Evidence-based approach to the medical management of trigeminal neuralgia

Assessment of mechanisms involved in antinociception caused by myrsinoic acid B

Myrsinoic acid B (AMB) is a prenylated-benzoic acid derivative isolated from the Rapanea genus. Recent studies suggest that AMB has antihyperalgesic and antinociceptive properties in different animal models. The present study was designed to investigate the mechanisms involved in antinociception elicited by AMB (60 mg/kg) when administered by intraperitonial route (i.p.) in mice. The antinociceptive response of the compound was characterized by a reduction in contractions of the abdominal muscle, together with stretching of the hind limbs in response to i.p. injection of acetic acid (0.6%, 0.45 ml/mouse). The antinociception caused by AMB in the acetic acid test was significantly attenuated by i.p. treatment of mice with nitric oxide precursor, (L-arginine, 600 mg/kg), alpha2 and alpha1-adrenoceptor antagonists (yohimbine, 0.2 mg/kg/prazosin, 0.2 mg/kg), p-chlorophenylalanine (PCPA) an inhibitor of serotonin synthesis (100 mg/kg), 1-(2-methoxyphenyl)-4-(4-phthalimidobutyl)piperazine (NAN 190), a 5-HT1(A) selective receptor antagonist (0.5 mg/kg) and a non-selective cholinergic antagonist (atropine, 10 mg/kg). Its action was also modulated by the adrenal-gland hormones. In contrast, antinociception was not affected by naloxone (non-selective opioid receptor antagonist, 1.0 mg/kg), phaclofen (2.0 mg/kg) and bicuculline (1.0 mg/kg) GABA(B) and GABA(A) receptor antagonists, respectively, ondansetron (0.3 mg/kg) and ketaserin (1.0 mg/kg), (5-HT3 and 5-HT2 receptors, respectively) and haloperidol (0.2 mg/kg), a non-selective dopaminergic receptor. The antinociceptive effects are not related to muscle-relaxant or sedative action. These results indicate that AMB produces antinociception through mechanisms that involve interaction with L-arginine-nitric oxide, the serotonergic and cholinergic systems, as well as interaction with the alpha-adrenoceptors.

Medical management of trigeminal neuropathic pains

IMPORTANCE OF THE FIELD

Although trigeminal neuralgia has traditionally been considered the prime neuralgic condition in the face region, other forms of neuropathic pain are now being more frequently recognized and require recognition and a different management approach.

AREAS COVERED IN THIS REVIEW

This review principally covers medical management of trigeminal neuralgia; but also included is glossopharyngeal neuralgia, trigeminal neuropathic pain (atypical odontalgia) and burning mouth syndrome. Systematic reviews and guidelines will be discussed.

WHAT THE READER WILL GAIN

An update will be provided of drug therapy for these relatively rare facial pains.

TAKE HOME MESSAGE

Trigeminal neuralgia continues to be best managed using anticonvulsant drugs, the primary ones being carbamazepine and oxcarbazepine; baclofen may be helpful and, of the newly emerging drugs, pregabalin has potential. Glossopharyngeal neuralgia remains managed in the same way as trigeminal neuralgia. Trigeminal neuropathic pain is probably best managed according to guidelines used for the management of neuropathic pain, which include the use of tricyclic antidepressants, gabapentin, pregabalin, duloxetine, venalafaxine and topical lidocaine. Burning mouth syndrome is a neuropathic pain managed initially with topical clonazepam and then with other neuropathic drugs. Patients need to be involved in their management.

Patient-reported outcomes in subjects with painful trigeminal neuralgia receiving pregabalin: evidence from medical practice in primary care settings

