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Treatment It is possible, in almost all cases, to relieve the pain of patients with trigeminal neuralgia. Therapy may employ either medical or surgical expertise, usually both (Loeser, 1978). Most authorities agree that medical treatment is indicated first, if only because its use may constitute a therapeutic challenge to the correct diagnosis (Dalessio, 1981). If, for example, a patient presumed to have trigeminal neuralgia does not respond to carbamazepine in 24---48 hours, then the physician may wish to reconsider the initial diagnosis (Miller, 1968). Carbamazepine (Tegretol) is thought to be the single most useful medication in the treatment of trigeminal neuralgia (Voorhies and Patterson, 1981). It is related to the tricyclic antidepressants and was reported by Blom (1962) to be effective in 90% of his patients when given in gradually increasing doses. Spillane (1964) confirmed the effectiveness of this drug in many but not all of his patients. Graham and Zilkha (1966) reported on the treatment of 96 patients with trigeminal neuralgia who were treated with carbamazepine. Of the 96 patients, 52 were followed for a year or more, and 10 patients were followed for over 2 years. Sixty-five of the 96 patients (68%) obtained satisfactory pain relief, and 26 patients (27%) were entirely pain-free. Rockliff and Davis (1966) performed a controlled study with carbamazepine and placebo and demonstrated a beneficial result with carbamazepine with less than a 5% probability of error. In their study, complete or major pain relief was maintained with the drug, either alone or combined with diphenylhydantoin (Dilantin). Taylor et al. (1981a) reviewed the results of 143 patients with trigeminal neuralgia who were treated with carbamazepine over a 16-year period. The drug was initially effective in 99 patients (69%). Nineteen patients ultimately developed resistance to the drug and required alternative therapy; however, 49 patients experienced pain relief over a period of time ranging from 1---4 years, and 31 patients experienced pain relief over a 5- to 16-year period. In most trials, carbamazepine has been effective in 60---80% of patients to whom it is given, but there are numerous adverse reactions that may occur (Rockliff and Davis, 1966; Al-Ubaidy and Nally, 1976; Stephens et al., 1977). Patients taking Tegretol must be given gradually increasing doses of the drug until a therapeutic level is reached, must be closely supervised, and should undergo a periodic complete blood count, platelet count, reticulocyte count, and serum electrolyte and iron determinations. In addition, liver and kidney function tests should also be performed on a regular basis. Nevertheless, if the patient with trigeminal neuralgia does respond to carbamazepine, then this is the treatment of choice, particularly when used in multiple divided doses (Thomson and Ekbom, 1981). Tomson and Bertilsson (1984) have also used carbamazepine-10,11-epoxide, a metabolite of carbamazepine, to treat patients with trigeminal neuralgia. These investigators found that, on a plasma concentration basis, carbamazepine-10,11-epoxide had a considerably higher pain-relieving potency than did carbamazepine. The analgesic action of carbamazepine has been said to result from the suppression of synaptic transmission at the nucleus reticularis dorsalis and the trigeminal nucleus caudalis (see Chapter 39) (Satoh and Foong, 1983). In the patient who does not respond or responds only partially to carbamazepine, other drugs may be of benefit, including diphenylhydantoin (Dilantin) (Bergouignan, 1942; Iannone et al., 1958; Dalessio, 1977), baclofen (Fromm et al., 1979, 1980, 1984), clonazepam (Smirne and Scarlato, 1977), sodium valproate (Peiris et al., 1980), and chlorphenesin carbamate (Dalessio, 1977). The most useful of these ``second line'' drugs appears to be baclofen. Fromm and his colleagues (Fromm and Terrence, 1983; Fromm et al., 1984) conducted a double-blind crossover trial in 10 patients with trigeminal neuralgia as well as a long-term open trial in 50 patients with trigeminal neuralgia whose symptoms were refractory to, or who could not tolerate, carbamazepine. Baclofen significantly decreased the number of attacks in seven of the 10 patients in the double-blind study. In the open trial, 37 of 50 patients (74%) experienced relief of pain, either with baclofen alone (12 patients) or with baclofen in combination with previously ineffective doses of carbamazepine or phenytoin (25 patients). During a follow-up period from 6 months to 4 years (average 1.5 years), only 7 of the 50 patients became refractory to baclofen. In the mid 1990's another agent used initially as an anticonvulsant, Neurontin (gabapentin) has been used with some success. Stilbamidine, which was recommended for the treatment of trigeminal neuralgia in 1953 (Smith and Miller, 1953), is no longer used for this disorder, primarily because of its toxicity (Arai and Snapper, 1947; Seager and Castelnueovo, 1947), and also because better therapeutic measures are available. Despite the numerous drugs that are available for the treatment of trigeminal neuralgia, between 25% and 50% of patients will eventually fail to respond to drug therapy and need some form of neurosurgical treatment (Dalessio, 1981). In the series by Van Loveren et al. (1982), of 1000 patients with trigeminal neuralgia, 90% had an initially favorable response to medical therapy, but 75% failed to achieve satisfactory long-term relief and required surgical intervention. The surgical