Medication for trigeminal neuralgia
The main drugs used in the treatment of trigeminal neuralgia are the anticonvulsants carbamazepine and phenytoin sodium. Clobenzaprine, gamma-aminobutyric acid, and almotriptan have been more recently introduced and have shown some efficacy. Other drugs are sometimes effective but are not used as primary agents. Sporadic reports of the effectiveness of other anticonvulsants have emerged, but they have not been established by controlled studies.
Carbamazepine
Carbamazepine is the drug of choice for the control of trigeminal neuralgia and has been reported to improve symptoms in approximately 2/3 of cases. The drug is started at a dose of 100 mg/d and increased by 100 mg every 2 days until 600 mg/d. Of course, if the pain is reduced at lower doses, the total amount does not need to be increased. After 1 week at a dose of 600mg/d, if there is still no relief of symptoms, the daily thorn dose can be increased to 800mg for 1 week. The maximum dose should not exceed 1800mg/d, and higher doses will not produce higher efficacy.
Carbamazepine has been associated with gastrointestinal irritation in some patients and needs to be taken with food or liquids. Some patients have central nervous system adverse reactions, and a small number of patients have blood pressure changes and liver dysfunction. Due to the presence of adverse effects, a complete blood count is required monthly for the first year of drug administration and once every 3 months thereafter. Most patients have low white blood cell counts and there is no need to discontinue treatment unless the white blood cell count drops below 3500/rnl. The therapeutic strategy of the drug is to achieve drug doses that provide pain relief without toxicity, but there are no reliable assays to predict the effective amount of treatment and the dose that will produce toxicity in each individual. About 25% of patients had unacceptable adverse effects to carbamazepine, while about 50% of patients who took the drug successfully reduced their symptoms without unacceptable adverse effects. Caution must be exercised when combining carbamazepine with many other drugs.
Phenytoin sodium
Phenytoin sodium is the second choice for patients with trigeminal neuralgia. Satisfactory results are achieved in approximately 25% of patients when phenytoin sodium is administered at serum concentrations of 15-25 μg/ml. The treatment strategy is to maintain adequate serum concentrations for 3 weeks; if no effect is seen, the drug should be discontinued, as increasing the dose can only lead to toxicity. The phenytoin sodium required to achieve optimal serum levels is usually, given in two divided doses. If the patient is in severe pain, a large dose may be given at once to achieve rapid serum concentrations of the drug. CNS adverse reactions are mainly related to milligram levels, and some patients cannot tolerate the drug even at low doses.
Other drugs
(1) Chlorambucil.
Originally used to treat spasticity, but found to be effective by Fromm and companions in some patients with trigeminal neuralgia. The drug must be increased gradually starting at 5 mg and increasing by 5 mg every 2 days until pain relief or toxicity develops. The maximum dose is 80 mg/d. The drug should be tapered and not abruptly discontinued, especially in elderly patients.
(2) γ-aminobutyric acid.
For the recent anticonvulsant used for the treatment of trigeminal neuralgia, the initial dose is lOOmg per day If resistance occurs, it can be rapidly increased to 300mg, 4 times/d; if resistance occurs again after 1 week, the dose can be gradually increased to the maximum dose of 4800mg/d The drug is more expensive than other drugs, and good clinical trial results have not been obtained.
(3) Almotriptan.
It has been shown to be effective in a small number of trials.
(4) Rindrochlorphenesin and cresyl glycerol ether.
No longer used.
Nerve block therapy for trigeminal neuralgia
Local anesthetic block
Local injection of anesthetic to the trigger point or painful area may temporarily stop trigeminal neuralgia. Occasionally, cases have been reported in which pain relief has lasted longer than the expected duration of effectiveness of local anesthetics. Performing a nerve block can give the patient the same results as a planned neurectomy or total spinal rhizotomy.
