n vs Surgery, exploring which treatment method is most effective in the management of Trigeminal Neuralgia.
By Yasmina Ajayi
Trigeminal neuralgia (TN) also known as ‘Tic douloureux’ is a rare, painful neuropathic disorder affecting one or more of the three branches of the trigeminal nerve, the fifth cranial nerve. The condition is also known as ‘Fothergill’s Disease’ after physician John Fothergill, who made the initial diagnosis and gave the disease its first full accurate description in 1773. 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 excruciating 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 from 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 first symptoms of another 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 providing 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 information from upper eyelid, side of the nose, forehead and part of the scalp. The trigeminal nerve is involved in facial sensation and movement. Sensory axons carry impulses to 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 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 blood vessels press on the nerve as it passes through. Excessive compression irritates and damages the nerve, eventually wearing away and causing irreparable destruction 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 nerve axons. This sheath serves 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 are common amongst sufferers. The condition usually occurs 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, usuallyG17 a patient’s first port of call may be a dental surgery, incorrectly believing they require dental treatment.G18
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’. (MedicineNetG19 G20 , 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. G21 G22 Although not fatal, the disease is known to cause severe anxiety, depression and can have a detrimental effect on a G23 patient’s quality of life. Suicide rates among sufferers are estimated at approximately 25% (NINDS,2017).G24 G25 G26
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 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) Generally, medications are used as first-line therapy. Anticonvulsant medicines such as 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, G27 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 witG28 h symptoms of TN2 often find these less effective. This form is a little more complex, patients often show a positive response to low levels of antidepressant medications for example ‘Nortriptyline’ and ‘Amitriptyline’, combined with a nonsteroidal anti-inflammatory drugs NSAIDs and opioids. These have shown to provide some limited pain relief.
Patients presenting symptoms caused by multiple sclerosis, tend to respond more effectively to the anticonvulsant drug ‘Gabapentin’.
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