Lockjaw, or trismus, is a painful condition characterized by the restricted ability to open the mouth fully. This limitation is typically caused by stiffness or a sustained spasm in the muscles used for chewing, known as the muscles of mastication. A normal adult mouth opening ranges between 35 to 45 millimeters, and trismus is diagnosed when this movement is significantly reduced. The total duration of this restriction is not fixed but varies dramatically depending on the underlying cause.
Duration When Caused by Tetanus
Tetanus represents the most severe and longest-lasting cause of lockjaw, as it results from a systemic bacterial infection. The bacterium Clostridium tetani produces a potent neurotoxin that interferes with nerve signals, causing widespread muscle rigidity and painful spasms. Symptoms of generalized tetanus, which begins with lockjaw, typically appear between 3 and 21 days after exposure to the bacteria, with an average incubation period of about 10 days.
The initial symptoms of jaw stiffness and difficulty swallowing progressively worsen over the first two weeks of the infection. During the peak severity of the disease, patients experience frequent, powerful muscle spasms that can last for several minutes. This intense, generalized muscle rigidity usually continues for approximately three to four weeks, requiring intensive medical support.
Even after the acute phase of muscle spasms subsides, the effects of the neurotoxin are prolonged, and full resolution takes time. The body must metabolize and clear the toxin, and the nerves must recover from the interference. Complete recovery from the prolonged muscle stiffness and spasms may take several months, which is a stark contrast to other, less severe causes of lockjaw.
Timelines for Non-Infectious Causes
When lockjaw is not caused by the tetanus infection, it is usually a localized, temporary condition triggered by physical trauma or inflammation. One of the most common causes is a post-operative complication following oral surgery, particularly the extraction of a wisdom tooth. This form of trismus is a reaction to inflammation or trauma to the jaw muscles during the procedure.
In these surgical cases, the restricted mouth opening is often minor and typically resolves quickly as the local swelling decreases. Patients generally notice a significant improvement within several days to one week. Most cases of post-operative trismus clear up completely within two to three weeks without long-term issues.
Other non-infectious causes, such as injury from a direct blow to the jaw or certain temporomandibular joint (TMJ) disorders, also tend to have a shorter course. Trismus resulting from a dental injection, for instance, usually resolves within about one week. However, if the cause is chronic, such as advanced radiation therapy for head and neck cancers, the resulting fibrosis and stiffness can be long-lasting or even permanent without intervention.
Medical Intervention and Prognosis
The duration of lockjaw is heavily influenced by how quickly and aggressively medical treatment is initiated, regardless of the cause. For non-infectious, temporary causes, the treatment is symptomatic and focused on restoring mobility. This management often involves non-steroidal anti-inflammatory drugs (NSAIDs) for pain and inflammation, along with muscle relaxants to ease the spasms in the chewing muscles.
Physical therapy is a fundamental element of reducing the total time of restriction by actively increasing the range of motion. Clinicians often prescribe specific jaw-stretching exercises and may use specialized devices to gently stretch the jaw muscles. Early compliance with these physical therapy protocols helps prevent the long-term tightening of muscles and joints that can extend the recovery period.
For tetanus-related lockjaw, the intervention is life-saving and focuses on neutralizing the remaining toxin and controlling the severe spasms. Treatment involves administering Tetanus Immune Globulin (TIG) to neutralize unbound toxin, along with sedatives and muscle relaxants. While these interventions cannot immediately reverse the effects of the toxin already bound to the nervous system, this supportive care minimizes complications and helps the patient survive the weeks it takes for the toxin’s effects to wear off.
Prevention
The most effective way to ensure lockjaw lasts zero days is through diligent prevention, particularly against the most dangerous cause, tetanus. The primary defense is the tetanus toxoid vaccine, which trains the immune system to recognize and neutralize the bacterial toxin. Adults require a booster dose of the tetanus and diphtheria (Td) or tetanus, diphtheria, and acellular pertussis (Tdap) vaccine every 10 years to maintain sufficient protection.
If a person sustains a deep or contaminated wound and their vaccination status is uncertain or out-of-date, immediate medical attention is necessary. In these situations, healthcare providers may administer a dose of Tdap along with Tetanus Immune Globulin (TIG) to provide rapid, temporary protection. This combined approach is designed to prevent the onset of the disease, ensuring the individual never develops the severe and prolonged symptoms of lockjaw.