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Trigeminal neuralgia

Fothergill's disease, Prosopalgia, Tic doloureux, TN, TGN

Overview

Trigeminal neuralgia is a neuropathic disorder characterized by episodes of intense pain in the face. It has been described as among the most painful conditions known. The pain originates from a variety of different locations on the face and may be felt in front of the ear, eye, lips, nose, scalp, forehead, cheeks, mouth, or jaw and side of the face.

Trigeminal neuralgia is a chronic pain condition that affects the trigeminal nerve, which carries sensation from your face to your brain. If you have trigeminal neuralgia, even mild stimulation of your face — such as from brushing your teeth or putting on makeup — may trigger a jolt of excruciating pain.

You may initially experience short, mild attacks. But trigeminal neuralgia can progress and cause longer, more-frequent bouts of searing pain. Trigeminal neuralgia affects women more often than men, and it's more likely to occur in people who are older than 50.
Because of the variety of treatment options available, having trigeminal neuralgia doesn't necessarily mean you're doomed to a life of pain. Doctors usually can effectively manage trigeminal neuralgia with medications, injections or surgery.

The pain of TN is from the trigeminal nerve. The trigeminal nerve is a paired cranial nerve that has three major branches: the ophthalmic nerve (V1), the maxillary nerve (V2), and the mandibular nerve (V3). One, two, or all three branches of the nerve may be affected. 1–6% of cases occur on both sides of the face but extremely rare for both to be affected at the same time. Trigeminal neuralgia most commonly involves the middle branch (the maxillary nerve or V2) and lower branch (mandibular nerve or V3) of the trigeminal nerve.

Symptoms - Trigeminal neuralgia

Trigeminal neuralgia symptoms may include one or more of these patterns:

  • Episodes of severe, shooting or jabbing pain that may feel like an electric shock
  • Spontaneous attacks of pain or attacks triggered by things such as touching the face, chewing, speaking and brushing teeth
  • Bouts of pain lasting from a few seconds to several minutes
  • Episodes of several attacks lasting days, weeks, months or longer — some people have periods when they experience no pain
  • Constant aching, burning feeling that's less intense than the spasm-like pain
  • Pain in areas supplied by the trigeminal nerve, including the cheek, jaw, teeth, gums, lips, or less often the eye and forehead
  • Pain affecting one side of the face at a time, though may rarely affect both sides of the face
  • Pain focused in one spot or spread in a wider pattern
  • Attacks that become more frequent and intense over time

Causes - Trigeminal neuralgia

The trigeminal nerve is a mixed cranial nerve responsible for sensory data such as tactition (pressure), thermoception (temperature), and nociception (pain) originating from the face above the jawline; it is also responsible for the motor function of the muscles of mastication, the muscles involved in chewing but not facial expression.

Several theories exist to explain the possible causes of this pain syndrome. It was once believed that the nerve was compressed in the opening from the inside to the outside of the skull; but newer leading research indicates that it is an enlarged blood vessel – possibly the superior cerebellar artery – compressing or throbbing against the microvasculature of the trigeminal nerve near its connection with the pons. Such a compression can injure the nerve's protective myelin sheath and cause erratic and hyperactive functioning of the nerve. This can lead to pain attacks at the slightest stimulation of any area served by the nerve as well as hinder the nerve's ability to shut off the pain signals after the stimulation ends. This type of injury may rarely be caused by an aneurysm (an outpouching of a blood vessel); by an AVM (arteriovenous malformation); by a tumor; by an arachnoid cyst in the cerebellopontine angle; or by a traumatic event such as a car accident.

Short-term peripheral compression is often painless, with pain attacks lasting no more than a few seconds. Persistent compression results in local demyelination with no loss of axon potential continuity. Chronic nerve entrapment results in demyelination primarily, with progressive axonal degeneration subsequently. It is, "therefore widely accepted that trigeminal neuralgia is associated with demyelination of axons in the Gasserian ganglion, the dorsal root, or both." It has been suggested that this compression may be related to an aberrant branch of the superior cerebellar artery that lies on the trigeminal nerve. Further causes, besides an aneurysm, multiple sclerosis or cerebellopontine angle tumor, include: a posterior fossa tumor, any other expanding lesion or even brainstem diseases from strokes.

Trigeminal Neuralgia is found in 3–4% of people with Multiple Sclerosis, according to data from seven studies. Only two to four percent of patients with TN, usually younger, have evidence of multiple sclerosis, which may damage either the trigeminal nerve or other related parts of the brain. It has been theorized that this is due to damage to the spinal trigeminal complex. Trigeminal pain has a similar presentation in patients with and without MS.

Postherpetic neuralgia, which occurs after shingles, may cause similar symptoms if the trigeminal nerve is damaged.

When there is no [apparent] structural cause, the syndrome is called idiopathic.

Triggers:

A variety of triggers may set off the pain of trigeminal neuralgia, including:

  • Shaving
  • Touching your face
  • Eating
  • Drinking
  • Brushing your teeth
  • Talking
  • Putting on makeup
  • Encountering a breeze
  • Smiling
  • Washing your face

Prevention - Trigeminal neuralgia

Trigeminal neuralgia cannot be prevented.

Diagnosis - Trigeminal neuralgia

Trigeminal neuralgia diagnose mainly based on description of the pain, including:

  • Type. Pain related to trigeminal neuralgia is sudden, shock-like and brief.
  • Location. The parts of your face that are affected by pain will tell your doctor if the trigeminal nerve is involved.
  • Triggers. Trigeminal neuralgia-related pain usually is brought on by light stimulation of your cheeks, such as from eating, talking or even encountering a cool breeze.

