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Introduction Trigeminal Neuralgia, also known as"TicDouloureux", is a disturbance which affects one or more of the three branches of the trigeminal nerve in the face and head. It is estimated that approximately 15 to 25,000 new cases occur in the United Kingdom each year, making it one of the "rare disturbances". Due to the difficulties the patients have in obtaining the diagnosis, this estimate may be considered low. In the initial stages, before the symptoms develop completely, the trigeminal neuralgia is often confused with other diseases or dental problems. Some patients experience "atypical" trigeminal neuralgia, with more constant pain at a level generally of lower intensity. The rarity of these disturbances and the variability of these symptoms have caused some patients to undergo endodontic treatment of multiple root canals or other oral or sinus surgeries before a neurological disturbance is recognized (1). Trigeminal Neuralgia is one of the most severe forms of pain, of great
intensity, that is known. It was described originally in 1773 by Fothergill
and the clinical symptoms described in details by Stookey and Ranshoff
(13). Anatomy of the Trigeminal Nerve The trigeminal nerve as the name indicates is composed of three large branches. They are the ophthalmic (V1, sensory), maxillary (V2, sensory) and mandibular (V3, motor and sensory) branches. The large sensory root and smaller motor root leave the brainstem at the midlateral surface of the pons. The sensory root terminates in the largest of the cranial nerve nuclei which extends from the pons all the way down into the second cervical level of the spinal cord. The sensory root joins the trigeminal or semilunar ganglion between the layers of the dura mater in a depression on the floor of the middle crania fossa. This depression is the location of the so called Meckle's cave. The motor root originates from cells located in the masticator motor nucleus of trigeminal nerve located in the midpons of the brainstem. The motor root passes through the trigeminal ganglion and combines with the corresponding sensory root to become the mandibular nerve. It is distributed to the muscles of mastication, the mylohyoid muscle and the anterior belly of the digastric. The mandibular nerve also innervates the tensor veli palatini and tensor tympani muscles. The three sensory branches of the trigeminal nerve emanate from the ganglia to form the three branches of the trigeminal nerve. The ophthalmic and maxillary branches travel in the wall of the cavernous sinus just prior to leaving the cranium. The ophthalmic branch travels through the superior orbital fissure and passes through the orbit to reach the skin of the forehead and top of the head. The maxillary nerve enters the cranium through the foramen rotundum via the pterygopalatine fossa. Its sensory branches reach the pterygopalatine fossa via the inferior orbital fissure (face, cheek and upper teeth) and pterygopalatine canal (soft and hard palate, nasal cavity and pharynx). There are also meningeal sensory branches that enter the trigeminal ganglion within the cranium. The sensory part of the mandibular nerve is composed of branches that carry general sensory information from the mucous membranes of the mouth and cheek, anterior two-thirds of the tongue, lower teeth, skin of the lower jaw, side of the head and scalp and meninges of the anterior and middle cranial fossae.
Etiology The lesion of the sensorial nerves of the face is expressed by painful phenomena called neuralgias of the brainstem or of its branches. They may be idiopathic or essential and secondary or symptomatic and their clinical evidences and courses are different from the first. The essential neuralgia, or tic douloureux, is the most frequent facial neuralgia. There are evidences of trigeminal neuralgia secondary to oral causes (dental, traumatic, post herpes zoster, etc) (4). Literature shows that there may be other causes, such as: temporal glioblastoma causing trigeminal neuralgia (5); trigeminal neuropathy secondary to the perineural invasion of carcinomas of the head and the neck, although an uncommon cause (6); trigeminal neuralgia provoked by auditive stimuli in multiple sclerosis (7); trigeminal neuralgia caused by the compression of the petrous vein transfixing the nerve (8); and familial trigeminal neuralgia and contralateral hemifacial spasm. The transmission of the neuralgia suggesting an autosomal dominant inheritance (9). In our service we also had some pathosis such as: cysts or tumors
adjacent to the nerve or to one of the trigeminal roots, tumors of the
cerebellar point angle, ischemical brain vascular diseases and vascular
compressions. Symptoms The typical trigemial neuralgia is characterized by sudden, severe and lancing pain in the face, like an "electric shock", frequently located to some few highly sensitive trigger points. These zones react to minor stimuli - change of temperature, scratch, touch of a scarf, speaking, tooth brushing may start an attack. The attacks last from seconds to minutes, but they may occur in repetitive discharges which last several hours. Paroxysmal characteristics is one of the most marked and prominent symptom, characteristic of Trigeminal Neuralgia. The pain typically affects one side of the face in regions which vary from the mandible to the forehead and skull above the ear. In some patients, the eye, the ear or the palate may be affected. In many patients, the attacks are less frequent at night or when the patient lies down. The onset of symptoms is more common in individuals between 50 and 60 years old, but it may occur in any age, including childhood. The disturbance is a little more common in women than in men. The incidence of Trigeminal Neuralgia is estimated to involve 4/100.000 inhabitants. (14) The pain usually begins in an intermitent way, with periods of months or sometimes years between the attacks. As the patient grows older, the periods of remission become shorter and the attacks more severe. Spontaneous recovery is extremely rare. There is an "atypical" form of trigeminal neuralgia which produces less well defined symptoms in some of the patients diagnosed with trigeminal neuralgia. Some patients feel the sensation of burning or pain which extends for longer periods of time, more often on one side of the face or the forehead. The causes of the atypical trigeminal neuralgia are less understood, and it may be difficult to distinguish from other medical problems like migraine, facial migraine, nerve lesion and sinus or dental problems. In the same manner, treatment for atypical trigeminal neuralgia may be less efficient in eliminating pain. The glossopharyngeal neuralgia is another neurological disturbance
potentially related which causes throat pain and difficulty in swallowing.
