Abstract
Trigeminal neuralgia is a condition involving severe, sharp, and stabbing pain in one of the three fifth cranial nerve distributions and is paroxysmal in nature. Red flags for trigeminal neuralgia that constitute a further in-depth workup include deafness, optic neuritis, age less than 40, a family history of multiple sclerosis, a history of skin or oral lesions, sensory changes, or poor response to treatment. Physical examination, including neurologic examination, is typically normal unless the pain is a result of another condition. Trigeminal neuralgia is typically managed with medications. For medically refractory pain, additional procedures or surgical interventions can be performed.
Definition
Trigeminal neuralgia is defined as pain in the distribution of at least one of the fifth cranial nerve distributions, usually occurring in the maxillary or mandibular branches. Pain associated with trigeminal neuralgia can last for a variable amount of time and frequency and between attacks, patients are usually pain-free. Triggers for a pain attack, also known as a paroxysm, can include eating, brushing the teeth, light touch to the face, or talking.
Trigeminal neuralgia is a relatively rare disorder and in one systematic review, the prevalence was 0.03% to 0.3%. Older investigation determined the overall incidence of trigeminal neuralgia to be 4.3 per 100,000 people with a slightly higher rate for women (5.9/100,000) than men (3.4/100,000). Women are generally more likely affected than men, with most cases occurring in individuals 40 years or older.
The trigeminal nerve is the largest cranial nerve and originates in the brainstem with one motor nucleus and three sensory nuclei. There are three divisions of the fifth cranial nerve, known as the ophthalmic (V1), maxillary (V2), and mandibular (V3) branches. The three branches of the trigeminal nerve form from the trigeminal, or Gasserian, ganglion. At the root entry zone where central myelin changes to peripheral myelin, the trigeminal nerve is thought to be susceptible to vascular compression, resulting in trigeminal neuralgia.
Symptoms
Trigeminal neuralgia is a painful unilateral condition occurring in one of the three branch distributions of the trigeminal nerve. The pain is paroxysmal with sudden onset and termination of pain episodes. The episodes can be brief, lasting only a few seconds, or can last up to 2 minutes and are stabbing, sharp, shooting, and electric shock in quality. The pain episodes can be induced by mechanical stimuli such as a light touch or a breeze or by movements such as smiling or applying makeup. The symptoms may be accompanied by trigger zones, weight loss, poor quality of life or depression, and may lessen with improving sleep hygiene. Occasionally patients may have ongoing background pain or autonomic features such as congestion or lacrimation.
Red flags for trigeminal neuralgia that constitute a further in-depth workup include deafness, optic neuritis, age less than 40, a family history of multiple sclerosis, a history of skin or oral lesions, sensory changes, or poor response to treatment. If these symptoms are present, a primary process may be the etiology and a diagnostic workup should be performed.
Physical Examination
Diagnosing trigeminal neuralgia is based primarily on symptom description. In cases of primary trigeminal neuralgia, the physical and neurologic examinations usually do not reveal any abnormalities. However, a full neurologic examination, including the cranial nerves, should be performed in order to rule out secondary causes of trigeminal neuralgia such as a tumor or multiple sclerosis. Additionally, physical examination of the oral cavity, dentition, and trigeminal nerve distribution should be performed to rule out other diseases as well, which can present with secondary trigeminal neuralgia.
Functional Limitations
In general, there are no impairments associated with trigeminal neuralgia. However, the pain from this entity may result in significant limitation in several activities of daily living. For example, during exacerbations, patients may be functionally incapacitated because of pain and may be unable to perform activities such as combing their hair, chewing food, or shaving. Talking on the telephone may be painful and wearing glasses or makeup may not be possible. Essentially any activity that involves contact with the face may become difficult or impossible.
Diagnostic Studies
The International Headache Society has defined diagnostic criteria for trigeminal neuralgia, which include (1) the presence of three or more attacks of unilateral facial pain that (2) occur in a division of the trigeminal nerve with no radiation outside of the trigeminal nerve distribution and (3) the pain has to have at least three of the following characteristics: recurring paroxysmal attacks lasting a fraction of a second to 2 minutes; severe intensity; electric shock-like, shooting, stabbing or sharp in quality; precipitated by innocuous stimuli and not occurring as the result of another disorder.
Practitioners should possess a low threshold to perform imaging of the brain in suspected cases of trigeminal neuralgia. Patients should undergo a brain magnetic resonance imaging (MRI) with and without contrast if they are younger, have abnormal “red flag” symptoms, or if they do not respond to standard medication treatment. MRI with gadolinium has sensitivity in demonstrating multiple sclerosis and enhancement of the trigeminal nerve in addition to identifying masses or lesions in the intracranial and extracranial areas along the trigeminal nerve pathway. While MRI may be able to detect vascular compression of the trigeminal nerve in the setting of primary trigeminal neuralgia, this study is not typically indicated.
Neurophysiologic testing of the trigeminal reflex has been proposed as a reliable test for the diagnosis of trigeminal neuralgia. Additional studies that may aid in the diagnosis of trigeminal neuralgia may be other radiographs such as intraoral x-rays when the trigeminal neuralgia is suspected to be secondary to another cause.
Treatment
Initial
Trigeminal neuralgia is generally treatable with pharmacotherapy, procedures, or surgical treatment. However, it can progress to become a chronic intractable pain syndrome in refractory cases.
