Continuing Education Activity

Trigeminal neuralgia (TN), also known as tic douloureux, is the most common neuropathic pain involving the craniofacial region. It is characterized by sudden, brief, usually unilateral severe recurrent episodes of stabbing pain in the distribution of one or more branches of the trigeminal nerve. This activity describes the evaluation and management of trigeminal neuralgia and explains the role of the interprofessional health care team in evaluating and treating patients with this condition.

Objectives:

• Identify the classic presentation of a patient with trigeminal neuralgia.
• Explain the diagnostic criteria for trigeminal neuralgia.
• Outline the management options available for trigeminal neuralgia.
• Describe interprofessional team strategies for improving care coordination and communication to advance trigeminal neuralgia and improve outcomes.

Introduction

Trigeminal neuralgia (TN), also known as tic douloureux, is the most common neuropathic pain involving the craniofacial region.[1] It is characterized by sudden, brief, usually unilateral severe recurrent episodes of stabbing pain in the distribution of one or more branches of the trigeminal nerve. Pain is usually described as stabbing, paroxysmal, electric shock-like, or burning pain and is limited to the area innervated by branches of the trigeminal nerve.[2][3]

Etiology

The exact cause of trigeminal neuralgia remains unknown.[3] The majority of cases are referred to as idiopathic, although many are associated with vascular compression of the trigeminal nerve close to its exit from the brainstem by an aberrant loop of an artery or vein. A minority of cases are due to conditions like multiple sclerosis or nerve compression by a tumor.[4] Some rare causes of trigeminal neuralgia include focal arachnoid thickening, adhesion, traction, tethering or torsion, fibrous ring around the root, cerebellopontine angle tumors, brain stem infarction, aneurysm, and arteriovenous malformation.[5][6][7][8]

Vascular Theory

Generally, it has been assumed that vascular contact at the root entry zone causes trigeminal neuralgia; however, TN also may be caused by contact at a transition zone between the central and peripheral myelin. Reportedly, the most common artery involved in this condition is the superior cerebellar artery, as seen in 75% to 80% of TN cases. Persistent primitive trigeminal artery variant, an anomaly that occurs between the carotid and basilar arteries or aneurysms of the persistent primitive trigeminal artery, vertebrobasilar dolichoectasia can cause TN. Sharper trigeminal-pontine angle cisterns and smaller cerebellopontine angle cisterns may facilitate the neurovascular compression (NVC).[9][5][10][11][12]

Extracranial Causes

The most common extracranial cause of trigeminal neuralgia is a perineural spread of head and neck malignancies, commonly squamous cell carcinoma, adenoid cystic carcinoma, lymphoma, melanoma, and sarcoma.[13][14][15][16][17] 

Classification

TN is classified into idiopathic TN, classic TN, and secondary TN.[2][18] Idiopathic TN is characterized by unknown causes and, in approximately 10% of patients, remains without a diagnosed cause, even after surgical procedures or magnetic resonance imaging (MRI). Classic TN is associated with NVC in the trigeminal root entry zone. Secondary TN may be caused by an underlying disease such as tumors, artery malformations, multiple sclerosis.[2][19][20][18][21][22]

Epidemiology

Trigeminal neuralgia has a prevalence of 0.1 to 0.2 per one thousand and an incidence ranging from 4 to 20 cases per 100,000 people per year. The female to male ratio is around 3 to 2.[23] While it is common after 50 years of age, TN is uncommon in young adults and rare in children.[5] The right side of the face reported being more commonly involved.[24]

Pathophysiology

Exact pathophysiology remains controversial. One theory is that chronic nerve compression can result in focal demyelination at the entry zone of the trigeminal nerve, atrophy or hypertrophy of peripheral axons, and damage to Schwann cells and peripheral myelin.[2] Demyelinated lesions may cause ectopic impulse generation, possibly causing ephaptic transmission. Ephaptic cross-talk between fibers mediating light touch and those involved in pain generation could account for the precipitation of painful attacks by light tactile stimulation of facial trigger zones.[25]

History and Physical

Trigeminal neuralgia causes episodes of spontaneous pain or a triggered intense facial pain limited to one or more divisions of the trigeminal nerve that last for a short duration (a few seconds to two minutes).[24] Pain may feel like stabbing, electric shocks, burning, pressing, crushing, shooting, migraine-like, piercing, prickling, or a combination of these.[5] Pain is usually unilateral and rarely bilateral.[26]

The distribution of TN pain may be in one or more of the territories of the three divisions: ophthalmic (V1), maxillary (V2), and mandibular (V3). V2 is the most frequent territory involved, followed by V3 and then V1.[27] Pain attacks usually occur by stimulation of trigger points within the territory supplied by the trigeminal nerve. Examples of stimulation include touching the face, tooth brushing, talking, and feeding. A refractory period that can last from a few seconds to several minutes can follow each pain episode. When attacks are frequent, patients may avoid talking, eating. This can impair the quality of life and mental health of these patients.[2]

Autonomic symptoms (e.g., mild lacrimation without conjunctival injection) may occur in association with TN attacks in the V1 trigeminal distribution. This is in clear contrast to the attacks involving short-lasting unilateral neuralgiform headaches with conjunctival injection, tearing, and rhinorrhea (SUNCT), which are always accompanied by lacrimation and conjunctival injection of the symptomatic side from the onset of symptoms.[28]

Diagnosis and Criteria[1][29]

 “International Classification of Headache Disorders-3 (ICHD-3) diagnostic criteria.”

