Pain

Trigeminal Neuralgia

Trigeminal neuralgia is a chronic pain condition that affects the trigeminal nerve, which carries sensation from your face to your brain.

Treatments and Drugs

Medical treatment:  The most common drug used is carbamazepine. The effective daily dose can be as small as 300mg to as large as 2000 mg. The principle of treatment is to administer the smallest single dose to control the pain. The frequency is adjusted to relieve the pain completely. Once achieved, the schedule is continued for 6-8 weeks without decreasing the dose to achieve stable remission. Following this the drug can be gradually tapered and stopped. In case of resurgence of pain this can be restarted. Over a period of time, the recurrences become less responsive, necessitating introduction of other drugs. Carbamazepine is usually well tolerated; however, some patients may experience ataxia, GI upset, leucopenia, hyponatremia, drowsiness or mental confusion. In these patients Oxcarbamazepine can be used (it has lesser side effects). Other drugs like Gabapentin, Phenytoin, Baclofen, etc. are also used, but their therapeutic efficacy is much less than Carbamazepine.

Role of peripheral Neurectomies: The common practice of peripheral neurectomies of mandibular and maxillary of the trigeminal nerve is highly discouraged. Peripheral neurectomies carry a high rate of recurrence. Beside , they also have a very high incidence of causing deafferentation pain which is one of the worst pain to manage ,requiring aggressive therapies like gasserian ganglion stimulation or motor cortex stimulation .The only place a peripheral neurectomy should be performed is in a case of V1 neuralgia as other therapies have higher incidence of side effect.

Surgical treatment:  The two most common forms of surgical treatments are (a) Microvascular Decompression (MVD) and (b) Radiofrequency thermocoagulation (RFTC)

Microvascular Decompression: This is highly controversial as in one paper Janetta noted that in cadaver dissection of patients who never suffered from TN there was no vascular compression, but the same group later on published an incidence of 35% of vascular compression in asymptomatic patients.  The MVD surgery involves posterior fossa exploration through a small table 1Comparison of Results of MVD and RFTC thermocoagulation (RFTC).

opening next to the mastoid process. Under magnification, the offending vascular loop is dissected free of the root entry zone and a Teflon graft is interposed. It has been found that in patients in whom arterial compression is identified the recurrence rate is 30% but in those patients where the conflict was either venous or none, the recurrence rate was high as 70%. The side effects of this surgery include damage to 7th and 8th nerve, and other complications like CSF leak, infection, haematoma etc (Table 1).

10 years after!!!! MVD RFTC
Recurrence3545
Painful dysesthesia00.9
Morbidity22%
Serious morbidityMore commonrare
Mortality0.8%Nil
Cost and HospitalisationMoreSignificantly small

Table 1 – Tronnier, Neurosurgery, 2001; Young RF, J Neurosurg, 1988

RADIOFREQUENCY THERMOCOAGULATION

Radiofrequency rhizotomy is based on temperature dependent selective destruction of pain transmitting C fibres whiles sparing the A-delta fibres. We recommend RFTC for most patients undergoing their first surgical treatment for typical Trigeminal Neuralgia, TN in multiple sclerosis and patients who have failed Mircovascular decompression. This is a day care procedure. Preoperative workup involves evaluation for fitness to undergo short general anaesthesia. Patient is explained the procedure in detail and what to expect during the procedure so as to ensure adequate cooperation.

The procedure involves retrogasserian needle placement by percutaneous technique. Needle is introduced through a point 2.5 cm lateral to the angle of the mouth on side of the lesion. It is passed medial to the mandible and aimed in the direction of the petrous bone and clivus junction, seen on lateral fluoroscopic view. Medial part of the foramen ovale is entered. Oblique view localizing the foramen is useful in case of difficult penetration.

RFTC Lateral-Radiograph
Lateral Radiograph showing needle placement
Oblique radiograph showing needle through foramen ovale
Oblique radiograph showing needle through foramen ovale

Once the needle is in position, the appropriate trigeminal division is stimulated using the current from the radiofrequency lesion generator.  Patient typically experiences paraesthesia in the territory of his pain. In case he does not feel the paraesthesia in the desired territory, the needle position is adjusted. Once the distribution of the paraesthesia is confirmed a short general anaesthetic (IV propofol) is administered and the division is lesioned using 70oC current for 60 sec. The patient is woken up while the needle is still in place. He is asked to check if he has got adequate pain relief. This procedure is suitable for the second and third division TN. For the first division TN supraorbital block and if successful followed by supraorbital neurectomy.

Radiofrequency lesion generator
Radiofrequency lesion generator
RFTC
OT set-up for RFTC

Results of RFTC  : We have been performing RFTC for last 15 years .we have compared our results with those published in the literature( Table 2).

Literature review (6205 cases)Personal Series ( 395 cases)
Pain relief98%92%
Recurrence23%20%
Mortality.030.0
Keratitis10
Dysesthesia2218
Anaesthesia dolorosa11

Table 2 – Results of RFTC

Treatment of Trigeminal Neuropathy

Gasserian Ganglion Stimulation: Patients with pain secondary to the damaged nerve or ganglion as occurs after some poorly performed surgery for trigeminal neuralgia or in cases of nerve infiltration by tumors, experience burning or nagging pain in the distribution of the trigeminal nerve. This is known as trigeminal neuropathy.

Neuromodulation by the way of gasserian ganglion stimulation or motor cortex stimulation is the only sensible alternative for treating this pain if the medical treatment fails. This involves implantation of the electrode at the target site and delivering current to the target nerve or cortex through a pacemaker.It is presumed that this will either increase their pain threshold or block the painful impulses from the periphery to relieve pain. This is a highly advanced form of treatment available at only select centres like Jaslok Hospital.