Trigeminal neuralgia (TN), also known as tic douloureux, is sometimes described as the most excruciating pain known to humanity. The pain typically involves the lower face and jaw, although sometimes it affects the area around the nose and above the eye. This intense, stabbing, electric shock-like pain is caused by irritation of the trigeminal nerve, which sends branches to the forehead, cheek and lower jaw. It usually is limited to one side of the face. The pain can be triggered by an action as routine and minor as brushing your teeth, eating or the wind. Attacks may begin mild and short, but if left untreated, trigeminal neuralgia can progressively worsen.
Although trigeminal neuralgia cannot always be cured, there are treatments available to alleviate the debilitating pain. Normally, anticonvulsive medications are the first treatment choice. Surgery can be an effective option for those who become unresponsive to medications or for those who suffer serious side effects from the medications.
The Trigeminal Nerve
The trigeminal nerve is one set of the cranial nerves in the head. It is the nerve responsible for providing sensation to the face. One trigeminal nerve runs to the right side of the head, while the other runs to the left. Each of these nerves has three distinct branches. “Trigeminal” derives from the Latin word “tria,” which means three, and “geminus,” which means twin. After the trigeminal nerve leaves the brain and travels inside the skull, it divides into three smaller branches, controlling sensations throughout the face:
Ophthalmic Nerve (V1): The first branch controls sensation in a person’s eye, upper eyelid and forehead.
Maxillary Nerve (V2): The second branch controls sensation in the lower eyelid, cheek, nostril, upper lip and upper gum.
Mandibular Nerve (V3): The third branch controls sensations in the jaw, lower lip, lower gum and some of the muscles used for chewing.
Prevalence and Incidence
It is reported that 150,000 people are diagnosed with trigeminal neuralgia (TN) every year. While the disorder can occur at any age, it is most common in people over the age of 50. The National Institute of Neurological Disorders and Stroke (NINDS) notes that TN is twice as common in women than in men. A form of TN is associated with multiple sclerosis (MS).
There are two types of TN — primary and secondary. The exact cause of TN is still unknown, but the pain associated with it represents an irritation of the nerve. Primary trigeminal neuralgia has been linked to the compression of the nerve, typically in the base of the head where the brain meets the spinal cord. This is usually due to contact between a healthy artery or vein and the trigeminal nerve at the base of the brain. This places pressure on the nerve as it enters the brain and causes the nerve to misfire. Secondary TN is caused by pressure on the nerve from a tumor, MS, a cyst, facial injury or another medical condition that damages the myelin sheaths.
Most patients report that their pain begins spontaneously and seemingly out of nowhere. Other patients say their pain follows a car accident, a blow to the face or dental work. In the cases of dental work, it is more likely that the disorder was already developing and then caused the initial symptoms to be triggered. Pain often is first experienced along the upper or lower jaw, so many patients assume they have a dental abscess. Some patients see their dentists and actually have a root canal performed, which inevitably brings no relief. When the pain persists, patients realize the problem is not dental-related.
The pain of TN is defined as either type 1 (TN1) or type 2 (TN2). TN1 is characterized by intensely sharp, throbbing, sporadic, burning or shock-like pain around the eyes, lips, nose, jaw, forehead and scalp. TN1 can get worse resulting in more pain spells that last longer. TN2 pain often is present as a constant, burning, aching and may also have stabbing less intense than TN1.
TN tends to run in cycles. Patients often suffer long stretches of frequent attacks, followed by weeks, months or even years of little or no pain. The usual pattern, however, is for the attacks to intensify over time with shorter pain-free periods. Some patients suffer less than one attack a day, while others experience a dozen or more every hour. The pain typically begins with a sensation of electrical shocks that culminates in an excruciating stabbing pain within less than 20 seconds. The pain often leaves patients with uncontrollable facial twitching, which is why the disorder is also known as tic douloureux.
