Secondary Short-Lasting Unilateral Neuralgiform Headache with Conjunctival Injection and Tearing: A New Case and a Literature Review.

Short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) is a primary headache syndrome with an unclear pathogenesis. However, there is increasing evidence in the literature for secondary SUNCT being attributable to certain known lesions. We explored the possible neurobiological mechanism underlying SUNCT based on all reported cases of secondary SUNCT for which detailed information is available. Here we report a case of neuromyelitis optica spectrum disorders that had typical symptoms of SUNCT that might have been attributable to involvement of the spinal nucleus of the trigeminal nerve. We also review cases of secondary SUNCT reported in the English-language literature and analyze them for demographic characteristics, clinical features, response to treatment, and imaging findings. The literature review shows that secondary SUNCT can derive from a neoplasm, vascular disease, trauma, infection, inflammation, or congenital malformation. The pons with involvement of the trigeminal root entry zone was the most commonly affected region for inducing secondary SUNCT. In conclusion, the neurobiology of secondary SUNCT includes structures such as the nucleus and the trigeminal nerve with its branches, suggesting that some cases of primary SUNCT have underlying mechanisms that are related to existing focal damage that cannot be visualized.