Trigeminal Neuralgia has been described as one of the most severe pain syndromes. It is characterized by excruciating, electric shock like, shooting/stabbing pain in the distribution of Trigeminal nerve in the face. It is unilateral during any one episode, abrupt onset with pain-free intervals between attacks. Pain is triggered by some non-noxious stimuli like touching of face, chewing, swallowing or even talking. Tumors, vascular malformations, dental disease, sinusitis may cause trigeminal neuralgia, but the etiology in the majority of the cases is unknown.
The condition occurs more often in the middle aged and is twice as common in females as in males. In most of the patients the pain is strictly unilateral; multiple sclerosis patients constitute the majority of the 2% patients with bilateral disease. Trigeminal neuralgia is twice as common on the right side. Most commonly patients present with pain maximum either in maxillary or mandibular divisions.
Investigations: A small group of patients have trigeminal neuralgia due to identifiable brain lesions. MR angiogram might show relationship between blood vessel and fifth cranial nerve. Sometimes it can pick up masses or multiple sclerosis pictures. Most of the patients in the initial stages respond very well to pharmacological therapy. As the duration of disease extends, the medications become ineffective and patient will require an interventional procedure.
I. Treatment with drugs:
- Carbamazepine in a dose of 200 mg BID/TID is the first line of treatment. Depending on the response the total dose needs to be titrated upto a maximum of 1600 mg per day. The side effects are nausea, vomiting, ataxia, skin rash and blood dyscrasia. Patients who are on long-term therapy should undergo regular monitoring of blood counts. If suspicious blood picture are seen at any stage, the drug should be stoped.
- Phenytoin 100 mg TID along with lowest tolerated dose of carbamazepine may be tried in patients, who are unable to tolerate carbamazepine in high doses.
- Baclofen in 5 to 10 mg thrice daily to start with and slowly increasing by 10 mg every alternative day can be of help. Patients usually require about 50-60 mg a day. The side effects are sedation, dizziness and dyspepsia.
- Gabapentin has been found to work in conjunction with carbamazepine in a dose of 300-3000 mg in divided doses per day.
- Pregabalin in a dose of 150 mg to 600 mg may be tried when other drugs have failed or withdrawn due to side effects.
- Other drugs like clonazepam, sodium valproate and tocainide may be tried.
II. Interventional pain management:
The Interventional pain management should be tried to provide pain relief when pharmacological management is unsuccessful.
1. Nerve blocks
Individual divisions of the fifth cranial nerve at their trunk (like maxillary nerve block & mandibular nerve block) or their peripheral branches (like supraorbital, infraorbital, inferiordental and mental nerves) may be blocked with local anaesthetic or neurolytic agent (like phenol/alcohol). In addition to their diagnostic value, it may relief pain for longer duration.
2. Gasserian ganglion block
The trigeminal ganglion/gasserian ganglion is located at the base of skull at Meckel’s cave. It may be blocked with glycerol, Radio-Frequency, or Balloon compression. Alcohol or phenol are rarely used nowadays because of their complications like: numbness, corneal ulceration, drooling and trophic lesion of skin and sometimes constant burning pain in the numb area. Success rate with Radio Frequency is 98%, glycerol 72-96% & balloon compression 90-100%. The recurrence rate with these procedures is highest with glycerol of about 54% on 4 years follow up. Complications of radio frequency procedures are rare but similar to alcohol. Gasserian ganglion block with radio frequency is the most commonly performed procedure because of its minimal complications, highest success rate and low recurrence rate.
III. Surgery : Microvascular Decompression
Vascular decompression surgery is undergoing lot of trials in view of its minimal complication rate and high recurrence rate. There are many other invasive procedures like posterior fossa section or decompression and medullary tractotomy, which have higher complication rate. The approach for treatment has been maximal relief with minimal morbidity. In recent times the reason for trigeminal neuralgia is presumed to be an abnormal blood vessel pressing over the fifth nerve at the site of origin. To prevent the pressure effects a Teflon pad is interposed between the blood vessel and the nerve. Once the pressure is relieved over the nerve, the neural transmission is supposed to return to normal. It has been reported to provide immediate complete relief in 79% of patients in a series of 708 patients. Long-term complete and partial relief was 73% and 8%. Mortality is low (0.3%) and overall major complications were about 2%.
Surgery vs. interventional pain management:
To compare these two options we should compare success rate, complications, recurrence rate & cost. Considering all these factors interventional pain management (like Radio Frequency ganglion block) in well-equipped centers and at expert hands are much better than surgical procedures.