Surgery, John Fothergill, who made the initial diagnosis back

 Surgery, exploring the most effective treatment,
in the management of Trigeminal Neuralgia.

 

 

 

 

By Yasmina Ajayi

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Introduction

 

Trigeminal neuralgia (TN) also
known as ‘Tic douloureux’, is a painful rare neuropathic disorder affecting one
or more of the three trigeminal nerve branches
(the fifth cranial nerve). The
condition is also known as ‘Fothergill’s Disease’. Named after the physician
John Fothergill, who made the initial diagnosis back in 1773, giving the
disease its first full accurate description. Or the ‘Suicide Disease’ as a
significant number of sufferers often commit suicide, due to the condition.
(BMJ,2017)

The disease is characterized by
episodes of extreme facial pain in areas including the eyes, lips, nose,
tongue, cheeks, ears, scalp, teeth and gums. Brought on by stimulation to areas
of the face known as trigger zones. Sensations from common daily activities
such as brushing your teeth, eating or drinking, changes in temperature or
speaking can cause either sudden sharp shocks lasting only a few seconds, to
long-term pain lasting anywhere between several minutes up to an hour or two.
Often, however, the pain can occur G1 spontaneously
without an obvious cause. Sufferers of trigeminal neuralgia, may initially only
experience mild intermittent attacks. However, the disease usually follows a
wave-like pattern, where a bout of attacks lasting from days to weeks, will go
into remission for months or even years. Over time, the intensity of pain and
the frequency of attacks increase. (Naish,2015)

The disease affects more women than
men in a 2:1 ratio, usually developing around the age of 40. The exact cause is
not always known, although it is believed that compression of the trigeminal
nerve along any of its three branches, or as the nerve leaves the cranium, can
lead to damage and loss of its protective myelin sheath. Possibly caused by
either a blood vessel or a tumour. G2 Stroke
and trauma can also lead to damage to the trigeminal nerve. The condition may
also be the symptoms of another underlying disease such as multiple sclerosis or
diabetes. As the exact cause is difficult to determine, finding an
effective treatment can be challenging. 
(NINDS,2017)G3 

There is currently no cure for this
disease, several treatment options exist, most of which deal with pain
management. This essay will explore the cause and pathology of the disease,
look at various types of medication and surgical treatments currently
available. Attempt to determine which option would provide the most effective
long-term patient outcome.   G4 

 

 

 

 

 

 

 

 

 

The Trigeminal (V) nerve is the
largest of the cranial nerves. It is a mixed nerve which provides both motor
and sensory functions. Split into three branches mandibular (lower jawbone)
receives sensation from lower teeth, skin and part of the tongue. Maxillary
(upper jawbone) sensations from upper teeth, nose, upper lip and lower eyelid.
Ophthalmic (the eye) receives sensory information from upper eyelid, the
forehead, side of the nose and part of the scalp. The trigeminal nerve is also involved
in facial sensation and movement. Sensory axons carry impulses which detect
sensation such as pain, touch and temperature. Whilst motor neurons supply
muscles responsible for mastication. (Tortora, 2014) 

The exact cause of trigeminal
neuralgia is idiopathic, however, it is generally considered that compression
of the trigeminal nerve is by surrounding blood vesselsG5 ,
injury or very rarely tumours, to be the primary cause in 95% of cases
(BMJ,2015). Its large sensory root called the trigeminal
ganglion is lG6 ocated
on the inner surface of the temporal bone. As the nerve exits, the brain stem
the ganglionG7 
splits into three branches, which pass through cranial bones, providing nerve
impulses to and from the relevant areas of the face. Surrounding vessels press
against the nerve as it passes through. The resulting, excessive compression
irritates and damages the nerve, eventually causing irreparable destruction
(wearing away) to its protective coating, known as the myelin sheath. (Tortora,
2014).G8 G9 

The trigeminal nerve is highly
myelinated by a protective sheath formed by oligodendroglial cells, which
encase the nerve axons. This sheath acts to both insulate and increase the
speed of action potentials (nerve impulse) conduction. Nerves are unable to
function normally with damage to the myelin sheath. The demyelination of the
sensory fibresG10  results in tG11 he misfiring of impulses through
voltage-gated sodium channels within the nerve. This is believed to cause the
acute neuropathic pain associated with the disease. (Tortora, 2014). The trigeminal nerve forms part of the
central nervous system (CNS), unlike Schwann cells which form nerve myelination
in the peripheral nervous system (PNS), oligodendrocytesG12  are unable to repair themselves once
damage has occurred. The disease is progressive, with cells unable to
regenerate, continual damage to the nerve results in increased severity of
pain. G13 G14 

The remaining 5% of cases are
usually associated with other diseases such as multiple sclerosis or diabetes.
In the UK, the annual reported incidence of TN is 27 cases per 100,000.
Affecting twice as many women as men, usually presenting from around 40 years
of age. (Tidy,2017).