Some patients complain of sensation of burning or of having a fish-bone
in the throat (1). Diagnosis The diagnosis of trigeminal neuralgia may be made by obtaining a history of paroxysmal ipsilateral facial pain activated by several facial stimuli. A slight stimulation of the trigger point provokes pain. The relief of pain by carbamazepine gives more credit to the diagnosis of trigeminal neuralgia and the treatment with a neurosurgeon (10). In the primary Trigeminal Neuralgia (idiopathic) the neurological
examination of the patient is usually normal. When there is a lesion involving
the gasserian ganglion, the dorsal root or the entrance area of the root
at the pons level, we may have associated neurological signs, which include
alterations of the face or cornea sensitivity, weakness and/or atrophy
of the chewing muscles, or the involvement of the adjacent cranial nerves.
Clinical Treatment There are several medical and surgical treatments of this painful condition. Many patients experience significant improvement or total cessation of symptoms, although for other patients the symptom may recur. If trigeminal neuralgia is suspected, the first care the physician takes may be the referral to a neurologist. MRI or CAT are frequently used to eliminate tumor or multiple sclerosis as causes of the pain. The treatment with drugs in the initial stages of the disturbance is often efficient for long periods; However, some drugs of choice may create side effects which must be effectively monitored, particularly if the dosage is high (1). Trigeminal neuralgia is first treated clinically and carbamazepine is the most efficient medicine. Other medicines may be prescribed or used such as phenytoin, lioresal (baclofen) and gabapentin. However, in many cases the patients experience pain or side effects. In which case, surgery is considered an option (3). In our experience, throughout these years the drug of choice has been
carbamazepine as the lone therapy or associated with phenytoin, where
75% of the patients respond well to the treatment, always being careful
with the side effects like dizziness and gait instability, mainly in older
patients. In some cases we also prescribe cortrosine (ACTH), mainly in
patients who still present significant symptoms after the beginning of
the conventional treatment. We have also used gabapentin with good results,
normally in association with carbamazepine, using the dosage around 800
to 1000 mg with few side effects, because of its great tolerability. This
drug does not link to plasmatic proteins, with no induction of hepatic
enzymes and it is excreted practically intact in urine, being useful in
the treatment of renal or hepatic patients. The literature reports results
around 83% as a drug of first choice and in little less than 60% in the
patients who had poor response to carbamazepine (15). Surgical Treatment There are several surgical procedures, each one with advantages and disadvantages depending on the nature of the pain of the patient, their age, general health, work situation, personal objectives and preocupations with the treatment. If the patient is having an initial acute facial pain, like electric shock, on one side of the face, the dentist must verify if there is a neurological problem like trigeminal neuralgia, before performing dental surgery or endodontic treatment. This is particularly true if the radiographic examination does not clearly show pathosis or dental abscess. Other diseases and disturbances may also produce similar symptoms which must be referred to the specialist. In all cases, the patient must be referred to the physician or dentist (1). We indicate surgery only when the patient is refractive to any type of clinical treatment. For a long time we used the retrogasserian neurotomy via extra dural sub temporal; at present the technique of Jannetta is the most used and with fewer post operative complications. Radiofrequency thermoneurolysis and thermogangliolysis may also be used, but with a liklihood of pain relapse after some time. There are also studies for the technique of radiosurgery as a choice for the treatment of Trigeminal Neuralgia. The surgery of microvascular decompression offers the best chance of relief for a long time and the best quality of life among all the surgical procedures available, because it relieves