What is Trigeminal Neuralgia
Trigeminal neuralgia (TN, or TGN), also known as prosopalgia and Fothergill’s disease is a neuropathic disorder characterized by episodes of intense pain in the face, originating from the trigeminal nerve. The clinical association between TN and hemifacial spasm is the so called tic douloureux. It has been described as among the most painful conditions known to mankind. It is estimated that 1 in 15,000 or 20,000 people suffer from TN, although the actual figure may be significantly higher due to frequent misdiagnosis. In a majority of cases, TN symptoms begin appearing more frequently over the age of 50, although there have been cases with patients being as young as three years of age. It is more common in females than males.
The trigeminal nerve is a paired cranial nerve that has three major branches: the ophthalmic nerve (V1), the maxillary nerve (V2), and the mandibular nerve (V3). One, two, or all three branches of the nerve may be affected. 10-12% of cases are bilateral (occurring on both the left and right sides of the face). Trigeminal neuralgia most commonly involves the middle branch (the maxillary nerve or V2) and lower branch (mandibular nerve or V3) of the trigeminal nerve, but the pain may be felt in the ear, eye, lips, nose, scalp, forehead, cheeks, teeth, or jaw and side of the face.
Symptoms
This disorder is characterized by episodes of intense facial pain that last from a few seconds to several minutes or hours. The episodes of intense pain may occur paroxysmally. To describe the pain sensation, patients may describe a trigger area on the face so sensitive that touching or even air currents can trigger an episode; however, in many patients the pain is generated spontaneously without any apparent stimulation. It affects lifestyle as it can be triggered by common activities such as eating, talking, shaving and brushing teeth. Wind, high pitched sounds, loud noises such as concerts or crowds, chewing, and talking can aggravate the condition in many patients. The attacks are said by those affected to feel like stabbing electric shocks, burning, pressing, crushing, exploding or shooting pain that becomes intractable.
- intense facial pain
- sensitive to wind, high pitched sounds, loud noises, chewing, and talking
- stabbing
- electric shocks
- burning
- pressing
- crushing
- exploding
- shooting
Individual attacks usually affect one side of the face at a time, lasting from several seconds to a few minutes and repeat up to hundreds of times throughout the day. The pain also tends to occur in cycles with remissions lasting months or even years. 10-12% of cases are bilateral, or occurring on both sides. This normally indicates problems with both trigeminal nerves since one serves strictly the left side of the face and the other serves the right side. Pain attacks are known to worsen in frequency or severity over time, in some patients. Many patients develop the pain in one branch, then over years the pain will travel through the other nerve branches. Some patients also experience pain in the index finger.
It may slowly spread to involve more extensive portions of the trigeminal nerve. The spread may even affect all divisions of the nerve, and sometimes simultaneously. Cases with bilateral involvement have not indicated simultaneous activity. The following suggest a systemic development: rapid spreading, bilateral involvement, or simultaneous participation with other major nerve trunks. Examples of systemic involvement include multiple sclerosis or expanding cranial tumor. Examples of simultaneous involvement include tic convulsive (of the fifth and seventh cranial nerves) and occurrence of symptoms in the fifth and ninth cranial nerve areas.
Outwardly visible signs of TN can sometimes be seen in males who may deliberately miss an area of their face when shaving, in order to avoid triggering an episode. Successive recurrences are incapacitating and the dread of provoking an attack may make sufferers unable to engage in normal daily activities.
There is also a variant of TN called atypical trigeminal neuralgia (also referred to as “trigeminal neuralgia, type 2”), based on a recent classification of facial pain. In some cases of atypical TN the sufferer experiences a severe, relentless underlying pain similar to a migraine in addition to the stabbing shock-like pains. In other cases, the pain is stabbing and intense but may feel like burning or prickling, rather than a shock. Sometimes the pain is a combination of shock-like sensations, migraine-like pain, and burning or prickling pain. It can also manifest as an unrelenting, boring, piercing pain.
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Treatments
As with many conditions without clear physical or laboratory diagnosis, TN is sometimes misdiagnosed. A TN sufferer will sometimes seek the help of numerous clinicians before a firm diagnosis is made.
There is evidence that points towards the need to quickly treat and diagnose TN. It is thought that the longer a patient suffers from TN, the harder it may be to reverse the neural pathways associated with the pain.
The dentist must ensure a correct diagnosis does not mistake TN as a temporomandibular disorder. Since triggering may be caused by movements of the tongue or facial muscles, TN must be differentiated from masticatory pain that has the clinical characteristics of deep somatic rather than neuropathic pain. Masticatory pain will not be arrested by a conventional mandibular local anesthetic block.
Dentists who suspect TN should proceed in the most conservative manner possible and should ensure that all tooth structures are “truly” compromised before performing extractions or other procedures.
The anticonvulsant carbamazepine is the first line treatment; second line medications include baclofen, lamotrigine, oxcarbazepine, phenytoin, gabapentin, pregabalin, and sodium valproate. Uncontrolled trials have suggested that clonazepam and lidocaine may be effective.
Low doses of some antidepressants such as amitriptyline are thought to be effective in treating neuropathic pain, but a tremendous amount of controversy exists on this topic,[citation needed] and their use is often limited to treating the depression that is associated with chronic pain, rather than the actual sensation of pain from the trigeminal nerve[citation needed]. Antidepressants are also used to counteract a medication side effect.
Duloxetine can also be used in some cases of neuropathic pain, and as it is also an antidepressant can be particularly helpful where neuropathic pain and depression are combined.
Opiates such as morphine and oxycodone can be prescribed, and there is evidence of their effectiveness on neuropathic pain, especially if combined with gabapentin.
The evidence for surgical therapy is poor and it is thus only recommended if medical treatment is not effective. While there may be pain relief there is also frequently numbness post procedure. Microvascular decompression appears to result in the longest pain relief. Percutaneous radiofrequency thermorhizotomy may also be effective as may gamma knife radiosurgery, however the effectiveness decreases with time.
Three other procedures use needles or catheters that enter through the face into the opening where the nerve first splits into its three divisions. Some excellent success rates using a cost-effective percutaneous surgical procedure known as balloon compression have been reported.[26] This technique has been helpful in treating the elderly for whom surgery may not be an option due to coexisting health conditions. Balloon compression is also the best choice for patients who have ophthalmic nerve pain or have experienced recurrent pain after microvascular decompression.
Glycerol injections involve injecting an alcohol-like substance into the cavern that bathes the nerve near its junction. This liquid is corrosive to the nerve fibers and can mildly injure the nerve enough to hinder the errant pain signals. In a radiofrequency rhizotomy, the surgeon uses an electrode to heat the selected division or divisions of the nerve. Done well, this procedure can target the exact regions of the errant pain triggers and disable them with minimal numbness.
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