Effects of pregabalin (PGB) on patient-reported health outcomes were assessed in 65 PGB-naive subjects with trigeminal neuralgia refractory to previous analgesic therapy in a prospective, multicentre observational study carried out in primary care. Twelve weeks' monotherapy with PGB (n = 36) or add-on (n = 29), reduced baseline intensity of pain by a mean +/- S.D. of -40.0 +/- 22.1 mm [-55.4%, effect size (ES) 2.32; P < 0.0001] with 59.4% of responders (pain reduction >or= 50%), and produced 34.6 +/- 29.3 additional days with no/mild pain. Anxiety/depression symptoms decreased by -3.8 +/- 3.5 and -4.5 +/- 4.2 points (ES 0.95 and 1.02; P < 0.0001), respectively. PGB improved sleep by -17.9 +/- 19.6 points (ES 1.18; P < 0.0001) and improved patient functioning (Sheehan Disability Index) by decreasing overall scoring by -8.6 +/- 5.9 points (ES 1.59; P < 0.0001). Health state (EQ-5D) increased by 31.6 +/- 22.2 mm (ES 1.67; P < 0.0001), with 0.0388 +/- 0.0374 gained quality-adjusted life-years. In spite of the small sample size, results support the effectiveness of PGB for the improvement in pain and related health symptoms.

Pilot study to evaluate the efficacy and tolerability of levetiracetam (Keppra) in treatment of patients with trigeminal neuralgia

BACKGROUND AND PURPOSE

The objective of this study was to determine whether levetiracetam (LEV) is an effective drug for treatment of trigeminal neuralgia (TN).

METHODS

Ten patients with TN were enrolled in a 10-week, prospective, open-label pilot study. The primary outcome measure was the visual analogue scale on daily pain diary and side effects. Serum levels of LEV were measured to assess correlation between drug levels and pain control.

RESULTS

There was a significant tendency towards improvement in pain severity compared with baseline in four patients with higher doses of 4,000 mg/day. The four treatment responders had less pain compared with baseline (50-90% improvement) and three subjects continued the drug after study completion. All patients rated themselves on the global evaluation scale as much improved (n = 2), minimally improved (n = 3), no change (n = 1), minimally worse (n = 2), much worse (n = 1) and very much worse (n = 1). LEV was very well tolerated and there was no difference in side effects between the low and high doses of LEV evaluations.

CONCLUSION

Given its established safety profile, a randomized, placebo-controlled, double-blind trial of LEV using enhancement enrollment design is needed to confirm these open-labelled findings using a wide variety of outcome measures.

Filicene obtained from Adiantum cuneatum interacts with the cholinergic, dopaminergic, glutamatergic, GABAergic, and tachykinergic systems to exert antinociceptive effect in mice

In the present study, we describe the antinociceptive effect of filicene, a triterpene isolated from Adiantum cuneatum (Adiantaceae) leaves, in several models of pain in mice. When evaluated against acetic acid-induced abdominal constrictions, filicene (10, 30 and 60 mg/kg, i.p.) produced dose-related inhibition of the number of constrictions, being several times more potent [ID(50)=9.17 (6.27-13.18) mg/kg] than acetaminophen [ID(50)=18.8 (15.7-22.6) mg/kg], diclofenac [ID(50)=12.1(9.40-15.6) mg/kg] and acetylsalicylic acid [ID(50)=24.0(13.1-43.8) mg/kg] in the same doses as those used for the standard drugs. Filicene also produced dose-related inhibition of the pain caused by capsaicin and glutamate, with mean ID(50) values of 11.7 (8.51-16.0) mg/kg and <10 mg/kg, respectively. Its antinociceptive action was significantly reversed by atropine, haloperidol, GABA(A) and GABA(B) antagonists (bicuculline and phaclofen, respectively), but was not affected by L-arginine-nitric oxide, serotonin, adrenergic and the opioid systems. Together, these results indicate that the mechanisms involved in its action are not completely understood, but seem to involve interaction with the cholinergic, dopaminergic, glutamatergic, GABAergic and tachykinergic systems.

Trigeminal neuralgia: historical notes and current concepts

BACKGROUND

Trigeminal neuralgia is a syndrome of paroxysmal excruciating, lancinating unilateral facial pain.

REVIEW SUMMARY

There are several clinical features that are characteristic of trigeminal neuralgia, but there may be red flags that should suggest alternative diagnoses. There is convincing evidence that the idiopathic form develops from focal demyelination at the trigeminal root entry zone with subsequent ephaptic cross-talk between axons. Vascular compression of the nerve root causes this demyelination in most patients. Medical management of this condition, using anticonvulsant therapy and other agents, aims to dampen the abnormal electrical signals and to ameliorate symptoms. In refractory cases, a number of surgical interventions can be considered, the most common of which is microvascular decompression of the trigeminal nerve. Gamma knife therapy is emerging as an alternative treatment for the patient with medically refractive trigeminal neuralgia, particularly in the elderly patient with comorbid conditions.

