|Year : 2015 | Volume
| Issue : 2 | Page : 165-167
Trigeminal neuralgia: An overview of the clinical entity
Nargis Qayoom1, Sumaya Syed2, Zulfiqar Ali3, Talib Khan2
1 Department of Orthodontics, Institute of Dental Sciences, Sehoora, Jammu, India
2 Department of Anesthesiology and Pain Medicine, Sheri Kashmir Institute of Medical Sciences, Soura, Srinagar, India
3 Department of Anesthesiology and Pain Medicine, Division of Neuroanesthesiology, Sheri Kashmir Institute of Medical Sciences, Soura, Srinagar, India
|Date of Web Publication||3-Sep-2015|
Division of Neuroanesthesiology, Department of Anesthesiology and Pain Medicine, Sheri Kashmir Institute of Medical Sciences, Soura, Srinagar
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Trigeminal neuralgia (TN) is a rare neurological disease that causes sudden, severe, brief, stabbing recurrent episodes of facial pain in one or more branches of the trigeminal nerve. Over the last few decades, there is evidence that TN may be a result of compression of the trigeminal nerve root at or near the dorsal root entry zone by a blood vessel. TN is treated on an outpatient basis, unless neurosurgical intervention is required. Treatment can be subdivided into pharmacologic therapy, percutaneous procedures, surgery, and radiosurgery. Medical therapy is often sufficient and effective, allowing surgical consideration only if pharmacological treatment fails. Medical therapy alone is an adequate treatment for 75% of patients.
Keywords: Management, pathogenesis, trigeminal neuralgia
|How to cite this article:|
Qayoom N, Syed S, Ali Z, Khan T. Trigeminal neuralgia: An overview of the clinical entity. J Int Clin Dent Res Organ 2015;7:165-7
|How to cite this URL:|
Qayoom N, Syed S, Ali Z, Khan T. Trigeminal neuralgia: An overview of the clinical entity. J Int Clin Dent Res Organ [serial online] 2015 [cited 2017 Sep 21];7:165-7. Available from: http://www.jicdro.org/text.asp?2015/7/2/165/164404
| Introduction|| |
The main sensory trigeminal pathway processes discriminative touch and proprioceptive information from the face. There are three sensory nuclei; mesencephalic nucleus, main sensory nucleus, and spinal nucleus arranged in a column from midbrain through the pons and medulla and into the upper cervical cord. International Association for the Study of Pain (IASP) defines trigeminal neuralgia (TN) as a sudden, usually unilateral, severe brief stabbing recurrent pain in distribution of one or more branches of the fifth cranial nerve.  TN mostly involves the maxillary or them andibular branch, though all the three branches of the nerve may be affected. Typically, brief attacks are triggered by talking, chewing, tooth brushing, shaving, a light touch, or even a cool breeze on a very localized spot on the face (the so-called "trigger zone"). The trigger zones are most commonly located on cheek, medial and lateral aspect of eyebrows, nose, lip, and buccal mucosa. Minimal stimulation in these areas initiates a painful attack. Patients with TN can pinpoint these areas and will assiduously avoid any stimulation of them. Not all patients with TN have trigger zones, but trigger zones are nearly pathognomonic for this disorder.  The pain is abrupt in onset and termination and may remit for varying periods. The International Headache Society,  made a distinction between classical and symptomatic TN (CTN and STN): CTN includes all cases without an established etiology, i.e. idiopathic, as well as those with potential vascular compression of the fifth cranial nerve, whereas the diagnosis of STN is made in cases secondary to tumor, multiple sclerosis (MS), structural abnormalities of the skull base, and the like.
| Etiology of TN|| |
Several causes of TN include compression of trigeminal sensory root by the bony irregularities along petrous temporal ridge, compression of the nerve near the pons by arterial loops, tumors, or irritation by sclerotic plaques. TN may be a result of compression of trigeminal nerve root near the dorsal root entry zone by a blood vessel. This compression may be related to an aberrant branch of the superior cerebellar artery that lies on the trigeminal nerve. Surgical decompression of the nerve has led to a long term pain relief in these patients.
