Short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT) with preserved refractory period: report of three cases

Short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT) and short-lasting unilateral neuralgiform attacks with cranial autonomic features (SUNA) are rare primary headache syndromes characterized by spontaneous or triggered attacks of unilateral, brief, multiple, orbitofrontal pain associated with ipsilateral autonomic features. SUNCT is considered as a subset of SUNA. In SUNA, there may be cranial autonomic symptoms other than conjunctival injection and lacrimation, or either of two is present. SUNCT/SUNA can be triggered immediately after or at the decrescendo phase of the ongoing attack without any intervening refractory period. Refractory period is usually present in trigeminal neuralgia. Absent refractory period is thought to reliably differentiate SUNCT/SUNA from trigeminal neuralgia and has been proposed for inclusion into the International Classification of Headache Disorders (ICHD) diagnostic criteria for SUNCT.

We report three patients of SUNCT syndrome with preserved intervening refractory period of variable duration observed at different times.

Trigeminal neuralgias with autonomic features, SUNA and SUNCT share a common pathophysiological mechanism and actually represent a continuum. It is well known that patient with trigeminal neuralgia may transform into SUNCT/SUNA. Similarly, being a continuum, the presence or the absence of refractory period and its duration may change in a patient with SUNCT/SUNA at different time points.

The presence of refractory period should not exclude the diagnosis of SUNCT in a patient with other clinical features suggestive of SUNCT.