CONCLUSION

Knowledge of the proper diagnosis and management of trigeminal neuralgia is essential to the successful management of these patients.

Gabapentin responsive audiovestibular paroxysmia

Trigeminal neuralgia and hemifacial spasm are well-documented vascular compression syndromes involving the 5th and 7th cranial nerves. Drugs that stabilize the irritated nerves and vascular decompression surgery are accepted treatments. By contrast, the diagnosis and treatment of a comparable syndrome involving the 8th cranial nerve is controversial. We describe two patients with brief, spontaneous, recurrent attacks of tinnitus and vertigo that responded to low dose gabapentin and we argue that this clinical presentation represents the prototypical 8th nerve vascular compression syndrome.

Trigeminal neuralgia treated with pregabalin in family medicine settings: its effect on pain alleviation and cost reduction

The purpose of this study is to analyze the effect of pregabalin (PGB) on pain alleviation, use of health care and non-health care resources, and associated costs in patients with trigeminal neuralgia under usual clinical practice in primary care settings. Sixty-five PGB-naïve patients receiving PGB as monotherapy (n = 36, 55%) or combined with other drugs (n = 29, 45%) fulfill criteria for inclusion in a secondary analysis from a 12-week, multicenter, observational prospective study aimed to ascertain the cost of illness in subjects with neuropathic pain. Pain is evaluated using the Short Form McGill Pain Questionnaire. Use of health care and non-health care resources and lost workdays equivalents (LWDEs) are also recorded. PGB significantly reduces pain scores, use of health care resources (ancillary tests and unscheduled medical visits), and number of LWDEs. Additional cost of PGB treatment (+euro 174 +/- 106) is broadly compensated for by a reduction in both health care costs (-euro 621 +/-1211, P < .001) and indirect costs (-euro 1210 +/- 1141, P < .001). It is concluded that PGB as monotherapy or combined with other drugs is effective in pain management in patients with trigeminal neuralgia and reduces the cost of illness.

[Improvement of diagnosis and treatment of glossopharyngeal neuralgia]

Differential diagnosis of neuralgias affecting the cranial nerves and of facial pain is often difficult. Glossopharyngeal neuralgia is much less common than trigeminal neuralgia and is not well known. Idiopathic neuralgia of the glossopharyngeal nerve sometimes occurs in association with neurovascular compression syndrome of the vagus and trigeminal nerves. High-resolution MRI of the brain stem with three-dimensional visualization allows a secure diagnosis of neurovascular compression and is useful in the planning of appropriate microsurgical decompression (Jannetta's operation).

Trigeminal neuralgia: for one nerve a multitude of treatments

Trigeminal neuralgia (TN) is reputed to be one of the most painful conditions in human experience. Thus, many treatments, both medical and surgical, have been developed for this relapsing and remitting, paroxysmal stabbing or electrical, facial pain syndrome. The likely etiology in many cases is vascular compression of the trigeminal nerve root entry zone, leading to focal demyelination and aberrant neural discharges. MRI may disclose neurovascular contact, although not with sufficient sensitivity or specificity to substitute for careful clinical diagnosis. In treating TN, antiepileptic drugs are superior to traditional analgesics. Carbamazepine is the first choice drug. Additional drugs for which there is evidence of efficacy include oxcarbazepine, baclofen, gabapentin, lamotrigine and phenytoin. Many patients eventually experience tachyphylaxis or may not tolerate effective doses. Surgical options include: microvascular decompression; balloon compression; radiofrequency thermocoagulation or glycerol rhizotomies; and subcutaneous alcohol branch blockade. Stereotactic gamma knife radiosurgery is a further option. Motor cortex stimulation and transcranial magnetic stimulation, although having shown initial promise for trigeminal neuropathic pain, seem to be ineffective for classical TN. The choice of drug, whether or when to operate, and which procedure to choose should be individualized to the particular needs and conditions of the patient.