treatment of trigeminal neuralgia is particularly important from an ophthalmologic viewpoint, because ocular complications may occur. Two procedures, local ablation (surgical or injection of alcohol or boiling water) of peripheral nerves and wide section of the sensory root of the trigeminal nerve, are rarely performed any longer because better methods are usually available for surgical pain relief. Nevertheless, certain patients whose pain is unresponsive to medical therapy and who are unable to tolerate more extensive surgical procedures may be candidates for such procedures. These have been described in detail by Bayer and Stenger (1979). The production of selective lesions of the trigeminal root by means of a radiofrequency electrode placed in the root under radiologic control (percutaneous radiofrequency trigeminal rhizotomy, PRTR) is an operative procedure that has gained wide acceptance (Sweet and Wepsic, 1974; Tew and Keller, 1977; Scarfo et al., 1980; Keet, 1982; Nugent, 1982; Rushworth and Smith, 1982) (Figure 36.16). It has the advantages of relative safety and simplicity. The anesthesia used is light. The patient is awake during some of the procedure and recovers rapidly. Unfortunately, after this procedure, there is a recurrence rate of about 25% (Sweet, 1976; Nugent, 1982). In addition, trigeminal-innervated muscle weakness is a significant early side effect, occurring in 23% of the patients operated upon by Tew (1979) and 25% of the patients operated upon by Nugent (1982). The muscle weakness resolves in most patients within 6 months. Altered sensation in the face is reported by many patients who undergo PRTR, but rarely is the sensory disturbance intolerable (e.g., anesthesia dolorosa--Tew and Keller, 1977; Tew, 1979). Occasionally, corneal anesthesia occurs (Lewis et al., 1981, 1982a, 1982b; Nugent, 1982), and neuroparalytic keratitis has also been described (Sweet and Wepsic, 1974; Thiry and Hotermans, 1974; Tew and Keller, 1977). Ocular motor nerve palsies have been reported following radiofrequency trigeminal rhizotomy. Onofrio (1975) described one patient who developed a sixth nerve palsy among 140 patients who underwent the procedure, and Rhoton et al. (1977) also reported one patient who developed an isolated sixth nerve palsy among 149 similar patients. Tew (1979) has reported transient diplopia in 3% of 500 patients in whom he has performed radiofrequency rhizotomy, and Tew and Keller (1977) documented five patients who developed sixth nerve palsies and two patients who developed fourth nerve palsies. Grimson and Boone (1981) have reported two patients who developed sixth nerve palsies following PRTR for trigeminal neuralgia. In both patients, the palsies resolved spontaneously within 4---7 months. Among the possible mechanisms responsible for these palsies are direct injury to the nerves, inadvertent penetration of the cavernous sinus by the radiofrequency needle, and indirect thermal injury during ablation of the trigeminal nerve rootlets (Onofrio, 1975; Sweet, 1976; Tew and Keller, 1977; Siegfried, 1977). That the cavernous sinus may be inadvertently penetrated during the procedure can be inferred by the reports of Sekhar et al. (1979) and Gökalp et al. (1980) describing the development of carotid-cavernous sinus fistulas following the procedure. Finally, we are aware of one patient who suffered blindness with eventual development of optic atrophy after percutaneous radiofrequency trigeminal rhizotomy. The mechanism for this complication was thought to be inadvertent passage of the needle through the inferior orbital fissure into the orbit. At The Johns Hopkins Hospital, Dr. Melvin Epstein has performed this procedure on over 300 individuals with trigeminal neuralgia. Among these patients, there have been no deaths, and there have been no cases of anesthesia dolorosa, neuroparalytic keratitis, or ocular motor nerve palsies. Broggi and Franzini (1982) have used PRTR for the treatment of symptomatic non-neoplastic facial pain in 20 patients. Fourteen of the patients had multiple sclerosis, three had Paget's disease with basilar impression, two had untreatable intracranial aneurysms, and one patient developed chronic ocular pain following a vitreous hemorrhage. All patients had immediate pain relief following the procedure; unfortunately, there was a high (40%) recurrence rate in the patients with multiple sclerosis, requiring, in most cases, a second procedure. An alternative procedure that is performed in patients with trigeminal neuralgia who are unresponsive to medical therapy is microsurgical decompression of the trigeminal root (Gardner, 1953, 1962; Apfelbaum, 1977; Jannetta, 1977; Rand, 1981; Klun, 1981; Voorhies and Patterson, 1981; Wilberger and Velo, 1981; Adams et al., 1982; Breeze and Ignelzi, 1982; Taarnhoj, 1982; Barba and Alksne, 1984). The neurosurgeon assumes that he will find a lesion, usually a vascular loop, compressing the trigeminal root adjacent to the brain-stem (Figure 36.17). According to Jannetta (1979), the advantages of this procedure are: (1) an improved quality of life; (2) a decreased rate of recurrence; (3) no anesthesia dolorosa; and (4) the ability of the surgeon to perform percutaneous radiofrequency trigeminal rhizotomy should the procedure fail to achieve the desired pain relief. In Jannetta's series of over 450 patients, the majority of patients were cured of their disease over a long follow-up period, and the majority of recurrences occurred within 6 months. Trigeminal
Neuralgia Treatment Part Two
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