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Trigeminal Neuralgia
Dr. M. Natarajan, MS
Definition and Incidence
Trigeminal Neuralgia is defined as short sharp lancinating or lightning paroxysmal unilateral pain in the area of trigeminal nerve distribution. The disease affects elderly age group and and is more common in women than men with the involvement of right side more frequent than the left. Statistically 10% of patients are less than 40 years old where as Trigeminal Neuralgia forms 5% of all neurological disorders reported.
Generally, the pain lasts for few seconds in the initial period and is different from other facial pains. There are pain free periods in between the attacks. Periodicity of pain occurs in almost all cases and as disease advances attacks increase in frequency with pain free periods becoming shorter and shorter till it disappears resulting continuous trigemimal pain.
Talking, chewing, washing the face, exposure to cold weather all trigger the pain and in turn have a trigger point. Gentle touch over that point results in shooting pain.
Etio Pathogenesis
There are several theories put forward as the exact cause has not been identified.
- Arterial compression at the trigeminal root entry zone (Trez). Commonly superior cerebellar artery or anterior inferior cerebellar artery compresses the nerve. As the age advances arteries become stiff and elongate due to arteriosclerotic changes and presses the TREZ.
- Demyelination of the nerve occurs due to unknown reasons. This results in ephaptic transmission of impulses, in other words 'cross talking' of the axons results, where in touch is observed as pain.
- 5% of cases have cerebellopontine angle lesions like meningioma, acoustic neuroma, epidermoid etc.
- Multiple Sclerosis
Diagnosis
History is important in the diagnosis of the disease. Most of the time patient brings out the symptom by fondling the trigger zone. Some patients may have darkish discoloration over the face due to constant rubbing. Generally, neurological examination reveals no abnormality. If sensory loss or motor involvement is noted, it is usually due to organic lesion in the CP angle.
Investigations
CT Scan and MRI Scan of the brain are essential to rule out a rare possibility of CP angle tumor. In the cases of idiopathic Trigeminal Neuralgia the scans are normal.
Differential Diagnosis
Pain due to caries tooth is at time mistaken for trigeminal neuralgia, but in all those cases pain is continuous. There are no pain free periods between the attacks, which is the hallmark of the disease.
Atypical facial pain, sphenopalatine neuralgia, glaucoma are other conditions to be considered in differential diagnosis.
Diabetes with cranial neuropathy may mimic trigeminal neuralgia. On the other hand, trigeminal neuralgia patients may have associated conditions such as diabetes mellitus, hypertension etc.
Treatment
Medical Management
Carbamazepine, Phenytoin, Baciofen, Clonazepam have all been tried with different degree of success. But all the patients become refractory to the treatment after some time.
Surgical Procedures
Although several nonspecific treatment have been advocated but only two have come into final stay.
- Rhizolysis by different methods
- Microvascular Compression in Microvascular Decompression Surgery
In this retromastoid craniotomy is performed and trigeminal root entry zone is explored. Usually an artery compressing the nerve is separated with a gelfoam, muscle or facial sling or cotton mesh. Face sensations are retained. In some cases no arterial compression is noticed. The opening of subarachnoid space will languish the pain.
Rhizolysis
Peripheral neurectomy gives relief for shorter period but recurs due to regeneration. Hence division of nerve proximal to trigeminal ganglion is advocated.
Trigeminal Injection
Wide bore needle is passed along the mandibular division into foramen ovale. Using radio image guide, needle is pushed into trigeminal cistern. Glycerol 0.5 ml is injected in sitting position.
In radio frequency lesion, needle is connected to RF generator and thermal lesion is made at preganglionic fibres..
Author has performed 260 Glycerol injections with good success rate. Pain free period lasts for 4-5 years. In about 5% of the patients recurrence of pain is noted with in 2 years. In diabetes mellitus patients pain recurrence rate is high. All patients will have sensory loss and varying degree of anesthesia dolorosa which improves in time.
Balloon Compression (Percutaneous Technique)
After training at Queen Square Neuro-Surgical Institute, London, we started doing balloon compression with good success rate. Sensory impairment is much less in this procedure. 35 patients have so far been treated in last 10 months with 100% success rate. Mild impairment of sensation in mandibular division was encountered for shorter period only. Sensations over tongue, cheek, soft palate are spared and retained fully. No corneal sensory loss or Herpes Perioralis is reported. No patient had recurrence till date. None of them are on any medication presently.
Trigeminal neuralgia is a disease of elderly. It is a benign disease. Ballon compression gives long lasting relief vathfairly well preserved sensation and is cost effective. Major surgery is avoided in the elderly, who may have other associated systemic diseases.
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