What Is Trigeminal Neuralgia? What Causes Trigeminal Neuralgia?

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Main Category: Pain / Anesthetics
Also Included In: Neurology / Neuroscience
Article Date: 10 Aug 2009 - 0:00 PDT

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Trigeminal Neuralgia, also known as Tic Douloureaux, is a nerve disorder that causes abrupt, searing, electric-shock-like facial pains, most commonly the pain involves the lower face and jaw, but symptoms may appear near the nose, ears, eyes or lips. Many experts say trigeminal neuralgia is the most unbearably painful human condition.

Neuralgia is severe pain along the course of a nerve. The pain occurs because of a change in neurological structure or function due to irritation or damage of a nerve.

Approximately 1 in every 15,000 people is estimated to suffer from trigeminal neuralgia. About 45,000 people have trigeminal neuralgia in the USA. It is thought to affect about one million people worldwide.

Two main types of pain, nociceptive and non-nociceptive pain

An example of nociceptive pain is when something very hot touches your skin; specific pain receptors sense the heat. Nociceptive pain is when pain receptors sense temperature, vibration, stretch, and chemicals released from damaged cells.

Non-nociceptive pain, or neuropathic pain, comes from within the nervous system itself. The pain is not related to activation of pain receptor cells in any part of the body. People often refer to it as pinched nerve, or trapped nerve. The nerve itself is sending pain messages either because it is faulty (damaged) or irritated. People with neuralgia have neuropathic pain (same meaning as non-nociceptive pain).

People with neuralgia describe it as intense burning or stabbing pain, which often feels as if it is shooting along the course of the affected nerve. There are two types of neuralgia - Trigeminal Neuralgia and Postherpetic Neuralgia. This article focuses on Trigeminal Neuralgia.

Description of trigeminal neuralgia (also called tic douloureux)

There is sudden and severe facial nerve pain. Patients typically describe it as a stabbing, shooting pain; like an electric-shock-like facial pain. Bouts of pain can last a few minutes. 97% of patients experience pain just on one side of the face, while 3% are affected on both sides.

Trigeminal neuralgia is twice as common in women as in men. It is extremely rare for people under 40 to be affected, and becomes slightly more common as people get older.

Trigeminal neuralgia is a long-term condition - a chronic condition - which usually gets gradually worse.

What are the causes of trigeminal neuralgia?

The human face has two trigeminal nerves, one on each side. Each nerve splits into three branches which transmit sensations of pain and touch from the face, mouth, and teeth to the brain.

Most cases of trigeminal neuralgia are believed to be caused by blood vessels pressing on the root of the trigeminal nerve. This is said to make the nerve transmit pain signals which are experienced as the stabbing pains of trigeminal neuralgia. However, experts are not completely sure of the cause. Pressure on the trigeminal nerve may also be caused by a tumor or multiple sclerosis.

Below is a list of known and suspected causes:

• A blood vessel presses against the root of the trigeminal nerve.


• Multiple sclerosis - due to demyelinization of the nerve. Trigeminal neuralgia typically appears in the advanced stages of multiple sclerosis.


• A tumor presses against the trigeminal nerve. This is a rare cause.


• Physical damage to the nerve - this may be the result of injury, a dental or surgical procedure, or infection.


• Family history (genes, inherited) - 4.1% of patients with unilateral trigeminal neuralgia (affects just one side of the face) and 17% of those with bilateral trigeminal neuralgia (affects both sides of the face) have close relatives with the disorder. Compared to a 1 in 15,000 risk in the general population, 4.1% and 17% indicate that inheritance is probably a factor.

What are the symptoms of trigeminal neuralgia?

Typically, a patient will have one or more of these symptoms:

• Intermittent twinges of mild pain.


• Severe episodes of searing, shooting, jabbing pain that feel like electric shocks.


• Sudden attacks of pain which are triggered by touching the face, chewing, speaking or brushing teeth.


• Spasms of pain which last from a couple of seconds to a couple of minutes.


• Episodes of cluster attacks which may go on for days, weeks, months, and in some cases longer. There may be periods without any pain.


• Pain wherever the trigeminal nerve and its branches may reach, including the forehead, eyes, lips, gums, teeth, jaw and cheek.


• Pain which affects one side of the face.


• Pain on both sides of the face (much less common).


• Pain that is focused in one spot or spreads in a wider pattern.


• Attacks of pain which occur more regularly and intensely over time.


• Tingling or numbness in the face before pain develops.