Carbamazepine and oxcarbazepine are typically used as the first-line agents to treat trigeminal neuralgia. Older studies demonstrated the effectiveness of carbamazepine in treating the pain of trigeminal neuralgia in the short and long term. Carbamazepine has been recommended as the initial drug of choice for trigeminal neuralgia, but is associated with Stevens-Johnson syndrome and other potentially serious side effects. Although carbamazepine can reduce the frequency and intensity of painful episodes, oxcarbazepine has a more favorable side effect profile. Oxcarbazepine is a derivative of carbamazepine and can effectively treat trigeminal neuralgia. Appropriate monitoring of labs should be performed when prescribing these medications.
In cases where carbamazepine or oxcarbazepine are ineffective, not tolerated, or contraindicated, clinicians can try other medications. However, there is less research in this area. Alternative medications to try in trigeminal neuralgia include baclofen (which can be useful in cases of multiple sclerosis), gabapentin, or lamotrigine; evaluation of the risks and benefits of each medication should be performed on a case-by-case basis. Overall, evidence is lacking for the routine use of baclofen, gabapentin, and lamotrigine in the treatment of trigeminal neuralgia. A recent Cochrane review determined there to be insufficient evidence to demonstrate that non-antiepileptic medications such as tizanidine are effective in treating trigeminal neuralgia. Pharmacologic therapy with nonsteroidal anti-inflammatory agents, acetaminophen, tricyclic antidepressants, and serotonin-norepinephrine reuptake inhibitors may be useful. Other suggested drugs with very limited investigation include phenytoin, clonazepam, valproate, topiramate, and intravenous lidocaine. One study showed that intranasal lidocaine administered by a metered-dose spray produced acute but temporary analgesia in patients with second-division trigeminal neuralgia.
Rehabilitation
Trigeminal neuralgia can be approached from a rehabilitative perspective by classifying it as a type of neuropathic pain. Modalities such as hot and cold packs, electric stimulation such as transcutaneous electric nerve stimulation, and neurostimulation techniques such as transcranial magnetic stimulation can be trialed in trigeminal neuralgia. Speech therapy may be indicated to help with oral motor deficits that affect speech or swallowing. As part of the rehabilitation program, the use of cognitive behavioral therapy, relaxation therapy, and increasing exercise can be trialed to assist with neuropathic pain management.
Adaptive equipment, such as a modified telephone earset, may be recommended to avoid triggering a paroxysm. General chronic pain rehabilitation approaches may also be useful, such as improved sleep hygiene, low-intensity aerobic exercise, biofeedback, cognitive-behavioral therapy, and relaxation techniques. Acupuncture may also have a role in the management of trigeminal neuralgia.
Rehabilitation programs may need to be adjusted pending response to medication, nonsurgical, or surgical procedures. If pain recurs, medications may need to be restarted, a procedure may need to be repeated, or a different treatment strategy may need to be conducted. If trigeminal neuralgia is secondary to an underlying disease or disorder, treating the primary pathology is important to address from the medical and rehabilitative standpoints.
Procedures
When medical management does not adequately provide pain control for trigeminal neuralgia, patients should be referred for procedural consultation. There are a number of procedures and surgical techniques that have been investigated to date to treat medically refractory pain associated with trigeminal neuralgia. The selection of a particular intervention should be performed on a case-by-case basis, which includes patient preference, high-risk elderly patients, or prior failed treatments.
Percutaneous neurosurgical techniques, such as radiofrequency thermocoagulation, balloon compression, or glycerol injection into the trigeminal cistern provide immediate but short-duration pain relief with typically excellent initial response rates. Patients can experience side effects from these procedures, including facial numbness, masseter weakness, pain, dysesthesias, trigeminal and other cranial nerve dysfunction, and vagal instability in addition to carotid injury and intracranial infection. Radiofrequency thermocoagulation targets the trigeminal nerve and root, resulting in destruction of pain-mediating fibers under fluoroscopic guidance, and has improved results when used conventionally compared to a pulsed manner; overall, there is significant initial pain relief post-procedure, though the pain can recur. Balloon compression, which is also performed under fluoroscopic guidance, causes compression of the affected ganglion and has a decompression-like effect post-procedure; while there is significant pain relief immediately, there is no standardization of the procedure. Glycerol gangliolysis under fluoroscopy results in trigeminal neuronal destruction with significant pain relief post-procedure, and patients often experience sensory changes during the procedure.
Technology
There is no specific technology for the treatment or rehabilitation of this condition.
Surgery
Microvascular decompression aims to relieve the trigeminal nerve from vascular compression, often from the superior cerebellar artery, anterior inferior cerebellar artery, or the superior petrosal veins. Microvascular decompression may have excellent immediate and long-term pain relief outcomes and by some is considered the “gold standard” surgery for managing trigeminal neuralgia in the appropriate patient population. The most common side effect of microvascular decompression is ipsilateral hearing loss.
Another operative technique in treating trigeminal neuralgia is stereotactic radiosurgery, commonly in the form of Gamma Knife radiosurgery. Gamma Knife radiosurgery uses a focused dose of radiation as an alternative for microvascular decompression and results in significant pain relief. Gamma Knife radiosurgery using a dose range of 70 to 90 Gy to target the trigeminal nerve is a safe and effective tool for managing trigeminal neuralgia pain in the short and long term. Gamma Knife radiosurgery does not have immediate pain-relieving effects and numbness is a common side effect. While patients may have long-term pain relief, relapse is possible; however, repeat Gamma Knife radiosurgery does provide additional pain relief.
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