pain without the production of numbness as occurs with the destructive/ablative procedures (3). Results: the microvascular decompression has been performed at the Medical Center of the University of Pittsburgh during the last 25 years in more than a thousand patients with trigeminal neuralgia. With careful follow-up it becomes clear that this surgery offers the best chance of cure of pain for a long time with no need of medication or any alternative surgical procedures. Initially almost all patients experience relief from discomfort, but there is, however, a certain rate of recurrence with time. Even so, the rate of recurrence is relatively small and after 20 years of follow-up, from 75% to 80% of the patients become completely free of pain with no need of medication, making this surgery the most efficient procedure to date. (3). According to Romansky et al, 85 patients suffering from trigeminal neuralgia resistant to the medical therapeutics underwent surgical treatment for the relief of pain at the Department of Neurosurgery at the University Alexander at the Sophia Hospital from 1981 to 1997. The microvascular decompression at the entrance region of the V nerve has been performed using the technique of Jannetta. The operative exploration of the entrance region of the parapontine root revealed neurovascular problems in 87.1% of the cases. They represented dislocation and/or distortion, some wrinkles, discoloration, and changed vascularity of the V nerve. The analysis of the first post operative results showed excellent result in 90.6% of the cases, good in 3.5% and fair results and recurrences in 6.1% of the cases (11). Manahan et al report a case of a 56 year old woman with the diagnosis
of trigeminal neuralgia, who did not respond to the clinical therapeutics,
and who received a block of the sphenopalatine ganglion using bupivacaine
0.5%. A total of ten treatments were made. The patient was free of pain
for 30 months after the initial treatment. The treatment seemed to be
efficient and deserves more studies (12). References 1 - Lawhern, R.A. About Trigeminal Neuralgia. Member of the Board of Directors. Trigeminal Neuralgia Association, Barnegat Light, NJ. Jan. 1999. 2 - Thackery G., Hisghman, J. - CN V. Trigeminal Nerve. Loyola University Medical Education Network, Chicago, Ill. Aug. 1997. 3 - Barker FG, Jannetta PJ, Bissonnette DJ, Larkins MV, Jho HD: The long-term outcome of microvascular decompression for trigeminal neuralgia. The New England Journal of Medicine, 334(17):1077-1083, 1996. 4 - Brito AJ. Trigeminal neuralgia. Acta Med Port 1999 Apr-Jun;12(4-6):187-93. 5 - Deshpande S, Kaptain GJ, Pobereskin LH. Temporal glioblastoma causing trigeminal neuralgia. Case illustration. J Neurosurg 1999 Sep;91(3):515. 6 - Boerman RH, Maassen EM, Joosten J, Kaanders HA, Marres HA, van Overbeeke J, De Wilde P. Trigeminal neuropathy secondary to perineural invasion of head and neck carcinomas. Neurology 1999 Jul 13;53(1):213-6. 7 - Hartmann M, Rottach KG, Wohlgemuth WA, Pfadenhauer K. Trigeminal neuralgia triggered by auditory stimuli in multiple sclerosis. Arch Neurol 1999 Jun;56(6):731-3. 8 - Kimura T, Sako K, Tohyama Y, Yonemasu Y. Trigeminal neuralgia caused by compression from petrosal vein transfixing the nerve. Acta Neurochir (Wien) 1999;141(4):437-8. 9 - Duff JM, Spinner RJ, Lindor NM, Dodick DW, Atkinson JL.Familial trigeminal neuralgia and contralateral hemifacial spasm. Neurology 1999 Jul 13;53(1):216-8. 10 - Jackson EM, Bussard GM, Hoard MA, Edlich RF. Trigeminal neuralgia: a diagnostic challenge. Am J Emerg Med 1999 Oct;17(6):597-600. 11 - Romansky K, Stoianchev N, Dinev E, Iliev I. Results Of Treatment Of Trigeminal Neuralgia By Microvascular Decompression Of The V(th) Nerve At Its Root Entry Zone. Arch Physiol Biochem 1998 Dec;106(5):392-396. 12 - Manahan AP, Malesker MA, Malone PM. Sphenopalatine ganglion block relieves symptoms of trigeminal neuralgia: a case report. Nebr Med J 1996 Sep;81(9):306-9 13 - Stookey B, Ranshoff J. Trigeminal Neuralgia - Its history and treatment - Sprigfield Il. CC Thomaz 1959 14 - Yoshimasu F et al. Neurology , 1972; 22 : 952-956. 15 - Valzania F et al. Neurology, 1998; 50 : A379. 16 - Trigeminal Nerve Poster, courtesy of Prof. Dr. Fausto Bérzin,
Dental School of Piracicaba, UNICAMP.
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