Transcranial Doppler in diagnosing and monitoring reversible cerebral vasoconstriction syndrome: a systematic review

INTRODUCTION: Digital subtraction angiography is considered the reference standard for diagnosing reversible cerebral vasoconstriction syndrome (RCVS); however, its invasive nature limits routine application. Transcranial Doppler ultrasonography (TCD) represents a noninvasive and bedside-accessible alternative, but its diagnostic and monitoring value in RCVS remains uncertain. EVIDENCE ACQUISITION: A systematic review was conducted in accordance with PRISMA 2020 guidelines. Searches were performed in PubMed, Embase, Cochrane Library, Scopus, and Web of Science up to January 2024. Eligible studies included case reports, case series, and observational designs involving adults with angiographically confirmed reversible vasoconstriction that reported TCD or color-coded sonography parameters (e.g., mean flow velocity, vasospasm). Risk of bias was assessed with ROBINS-I or Joanna Briggs Institute tools. Due to heterogeneity, results were synthesized descriptively. EVIDENCE SYNTHESIS: From 709 records, 8 studies encompassing 128 patients were included. TCD demonstrated increased mean flow velocities in the middle cerebral artery during the acute phase of RCVS, with reported peaks up to 146 cm/s, followed by gradual return to baseline within 6-12 weeks. Vasospasm was observed in up to 93.3% of patients, usually peaking between days 13 and 28. The Lindegaard index, ranging from 2.2 to >7, was valuable in distinguishing hyperemia from vasospasm. Serial bedside examinations, often every 24-48 hours during hospitalization, facilitated timely detection and monitoring of evolving hemodynamic changes. Nonetheless, included studies were small, heterogeneous, and methodologically limited. CONCLUSIONS: Transcranial Doppler ultrasonography appears promising as a noninvasive method for detecting cerebral vasospasm and monitoring temporal hemodynamic trajectories in RCVS.