Trigeminal neuralgia, also known as prosopalgia, or 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 humankind.
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.
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.
The trigeminal nerve is a paired cranial nerve that has three major branches: the ophthalmic
nerve, the maxillary nerve, and the mandibular nerve.
One, two, or all three branches of the nerve may be affected.
10-12% of cases are bilateral.
Trigeminal neuralgia most commonly involves the middle branch and lower branch 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.
TN is not easily controlled but can be managed with a variety of treatment options.
Signs and 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.
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 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, 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.
Causes The trigeminal nerve is a mixed cranial nerve
responsible for sensory data such as tactition, thermoception, and nociception 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 newer leading research indicates that it is an enlarged blood vessel - possibly
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; by an AVM; by a tumor; by an
arachnoid cyst in the cerebellopontine angle; or by a traumatic event such as a car accident.
Short-term peripheral compression is often painless, with pain attacks lasting no more
than a few seconds.
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.
Only two to four percent of patients with TN, usually younger, have evidence of multiple
sclerosis, which may damage either the trigeminal nerve or other related parts of the brain.
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.
Postherpetic neuralgia, which occurs after shingles, may cause similar symptoms if the
trigeminal nerve is damaged.
When there is no [apparent] structural cause, the syndrome is called idiopathic.
Management 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.
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.
Medical The anticonvulsant carbamazepine is the first
line treatment; second line medications include baclofen,(Tegral 200) lamotrigine, oxcarbazepine,
phenytoin, gabapentin, pregabalin, and sodium valproate.
Uncontrolled trials have suggested that clonazepam and lidocaine may be effective.
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.
Gallium maltolate in a cream or ointment base has been reported to relieve refractory postherpetic
trigeminal neuralgia.
Surgical 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.
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.
History, society and culture
Historically TN has been called "suicide disease" due to Dr. Harvey Cushing's 0.6% mortality
rates involving 123 cases of TN during 1896 and 1912.
Some example cases of 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.
See also Trigeminal trophic syndrome
John Murray Carnochan James Ewing Mears
References
External links Trigeminal neuralgia at DMOZ