Cerebral amyloid angiopathy (CAA) is a prominent cause of lobar intracerebral hemorrhage (ICH) in elderly populations. Emerging research suggests aquaporin 4 (AQP4) may contribute to the pathology of amyloid-beta-related conditions, including CAA. This study assessed serum AQP4 levels in patients with CAA-associated lobar ICH. Using enzyme-linked immunosorbent assay (ELISA), AQP4 was measured in 60 patients with CAA-related ICH and 19 non-stroke control participants. The patient cohort was further subdivided according to the timing of functional outcome evaluation: mid-term (12 ± 18.6 months) and long-term (38.5 ± 32.9 months) post-ICH. Overall, AQP4 concentrations did not differ significantly between patients and controls; however, lower levels were detected in patients exhibiting specific hemorrhagic patterns, such as having ≥2 lobar ICHs or ≥5 lobar microbleeds on MRI. Notably, individuals who achieved favorable long-term functional recovery had higher circulating AQP4 than those with poor outcomes or controls. These results indicate that AQP4 may serve as a prognostic marker for long-term recovery and might have a protective effect following lobar ICH.
