Trigeminal Neuralgia

Question 1

What is Trigeminal Neuralgia?

Answer 1

A sudden, usually unilateral severe brief stabbing recurrent episodes of pain in the distribution of one or more branches of the trigeminal nerve.

Question 2

Describe the epidemiology of TN?

Answer 2

More common in women than men.
Usually in patients aged 60 and above- peak incidence is 50-80 years old.
More common in maxillary and mandibular branches than the ophthalmic.

Question 3

Describe the classification of TN?

Answer 3

Idiopathic- no known cause

Classical- vascular compression of the trigeminal nerve. High resolution MRI is needed to confirm this.

Secondary- caused by something else that is not related to the trigeminal nerve. i.e. MS, space-occupying lesion.

Question 4

What are the clinical features of TN?

Answer 4

Unilateral maxillary or mandibular division pain
Stabbing pain, leectric-shock pain.
Localised
5-10 second duration
Paroxysmal or with concomitant dull continuous pain between attacks
Remissions and relapses
Mask-like face

Triggers- touch, cold, wind, chewing, speaking, sometimes nothing.

No obvious precipitating pathology

Question 5

What are the red flag signs of TN?

Answer 5

Younger patient- younger than 40 years old.
Sensory deficit in facial region0 hearing loss.
Other cranial nerve lesions.

Question 6

If a patient presents with TN symptoms, what must you do?

Answer 6

Full history
Examine all cranial nerves.
Pain diary- determine when the pain is at it’s worst and this will help with medication dosages
Referral for MRI.

Question 7

Describe the pathogenesis of TN?

Answer 7

Largely unknown.

Classical TN may be explained by
- Neuromuscular compression of trigeminal nerve root entry.
- Causes demyelination of nerve fibres, which start firing ectopically.
- Atrophy of/hypertrophy of peripheral axons and damage to Schwann cells causes further hyper excitability of nerves.

Patients may have NVC but not have TN.

Question 8

What diagnostic criteria is used to diagnose TN?

Answer 8

International Classification of Orofacial Pain.

Question 9

What criteria does a patient need to meet in order to be diagnosed with TN?

Answer 9

Pain has all of the following characteristics-
- lasts from a fraction of a second to 2 seconds.
- Severe intensity
- Electric shock-like pain, shooting, stabbing or sharp in quality
- Precipitated by innocuous stimuli within the affected trigeminal distribution
- Not accounted for by another ICOP or ICHD-3 diagnosis.

Question 10

What is the first line drug therapy for TN?

Answer 10

Carbamazepine- slow release tablets given to avoid fluctuations of serum concentration to reduce unwanted side effects.

Then oxcarbazepine then lamotrigine.

Second line
- Gabapentin
- Pregablain
- Phenytoin
- Baclofen

Question 11

Describe the mode of action of Carbamazepine?

Answer 11

Sodium channel blockade- inhibition of voltage-gated sodium channels, reduces firing of nerve impulses, stabilising electrical activity in the brain and nerves.

Question 12

What dosage of Carbamazepine is recommended for TN?

Answer 12

Initial dosage is 100-200mg 1-4 times a day.

This is gradually increased over a period of about one month.
- eventually achieve a therapeutic dosage, this is to reduce the chance of unwanted side effects.

Maximum dosage if 1600mg per day.

Question 13

What are the potential side effects of Carbamazepine?

Answer 13

Blood dyscrasia- thrombocytopenia, neutropenia, pancytopenia.

Electrolyte imbalance- hyponatraemia

Neurological deficits- paraesthesia, vestibular problems

Liver toxicity

Skin reactions

Question 14

What tests are required for someone that is taking Carbamazepine?

Answer 14

FBC, urea and electrolytes, LFT.
Blood pressure
Balance test

Question 15

What is the mode of action of Oxcarbazepine?

Answer 15

Similar mode of action to carbamazepine- blocks VGSC.

Question 16

Is Oxcarbazepine better than Carbamazepine?

Answer 16

Lower efficacy but less unwanted side effects- only give oxcarbazepine if Carbamazepine is not tolerated.

Reduce risk of blood dyscrasia in comparison to Carbamazepine.

Question 17

Should you prescribe Carbamazepine in general dental practice?

Answer 17

SDCEP Drug prescribing for Dentistry guidelines state that you can.

Take into consideration the risks of side effects- do you have the facilities to monitor this? Blood tests?

Liaise with GMP regarding carbamazepine use.

Question 18

What are the indications for surgical treatment in TN?

Answer 18

Not usually recommended if the patient is managing on medical therapy with moderate drug dose and no significant side effects.

Consider surgery-
- when approaching maximum tolerable medical management even if pain is controlledd.
- Younger patients with significant drug use.

Question 19

What are the surgical options for TN?

