Reversible cerebral vasoconstriction syndrome (RCVS) is characterized by recurrent thunderclap headaches and segmental vasoconstriction of cerebral arteries resolutive within three months. However, two case reports in the literature revealed diffuse cerebral vasodilatation rather than vasoconstriction at the early phase of RCVS (Kobayashi, 2016; Oikawa et al., 2017). This study aims at reporting the occurrence of diffuse cerebral vasodilatation at the initial stage of RCVS and at analyzing the clinical and prognostic characteristics of patients with diffuse vasodilatation.

Patients with RCVS were retrospectively gathered from medical files. Initial and follow-up vascular imaging were compared to assess vasodilatation and vasoconstriction for each segment of the circle of Willis on the initial angiogram. Diffuse vasodilatation was defined as dilatation of four or more of the circle of Willis arteries both in the anterior and posterior circulations, without previously described “string of beads” appearance of cerebral arteries. Patients were split into two groups based on the presence of diffuse cerebrovascular dilatation for comparison.

Among 148 patients with RCVS, 45 patients (30%) had diffuse cerebral vasodilatation. Diffuse vasodilatation was proved to occur at the early phase of RCVS (mean delay between thunderclap headache onset and initial imaging of 2.25days versus 7.63days, P=0.047) and mainly affected the first and second segments of major cerebral arteries. It was significatively associated with distal vasoconstriction (44.44% versus 25.24%, P=0.033). Patients with diffuse cerebral vasodilatation had a greater risk of hemorrhage (15.56% for subarachnoid hemorrhage versus 3.88%, P=0.035; 8.89% for intracranial hemorrhage versus 0.97%, P=0.03). Vasodilatation was more frequent in women (71.11% versus 41.75%, P=0.001). Secondary forms of RCVS were associated with diffuse vasodilatation (51% versus 27%, P=0.008).

The early cerebral angiogram may reveal diffuse cerebrovascular dilatation in patients with RCVS. Vasodilatation might have a pathophysiological implication in RCVS with clinical and prognostic consequences for patients.