Pain can be focused in one spot or it can spread throughout the face. Typically, it is only on one side of the face; however, in rare occasions and sometimes when associated with multiple sclerosis, patients may feel pain in both sides of their face. Pain areas include the cheeks, jaw, teeth, gums, lips, eyes and forehead.
Attacks of TN may be triggered by the following:
Touching the skin lightly
Blowing the nose
Drinking hot or cold beverages
Encountering a light breeze
The symptoms of several pain disorders are similar to those of trigeminal neuralgia. The most common mimicker of TN is trigeminal neuropathic pain (TNP). TNP results from an injury or damage to the trigeminal nerve. TNP pain is generally described as being constant, dull and burning. Attacks of sharp pain can also occur, commonly triggered by touch. Additional mimickers include:
Ernest syndrome (injury of the stylomandibular ligament
Cluster headaches/ migraines
Giant cell arteritis
Temporomandibular joint syndrome (TMJ)
TN can be very difficult to diagnose, because there are no specific diagnostic tests and symptoms are very similar to other facial pain disorders. Therefore, it is important to seek medical care when feeling unusual, sharp pain around the eyes, lips, nose, jaw, forehead and scalp, especially if you have not had dental or other facial surgery recently. The patient should begin by addressing the problem with their primary care physician. They may refer the patient to a specialist later.
Magnetic resonance imaging (MRI) can detect if a tumor or MS is affecting the trigeminal nerve. A high-resolution, thin-slice or three-dimensional MRI can reveal if there is compression caused by a blood vessel. Newer scanning techniques can show if a vessel is pressing on the nerve and may even show the degree of compression. Compression due to veins is not as easily identified on these scans. Tests can help rule out other causes of facial disorders. TN usually is diagnosed based on the description of the symptoms provided by the patient, detailed patient history and clinical evaluation. There are no specific diagnostic tests for TN, so physicians must rely heavily on symptoms and history. Physicians base their diagnosis on the type pain (sudden, quick and shock-like), the location of the pain and things that trigger the pain. Physical and neurological examinations may also be done in which the doctor will touch and examine parts of your face to better understand where the pain is located.
There are several effective ways to alleviate the pain, including a variety of medications. Medications are generally started at low doses and increased gradually based on patient’s response to the drug.
Carbamazepine, an anticonvulsant drug, is the most common medication that doctors use to treat TN. In the early stages of the disease, carbamazepine controls pain for most people. When a patient shows no relief from this medication, a physician has cause to doubt whether TN is present. However, the effectiveness of carbamazepine decreases over time. Possible side effects include dizziness, double vision, drowsiness and nausea.
Gabapentin, an anticonvulsant drug, which is most commonly used to treat epilepsy or migraines can also treat TN. Side effects of this drug are minor and include dizziness and/or drowsiness which go away on their own.
Oxcarbazepine, a newer medication, has been used more recently as the first line of treatment. It is structurally related to carbamazepine and may be preferred, because it generally has fewer side effects. Possible side effects include dizziness and double vision.
Other medications include: baclofen, amitriptyline, nortriptyline, pregabalin, phenytoin, valproic acid, clonazepam, sodium valporate, lamotrigine, topiramate, phenytoin and opioids.
There are drawbacks to these medications, other than side effects. Some patients may need relatively high doses to alleviate the pain, and the side effects can become more pronounced at higher doses. Anticonvulsant drugs may lose their effectiveness over time. Some patients may need a higher dose to reduce the pain or a second anticonvulsant, which can lead to adverse drug reactions. Many of these drugs can have a toxic effect on some patients, particularly people with a history of bone marrow suppression and kidney and liver toxicity. These patients must have their blood monitored to ensure their safety.
If medications have proven ineffective in treating TN, several surgical procedures may help control the pain. Surgical treatment is divided into two categories: 1) open cranial surgery or 2) lesioning procedures. In general, open surgery is performed for patients found to have pressure on the trigeminal nerve from a nearby blood vessel, which can be diagnosed with imaging of the brain, such as a special MRI. This surgery is thought to take away the underlying problem causing the TN. In contrast, lesioning procedures include interventions that injure the trigeminal nerve on purpose, in order to prevent the nerve from delivering pain to the face. The effects of lesioning may be shorter lasting and in some keys may result in numbness to the face.
