Trigeminal Neuralgia – dribrahimelpum.com

Author: Dr Ibrahim Elpum

Introduction

Trigeminal neuralgia is a classic and frequently tested cause of severe facial pain in MRCP, USMLE, and medical school examinations. Although it can appear complex, the condition becomes easy to understand when approached through its neuroanatomy and pathophysiology. This guide focuses on building clear conceptual understanding to help candidates confidently recognise and answer exam questions.

What is Trigeminal Neuralgia?

Trigeminal neuralgia is a disorder of the fifth cranial nerve (CN V) characterised by:

Recurrent, sudden, severe facial pain
Electric shock–like or stabbing quality
Attacks lasting seconds to minutes
Pain occurring in the distribution of one or more branches of the trigeminal nerve

It is a neuropathic pain syndrome, not an inflammatory one.

Relevant Anatomy (Concept First)

The trigeminal nerve (CN V) provides:

Sensory supply to the face
Motor supply to muscles of mastication

It has three branches:

V1 (Ophthalmic) – forehead, eye, scalp
V2 (Maxillary) – cheek, upper lip, upper teeth
V3 (Mandibular) – lower lip, jaw, lower teeth (also motor fibres)

Pain most commonly affects:

V2 and V3 divisions

Pathophysiology (Why it happens)

The most common mechanism is:

Compression of the trigeminal nerve root by an aberrant blood vessel

Usually:

Superior cerebellar artery compressing the nerve near the brainstem

This leads to:

Demyelination
Abnormal electrical transmission
Hyperexcitability of the nerve

Secondary causes (important in exams and clinical practice):

Multiple sclerosis (especially in younger patients)
Tumours (e.g. cerebellopontine angle tumours)
Structural brainstem lesions

Clinical Features

The diagnosis is mainly clinical.

Typical features include:

Severe, sharp, stabbing, or electric shock–like facial pain
Lasts seconds (rarely more than 2 minutes per attack)
Occurs in brief paroxysms
Unilateral (almost always)
Pain-free intervals between attacks

Trigger zones

Pain can be precipitated by non-painful stimuli:

Talking
Chewing
Brushing teeth
Washing face
Cold wind

This feature is highly characteristic and frequently tested.

What is NOT seen in Trigeminal Neuralgia

This helps distinguish it in exams:

No sensory loss on examination
No facial weakness
No swelling or redness
Normal neurological examination between attacks

If sensory loss is present → think secondary cause.

Diagnosis

Trigeminal neuralgia is primarily a clinical diagnosis.

However, patients should have:

MRI brain (especially if young or atypical features)

This is to exclude:

Multiple sclerosis
Tumours
Structural lesions

First-Line Treatment (Very High-Yield)

Carbamazepine

This is the drug of choice in exams and real practice.

Key exam facts:

First-line treatment
Highly effective
Also used in epilepsy

Alternative options if not tolerated:

Oxcarbazepine
Gabapentin
Lamotrigine
Baclofen

Exam pearl:

Facial electric shock pain → treat with carbamazepine.

Surgical Options (If medical therapy fails)

These are lower-yield but good to know:

Microvascular decompression
Radiofrequency ablation
Gamma knife radiosurgery

Classic Exam Presentation

A typical question may describe:

A 55-year-old woman with sudden severe stabbing pain over the right cheek, lasting seconds, triggered by brushing teeth, with normal neurological examination between attacks.

Diagnosis: Trigeminal neuralgia
Treatment: Carbamazepine

Key Differentials (Exam Traps)

Condition	Key Difference
Dental pain	Local tenderness, continuous pain
Sinusitis	Dull ache, fever, nasal symptoms
Cluster headache	Autonomic features (tearing, red eye)
Post-herpetic neuralgia	History of shingles

Final Take-Home Message

Trigeminal neuralgia is a high-yield diagnosis characterised by:

Severe unilateral electric-shock facial pain
Triggered by light touch or movement
Normal neurological exam
Treated first-line with carbamazepine

If you understand the anatomy and mechanism, the diagnosis becomes straightforward.

Written by Dr Ibrahim Salaheldin