Some patients may experience bouts of pain regularly for days, weeks or months at a time. Attacks of pain may occur hundreds of times each day in severe cases. Some patients may have periods without any symptoms which last for months or even years.

Some patients will have specific points on their face that if touched trigger attacks of pain. It is not uncommon for many patients to avoid potential triggering activities, such as eating, brushing their teeth, shaving, and even talking.

Area of pain

The area of pain can be broken down into the three branches of the trigeminal nerve. In medicine the trigeminal nerve is known as the fifth cranial nerve. It is often referred to using the Roman numeral 'V'. Below are the three branches broken down - 'V' refers to the trigeminal nerve:

• V1, ophthalmic, the first branch of the trigeminal nerve.
  Affects the forehead, nose and eye.


• V2, maxillary, the second branch of the trigeminal nerve.
  Affects the lower eyelid, side of nose, cheek, gum, lip, and upper teeth.


• V3, mandibular, the third branch of the trigeminal nerve.
  Affects the jaw, lower teeth, gum, and lower lip.

Some people with trigeminal neuralgia may have just one branch affected, while others are affected by more branches.

The pain felt by people with Typical Trigeminal Neuralgia differs from what people with Atypical Trigeminal Neuralgia experience:

• Typical trigeminal neuralgia pain (Typical facial pain)
  
  Pain is extremely sharp, throbbing, and electric-shock-like. There is no facial weakness or numbness.


• Atypical trigeminal neuralgia pain (Atypical facial pain - ATFP)
  
  As well as extremely sharp, throbbing, and electric-shock-like, patients may experience other types of pain. Their condition does not have just the hallmark symptoms of classic trigeminal neuralgia pain. Facial pain is often described as burning, aching or cramping. It may occur on one side of the face, often in the region of the trigeminal nerve and can extend into the upper neck or back of the scalp. The pain can fluctuate in intensity from mild aching to a crushing or burning sensation. It is much harder to diagnose people with Atypical Trigeminal Neuralgia.

How is trigeminal neuralgia diagnosed?

If the GP (general practitioner, primary care physician) believes the symptoms indicate trigeminal neuralgia the patient's face will be examined more carefully to determine exactly which parts are affected. The doctor will also attempt to eliminate other conditions which sometimes have similar symptoms, such as tooth decay, a tumor, or sinusitis.

MRI (magnetic resonance imaging scan) - this device uses a strong magnetic field and radio waves to create images of the inside of the patient's brain and the trigeminal nerve - it can help the doctor determine whether the neuralgia is caused by another condition, such as multiple sclerosis or a tumor. Unless a tumor or multiple sclerosis is the cause, the MRI will rarely reveal why the nerve is being irritated. It is very difficult to see the blood vessel next to the nerve root, even on a high quality MRI.

What is the treatment for trigeminal neuralgia?

Medications are typically the first treatment for trigeminal neuralgia, and most patients respond well and require no subsequent surgery. However, some may find that their medications become less effective over time, or they experience undesirable side effects. In such cases injections and/or surgery may be required.

Medications

These medications lessen or block the pain signals sent to the brain.

• Anticonvulsants - normal painkillers, such as Tylenol (paracetamol) do not relieve the pain in trigeminal neuralgia, so doctors prescribe anticonvulsant medication. Although these medications are used to prevent seizures (epilepsy), they are effective in calming down nerve impulses, which helps people with neuralgia.
  
  The most common anticonvulsants for trigeminal neuralgia are carbamazepine (Tegretol, Carbatrol), phenytoin (Dilantin, Phenytek) and oxcarbazepine (Trileptal). Doctors sometimes prescribe lamotrigine (Lamictal) or gabapentin (Neurontin).
  
  Sometimes the anticonvulsant begins to lose its effectiveness over time. If this happens the doctor may either up the dosage or switch to another anticonvulsant.
  
  Side effects of anticonvulsants include:
  
  
  • Dizziness
  • Confusion
  • Drowsiness
  • Vision problems
  • Nausea
  
  Suicidal thoughts - some studies indicate anticonvulsants may be linked to suicidal thoughts in some cases. The patient and doctor should monitor mood closely.
  
  Carbamazepine allergy - some patients, especially those of Asian ancestry, may have a serious drug reaction to Carbamazepine. Genetic testing may be recommended beforehand.


