Clinical aspects and pharmacological treatment of trigeminal neuralgia

Introduction: Trigeminal neuralgia (TN) is defined as sudden, usually unilateral, severe and brief pain episodes within the distribution of one or more branches of the trigeminal nerve. In some patients a constant background pain may persist, additionally to pain attacks, which can make difficult to differentiate the trigeminal neuralgia from other orofacial pain types. Objective: To review the classification, physiopathological aspects, epidemiologic data and pharmacological options to control pain related to trigeminal neuralgia. Literature review: One of the proposed etiologies for this condition is a localcircumscribed demyelination of the trigeminal nerve resulting in neuronal hyperexcitability and generation of ephaptic coupling, which would be responsible for the pain paroxysms. Initially, the treatment of patients with these pain characteristics is based on the use of anticonvulsants, in order to attenuate the ectopic-generated pain impulses. Carbamazepine is the first-line drug, but other anticonvulsants may be employed and have shown variable efficacy in the treatment of trigeminal neuralgia. Conclusion: According to the new classification of the International Headache Society, classic trigeminal neuralgia is divided in purely paroxysmal and with concomitant persistent facial pain. The pathophysiology is unclear, but trigeminal neuralgia seems to be the consequence of vascular 287 – RSBO. 2014 Jul-Sep;11(3):286-92 Reis et al. – Clinical aspects and pharmacological treatment of trigeminal neuralgia compression of the trigeminal nerve near the brain stem. Although TN presents a low prevalence in general population (i.e. 5-30 new patients per 100,000), trigeminal neuralgia is an important clinical concern both by pain severity and difficulty of its satisfactory control. Anticonvulsants are the medication of choice in the treatment of trigeminal neuralgia; however, their use is associated with several adverse effects and possibility of treatment refractoriness. trigeminal neuralgia is caused by neurovascular compression more frequently through the superior cerebellar artery and is divided into classical trigeminal neuralgia purely paroxysmal and classical trigeminal neuralgia with concomitant facial persistent facial pain. Before this new classification, trigeminal neuralgia was also classified as symptomatic and included cases in which the neuralgia was associated with other disorders such as traumas, tumors and multiple sclerosis. Regardless of the etiology, neuropathic pain affecting trigeminal nerve reaches high rates in pain scales, which raises further interest in its study [17]. The treatment of choice of trigeminal neuralgia is pharmacological. Firstly, many patients have been beneficiated with anticonvulsants, such as carbamazepine, gabapentin and pregabalin. Notwithstanding, many patients do not respond to or become refractory to pharmacological treatment. Also, some patients have pain reduction together with side effects intolerable enough to justified pharmacological treatment suspension. The aforementioned cases require multimodal management, associating drugs with surgery [1]. Nevertheless, neither pharmacological nor surgical treatment for trigeminal neuralgia provides considerable pain relief in all patients, justifying the need of further studies to contribute in understanding the physiopathology of this disorder [7]. The aim of this study was to review the classification, physiopathological, epidemiological data and the pharmacological options for pain control associated with trigeminal neuralgia.