Trigeminal neuralgia (TN) is one of the most common, and also the most well-defined causes of facial pain. It is defined 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. 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 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.
Trigeminal Neuralgia Treatments Options
Controlling facial pain with current medical and surgical treatments is known to be very difficult. 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. 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.
- 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.