• Antispasticity agents - Baclofen is a muscle-relaxing agent which is sometimes prescribed on its own, or together with Carbamazepine or Phenytoin. Some patients may experience nausea, drowsiness and confusion as side effects.


• Alcohol injection - this numbs the affected areas of the face and provides temporary pain relief. The doctor injects alcohol into the part of the face where the trigeminal nerve branch is causing the pain. As pain relief is only temporary, the patient may either require further injections or a change of treatment later on.

Surgery for trigeminal neuralgia

Surgery for trigeminal neuralgia has two aims: 1. To stop a vein or artery from pressing against the trigeminal nerve. 2. To damage the trigeminal nerve so that the uncontrolled (random, chaotic) pain signals stop. Surgery that damages the nerve may cause temporary or even permanent facial numbness.

In many cases surgery helps, but symptoms may return months or even years later. Surgical options for trigeminal neuralgia include:

• Microvascular decompression (MVD) - this involves relocating or removing the blood vessel which is pressing against the trigeminal nerve - at its root - and separating the nerve root and blood vessels.
  
  The surgeon makes a small incision behind the ear on the same side of the head where the pain is. A small hole is made in the skull and the brain is lifted, exposing the trigeminal nerve. A pad is placed between arteries that touch the nerve and the nerve - effectively redirecting them away from the nerve.
  
  If the surgeon finds no blood vessels pressing against the nerve, the nerve may be severed instead.
  
  MVD has a good success rate at eliminating or significantly reducing pain. However, in some cases pain may recur.
  
  MVD carries a very small risk of some hearing loss, facial weakness, facial numbness, and double vision. There is an extremely small risk of stroke, and even death.


• Percutaneous glycerol rhizotomy (PGR) - also called glycerol injection. A needle is inserted through the face and into an opening at the base of the skull. Imaging guides the needle to where the three branches of the trigeminal nerve join and a small amount of sterile glycerol is injected. Within a few hours the trigeminal nerve is damaged and the pain signals are blocked.
  
  Most people experience significant pain relief with PGR. However, there are cases of later recurrences of pain. Many patients experience facial tingling or numbness.


• PBCTN (percutaneous balloon compression of the trigeminal nerve) - a hollow needle is inserted through the face and into an opening in the base of the skull. A catheter (thin flexible tube) with a balloon at the end goes through the hollow of the needle. The balloon is inflated. The pressure from the balloon damages the nerve and blocks pain signals.
  
  PBCTN is effective in treating pain for patients with trigeminal neuralgia. In some cases the pain comes back later. Most patients experience some facial numbness, and over half experience temporary or permanent weakness of the muscles used for chewing.


• PSRTR (Percutaneous stereotactic radiofrequency thermal rhizotomy) - this procedure uses electric currents to destroy specifically selected nerve fibers linked to pain. First the patient is sedated. Then, a hollow needle is inserted through the face into an opening in the skull. An electrode goes through the hollow of the needle to the nerve root. The patient is then awakened from sedation so that he/she can tell the doctor when electric currents are felt - the patient will have a tingling sensation. This helps the doctor locate the part of the nerve involved in pain. When the doctor has found it the patient is sedated again. The electrode heats up and damages the targeted nerve fibers - these are known as lesions. The doctor carries on doing this, adding more lesions if necessary, until pain is eliminated.
  
  Most patients undergoing PSRTR will experience some facial numbness afterwards.


• PSR (partial sensory rhizotomy) - part of the trigeminal nerve at the base of the brain is severed (cut). The doctor makes an incision behind the ear, makes a small hole in the skull, and severs the nerve. As the base of the nerve is severed the patient will have permanent facial numbness. Sometimes the doctor rubs the nerve instead of severing it.


• GKR (gamma-knife radiosurgery) - a high dose of radiation is aimed at the root of the trigeminal nerve. This results in nerve damage, which eliminates or reduces the pain. As the damage from radiation is gradual, the patient will experience slowly improving pain relief over several weeks. Initial benefits may take several weeks to appear.
  
  GKR is effective for most patients, however some may experience recurrence of pain later on.

Prevention

There are no guidelines for preventing the development of trigeminal neuralgia. However, the following steps may help prevent attacks:

• Eat soft foods.
• Make sure your drinks and foods are not too cold or hot when you consume them.
• Wash you face with lukewarm water (body temperature).
• Use cotton pads when washing your face.
• Rinse your mouth with lukewarm water after eating if tooth brushing triggers an attack.
• Avoid known triggers as much as possible.

Written by Christian Nordqvist


Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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