 

To conduct many tests to diagnose trigeminal neuralgia and determine underlying causes for your condition, including:

Neurological examination:

Touching and examining parts of the face can help determine exactly where the pain is occurring and -if it appear to have trigeminal neuralgia-which branches of the trigeminal nerve may be affected. Reflex tests also can help determine if the symptoms are caused by a compressed nerve or another condition.

Magnetic resonance imaging (MRI):

MRI scan of the head to determine if multiple sclerosis or a tumor is causing trigeminal neuralgia. In some cases,the doctor may inject a dye into a blood vessel to view the arteries and veins and highlight blood flow (magnetic resonance angiogram).

Prognosis - Trigeminal neuralgia

After an initial attack, the disorder may remit for months or even years. Thereafter the attacks may become more frequent, more easily triggered, disabling, and may require long-term medication. Overall, the prognosis depends on the cause of the problem. If there is no underlying disease, some people find that treatment provides at least partial relief. In some patients, however, the pain may become constant and severe.

Most cases,the prognosis is good.80% of patients become pain free with medication alone.

Treatment - Trigeminal neuralgia

As with many conditions without clear physical or laboratory diagnosis, TN is sometimes misdiagnosed. A TN sufferer will sometimes seek the help of numerous clinicians before a firm diagnosis is made.

There is evidence that points towards the need to quickly treat and diagnose TN. It is thought that the longer a patient suffers from TN, the harder it may be to reverse the neural pathways associated with the pain.

The differential diagnosis includes temporomandibular disorder. Since triggering may be caused by movements of the tongue or facial muscles, TN must be differentiated from masticatory pain that has the clinical characteristics of deep somatic rather than neuropathic pain. Masticatory pain will not be arrested by a conventional mandibular local anesthetic block.

Dentists who suspect TN should proceed in the most conservative manner possible and should ensure that all tooth structures are "truly" compromised before performing extractions or other procedures.

Treatment options include medicines, surgery, and complementary approaches.

Anticonvulsant medicines—used to block nerve firing—are generally effective in treating trigeminal neuralgia. These drugs include carbamazepine, oxcarbazepine, topiramate, clonazepam, phenytoin, lamotrigine, and valproic acid. Gabapentin or baclofen can be used as a second drug to treat trigeminal neuralgia and may be given in combination with other anticonvulsants.

Tricyclic antidepressants such as amitriptyline or nortriptyline are used to treat pain described as constant, burning, or aching. Typical analgesics and opioids are not usually helpful in treating the sharp, recurring pain caused by trigeminal neuralgia. If medication fails to relieve pain or produces intolerable side effects, surgical treatment may be recommended.

Several neurosurgical procedures are available to treat trigeminal neuralgia. The choice among the various types depends on the patient's preference, physical well-being, previous surgeries, presence of multiple sclerosis, and area of trigeminal nerve involvement. Some procedures are done on an outpatient basis, while others may involve a more complex operation that is performed under general anesthesia. Some degree of facial numbness is expected after most of these procedures, and trigeminal neuralgia might return despite the procedure's initial success. Depending on the procedure, other surgical risks include hearing loss, balance problems, infection, and stroke.

A rhizotomy is a procedure in which select nerve fibers are destroyed to block pain. A rhizotomy for trigeminal neuralgia causes some degree of permanent sensory loss and facial numbness. Several forms of rhizotomy are available to treat trigeminal neuralgia:

  • Balloon compression works by injuring the insulation on nerves that are involved with the sensation of light touch on the face.
  • Glycerol injection involves bathing the ganglion (the central part of the nerve from which the nerve impulses are transmitted) and damaging the insulation of trigeminal nerve fibers.
  • Radiofrequency thermal lesioning involves gradually heating part of the nerve with an electrode, injuring the nerve fibers.
  • Stereotactic radiosurgery uses computer imaging to direct highly focused beams of radiation at the site where the trigeminal nerve exits the brainstem. This causes the slow formation of a lesion on the nerve that disrupts the transmission of pain signals to the brain.

Microvascular decompression is the most invasive of all surgeries for trigeminal neuralgia, but it also offers the lowest probability that pain will return. While viewing the trigeminal nerve through a microscope, the surgeon moves away the vessels that are compressing the nerve and places a soft cushion between the nerve and the vessels. Unlike rhizotomies, there is usually no numbness in the face after this surgery. A neurectomy, which involves cutting part of the nerve, may be performed during microvascular decompression if no vessel is found to be pressing on the trigeminal nerve.

Some patients choose to manage trigeminal neuralgia using complementary techniques, usually in combination with drug treatment. These therapies offer varying degrees of success. Options include acupuncture, biofeedback, vitamin therapy, nutritional therapy, and electrical stimulation of the nerves.

Support:
Psychological and social support has found to play a key role in the management of chronic illnesses and chronic pain conditions, such as Trigeminal Neuralgia. Chronic pain can cause constant frustration to an individual as well as to those around them. As a result, there exists a wealth of support groups for Trigeminal Neuralgia, sufferers and carers, the largest of which is the Trigeminal Neuralgia Association (TNA) which exists in several different countries, including the UK (TNA UK), Australia and America (TNA - Facial Pain Association)

Resources - Trigeminal neuralgia

  • Mayo Clinic
  • NIH
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