Health

Which nerve causes trismus?

Which nerve causes trismus?

    We all must have at least experienced immense stress or pain around the jaw that causes discomfort when there is jaw movement such as when eating or talking. While it is sensible to feel that way to a certain degree, there are conditions that can cause difficulty to the jaw to move, making it painful for the person experiencing it. One of them is trismus. In this DoctorOnCall’s article, we will learn about trismus.

   Trismus is a general term describing a condition where a person has difficulty opening the mouth. The normal full jaw opening is 40 to 60 millimetres. This measurement is taken from the edge of the lower front teeth to the edge of the upper front teeth. Thus, when the jaw opens less than 40 millimetres, it can be suspected as a trismus. Studies show that the maximum mouth opening less than 35 millimetres is already considered as trismus. Trismus itself is a symptom or sign for many medical conditions. It should not be considered a diagnosis or a disease as an entity itself.

    In the past, trismus was restricted to the effect from tetanus known as ‘lock-jaw’. However, the term is now used to describe any restrictions to mouth opening caused by many reasons. Trismus are usually a temporary issue and should disappear in less than 2 weeks but there are reports that trismus can be a permanent issue. Due to the fact that trismus can be caused by many causes, the true number of those affected by trismus is unclear. One thing for sure, trismus is common in certain groups of people such as those with congenital micrognathia syndrome (a condition of undersized jaw with a variety of conditions affecting face and head) and those undergoing radiation therapy for cancers affecting head or neck.

    Since trismus makes the opening of the mouth difficult or small, have you ever wondered what nerve is affected? The nerves affected are known as the trigeminal nerve. Trigeminal nerve is the 5th cranial nerve and the largest cranial nerve. Trigeminal nerve is branched into three. One of the three branches, known as mandibular division, is responsible for jaw movement, specifically mastication (chewing action). Thus, trismus occurs when this specific branch from the trigeminal nerve, innervating the muscles related to the jaw, is affected.

   There are many causes that could lead to trismus. This includes tumours that grow into the muscle of the jaw, surgery to remove tumour of head and neck, radiation therapy to treat neck or head cancer, complication from dental extraction specifically the molar teeth, trauma to the face or jaw, complication of dental infection and psychological effect such as from anxiety disorder. Due to the fact that there are many causes possible for trismus, patients who have symptoms should get checked by doctors.

    Beside symptoms or signs of the difficulty to open the jaw fully or mouth opening less than 35 millimetres, there are other signs a person could be having trismus. Symptoms are pain when trying to open the mouth, gum pain or swelling, facial pain and fever. Headache and earache may also be symptoms. Difficulty chewing or swallowing food can be a subtle sign of trismus. Patients may also have difficulty speaking as there is limitation to mouth opening. Unintentional weight loss is considered a suspect for trismus caused by tumour or cancer. Infection may cause voice changes such as a ‘hot potato voice’ when it infects the throat due to the trismus.

   You can check for yourself if you may have trismus. You do not necessarily need to measure it in a mathematical manner. The 3 finger test is the easiest way to check trismus for yourself. Stack the 3 fingers between the upper and lower teeth. When it is possible to stack the finger comfortably and the mouth opens wide enough, it is unlikely to be a trismus.

  Treatment depends on the cause of trismus. In general, the earlier a person gets treatment, the better outcome is. This is especially true in cases with suspicion of cancer as detecting earlier can provide better treatment options. Common treatments are pain relief such as nonsteroidal anti-inflammatory drugs (NSAIDs), muscle relaxants such as diazepam and heat therapy. Heat therapy is done by placing hot damp towels around 15 to 20 minutes per hour. Patients are encouraged to have a soft diet such as soup, mashed potato, steamed vegetables, fish and smoothies to ease symptoms. Extensive dental treatments have to be avoided until trismus disappears. There is a jaw-stretching device that can help improve trismus. Surgery may be offered to those with extreme trismus.

  Trismus is more than just difficulty to open the mouth. It can lead to many issues that can affect a person’s quality of life. Issues such as difficulty eating, infection to the skin and oral hygiene problems are among the common problems faced by those with trismus. It may also lead to speaking problems which may affect a person’s daily life in a social setting.

Also read – Dengue Prevention.

 

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