 

Symptoms vary depending on the type
of trigeminal neuralgia. Chronic painful attacks are triggered by everyday
activities such as eating, drinking, talking and brushing teeth, seriously
impairing a patient’s quality of life. Stress and depression is commonly
reported amongst sufferers. The condition usually repeats in cycles with
painful periods followed by pain-free intervals. G15 Patients avoid triggers, often social
activities in the fear that the extreme facial pain will return. This results
in further depression and isolation.

 TN presents in two forms, unpredictable bouts
of sharp, shock-like, stabbing pain lasting anywhere from a few seconds to
several minutes is often classified as “Type 1”, ‘Typical’ or ‘the classic
form’ of TN. Attacks can repeat many times, varying from a few minutes up to
several hours between bouts. The pain of the ‘Atypical’ form of the disorderG16  or ‘TN2’ tend to present at a lower
intensity (a burning, stabbing, tingling or constant dull ache), however rather
than occurring in shorts bursts, the pain is felt constantly. Lasting anywhere
from several hours to days or even weeks. The pain is usually compared to that
of a tooth abscess, pulsating simultaneously in all teeth (on the affected side
of the face). As the pain is often confused with a toothache, a patient often
will visit their dental surgery, incorrectly believing they require dental
treatment.G17 

The condition is almost always
unilateral, affecting one side of the face. Most commonly affecting the right
side at a rate of 5:1. Occasionally in patients whose symptoms are caused by
another disease such as multiple sclerosis or diabetes. Pain occurs on both
sides, known as ‘bilateral TN’. (MedicineNetG18 G19 , 2017). In all cases, the condition will
often enter periods of remission lasting weeks, months even years. Eventually,
these pain-free intervals become shorter, with longer periods of pain between.
The pain often intensifies as the condition progresses. G20 G21 Although not fatal, the disease is known to
cause severe anxiety, depression and can have a detrimental effect on a G22 patient’s quality of life. Suicide rates
among sufferers are estimated at approximately 25% (NINDS,2017).G23 G24 G25 

 

Effective treatment of Trigeminal
neuralgia (TN) depends on making the correct clinical diagnosis.  Once it has been confirmed that the condition
is not dental related but the patient is symptomatic of trigeminal neuralgia, a
doctor will refer the patient for further tests to determine the exact cause.
Magnetic resonance imaging (MRI) of the head identifies any structural
abnormalities such injury to the nerve; compression from a tumour, tangle of
arteries or vessels; multiple sclerosis (MS) plagues; mass lesion and pontine
gliomas. Particularly if the patient presenting symptoms is younger than 40
years old. Approximately 15% of patients, do show abnormalities most commonly
tumours and multiple sclerosis, upon neuroimaging. (NINDS,2017).

Trigeminal neuralgia has no cure,
treatment options include medication and surgery which deal with pain
management rather than to seek a full cure (although some surgical
interventions have shown successful results) However, generally, medications
are used as first-line therapy. Anticonvulsant medicines most usually
Carbamazepine are used to block nerve firing, these interrupt hyper-excited
sodium channels, stabilizing the misfiring of nerve impulses, slowing down
electrical impulses, resulting in pain reduction. Carbamazepine is the
preferred drug prescribed by doctors, designed originally to treat epilepsy,
this medication has proved effective in the management of TN. Patients receive
a relatively low dose of 100mg increasing to a maximum dose of 1200mg daily
until satisfactory pain control is achieved. (Montano, N et al,2015). It has
been used with relative success for many years however, many patients find that
initial pain management diminishes. Also, due to its toxicity, high levels of
intolerable side effects such as fatigue, nausea, migraines, tremors, seizures,
slurred speech, drowsiness and dangerous (sometimes fatal) dermatologic
reactions including ‘Steven Johnson syndrome’ prevent continuous use.
Alternative antiepileptic medications such as ‘Oxcarbazepine, ‘Lamotirine’ and
‘Pregabalin’ are prescribed as second-line therapies, G26 although due to the rarity of the
condition, rigorous clinical trials into their effectiveness in the treatment
of TN is very limiting. (NHS.2017) 

Anticonvulsant drugs are generally
successful in the treatment of TN1, however, patients witG27 h symptoms of TN2 more often than not, find
these less effective. This form is a little more complex, patients often show a
positive result to low levels of antidepressant medications for example
‘Nortriptyline’ and ‘Amitriptyline’, combined with a nonsteroidal
anti-inflammatory drugs NSAIDs and opioids. These have proven to provide some
limited pain relief.

Patients presenting symptoms caused
by multiple sclerosis, tend to respond more effectively to the anticonvulsant
drug ‘Gabapentin’.

 

As trigeminal neuralgia is a
progressive disorder, it often becomes resistant to the various medications
currently available. Surgical intervention is required to treat patients whom
have exhausted all or found medication unsuitable. (NCBI,2010)

Many surgical procedures are
currently available with a varying degree of success and risks.