Answer 19

Microvascular decompression
- Preferred surgical treatment.
- Reposition the artery/vein that is compressing the trigeminal nerve.
- 12 months0 1% mortality/10% morbidity.

Stereotactic Radiosurgery
- Needle goes into the cheek and a gamma knife is used to target radiation at the trigeminal ganglion to kill trigeminal nerve cells that are signalling the pain.
- Patient must be awake for this part.

Destructive Central Procedures
- Radiofrequency thermocoagulation
- Retrogasserin glycerol injection
- balloon compression- under GA, needle inserted into cheek, through foramen ovale, the balloon is inflated and compresses the nerve.

Destructive Peripheral Neurectomies
- Surgical destruction of peripheral branches of trigeminal nerve.
- Only do this when other medical therapy and surgery has failed.

Question 20

What are the potential complications after surgery for TN?

Answer 20

Sensory loss- corneal reflex, general sensation, hearing loss.

Motor deficits

Dysaesthesia, paraesthesia, facial numbness

Vascular injuries

Question 21

What is Painful Trigeminal Neuropathy?

Answer 21

Pain is localised to the distribution of the trigeminal nerve but the pain is continuous or near-continuouss, described as a burning or squeezing, pins and needles.

Cutaneous allodynia is present and has a much larger trigger zone present than in TN.

Sensory deficits also present.

Question 22

What might be the cause of Painful trigeminal neuropathy?

Answer 22

Herpes zoster virus (post-herpetic neuralgia)
Trauma- pain develops less than 6 months after traumatic event
Idiopathic.

Question 23

What are Trigeminal Autonomic Cephalgias?

Answer 23

A group of disorders that are all characterised by unilateral head pain- predominantly ophthalmic division of the trigeminal nerve.

Severe, excruciating pain.

In the area ipsilateral to the pain- conjunctival inject/lacrimation, nasal congestion/rhinorrhoea, eyelid oedema, ear fullness, mitosis and ptosis.

Question 24

What disorders make up Trigeminal Autonomic Cephalgias?

Answer 24

Cluster headache
Paroxysmal hemicrania
SUNCT

Question 25

Describe a Cluster Headache attack?

Answer 25

Pain around orbital and temporal region

Attacks are strictly unilateral
Rapid onset
Last for 15 minutes to 3 hours.
Rapid cessation of pain
Patients are restless and agitated during attack

Prominent ipsilateral autonomic symptoms

Migrainous symptoms often present
- premonitory symptoms- tiredness, yawning
- associated symptoms- nausea, vomiting, photophobia, phonophobia.

Question 26

Describe a cluster headache bout?

Answer 26

Episodic in 80-90% of cases
- attacks cluster into bouts typically 1-3 months with remission lasting at least 1 month.

Frequency- 1 every other day to 8 per day.
May be continuous background pain between attacks.

Circadian periodicity- attacks occur at the same time each year and bouts occur at the same time each year.

Question 27

Describe Paroxysmal Hemicrania?

Answer 27

Pain from the orbital and temporal region of the head.

Attacks are strictly unilateral
Rapid onset- last for 2-30 minutes.
Rapid cessation of pain.
2-40 attacks per day- no circadian rhythm.
Excruciatingly severe.

Prominent ipsilateral autonomic symptoms
Migranous symptoms

Attacks may be precipitated by bending or rotating the head
Background continuous pain may be present

Very responsive to indomethacin

Question 28

If someone presented with symptoms of Trigeminal autonomic cephalgia, what questions would you wish to ask during the history?

Answer 28

SOCRATES

Any other associated symptoms? Do you feel sick when you have the pain? What are you doing when the pain happens? Do your eyes get watery? (autonomic symptoms)
How long do the pain episodes last?
How often do you get th pain episodes?
Do they always happen at the same time of day when you get them? Same time of year?

Question 29

What drug therapy is required for Cluster Headache?

Answer 29

During attack
- Subcutaneous Sumatriptan 6mg or nasal zolmatriptan 5mg
- 100% oxygen via a non-rebreathing mask

During bout- occipital depomedrone.lidocaine injection.
- Tapering dose of prednisolone.

Preventaive- Verapmil, lithium, methysergide, Topiramate

Question 30

What drug therapy is required for Paroxysmal Hemicrania?

Answer 30

No treatment for the attacks.

Prophylaxis with indomethacin.

Question 31

Some patients find it difficult to control pain first thing in the morning, what could you do to combat this?

Answer 31

Increase the nightly dose of Carbamazepine

Question 32

What could you do in the dental setting to reduce the patient’s pain?

Answer 32

Give them LA into the area.

Question 33

What other non-pharmacological and non-surgical therapies might help TN?

Answer 33

Acupuncture
Hypnosis
Facial exercises
Food supplements
Relaxation technique
Homeopathic medicines