|Classification and external resources|
Trigeminal neuralgia (TN, or TGN), also known as prosopalgia, tic douloureux, or Fothergill's disease is a neuropathic disorder characterized by episodes of intense pain in the face. It has been described as among the most painful conditions known. The pain originates from a variety of different locations on the face and may be felt in front of the ear, eye, lips, nose, scalp, forehead, cheeks, mouth, or jaw and side of the face.
The pain of TN is from the trigeminal nerve. 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. 1–6% of cases occur on both sides of the face but extremely rare for both to be affected at the same time. Trigeminal neuralgia most commonly involves the middle branch (the maxillary nerve or V2) and lower branch (mandibular nerve or V3) of the trigeminal nerve.
It is estimated that 1 in 15,000 or 20,000 people have TN, although the actual figure may be significantly higher due to misdiagnosis. In most cases, TN symptoms begin appearing over the age of 50, although there have been cases with people being as young as three years of age. It is more common in females than males. Trigeminal neuralgia was first described by physician John Fothergill and treated surgically by John Murray Carnochan, both of whom were graduates of the University of Edinburgh Medical School.
Signs and symptoms
This disorder is characterized by episodes of intense facial pain. Each individual attack of pain lasts from a few seconds to several minutes or hours, but these can repeat for hours with very short intervals between each attack. In other instances only 4-10 attacks are experienced daily. The episodes of intense pain may occur paroxysmally. To describe the pain sensation, patients often 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, chewing and talking can aggravate the condition in many patients. The attacks are said by those affected to feel like stabbing electric shocks, burning, sharp, pressing, crushing, exploding or shooting pain that becomes intractable.
The pain also tends to occur in cycles with remissions lasting months or even years. 1-6% of cases occur on both sides of the face. 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. Pain may migrate to other branches over time but in some patients remains very stable.
Rapid spreading of the pain, bilateral involvement or simultaneous participation with other major nerve trunks (such as Painful Tic Convulsif of nerves V & VII or occurrence of symptoms in the V and IX nerves) may suggest a systemic cause. Systemic causes could include multiple sclerosis or expanding cranial tumours.
The severity of the pain makes it difficult to wash the face, shave, and perform good oral hygiene. The pain has a significant impact on activities of daily living especially as patients live in fear of when they are going to get their next attack of pain and how severe it will be. It can lead to severe depression and anxiety.
However, not all patients will have the symptoms described above and there are variants of TN. One of which is atypical trigeminal neuralgia ("trigeminal neuralgia, type 2" or trigeminal neuralgia with concomitant pain ), based on a recent classification of facial pain. In these instances there is also a more prolonged lower severity background pain that can be present for over 50% of the time and is described more as a burning or prickling, rather than a shock.
Trigeminal neuropathic pain is similar to TN2 but can have the electric pulses associated with classic TN. The pain is usually constant and can also give off a tingling, numbness sensation. This pain is due to unintentional damage to one or more of the trigeminal nerves from trauma, oral surgery, dentistry work, etc. It is difficult to treat but sufferers are usually given the same anticonvulsant and tricyclics antidepressant medicines as with the other types of neuralgias. Surgical options are DREZ (dorsal root entry zone) lesion and MCS or Motor Cortex Stimulation.
TN needs to be distinguished from other forms of unilateral pain which is related to damage to the trigeminal nerve by trauma to the face or dental treatments. This is often termed painful trigeminal neuropathy or post traumatic neuropathy as some sensory changes can be noted e.g. decrease in pain sensation or temperature. This is important as different carepathways are used. Trigeminal pain can also occur after an attack of herpes zoster and post herpetic neuralgia has the same manifestations as in other parts of the body. Trigeminal deafferentation pain (TDP) also termed anaesthesia dolorosa is from intentional damage to a trigeminal nerve following attempts to surgically fix a nerve problem. this pain is usually constant with a burning sensation and numbness. TDP is very difficult to treat as further surgeries are usually ineffective and possibly detrimental to the patient.
The trigeminal nerve is a mixed cranial nerve responsible for sensory data such as tactition (pressure), thermoception (temperature), and nociception (pain) originating from the face above the jawline; it is also responsible for the motor function of the muscles of mastication, the muscles involved in chewing but not facial expression.
Several theories exist to explain the possible causes of this pain syndrome. It was once believed that the nerve was compressed in the opening from the inside to the outside of the skull; but leading research indicates that it is an enlarged or lengthened blood vessel – most commonly the superior cerebellar artery – compressing or throbbing against the microvasculature of the trigeminal nerve near its connection with the pons. Such a compression can injure the nerve's protective myelin sheath and cause erratic and hyperactive functioning of the nerve. This can lead to pain attacks at the slightest stimulation of any area served by the nerve as well as hinder the nerve's ability to shut off the pain signals after the stimulation ends. This type of injury may rarely be caused by an aneurysm (an outpouching of a blood vessel); by an AVM (arteriovenous malformation); by a tumor; such as an arachnoid cyst or meningioma in the cerebellopontine angle; or by a traumatic event such as a car accident.
