Radiofrequency Treatment for Trigeminal Neuralgia

Radiofrequency treatment for trigeminal neuralgia uses a thin electrode, passed through the cheek, to reach the ganglion of the face’s sensory nerve (the trigeminal nerve) at the base of the skull and to switch off the pain-carrying fibres with controlled heat. There is no incision; the procedure is done under fluoroscopy with brief sedation.

It is considered for patients whose pain is not controlled by medication or who cannot tolerate its side effects. Other options include microvascular decompression surgery and radiosurgery; which one suits a patient depends on the MRI findings, age and general health.

What is trigeminal neuralgia?

Trigeminal neuralgia causes attacks of pain on one side of the face lasting seconds, described as an electric shock or a stab. The pain is usually in the cheek, jaw and gums. Eating, talking, brushing teeth, touching the face or wind can trigger attacks.

In most patients a blood vessel touching the nerve where it enters the brainstem is responsible (classical trigeminal neuralgia). Less often, another condition such as multiple sclerosis or a tumour causes the pain.

Diagnosis

The diagnosis rests on the description of the pain. The European Academy of Neurology guideline recommends MRI with special high-resolution sequences to look for another underlying cause and for contact between a vessel and the nerve. This also guides the choice of treatment.

Treatment options

• Medication: carbamazepine or oxcarbazepine is the first choice. In most patients the pain is controlled with medication at first.
• Microvascular decompression: an operation behind the ear separates the vessel pressing on the nerve. It is the preferred surgery in classical trigeminal neuralgia with clear vessel contact on MRI.
• Radiofrequency thermocoagulation: one of the percutaneous methods. It needs neither general anaesthesia nor opening the skull, and stands out for older patients or those at high surgical risk.
• Radiosurgery: focused radiation is aimed at the nerve from outside. The effect begins over weeks.

The guideline recommends neuroablative methods such as radiofrequency for patients in whom MRI shows no vessel contact.

How is the procedure done?

• The patient lies on their back. Local anaesthetic is given in the skin of the cheek, next to the corner of the mouth.
• Using fluoroscopy, the thin electrode is guided through an opening in the skull base called the foramen ovale to the Gasserian ganglion.
• The patient is woken briefly for a test stimulation, to confirm that the tingling falls in the painful area (forehead, cheek or jaw).
• Once the position is confirmed, the patient is sedated again and heat is applied to the branch carrying the pain.

The procedure usually takes less than an hour. Patients are often discharged the same day or the next day.

After the procedure and possible side effects

In most patients the pain eases straight after the procedure. Some numbness in the treated area is an expected result; the test during the procedure is done to keep this area limited to where the pain is.

In the 25-year series of 1,600 patients reported by Kanpolat and colleagues from the Department of Neurosurgery at Ankara University, the main side effects were:

• Reduced corneal reflex: 5.7% (needs care against dry eye and irritation of the eye surface)
• Weakness of the chewing muscle: 4.1%
• Unpleasant change in sensation (dysaesthesia): 1%
• Anaesthesia dolorosa (lasting pain in the numb area): 0.8%

These figures are retrospective data from a single centre and may vary with the team and technique.

Does the pain come back?

It can. In the same series, pain returned within the first six months in 7.7% of patients and later in 17.4%. Complete pain relief at five years after a single procedure was reported in 57.7%. When the pain returns, the procedure can be repeated or other options considered.

Pulsed RF does not make a lesion in the nerve, so it carries a lower risk of numbness; however, its effect in trigeminal neuralgia has been reported to last less long than thermal RF.