Why SWI? The sensitivity of susceptibility weighted imaging in aneurysmal subarachnoid haemorrhage in the chronic phase

Abstract

Background: Incidentally detected unruptured intracranial aneurysms have a prevalence of 3% with some predisposed to rupture and others remaining static. Diagnostic knowledge of previous aneurysmal subarachnoid haemorrhage (ASAH) in the chronic phase could identify patients requiring treatment. Objectives: To assess the sensitivity of susceptibility weighted imaging (SWI) in the detection of ASAH at 3 months post ictus and determine any influencing effects. Method: A retrospective chart analysis of 46 patients with ASAH who underwent postembolisation SWI imaging at 3 months. The SWI and available initial CT brain scans or CT reports were evaluated and correlated with patient demographics and clinical severity. Results: Susceptibility weighted imaging indicated a sensitivity of 95.7% in the detection of ASAH at 3 months. Increased number of haemosiderin zones on SWI correlated with older patient age (p = 0.0003). Clinical severity (World Federation Neurosurgical Societies Score) showed a tendency towards a statistically relevant relationship (p = 0.07). No statistically significant relationship was identified between the number of haemosiderin zones and initial CT modified Fisher score (p = 0.34) or the causative aneurysm location (p = 0.37). Conclusion: Susceptibility weighted imaging is sensitive in the detection of ASAH at 3 months, increasing in sensitivity with patient age and higher initial clinical severity.