Short-term peripheral compression is often painless. Persistent compression results in local demyelination with no loss of axon potential continuity. Chronic nerve entrapment results in demyelination primarily, with progressive axonal degeneration subsequently. It is, "therefore widely accepted that trigeminal neuralgia is associated with demyelination of axons in the Gasserian ganglion, the dorsal root, or both." It has been suggested that this compression may be related to an aberrant branch of the superior cerebellar artery that lies on the trigeminal nerve. Further causes, besides an aneurysm, multiple sclerosis or cerebellopontine angle tumor, include: a posterior fossa tumor, any other expanding lesion or even brainstem diseases from strokes.
Trigeminal Neuralgia is found in 3–4% of people with Multiple Sclerosis, according to data from seven studies. It has been theorized that this is due to damage to the spinal trigeminal complex. Trigeminal pain has a similar presentation in patients with and without MS.
When there is no [apparent] structural cause, the syndrome is called idiopathic.
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 differential diagnosis includes 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. One quick test a dentist might perform is a conventional inferior dental local anaesthetic block, if the pain is in this branch, as it will not arrest masticatory pain but will TN.
- The anticonvulsant carbamazepine is the first line treatment; second line medications include baclofen, lamotrigine, oxcarbazepine, phenytoin, gabapentin and pregabalin. Uncontrolled trials have suggested that clonazepam and lidocaine may be effective.
- Antidepressant medications, such as Amitriptyline have shown good efficacy in treating Trigeminal Neuralgia, especially if combined with an anti-convulsant drug such as Pregabalin.
- There is some evidence that Duloxetine can also be used in some cases of neuropathic pain, especially in patients with Major Depressive Disorder as it is an antidepressant. However, it should, by no means, be considered a first line therapy and should only be tried by specialist advice.
- There is a lot of controversy around opiate use such as morphine and oxycodone for treatment of TN, with varying evidence on its effectiveness for neuropathic pain. Generally, opioids are considered ineffective against TN and thus should not be prescribed.
The evidence for surgical therapy is extensive and surgery is normally recommended only after medical treatment has proved ineffective, or if side effects of medication are intolerable. 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 stereotactic radiosurgery, however the effectiveness decreases with time.
We can split surgical procedures into non-destructive and destructive as follows:
- Microvascular Decompression - this involves a small incision behind the ear and some bone removal from the area. The surgeon will make an incision through the meninges and expose the nerve. Any vascular compressions of the nerve are carefully moved and PTFE (poly-tetra-fluoro-ethylene), also referred to by its trade name "Teflon", felt is placed between the compression and nerve, stopping unwanted pulsation and allowing myelin sheath healing. This technique appears to result in the longest pain relief.
Destructive: All destructive procedures will cause facial numbness, post relief, as well as pain relief.
- Percutaneous techniques which all involve a needle or catheter entering the face up to the origin where the nerve splits into three divisions and then damaging this area, purposely, to produce numbness but also stop pain signals. These techniques are proven effective especially in those where other interventions have failed or in those who are medically unfit for surgery such as the elderly.
- Balloon compression - inflation of a balloon at this point causing damage and stopping pain signals.
- Glycerol rhizotomy - deposition of a corrosive liquid called glycerol at this point causes damage to the nerve to hinder pain signals.
- Radiofrequency thermocoagulation rhizotomy - application of a heated needle to damage the nerve at this point.
- Stereotactic Radiosurgery (often erroneously referred to as “Gamma Knife Surgery”) is “a form of radiation therapy that focuses high-power energy on a small area of the body”
Psychological and social support has found to play a key role in the management of chronic illnesses and chronic pain conditions, such as Trigeminal Neuralgia. Chronic pain can cause constant frustration to an individual as well as to those around them. As a result, there exists a wealth of support groups for Trigeminal Neuralgia, sufferers and carers, the largest of which is the Trigeminal Neuralgia Association (TNA) which exists in several different countries, including the UK (TNA UK), Australia and America (TNA - Facial Pain Association)
History, society and culture
Historically TN has been called "suicide disease" due to studies by Dr Harvey Cushing which demonstrated 0.6% mortality involving 123 cases of TN during 1896 and 1912. Some individuals of note with TN include:
- Entrepreneur and author Melissa Seymour was diagnosed with TN in 2009 and underwent microvascular decompression surgery in a well documented case covered by magazines and newspapers which helped to raise public awareness of the illness in Australia. Seymour was subsequently made a Patron of the Trigeminal Neuralgia Association of Australia.
- One of India's biggest film stars, Salman Khan, was diagnosed with TN in 2011, resulting in tremendous media coverage in the country and abroad. He underwent surgery in the US.
- All-Ireland winning Gaelic footballer Christy Toye was diagnosed with the condition in 2013. He spent five months in his bedroom at home, returned for the 2014 season and lined out in another All-Ireland final with his team.
- Jim Fitzpatrick - Member of Parliament for Poplar and Limehouse - disclosed he suffered from Trigeminal Neuralgia before undergoing neurosurgery. He has openly discussed his condition at parliamentary meetings and is a prominent ﬁgure in the TNA UK charity.
- Andrea Jenkyns - Member of Parliament for Morley and Outwood - diagnosis with TN came to light during her television debate on Prime Minister’s Questions where she struggled to get her words out.
- Jefferson Davis - President of the Confederate States of America 
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