by Tory McJunkin, MD, and Paul Lynch, MD
Trigeminal neuralgia (TN) is one of the most common, and also the most well-defined causes of facial pain. TN is defined by the International Association for the Study of Pain (IASP) as sudden, usually unilateral, severe, brief stabbing or lancinating, recurrent episodes of pain in the distribution of one or more branches of the trigeminal nerve (Merskey et al.). Less often, patients may have a constant aching or burning sensation most of the time. A tingling sensation or aching may also precede the pain episodes. Vibration or contact with the face may trigger the intense flashes of pain. The attacks usually last several seconds to a couple of minutes and repeat over the subsequent hours to weeks. The episodes then disappear for months to years before recurring. It can be bilateral, but does not involve both sides simultaneously. Rarely does the pain occur at night when the patient is sleeping. It tends to affect females slightly more than males at a ratio of 1.5:1, and increases slightly with age. Generally, the attacks worsen over time, and the latent periods become more infrequent and shorter. The exact incidence of trigeminal neuralgia is unknown, but it is estimated that about 15,000 new cases occur each year in the United States (Rozen et. Al).
Trigeminal Neuralgia Anatomy
The trigeminal nerve, also known as the fifth cranial nerve, has three major branches. It provides sensory innervation to the face and motor innervation to the muscles that are used for chewing and swallowing.
- The first branch is the ophthalmic nerve (V1), which covers the scalp and forehead, the upper eyelid, the conjunctiva and cornea of the eye, the nose, and frontal sinuses.
- The second branch is the maxillary nerve (V2), which covers the lower eyelid, cheek, upper lip, teeth, and gums, the nasal mucosa, the palate, part of the pharynx, the maxillary, ethmoid, and sphenoid sinuses.
- The third branch is the mandibular nerve (V3), which covers the lower lip, teeth, and gums, the floor of the mouth, the anterior of the tongue, the chin, the jaw, and parts of the external ear. The mandibular branch is the nerve that also provides the motor function.
- All three branches supply parts of the meninges.
Trigeminal Neuralgia PathologyThe origin of the trigeminal nerve is in the mid-lateral pons, and the major branches converge to form the gasserian ganglion (sensory ganglion) in the base of the middle cranial fossa. Each branch leaves the skull from a different foramina. V1 leaves through the superior orbital fissure, V2 through the foramen rotundum, and V3 through the foramen ovale.
Compression of the trigeminal nerve root is the recognized cause of trigeminal neuralgia most of the time. 80-90% of the time it is the abnormal loop of an intercranial artery, or less commonly, vein, that compresses the nerve root close to the location where it enters the brain stem (Love). Other causes of compression are tumors (vestibular schwannoma or meningioma), epidermoid cyst, or aneurysm (outpouching of a blood vessel). The compression then leads to damage of the protective covering of the nerve, called myelin. As a result, the nerve acts in an erratic manner, causing pain signals to be sent sporadically at the trigger of light touch, chewing, or brushing the teeth. Rarely, traumatic injuries of the trigeminal nerve, such as a car accident, can lead to similar damage. In multiple sclerosis, loss of myelin in one or more of the trigeminal nerve nuclei can also cause trigeminal neuralgia.
Trigeminal Neuralgia Diagnosis
Diagnosis of trigeminal neuralgia is made clinically based on the above-mentioned features. Diagnostic criteria for classic trigeminal neuralgia have been developed and published by the International Headache Society (IHS), and are listed:
- Paroxysmal attacks of pain lasting from a fraction of a second to two minutes, affecting one or more of the subdivisions of the trigeminal nerve
- Pain has at least one of the following characteristics:
- Intense, sharp, superficial, or stabbing
- Precipitated from trigger areas or by trigger factors
- Attacks are stereotyped in the individual patient
- There are no clinically evident neurologic deficits
- Not attributed to another disorder
It can be difficult to diagnose TN. The pain physicians at Arizona Pain Specialists have received extra training to examine and diagnose your painful condition. The physician may be able to demonstrate the trigger zones, while the neurological examination is normal. Most neurologic deficits indicate an alternative cause of pain. The physician may also order radiological imaging depending on his clinical suspicion and the history obtained.
