Trigeminal Neuralgia

What is trigeminal neuralgia?

Trigeminal neuralgia is a cause of severe facial pain. The pain is typically described as sudden, excruciating, brief, stabbing, electric pain on one side of the face. It is provoked by light touch and attacks last a few seconds each but volleys of multiple attacks often occur. Patients invariably say it is the worst pain they have ever experienced. Triggers include eating, brushing teeth, shaving and cold wind blowing on the face. As it most often affects the cheek and jaw region, patients often think the cause of their pain is dental. Some may even have teeth extracted to no avail.

It affects women slightly more frequently than men and usually starts between the ages of 40 and 70.

What causes trigeminal neuralgia?

The trigeminal nerve can be thought of as an electric cable that contains numerous fibres sending different messages to the brain.  There are pain, touch, temperature and vibration fibres, each insulated from one another by a protective sheath called myelin.

Classical trigeminal neuralgia is caused by a blood vessel (or vessels) pressing on the nerve as it enters the brainstem. The pressure of the blood vessel on the nerve over time damages the myelin nerve sheaths causing erratic messages to be transmitted along the nerve. These erratic impulses can cause a ‘short circuit’ between light touch and pain pathways.

There are other causes of trigeminal neuralgia symptoms aside from vascular compression, although they are much less common, such as multiple sclerosis, stroke or tumours. The most common cause by far, however, is vascular compression as described above.

Treatment

Trigeminal neuralgia can often be well controlled with medication. Carbamazepine is the gold standard medication and first line treatment. Oxcarbazepine can be used if carbamazepine side effects are not tolerated. Monitoring with blood tests and for skin rash is required when starting these medications because of potential side effects. Other medications, such as pregabalin, lamotrigine, phenytoin baclofen, can be trialled if required. All these medications also have potential side effects; most commonly, sleepiness, difficulty concentrating, forgetfulness or feeling off balance.

A significant group of patients will find that their medication dose needs to be increased as time progresses.  When the medication becomes ineffective, or the side effects are so pronounced that the patient is unable to perform daily tasks then the patient may wish to consider other treatments such as ablative procedures, radiosurgery or surgery. Of these, surgery has the best long-term cure rate.

The surgical procedure is known as microvascular decompression. This operation deals with the cause of classical trigeminal neuralgia; the blood vessel or vessels pressing on the trigeminal nerve. Unlike the other invasive treatment options, it relieves pain without intentionally damaging the trigeminal nerve. Through a small incision behind your ear, Dr Laban can separate the offending blood vessel(s) from the trigeminal nerve using a small piece of Teflon felt or sling. Surgery is performed under general anaesthetic and usually lasts about 2 hours. Patients are generally in hospital for 3 to 5 days after surgery.

Most people find this surgery cures their trigeminal neuralgia. The risks of surgery are potentially serious, including facial numbness or weakness, hearing loss, double vision, anaesthesia dolorosa (a very painful and numb face), infection, stroke and even death, but significant complications are fortunately rare.

Alternative methods of treatment include one of the percutaneous ablative techniques; glycerol injection, radiofrequency rhizotomy or balloon compression. These involve passing a needle into the cheek and through a small hole in the base of the skull onto the trigeminal nerve. X-rays are used to guide the needle and are performed under sedation or general anaesthetic. These procedures work on the premise of deliberately damaging the trigeminal nerve to disrupt the pain signals.

  • Glycerol injections: Glycerol is injected around the nerve. More than ninety percent of patients with trigeminal neuralgia will experience relief of their pain with a few days of the procedure. Most patients will wake up with numbness in the face but this gradually improves.
  • Radiofrequency rhizotomy: A needle is used to apply heat to the trigeminal nerve.
  • Balloon compression: The nerve is compressed by a small inflated balloon.

There is, however, a recurrence of pain in about 50% of patients over three years and for this reason the procedure is recommended in patients who are frail or may otherwise not tolerate the microvascular decompression. The injection can be repeated but is less likely to be effective and complications are slightly more common. The risks include persistent facial numbness, weakness, infection/meningitis, anaesthesia dolorosa (a very painful and numb face which is very difficult to treat), injury to an artery resulting in a stroke or death.

Finally, there is the option of radiosurgery to the nerve. This is a type of radiotherapy and, like the percutaneous techniques, it is a destructive procedure. Performed as a day case, a frame is fitted to the patient’s head and a very focused beam of radiation is targeted at the trigeminal nerve. There is a 30-40% recurrence rate 3 to 4 years after the procedure. This is a useful treatment for patients with serious medical problems who might not be suitable for a microvascular decompression.