disease
- Brain tumor
- CONGENITAL diseases:
- Abnormal bony elongation of the coronoid process in the lower jaw
- Gaucher’s disease
- Iida-Kannari syndrome
- Hecht syndrome (trismus-pseudocamptodactyly syndrome)
- Trotter’s syndrome
- Antimalarials (chloroquine, quinine), antipsychotics (phenothiazines: chlorpromazine), antihistamines (diphenhydramine, loratadine), antiemetics (domperidone, metoclopramide, prochlorperazine), tetrabenazine, chemotherapy, succinylcholine, tricyclic antidepressants
- Illegal drugs (stimulants) : amphetamine, cocaine , ecstasy (MDMA), gamma-hydroxybutyrate (GHB)
- SURGERY-related: tracheal intubation and general anesthetics (halothane)
- RADIATION THERAPY of cancer in the head or neck area (trismus can develop within 12 months after the onset of the therapy)
- Poisonous snake or spider bite
- Horseshoe crab poisoning
- Strychnine poisoning
- References: 1,4,5,6,8
Severe lockjaw increases the risk of choking (aspiration of food), malnutrition and bad mouth hygiene.
Treatment And Prevention
If you have trismus, you should seek treatment early to prevent wasting (atrophy) of the chewing muscles and eventual permanent jaw hypomobility. It is usually a dentist who treats trismus.
Treatment of trismus can include removal of the cause, massage, physiotherapy, jaw exercises, analgesics (aspirin, acetaminophen, ibuprofen), muscle relaxants . and, in severe trismus after radiation therapy, botulinum toxin injection .
Apply warm, moist compresses for 15-20 minutes every hour to decrease the pain .
Avoid hard-to-chew foods, chewing gum, nail biting, singing and wide yawning.
“Passive motion” of the jaw after radiation therapy is described here.
Several other exercises to relieve lockjaw are described here.
Frequently Asked Questions
What does lockjaw feel like?
Lockjaw can be associated with severe or dull pain or no pain at all.
How long does lockjaw last?
Lockjaw can last from few hours to months or years (until the underlying condition is present).
Why does lockjaw occur in TMJ?
In temporomandibular joint dysfunction (TMJ, TMD), lockjaw can occur due to:
- Stress that results in an increased tension of the chewing muscles
- “Muscle guarding,” which is a muscle spasm that develops as a reaction to a painful condition in the jaw, chewing muscles, mouth or ear.
- TMJ dislocation
- TMJ disc displacement
Can you die from lockjaw?
Lockjaw alone does not cause death but can make you unable to eat.
What causes lockjaw after wisdom tooth extraction?
An inflammation called “dry socket,” which can develop several days (3-5) after wisdom tooth removal can cause lockjaw, throbbing pain in the jaw and numbness in the gum .
What disease is also known as lockjaw?
The term lockjaw is sometimes used as a synonym for tetanus — a rare bacterial infection that causes muscle spasms all over the body.
- Trismus The Oral Cancer Foundation
- Trismus Online Etymology Dictionary
- How do I Manage a Patient with Trismus? Canadian Dental Association
- Causes of trismus RightDiagnosis
- Trismus, Jaw Hypomobility, and Lockjaw CranioRehab.com
- Walker M et al, 2006, Trismus: diagnosis and management, considerations for speech pathologist American Speech-Language-Hearing Association
- Wisdom tooth removal complications NHS Choices
- Gahlinger PM et al, 2004, Club Drugs: MDMA, Gamma-Hydroxybutyrate (GHB), Rohypnol, and Ketamine American Family Physician
- Grosset KA et al, 2004, Prescribed drugs and neurological complications BMJ Journals
- Hartl DM et al, 2008, Botulinum toxin for radiation-induced facial pain and trismus PubMed
- Burnett LB, Cocaine toxicity, clinical presentation Emedicine