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Microvascular Decompression Surgery For Trigeminal Neuralgia

Aaron Cohen-Gadol, M.D.

January 01, 2009

What is trigeminal neuraliga?

Trigeminal neuralgia is a chronic condition causing shock-like extreme pain in the face - usually one side of the jaw or cheek set off by triggers related to facial pressure and motion. Although the pain is short and intermittent (a typical attack may last anywhere from a few seconds to a couple of minutes), it is extreme and can be incapacitating.

The attacks of pain generally occur together and may repeat in succession, taking place sporadically over the course of days, weeks or months. Episodes of repeated attacks can be separated by asymptomatic periods for months or even years.

What causes trigeminal neuralgia?

The most common cause of trigeminal neuralgia is compression of the trigeminal nerve (also called the fifth cranial nerve) by an artery or vein at the base of the brain behind the ear. Compression from the blood vessel causes the myelin sheath - a special coating around a nerve that helps it transmit signals faster through the body - to wear down and the nerve to send abnormal pain signals to the brain.

Trigeminal neuralgia is also associated with multiple sclerosis and other disorders affecting the myelin sheath, as well as nerve compression by a tumor.

The pain is generally set off by triggers related to facial pressure or motion, such as:

  • Eating
  • Drinking
  • Shaving
  • Talking
  • Smiling
  • Brushing your teeth
  • Applying makeup

Who is affected by trigeminal neuralgia?

Trigeminal neuralgia can occur at any age, but it is more common among those over 50 years of age. In general, women are affected more than men.

Symptoms

Trigeminal neuralgia is usually associated with episodic intense sharp, shock-like and electrical pains in the face. The pain is generally felt on one side of the jaw or cheek, although it may be occasionally around the eye. Less commonly, the pain may also present in other areas innervated (supplied with nerves) by the trigeminal nerve, such as the lips, teeth, gums or forehead.

The bouts of pain are triggered by some form of vibration or contact (see previous section).

The pain is often described as incapacitating and it occurs in attacks that last from several seconds up to two minutes. The attacks may occur in rapid succession or spaced more sporadically over the course of days, weeks, or even months. The periods of time during which the attacks are prevalent are referred to as episodes. Patients may have long asymptomatic (pain free) periods between episodes that last for months or years.

Prior to the onset of an episode, patients may experience warning signs such as a numb feeling or a chronic aching pain in the areas of face innervated by the trigeminal nerve.

As time goes on, the attacks usually become more frequent and intense.

Diagnosis

To diagnose trigeminal neuralgia, a physician will take your history and perform a physical examination. Clinical history is the key component in the diagnosis of trigeminal neuralgia.

Trigeminal Neuralgia must be differentiated from atypical facial pain.
In atypical facial pain, the pain is more burning, non-episodic (constant,) and not in a specific distribution corresponding to the trigeminal nerve. Atypical facial pain does not respond to the surgical treatments designated for patients with typical trigeminal neuralgia.

If the patient is suffering from trigeminal neuralgia, the physician may order a magnetic resonance imaging (MRI) scan to look for the blood vessel compressing the nerve or to rule out multiple sclerosis or a tumor as the cause of trigeminal neuralgia.

Additional tests may be ordered to rule out other possible causes of face pain.

Treatments

Medications are the most common initial treatment, although their effectiveness may diminish over time. Medications used include anticonvulsants (e.g., Tegretal or Neurontin) muscle relaxants and tricyclic antidepressants. Tegretal and Neurontin are the first line of medical therapy. Temporary relief of pain after administration of these two drugs further solidifies the diagnosis of trigeminal neuralgia.

Anticonvulsants block nerve firing to control pain. However, these medications may have several unpleasant side effects (such as confusion, drowsiness and nausea) that should be discussed with your physician prior to their use. The use of Tegretal requires careful monitoring of your blood count and salt by your family doctor for the first few weeks of use. This monitoring requires a blood test.

Muscle relaxants may be used on their own or in conjunction with anticonvulsants to treat pain. Tricyclic antidepressants are used specifically to treat pain described as constant, burning or aching.

No patient should live with the severe pain of trigeminal neuralgia. We recommend early consultation with a neurosurgeon if the medications are not effective or if you have unpleasant side effects from the medications.

Your surgeon may suggest one of many different surgical options, including:

The above procedures fall into two main categories:

Physiologic

Microvascular decompression: Usually reserved for patients younger than 70 years old, it is more invasive requiring surgery (craniotomy: removal of a small piece of skull and going around the brain to decompress the nerve.) This procedure is the most definitive and durable procedure to relieve the pain.