Multiple sclerosis is seen in 2-4% of patients with TN. These patients are younger with bilateral neuralgias. Tumors, usually posterior fossa meningiomas or neuromas, are present in around 2% of patients.
| Investigations|| |
No specific tests exist for the diagnosis of TN. A clinical examination with assessment of the cranial nerve function is helpful to rule out multiple sclerosis and tumors. If there is a cranial nerve dysfunction or a facial sensory loss, it should be followed by cerebral imaging. Imaging of the relationship of the nerves and the blood vessels in its vicinity is done by magnetic resonance tomographic angiography (MRTA). Though arteries are easily visualized, veins are seen after enhancement with intravenous gadolinium. A three-dimensional constructive interference in steady state (3D-CISS) is useful in delineating the pathology.
| Treatment|| |
A suboccipital craniotomy is done. After retracting the cerebellum, a segment of the superior cerebellar artery compressing the nerve at the root entry zone may be seen. Sometimes the anterior inferior cerebellar artery or superior petrosal veins is compressing the nerve. A piece of shredded Teflon is placed between the vessel and the nerve to separate them. From the group of patients with typical TN followed over median follow-up of 9.7 years, 82% had good long-term results after operation. 
The procedure is carried out under fluoroscopy with radiofrequency needle through the foramen ovale into Meckel's cave. A stepwise advancement of needle will stimulate in succession the third, second, and first divisions of the trigeminal nerve. On entering the Meckel's cave, aspiration will yield cerebrospinal fluid. Stimulation of the affected nerve is followed by lesioning of the affected division. Immediate pain relief is high; but after a period of around 3 years, one-third of the patients reported recurrent neuralgia.
The needle is inserted under fluoroscopy through the foramen ovale into trigeminal cistern. Sterile anhydrous glycerol up to 0.1-0.4 ml is injected. After 12 months, recurrence may be as high as 10-53%. Complications such as meningitis, cranial nerve palsies, and local hematomas can occur.
Under fluoroscopic control, a guide needle is inserted into the foramen ovale. A Fogarty catheter is passed through till its tip reaches the Meckel's cave; and after this, balloon is inflated with 0.5-1.0 ml of contrast causing adequate compression. Masseter weakness, due to compression of motor branch, may result which recovers over several weeks.
A stereotactic frame is fixed to the patient's head. After fixation, the patient is taken for magnetic resonance imaging. Trigeminal nerve is identified on imaging. Radiosurgery is carried out in the supine position. Pain relief is not immediate and occurs after 1 month.
Peripheral neurectomy is done by maxillofacial surgeons with remarkable pain relief lasting for 1-5 years in 75% of patients. Ali et al.,  observed that postsurgical pain relief varied from 15 to 24 months in cases where neurectomy was done without placing stainless steel screws in the foramina.
Neurectomies may be done through an incision made at the eyebrow (supraorbital nerve) or intraorally (infraorbital, alveolar, and lingual nerves). The neural branches are divided and avulsed with blocking of the foramina by bone wax. Peripheral neurectomies do not appear to offer any advantages over other surgical procedures.
In cryotherapy, a peripheral branch of the three major divisions of the trigeminal nerve is frozen by a cryoprobe ata temperature of -50 to -70°C.
Alcohol injections are given directly into the nerve. There is a high risk of recurrence of pain. However, they are used because of their simplicity in elderly and frail patients.
Pharmacological therapy is main stay of treatment of TN. Carbamazepine is the gold standard drug. When compared with placebo in several studies, there was a good clinical response in around 70% of patients. The other drugs commonly used for TN are oxcarbazepine, phenytoin, lamotrigine, baclofen, tizanidine, pimozide, and tocainade. Currently, there is no published data showing the advantage of polytherapy over monotherapy for the treatment of TN. The American Academy of Neurology (AAN) and the European Federation of Neurological Society (EFNS)  recommends the use of carbamazepine oroxcarbazepine as the first choice for pharmacological treatment ofCTN, and baclofen or lamotrigine as second choice.
| Which Treatment to Choose First?|| |
The choice of treatment in TN may be influenced by expertise and available gadgets.
There is currently no available literature showing superiority of surgical treatment over gangliolysis. The patient should be informed about all the treatment options available. The AAN and the EFNS  summarize that the percutaneous Gasserian lesions can be safely performed in the elderly but often engender facial numbness. Microvascular decompression provides long-lasting pain relief, but involves some risk of major neurological complications. Gamma-knife is the least invasive and safest procedure, but pain relief may take 1month to develop. A Cochrane review  concluded that there is a very low quality evidence for the efficacy of most neurosurgical procedures for TN because of the poor quality of trials. All procedures produce variable pain relief, but many result in sensory side effects. There is little evidence to help comparative decision making about the best surgical procedure. Well-designed studies are urgently needed.
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