Atypical Reversible Cerebral Vasoconstriction Syndrome Without Thunderclap Headache: The Crucial Role of Medical History in Its Diagnosis and Management.

Reversible cerebral vasoconstriction syndrome (RCVS) is a secondary headache disorder characterized by reversible intracranial vasoconstriction. Although thunderclap headache (TCH) is a key feature of RCVS, it does not occur in all cases. We herein describe a case of a 49-year-old female patient with a history of migraine who developed RCVS. Her headache was persistent, throbbing, and located in the occipital region. It was not TCH-like, which was consistently triggered by sexual activity, and was non-responsive to non-steroidal anti-inflammatory agents (NSAIDs). Brain magnetic resonance imaging was unremarkable. Magnetic resonance angiography revealed the characteristic "strings and beads" appearance in the bilateral middle and posterior cerebral arteries and basilar artery. Therefore, she was diagnosed with RCVS. After avoiding headache triggers, including NSAIDs and sexual activity, symptoms improved within two months, with the complete resolution of vascular abnormalities and no recurrence during the follow-up period. Cases of RCVS without typical TCH are more likely to develop complications, such as coma due to stroke; however, our patient had mild symptoms and no abnormal findings in the brain parenchyma on brain MRI, which is rare. It is crucial to identify characteristic triggers, such as sexual activity, through a detailed medical history. Since RCVS and migraine share some clinical features, they may be misdiagnosed as one another. The treatment of RCVS with inappropriate drugs, including NSAIDs, triptans, and serotonin selective reuptake inhibitors, may worsen symptoms. Clinicians need to consider RCVS when patients with migraine complain of an "unusual headache" or exhibit headaches that do not respond to their usual medications. A thorough medical history and assessment of headache triggers are essential for the accurate diagnosis of RCVS, including a differential diagnosis of headache due to migraine, and the prompt identification and elimination of triggers may be the most important aspect of its management because there is currently no evidence-based medication for RCVS.