16

Andrew Blitzer, Lesley French Childs,
and Ronda E. Alexander

Trigeminal neuralgia (TN), as defined by the International Association for the Study of Pain (IASP), is a unilateral facial pain disorder that is characterized by brief, paroxysmal, sharp lancinating pains that are recurrent, and limited to the distribution of one or more divisions of the trigeminal nerve.1 The prevalence of this disorder is approximately 1 in 25,000, and it is slightly more common in women than in men. It also affects middle-aged or older people more frequently.²

In the latest classification of the International Headache Society, a distinction was made between classical and symptomatic TN: classical TN (CTN) includes idiopathic cases in addition to those with vascular compression of the fifth cranial nerve; symptomatic TN (STN) is diagnosed in cases secondary to multiple sclerosis, tumors, and structural abnormalities of the skull base.³ The pain attacks can be either spontaneous, or precipitated by certain cutaneous stimuli within specific “trigger zones,” leaving some patients unable to eat, drink, brush their teeth, or shave. The attacks come in bouts of weeks to months with intervening symptom-free periods. There are usually diurnal variations in symptoms with exacerbations during mornings and characteristic absence during sleep.⁴

Many theories have been proposed to explain the disease process, but a recent leading theory implicates demyelination of the sensory fibers within the proximal nerve root of the trigeminal nerve.⁵ Most cases of trigeminal neuralgia (80 to 90%) have an overlying blood vessel causing compression at the root entry zone. The offending vessel can be the superior cerebellar artery (75%), the anterior inferior cerebellar artery (10%), or a vein.⁶ Focal demyelination within or near this area has been documented on histologic examination of specimens taken during microvascular decompression in the immediate vicinity of the indentation, with the demyelinated axons found to be in direct apposition.7 The A-δ thinly myelinated nociceptive fibers may be particularly vulnerable to such changes.⁸ This pathologic arrangement may lead to abnormal nonsynaptic ephaptic transmission to adjacent fibers.⁹ Moreover, because fibers for light touch and pain are closest in proximity within the root entry zone, this theory provides a ready explanation for the paroxysmal pain provoked by cutaneous stimuli.⁵

Many approaches have been employed to alleviate the pain and reduce the frequency of pain attacks in this disorder. Pharmacotherapy with anticonvulsive drugs remains the first-line therapy. Carbamazepine or oxcarbazepine is often used for pain control. In patients with TN refractory to medical therapy, microvascular decompression, percutaneous approaches to the gasserian ganglion, and the gamma knife may also be considered, depending on surgeon experience and patient preference.¹⁰

Botulinum neurotoxin type A (BoNT/A) has been successfully utilized to treat pains such as migraine and occipital neuralgia as discussed in previous chapters in this book. BoNT/A has recently gained popularity in treating patients with TN, more specifically TN refractory to medical and occasionally surgical treatment.^11–15

Stay updated, free articles. Join our Telegram channel

Join