Response to Trigeminal Nerve Block in SUNCT/SUNA
Yes, a patient can still have SUNCT/SUNA even if they experience relief from a trigeminal nerve block, because response to peripheral nerve blockade does not exclude these diagnoses and may actually support the emerging concept that SUNCT/SUNA and trigeminal neuralgia exist on a continuum of the same disorder. 1, 2
Diagnostic Overlap and Nosological Considerations
The traditional separation of SUNCT/SUNA from trigeminal neuralgia is increasingly challenged by clinical evidence:
SUNCT, SUNA, and trigeminal neuralgia may constitute a continuum of the same disorder rather than separate clinical entities, with considerable clinical, therapeutic, and radiological overlap. 3, 2
Both conditions can respond to similar interventions, including peripheral nerve blocks, anticonvulsants (particularly lamotrigine and carbamazepine), and surgical approaches targeting the trigeminal nerve. 4, 2
Greater occipital nerve block has been reported as temporarily effective in SUNCT syndrome, demonstrating that peripheral interventions can provide relief in these conditions. 4, 5
Key Distinguishing Features That Remain Diagnostic
Despite treatment response overlap, maintain the SUNCT/SUNA diagnosis if these features are present:
Prominent autonomic features including conjunctival injection, tearing, rhinorrhea, nasal blockage, facial redness, and ear fullness occurring with attacks. 6, 1
Attack frequency and pattern: up to 200 attacks daily with no mandatory refractory period between attacks (unlike trigeminal neuralgia which requires refractory periods). 1
Attack duration: rapid attacks lasting seconds to several minutes, mainly in the first and second trigeminal divisions. 1
SUNCT specifically requires both conjunctival injection AND tearing, while SUNA has only one or neither of these features but other autonomic symptoms. 3
Clinical Pitfalls to Avoid
Do not use treatment response as the sole diagnostic criterion. The pathophysiology may involve both peripheral trigeminal nerve mechanisms and central dorsolateral medullary circuits, explaining why peripheral interventions can provide relief in both conditions. 7
The presence of neurovascular compression on imaging does not exclude SUNCT/SUNA, as emerging structural neuroimaging findings suggest neurovascular conflict with the trigeminal nerve may occur in SUNCT, similar to trigeminal neuralgia. 7, 2
Management Implications
If autonomic features are prominent, proceed with SUNCT/SUNA-specific management:
Lamotrigine remains the first-line preventive treatment for SUNCT/SUNA despite any response to nerve blocks. 8, 4
Intravenous lidocaine may decrease attack intensity during severe periods. 4, 3
Gabapentin may be more effective for SUNA specifically. 4
The relief from trigeminal nerve block suggests peripheral trigeminal nerve involvement but does not negate the diagnosis when characteristic autonomic features and attack patterns are present. 1, 2