Microvascular decompression involves microsurgical exposure of the trigeminal nerve root, identification of a blood vessel that may be compressing the nerve and gentle movement of the blood vessel away from the point of compression. Decompression may reduce sensitivity and allow the trigeminal nerve to recover and return to a more normal, pain-free condition. While this generally is the most effective surgery, it also is the most invasive, because it requires opening the skull through a craniotomy. There is a small risk of decreased hearing, facial weakness, facial numbness, double vision, stroke or death.
Percutaneous radiofrequency rhizotomy treats TN through the use of electrocoagulation (heat). It can relieve nerve pain by destroying the part of the nerve that causes pain and suppressing the pain signal to the brain. The surgeon passes a hollow needle through the cheek into the trigeminal nerve. A heating current, which is passed through an electrode, destroys some of the nerve fibers.
Percutaneous balloon compression utilizes a needle that is passed through the cheek to the trigeminal nerve. The neurosurgeon places a balloon in the trigeminal nerve through a catheter. The balloon is inflated where fibers produce pain. The balloon compresses the nerve, injuring the pain-causing fibers, and is then removed.
Percutaneous glycerol rhizotomy utilizes glycerol injected through a needle into the area where the nerve divides into three main branches. The goal is to damage the nerve selectively in order to interfere with the transmission of the pain signals to the brain.
Stereotactic radiosurgery (through such procedures as Gamma Knife, Cyberknife, Linear Accelerator (LINAC) delivers a single highly concentrated dose of ionizing radiation to a small, precise target at the trigeminal nerve root. This treatment is noninvasive and avoids many of the risks and complications of open surgery and other treatments. Over a period of time and as a result of radiation exposure, the slow formation of a lesion in the nerve interrupts transmission of pain signals to the brain.
Overall, the benefits of surgery or lesioning techniques should always be weighed carefully against its risks. Although a large percentage of TN patients report pain relief after procedures, there is no guarantee that they will help every individual.
For patients with TNP, another surgical procedure can be done that includes placement of one or more electrodes in the soft tissue near the nerves, under the skull on the covering of the brain and sometimes deeper into the brain, to deliver electrical stimulation to the part of the brain responsible for sensation of the face. In peripheral nerve stimulation, the leads are placed under the skin on branches of the trigeminal nerve. In motor cortex stimulation (MCS), the area which innervates the face is stimulated. In deep brain stimulation (DBS), regions that affect sensation pathways to the face may be stimulated.
How to Prepare for a Neurosurgical Appointment
Write down symptoms. This should include: What the pain feels like (for example, is it sharp, shooting, aching, burning or other), where exactly the pain is located (lower jaw, cheek, eye/forehead), if it is accompanied by other symptoms (headache, numbness, facial spasms), duration of pain (weeks, months, years), pain-free intervals (longest period of time without pain or in between episodes), severity of pain (0=no pain, 10=worst pain)
Note any triggers of pain (e.g. brushing teeth, touching face, cold air)
Make a list of medications and surgeries related to the face pain (prior medications, did they work, were there side effects), current medications (duration and dose)
Write down questions in advance
Understand that the diagnosis and treatment process for TN is not simple. Having realistic expectations can greatly improve overall outcomes.
Patients should follow-up with their primary care providers and specialists regularly to maintain their treatment. Typically, neuromodulation surgical patients are asked to return to the clinic every few months in the year following the surgery. During these visits, they may adjust the stimulation settings and assess the patient’s recovery from surgery. Routinely following-up with a doctor ensures that the care is correct and effective. Patients who undergo any form of neurostimulation surgery will also follow-up with a device representative who will adjust the device settings and parameters as needed alongside their doctors.
Article Provided By: aans.org
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