How do you diagnose trigeminal neuralgia in a middle-aged to elderly emergency department patient with a history of multiple sclerosis, stroke, or facial trauma, presenting with sudden, severe, shock-like facial pain?

Diagnosing Trigeminal Neuralgia in the Emergency Department

The diagnosis of trigeminal neuralgia in the ED is made almost entirely on clinical history—specifically, the presence of paroxysmal attacks of sharp, shooting, electric shock-like pain lasting seconds to minutes with a mandatory refractory period between attacks, triggered by innocuous stimuli like light touch, and confined to one or more trigeminal nerve distributions. 1, 2

Essential Clinical Features to Elicit

The following pain characteristics are pathognomonic and must be documented:

• Pain quality: Sharp, shooting, or electric shock-like—patients often describe it as "a sudden jolt of electricity through the face" 3, 4
• Pain duration: Individual attacks last seconds to minutes, not hours or days 2, 5
• Refractory period: A mandatory pain-free interval exists between attacks where pain cannot be triggered—if the patient can trigger attacks repeatedly without pain-free intervals, consider alternative diagnoses 2, 6
• Trigger factors: Light touch, washing the face, cold wind, eating, or brushing teeth provoke attacks 3, 4
• Distribution: Unilateral pain following V2 (maxillary) and/or V3 (mandibular) branches most commonly; bilateral symptoms are atypical and warrant expanded differential 3, 6

Critical Red Flags Requiring Urgent MRI

Order contrast-enhanced brain MRI immediately if any of the following are present:

• Sensory deficits in the trigeminal distribution—this is never normal in classical trigeminal neuralgia and suggests secondary causes like tumors or multiple sclerosis 2, 3
• Continuous pain from onset rather than paroxysmal attacks—this indicates Type 2 trigeminal neuralgia or alternative diagnoses requiring imaging to exclude structural lesions 2, 6
• Autonomic features (tearing, conjunctival injection, rhinorrhea, nasal congestion)—these indicate trigeminal autonomic cephalgias (SUNCT/SUNA), not true trigeminal neuralgia 2, 3
• History of multiple sclerosis—demyelinating plaques can cause secondary trigeminal neuralgia 7, 1
• Bilateral symptoms—highly atypical for classical trigeminal neuralgia 6

Physical Examination Findings

The neurological examination is typically normal between attacks in classical trigeminal neuralgia 1, 4. However, you must:

• Test for sensory changes in all three trigeminal divisions—any deficit mandates urgent imaging 2, 3
• Identify trigger points by light touch to the face—reproduction of pain supports the diagnosis 6
• Assess for autonomic signs (tearing, eye redness, swelling)—their presence excludes classical trigeminal neuralgia 2

Key Differential Diagnoses to Exclude in the ED

Trigeminal Autonomic Cephalgias (SUNCT/SUNA)

• Rapid attacks lasting seconds to several minutes with up to 200 attacks daily and no refractory period 2
• Prominent autonomic features: tearing, conjunctival injection, rhinorrhea, facial redness 2
• Pain mainly in V1 and V2 distributions 2

Post-Herpetic Neuralgia

• Continuous burning pain at the site of previous herpes zoster eruption 2, 6
• Associated with allodynia and hyperalgesia 2
• History of vesicular rash in trigeminal distribution 2

Glossopharyngeal Neuralgia

• Pain in deep ear, back of tongue, tonsils, or neck—not V2/V3 distribution 2
• Triggered by swallowing or coughing 2
• May be associated with syncope 2

Post-Traumatic Trigeminal Neuropathy

• Continuous burning or tingling pain developing within 3-6 months of dental procedure or facial trauma 2
• Clear history of inciting event 2

Atypical Odontalgia

• Continuous aching, dull, throbbing pain localized to tooth or tooth-bearing area 2
• Requires intraoral examination and consideration of dental pathology 2

Imaging Recommendations from the ED

MRI with contrast is the gold standard and should be ordered for all suspected trigeminal neuralgia cases to distinguish classical TN (neurovascular compression), secondary TN (MS, tumor), and idiopathic TN 6, 1, 4. The American College of Radiology recommends:

• High-resolution thin-cut sequences through the entire course of the trigeminal nerve from brainstem to peripheral branches 7, 6
• 3D heavily T2-weighted sequences combined with MR angiography to characterize potential vascular compression 7, 6
• Pre- and post-contrast imaging provides the best opportunity to identify and characterize lesions 6
• Imaging evidence of neurovascular compression has 83-100% congruence with surgical findings 6

CT is complementary for evaluating osseous skull base and neural foramina but insufficient as sole imaging 7, 6.

Common Pitfalls to Avoid

• Do not diagnose trigeminal neuralgia if pain is continuous—this suggests Type 2 TN, post-herpetic neuralgia, or atypical odontalgia and requires MRI to exclude secondary causes 2, 3
• Do not miss autonomic features—their presence indicates SUNCT/SUNA, not trigeminal neuralgia, and requires different management 2, 3
• Do not attribute sensory deficits to trigeminal neuralgia—any sensory loss mandates urgent imaging for tumors or MS 2, 3
• Do not delay MRI in patients with MS history—demyelinating disease is a known cause of secondary trigeminal neuralgia 7, 1