Evolution of Subarachnoid Hemorrhage Extension in Lobar Hemorrhage in the Early Chronic Phase and the Impact on Cerebral Amyloid Angiopathy Criteria

Background: Subarachnoid hemorrhage extension (SAHE) in acute lobar hemorrhage (LH) is frequent. Little is known about the short-and medium-term radiological evolution of SAHE. Our aim was to study this evolution by magnetic resonance imaging (MRI). Methods: We performed an observational study and analyzed retrospectively MRIs of patients with LH with possible/probable/definite cerebral amyloid angiopathy (CAA), and compared initial MRI performed between 3 hours and 21 days after symptom onset with follow-up MRI performed between 2 and 12 months after initial MRI. Results: Twenty patients were analyzed. Initial MRI showed 11 of 20 patients (55%) with SAHE. Follow-up MRI showed, compared with initial MRI, an increase of 77% (45% versus 80%) of patients with chronic intrasulcal hemorrhage, an increase of 36% (22% versus 30%) of the number of lobes with chronic intrasulcal hemorrhage, and an increase of 37% (1.75 versus 2.4) of lobes with chronic intrasulcal hemorrhage seen per patient. All new chronic intrasulcal hemorrhages involved the brain lobe with initial LH except 1 lobe in 1 patient. Three patients switched from possible to probable CAA according to the modified Boston criteria after follow-up MRI due to chronic intrasulcal hemorrhage in the lobe involved by LH. In 6 patients, follow-up MRI showed more diffuse chronic intrasulcal hemorrhage than pre-existing combined SAHE and chronic intrasulcal hemorrhage in the LH lobe, or showed presence of chronic intrasulcal hemorrhage in the absence of initial SAHE and/or chronic intrasulcal hemorrhage in the LH lobe. Conclusion: In LH patients, presence of SAHE on initial MRI changes the modified Boston CAA criteria on follow-up MRI in a portion of patients. On follow-up MRI, SAHE/chronic intrasulcal hemorrhage extension or chronic intrasulcal hemorrhage appearance in the LH lobe is relatively frequent.