Viral Screening in Trigeminal Neuralgia
Viral screening is not mandatory or routinely recommended in trigeminal neuralgia. The diagnosis is made almost entirely based on clinical history and characteristic pain features, with MRI being the primary imaging modality to rule out secondary causes 1, 2.
Diagnostic Approach
The evaluation of trigeminal neuralgia focuses on clinical criteria and structural imaging rather than viral testing:
Clinical diagnosis is paramount: Trigeminal neuralgia is diagnosed based on characteristic paroxysmal attacks of sharp, shooting, electric shock-like pain lasting seconds to minutes with refractory periods between attacks 3, 2.
MRI with contrast is the gold standard imaging: High-resolution thin-cut sequences through the trigeminal nerve course should be obtained to evaluate for neurovascular compression and exclude secondary causes such as multiple sclerosis or tumors 4, 5, 1.
Neurological examination is typically normal in classical trigeminal neuralgia, whereas examination in secondary cases focuses on detecting signs of multiple sclerosis or cerebellopontine tumors 1.
When Viral Etiology Should Be Considered
Viral screening becomes relevant only when the clinical presentation deviates from classical trigeminal neuralgia:
Post-herpetic neuralgia presents differently: This condition causes continuous burning pain at the site of previous herpes zoster eruption with allodynia and hyperalgesia, not the paroxysmal attacks characteristic of trigeminal neuralgia 3, 5.
Continuous pain is a red flag: The presence of continuous pain rather than paroxysmal attacks should prompt MRI evaluation to rule out secondary causes including structural lesions, not viral screening 3.
History of herpes zoster is diagnostic: If there is a clear history of previous shingles in the trigeminal distribution with subsequent continuous pain, the diagnosis is post-herpetic neuralgia, which is clinical and does not require viral screening 3.
Key Diagnostic Distinctions
Classical trigeminal neuralgia has mandatory refractory periods between paroxysmal attacks lasting seconds to minutes, distinguishing it from continuous pain syndromes 3.
Imaging evidence of neurovascular compression has congruence rates of 83-100% with surgical findings, making MRI far more valuable than viral studies 4, 5.
Secondary causes require structural imaging: Multiple sclerosis and tumors are identified through MRI with contrast, not viral screening 5, 1.
Common Pitfalls to Avoid
Do not order viral screening for typical trigeminal neuralgia: The characteristic paroxysmal pain pattern with trigger zones and refractory periods does not warrant viral testing 3, 2.
Recognize that continuous pain changes the differential: If pain is continuous rather than paroxysmal, consider post-herpetic neuralgia, persistent idiopathic facial pain, or post-stroke pain—but diagnosis remains clinical with MRI support, not viral serology 3.
MRI findings must be interpreted in clinical context: Both false-positive and false-negative imaging results occur for neurovascular contact, but this does not justify adding viral screening to the workup 5.