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Trigeminal neuralgia
OSCE/PLAB2
8
Medical
Graduate
04/17/2025
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Term
What are the key clinical features of trigeminal neuralgia (TN)?
 Definition
Pain characteristics: Sudden, severe, electric shock-like or stabbing pain. Unilateral (usually V2 or V3 distribution – cheek, jaw, teeth). Brief episodes (seconds to minutes) but recurrent. Triggers: Light touch, cold wind, chewing, brushing teeth, shaving. No sensory loss (distinguishes from structural causes like MS). Refractory to standard painkillers (e.g., paracetamol, ibuprofen).Why this matters: Classic TN is idiopathic (vascular compression of the trigeminal nerve). Atypical TN (constant burning pain + sensory loss) suggests secondary causes (e.g., MS, tumour).
Term

How would you differentiate TN from other causes of facial pain?

 Definition
Condition Key Features
Trigeminal Neuralgia Electric shock-like pain, triggered by light touch, no sensory loss.
Migraine Throbbing headache ± nausea, photophobia, lasts hours.
Giant Cell Arteritis (GCA) Jaw claudication, scalp tenderness, ↑ESR/CRP.
Dental Pain Localised to tooth, worsens with hot/cold, percussion tenderness.
Post-herpetic Neuralgia History of shingles, burning pain, allodynia.
Multiple Sclerosis (MS) Atypical TN + neurological deficits (e.g., limb weakness, optic neuritis).

Why this matters:

  • TN is a clinical diagnosis (MRI needed only if atypical features).

  • GCA is an emergency (risk of blindness).
Term

What is the first-line treatment for TN?

 Definition

  • First-line: Carbamazepine (start low dose, e.g., 100mg BD, titrate up).

  • Alternatives if ineffective/intolerant:

    • Oxcarbazepine (less side effects).

    • Gabapentin / Pregabalin (if neuropathic component).

  • Refractory cases:

    • Neurosurgery (microvascular decompression, gamma knife).

Why this matters:

  • Carbamazepine is 80% effective but has side effects (dizziness, hyponatraemia, rash).

  • Avoid opioids (ineffective in TN).
Term

What red flags suggest secondary TN (e.g., MS, tumour)?

 Definition

  • Bilateral pain.

  • Sensory loss or weakness (e.g., facial numbness).

  • Young age (<40) or progressive symptoms.

  • Other neurological signs (e.g., diplopia, ataxia).

Why this matters:

  • MRI brain is needed if red flags to rule out MS, cerebellopontine angle tumours.
Term

How would you counsel a patient starting carbamazepine?

 Definition

  • Dosing: Start low (100mg BD), increase gradually.

  • Side effects:

    • Drowsiness, dizziness (avoid driving initially).

    • Hyponatraemia (monitor sodium if on high doses).

    • Stevens-Johnson syndrome risk (stop if rash develops).

  • Monitoring:

    • FBC, LFTs, sodium (baseline + periodic checks).

Why this matters:

  • Non-compliance is common due to side effects.

  • Drug interactions (e.g., warfarin, OCP).
Term

When would you refer to neurology/neurosurgery?

 Definition

  • Atypical features (sensory loss, bilateral pain).

  • Poor response to medications.

  • Consider surgery (microvascular decompression if vascular compression on MRI).

Why this matters:

  • Early referral prevents unnecessary suffering in refractory cases.
Term

What safety-netting advice would you give?

 

 Definition

  • Return if:

    • Rash (Stevens-Johnson risk).

    • New neurological symptoms (MS/stroke).

    • Pain worsens/unresponsive to treatment.

  • Avoid triggers (cold wind, chewing hard foods).

Why this matters:

  • Ensures early detection of complications.
Term

Key OSCE/PLAB 2 Tips

 Definition
"Electric shock-like pain" = TN until proven otherwise.
✔ Rule out GCA in elderly (ESR/CRP if suspected).
✔ MRI only if atypical features.
✔ Carbamazepine = gold standard treatment.
✔ Avoid opioids (ineffective).
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