Other causes of facial pain can be differentiated by as follows.
- Postherpetic pain has a persistent, typical rash that tends to involve the ophthalmic branch
- Migraine pain is more prolonged and often throbbing
Trigeminal Neuralgia Treatments Options
Controlling facial pain with current medical and surgical treatments is known to be very difficult (Slavin). The standard medical approaches are anti-inflammatory, anticonvulsant, and antidepressant medications. After these fail, local anesthetic blocks are attempted, but they only provide temporary pain relief. Lastly, percutaneous or open procedures may be done or even more rarely, neurostimulation. However, peripheral nerve stimulation may be a viable option earlier in the treatment of chronic facial pain. Medical treatment is usually the first-line therapy. Carbamazepine is the most effective and usually has manageable side effects. If it is ineffective or not tolerated, then combination with gabapentin, phenytoin, baclofen, lamotrigine, topiramate, or tizanidine may be beneficial (Lance). It is recommended to periodically taper the medications down in patients experiencing pain relief in order to check for the occasional permanent remission.
In patients refractory to medical treatment, there are several options for surgical procedures (Jannetta and Nurmikko et al).
- Microvascular decompression: An invasive procedure involving removal or separation of vasculature, which is often the superior cerebellar artery, away from the trigeminal nerve.
- Balloon compression: A balloon catheter is inflated and used to compress the gasserian ganglion.
- Gamma knife radiosurgery: A noninvasive treatment that creates lesions by using focused gamma radiation. The radiation is targeted at the proximal trigeminal root with the aid of stereotactic frame and MRI.
- Electrolytic rhizotomy: A percutaneous procedure that creates a lesion in the gasserian ganglion of the trigeminal nerve by using the heat of radiofrequency.
- Linear accelerator radiosurgery: A noninvasive approach similar to gamma knife, but uses a different form of radiation, linear acceleration.
- Peripheral neurectomy: An incision, radiofrequency lesioning, alcohol injection, or cryotherapy is used on a peripheral branch of the trigeminal nerve.
- Chemical rhizotomy: An injection of glycerol into the trigeminal cistern. Tingling or burning is felt in the face, and pain relief is usually immediate, but may take up to a week.
- All of the above mentioned treatments have a high recurrence of pain.
At Arizona Pain Specialists, your physician may talk to you about peripheral nerve stimulation (PNS) or spinal cord stimulation (SCS) of the nucleus caudalis for severe facial pain. These treatments may offer the potential for long-term management of the pain and may offer obvious benefit and less risk than neurodestructive procedures. Because there is a trial period for SCS or PNS the procedure is often less invasive, reversible, adjustable, and testable for patients in pain.
- Headache Classification Subcommittee of the International Headache Society. The International Classification of Heachache Disorders: 2nd edition. Cephalalgia 2004; 24 (Suppl1):9.
- Janneta, PJ. Microsurgical management of trigeminal neuralgia. Arch Neurol 1985; 42:800.
- Lance, JW. Mechanism of and management of headache, Butterworth Heinemann, Oxford 1993, p. 260.
- Love, S, Coakham, HB. Trigeminal neuralgia: pathology and pathogenesis. Brain 2001; 124:2347.
- Merskey, H, Bogduk, N. Classification of chronic pain. Descriptions of chronic pain syndromes and definitions of pain terms, IASP Press, Seattle 1994, pp. 59-71.
- Nurmikko, TJ, Eldridge, PR. Trigeminal neuralgia—pathophysiology, diagnosis and current treatment. Br J Anaesth 2001; 87:117.
- Rozen, TD, Capobianco, DJ, Dalessio, DJ. Cranial neuralgias and atypical facial pain. In: Wolff’s Headache and Other Head Pain, Siblerstein, SD, Lipton, RB, Dalessio, DJ (eds), Oxford University Press, New York 2001, pp. 509.
- Slavin, KV, Wess C. Trigeminal branch stimulation for intractable neuropathic pain: technical note. Neuromodulation 8:7-13, 2005