Ablative

The other procedures mentioned above, including glycerol injection, balloon compression, radiofrequency thermal lesioning and stereotactic radiosurgery. These procedures do not require surgery and cause trigeminal nerve injury (numbness) so the nerve does not cause more pain. The primary problem with these procedures is that the compressive artery is not addressed. And while these procedures pose less of a risk to the patient than surgery, the risk of pain recurrence is also higher.

Microvascular decompression

Microvascular decompression avoids directly damaging the trigeminal nerve and is the procedure with the lowest probability of pain returning in the future. The patient is put completely to sleep using general anesthesia and the surgeon enters the head through an incision made behind the ear. A small piece of skull is removed. Using a surgical microscope, the surgeon locates the blood vessels compressing the nerve and gently separates them from the nerve. A piece of Teflon padding is placed between the nerve and offending blood vessels to prevent further compression of the nerve (please see surgical video.) This technique halts further pain in most patients (90%), and, because the nerve is not damaged, there is generally no permanent facial numbness. The risk of pain recurrence is less than 10% in five years.

Decompression of the facial nerve using teflon padding

As with all surgeries, there are possible complications and patients very rarely (less than 5% of the time) experience facial weakness, numbness, double vision, or decreased hearing.

In instances where the surgeon is unable to find a blood vessel pressing on the nerve during a microvascular decompression procedure (about 10-20% of the time), the surgeon may cut part of the trigeminal nerve; if this is done, the patient will be most likely relieved of his or her facial pain but will experience permanent numbness in the area of the face having pain.

After the surgery, the patient is monitored in the intensive care unit overnight and is then transferred to a private, less monitored floor next day. Nausea and slight dizziness may be temporarily present (1-2 days). After approximately 2-3 days of hospitalization, the patient returns to his or her daily activities and may resume driving in one week. Heavy physical activity is avoided for six weeks and patients with less physically demanding jobs may return to work within two weeks.

Glycerol injection

Glycerol injection is an outpatient procedure using glycerol to damage the nerve and block pain signals. The patient is sedated and a needle is inserted through the face toward the base of the skull. The needle is carefully guided to the point where the trigeminal nerve divides into its three branches and a small amount of glycerol injected around the nerve. The damage caused to the nerve by the glycerol blocks pain signals; some patients experience numbness and tingling as a result of the procedure. The risk of pain recurrence is approximately 30% in five years.

Balloon compression

Balloon compression likewise damages the trigeminal nerve in an attempt to block the pain signals traveling to the brain. A needle is inserted through a small incision in the cheek toward the trigeminal nerve at the base of the skull. A small balloon is threaded through the needle and inflated to compress the nerve against the skull bone. After approximately 1-2 minutes, the balloon is deflated and removed. The pressure from the balloon damages the nerve, inhibiting the abnormal signaling that causes the pain. Balloon compression is generally an outpatient procedure. Patients may experience some degree of facial numbness. The risk of pain recurrence is approximately 30% in five years.

Radiofrequency thermal lesioning

Radiofrequency thermal lesioning involves more selective damaging of the trigeminal nerve. The patient is sedated and a hollow needle is inserted through a small incision in the cheek to where the nerve exits the base of the skull. The patient is awakened, and using an electrode threaded through the needle, the surgeon gently stimulates the nerve at different positions, causing a mild tingling sensation in the different areas of the face innervated by the trigeminal nerve. The patient is asked to identify when the tingling occurs in the area typical of pain attacks. The patient is then re-sedated and the electrode is heated to damage the nerve fibers associated with the pain. Additional lesioning of the nerve may be necessary to completely eliminate the pain. Most people who undergo radiofrequency thermal lesioning experience some degree of facial numbness post-operatively. The risk of pain recurrence is approximately 30% in five years.

Stereotactic radiosurgery

Stereotactic radiosurgery is a non-invasive procedure using high-energy radiation to damage the nerve as it exits the brainstem. The patient has a head frame placed on his or her head on the day of procedure. After administration of radiation which takes about two hours, the head frame will be removed at the end of the day and the patient is discharged.

There is minimal pain involved with the procedure itself and extensive anesthesia is typically not used. Patients usually leave the hospital the same day.

Lesioning is slow and it may take several weeks to months for the facial pain to begin to subside. The recurrence rate is about 50% in five years.

Prognosis

Trigeminal neuralgia is not fatal, but the pain can be incapacitating; and, without medical intervention, the pain will continue episodically throughout life. This disorder can be managed or cured through the use of medication or surgery. There is a risk that the pain will return later in life.

Resources

National Institute of Neurological Disorders and Stroke Visit website
National Institute of Neurological Disorders and Stroke [additional info] Visit website
Medline Plus Visit website
Mayo Clinic Visit website

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