Several techniques only offer
temporary results whilst others have shown to have higher success rates. TN
will often return after an initial pain-free period (up to several years)G28 

Rhizotomy
(rhizolysis) techniques aim to deliberately damage or injure the trigeminal
nerve to block pain, therefore all produce a numbness sensation in the face.
Several forms of this procedure are used to treat TN such as;

Balloon compression.
This is performed under general anaesthesia in the operating room. A cannula is
inserted into the cheek through which a balloon is passed. The balloon is
inflated and squeezed against the nerve aiming to damage the nerve insulation.
This treatment usually achieves around two year’s pain-free post-surgery.
(NINDS,2017)

Radiofrequency lesioning (RF lesion) Also performed under general
anaesthesia, a hollow needle is passed through the cheek in a similar location
as the balloon G29 compression. However, this time the patient
is woken up during surgery whilst an electric current is passed through the
needle. A tingling sensation allows the patient to guide the surgeon to the
exact location of TN pain zone. The patient is then sedated whilst an electrode
is used to heat and damage the nerve fibresG30 . Approximately half of the patients
receiving this treatment report reoccurrence of pain within three to four
year’s post-surgery. G31 (NINDS,2017)G32 

Glycerol injections, with the patient sedated, glycerol is injected
through the cheek, into the spinal fluid that surrounds the trigeminal
ganglion. Glycerol damages the nerve fibre insulation providing pain relief for
between one to two years. Less invasive this procedure can be repeated many
times.G33 G34 

Stereotactic (Gamma Knife) computer technology is used to focus a
concentrated beam of radiation directly onto the trigeminal nerve, as it exits
the brain stem. Lesions form on the nerve disrupting sensory signals. G35 G36 This technique is the least invasive, it
does not require general anaesthesia. Only a local anaestheticG37  is needed, nor does in involve incisions
to the face. Pain relief is not felt for several weeks, however, only 50% of
patients treated report pain recurrence within three year’s post-surgery.G38  (NHS,2017)

All the above rhizotomy procedures
carry the possible risk of permanent pins and needles sensation of the
face. In extremely rare incidences, a combination of numbness and continuous
facial pain occurs, known as anaesthesia DoloG39 rosa. 
G40 G41 

 

Microvascular decompression (MVD) an inpatient treatment, this is
the most invasive of all TN treatments, however, offers the most success. G42 G43 Performed under a general anaesthetic by a
neurosurgeon. The surgery involves opening the skull, an incision is made
through the mastoid bone behind the ear, revealing the compressed nerve. A soft
cushion is placed between the nerve and usually an artery or blood vessel,
freeing the nerve from pressure. Only half of the patients experieG44 nce the return of pain within 10-20 year’s
post-surgery. Unlike rhizotomy techniques, this surgery does not leave a
numbness in the face. Possible risks caused by this procedure include hearing
loss, stroke even death has been reported in around 1 in every 200 procedures.
(NHS.2017)

 

 

 

 

 

Conclusion

 

Treatment of trigeminal neuralgia
varies widely. Patients respond differently to treatment giving doctors the
difficult task of predicting which treatment will have the best outcome. Due to
the rarity of the disease and the lack of effective clinical trials, specific
TN drugs have currently not been developed. Patients are treated with
anti-epilepsy drugs which have shown some positive results. Initially, a
patient is prescribed G45 a milder form, if drug resistance occurs,
other forms or a combination of medications are prescribed in a trial and error
fashion until a suitable level of pain management is achieved. The high
toxicity of many of these drugs themselves cause devastating side effects and
often prove unsuitable for patients. Doctors consider a successful response to
be that of a 50% pain reduction. Full pain relief is generally considered
unachievable. Many patients do successfully manage their condition with drugs
alone, leading relatively healthy lives.

Surgical techniques show promising
results although most only produce short-term results which weighed up against
the high risk of factors, G46 do not prove as popular as medication.

Doctors tend to only recommend
surgery as a last resort once all other options have been exhausted. However,
evidence shows that surgery (even with its high-risk factor) is the most
effective treatment for trigeminal neuralgia. Of the various technique’s
available, microvascular decompression
is currently the most successful surgical option. Long term, this does offer a
patient the closest result to a total cure. Up to 15-20 year’s pain-free.  Although it is the most invasive of the
surgical techniques (performed under general anaesthesia). Fit healthy patients
find the risks far outweigh the effects of a lifetime on medication.

Patients that are infirm, elderly
or those that would not tolerate a general anaesthesia. The Stereotactic (Gamma Knife) would prove
more suitable performed under a local anaesthetic. The resulting pain-free
period is much shorter, up to 3 years, however, the procedure may be repeated
many times as required.G47  (McMillan, R.2015)

 

In conclusion, until such a time
when clinical trials and more research result in the development of effective
dedicated trigeminal neuralgia drugs. Doctors should be less reluctant to refer
and aim to provideG48  patients diagnosed with TN, surgical
options much earlier on in their treatment rather than “as a last resort”. Avoiding
years of unnecessary drug G49 G50 G51 useG52  and possible G53 medication related side effects.G54 G55 G56 G57 

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