Nerve Destructive Blocks
Blocking the peripheral branches of the trigeminal nerve or hemimelia with alcohol has a long history in the treatment of trigeminal neuralgia. The use of alcohol blocks rarely lasts more than one year, and repeated blocks have a low success rate and an increased morbidity. Significant sensory loss and hyperalgesia are difficult to manage unless expert assistance is available. Alcohol blocks are less satisfactory than ganglion blocks and are no longer routine treatment when modern techniques are used. However, when experienced ganglion block surgeons are not available. Alcohol blocks may be the best option. Alternatively, glycerol is often used as a blocking agent. There are increasing reports of treatment with trigeminal ganglion adriamycin injections, which may have better efficacy than alcohol or glycerol blocks.
Surgical treatment of trigeminal neuralgia
No single surgical treatment is guaranteed to cure trigeminal neuralgia. Surgical treatment is not advocated unless pharmacologic treatment has failed because it is unlikely to provide both complete pain relief and unacceptable complications. The trend in surgical treatment of trigeminal neuralgia is to shift from the peripheral nerves to the brainstem. Commonly used surgical treatments include peripheral neurectomy, peripheral nerve radiofrequency or cryoinjury, ganglion block (radiofrequency, mechanical, glycerol), hemicranial ganglion compression and decompression, posterior temporal hemicranial ganglion rhizotomy, posterior occipital hemicranial ganglion rhizotomy, trigeminal nerve bundle dissection, trigeminal nerve manifest microvascular decompression, and stereotactic radiosurgery. Currently, the two main surgical approaches for the treatment of trigeminal neuralgia are ganglion block and trigeminal nerve microvascular decompression through suboccipital partial craniectomy.
Microvascular decompression
The popularity of microvascular decompression stems from Jannetta’s study. The procedure is performed under conventional anesthesia, with a partial craniectomy through the suboccipital bone and microscopic observation of how the trigeminal nerve leaves the pontine brain, relieving vascular-induced compression by displacing the invasive artery or coagulated vein. This approach has an 85% 5-year success rate and does not produce sensory deficits. The recurrence rate is 5% and the mortality rate is 0.5%.
Posterior rhizotomy of the semilunar ganglion
Resection of the trigeminal nerve root between the semilunar ganglion of the trigeminal nerve and the pontine brain was the routine procedure in the first half of the 20th century. It is used to relieve long-term pain when no trigeminal nerve compression is found during partial suboccipital craniectomy, or when manifest microvascular decompression fails. Performing a partial nerve rhizotomy is most advisable because it reduces the incidence of painful sensory loss and reduces the incidence of generalized numbness. The common approach today is through the posterior cranial recess, and the transtemporal inferior approach is rarely used.
Peripheral neurectomy
Peripheral neurectomy is used when ganglion blocks fail and the patient cannot tolerate suboccipital partial craniectomy with microvascular decompression. It produces profound postoperative paralysis and pain relief for no more than a year. Repeated tears of the peripheral branches of the trigeminal nerve are rarely successful.
Compression into decompression of the semilunar ganglion
Decompression or decompression maneuvers were popular before manifest microvascular decompression and ganglion blocks. They are effective because of the minimal damage to the trigeminal nerve, ganglion or root filaments and the craniotomy through the middle cranial recess.
Trigeminal nerve bundle dissection
Dissection of the inferior bundle of the trigeminal nerve in the medulla will produce an absence of ipsilateral facial and pharyngeal nociception and temperature sensation, without affecting the sense of touch. This procedure may relieve pain when rhizotomy and all other methods have failed. This procedure is accomplished by a small suboccipital partial craniectomy and C1 and C2 laminectomy. Kunc shows the nociceptive-temperature fibers in the three-branch pathway of the inferior trigeminal nerve bundle.
Stereotactic radiosurgery
Radioactive damage is placed in the root of the trigeminal nerve without damaging the surrounding brain tissue or vascular structures. The effects of this radiation therapy can last from a few weeks to a few months, but what the results are beyond 5 years is not documented. The short-term results of this approach are as good as those of other surgical treatments and will likely be used more widely in the coming years.