1. At least three attacks of facial pain, mostly unilateral 
2. Occurs in one or more divisions of the trigeminal nerve and no radiation beyond the trigeminal distribution.
3. Pain has all of the following characteristics.
   1. It lasts from a fraction of a second to nearly two minutes.
   2. Severe intense pain
   3. Electric shock-like, shooting, sharp, or stabbing in quality
4. Precipitated by innocuous stimuli within the affected trigeminal division
5. Not accounted for by another ICHD-3 diagnosis

Evaluation

The diagnosis of trigeminal neuralgia is mainly clinical. Determining the presence of trigeminal sensory deficits or bilateral involvement of trigeminal nerves should be considered useful to distinguish symptomatic TN from classical TN.[30]

TN can occur secondary to another disease process, such as multiple sclerosis or a cerebellopontine-angle tumor. This is referred to as “symptomatic TN.”[31]

An MRI detects changes in the trigeminal root, identifies NVC, and may rule out secondary pathology.[5]

In patients with refractory TN undergoing microvascular decompression (MVD), preoperative high-resolution three-dimensional MRI is a reliable tool in diagnosing NVC.[32] Imaging consisting of high-resolution three-dimensional fast low-angle shots with three-dimensional constructive interference in steady-state can depict the relationship between the intracisternal segment of the trigeminal nerve and the adjacent vessels.[33]

Lastly, extracranial causes like head and neck malignancies should be considered and evaluated.[13]

Treatment / Management

The treatment of trigeminal neuralgia is challenging in the field of neurology and neurosurgery.[30] Medical therapy is the first-line therapy.[34] Carbamazepine or oxcarbazepine should be offered first for pain control.[35] The usual doses of carbamazepine (200 to 1200 mg/day) and oxcarbazepine (600 to 1800 mg/day) may be administered.[36] Baclofen, lamotrigine, clonazepam, topiramate, phenytoin, gabapentin, pregabalin, and sodium valproate can be used. When patients cannot take or cannot tolerate high doses of carbamazepine, consider multidrug therapy.[5] If pain relief is incomplete with carbamazepine, adding a second agent or switching drugs are additional options.[4]

Lamotrigine (200 to 400 mg/day), pregabalin (150 to 600 mg/day), gabapentin (1800 to 4200 mg/day), or topiramate (100 to 400 mg/day) may be considered. If the combination therapy fails, a switch to baclofen (40 to 80 mg/day) may be considered.[36]

Intravenous infusion of a combination of magnesium and lidocaine can be very effective in some patients. Botulinum toxin type A injections may be offered before surgery or to those unwilling to undergo surgery and in cases where drug treatments failed. Tetracaine nerve block may be used as an additional treatment after carbamazepine, as can acupuncture and/or peripheral nerve stimulation.[5]

For patients with refractory pain, various surgical procedures are available, including MVD, percutaneous radiofrequency rhizotomy, percutaneous glycerol rhizotomy, percutaneous balloon compression, and stereotactic radiosurgery.[34] MVD has been widely accepted as the gold standard surgical procedure for treating this disease.[37]

Differential Diagnosis

Because trigeminal neuralgia is primarily unilateral, the main differential diagnoses include dental pain (e.g., caries, cracked tooth, chronic periodontitis), temporomandibular disorder, glossopharyngeal neuralgia, postherpetic neuralgia, and SUNCT.[38][39]

Prognosis

Most patients respond well to drugs. If drug treatment fails or is not tolerated, surgical treatments may be offered.[4] Pain recurrence is common, with most relapses occurring within the first 2 years. The estimated annual recurrence rate after MVD is 3.5%.[40][41][42]

Reported risk factors for recurrence after MVD include the female sex, left-sided pain, and duration of symptoms longer than 11 years.[42]

Complications

Neurotologic complications that have been reported with MVD include postoperative hearing loss, tinnitus, vertigo, hemifacial paresis.[43] Ablative surgical treatments may cause facial sensory loss.[4]

Pearls and Other Issues

• Trigeminal neuralgia is the most common type of craniofacial neuropathic pain.[2][3]
• The majority of cases are idiopathic.[4]
• The most common artery reported to be involved in neurovascular compression in trigeminal neuralgia is the superior cerebellar artery.[9]
• Trigeminal neuralgia is primarily unilateral.[26]
• The distribution of TN pain is usually in one or more of the territories of the three divisions: ophthalmic (V1), maxillary (V2), and mandibular (V3). V2 is the most frequent territory involved. [27]
• The diagnosis is made clinically.[30]
• Medical therapy with carbamazepine or oxcarbazepine is the first-line therapy.[44][35]
• If drug treatment fails or is not tolerated, surgical options may be offered.[4]
• Microvascular decompression has been widely accepted as the gold standard surgical procedure for treating this disease.[37]

Enhancing Healthcare Team Outcomes

When a physician evaluates a patient with facial pain and is concerned for trigeminal neuralgia, referral to a neurologist is recommended. The interprofessional team may include a neurologist, neurosurgeon, dentist, nurses, and pharmacist, and all team members should collaborate and engage in open communication to optimize patient care and outcomes. [Level 5] Persistent orofacial pain without obvious physical cause is one of the most challenging clinical issues confronted by the dentist. Therefore, it is recommended that the dentist should gain familiarity with the pathophysiology, presentation, diagnosis, and management of orofacial neuropathic pain.[31]