Cerebral amyloid angiopathy (CAA) is an entity that previously was very inconsistently described and diagnosis. This is inherent in any diagnostic criteria (in this case, Boston) that contains terms such as possibly and probably in the different grading levels. With the advent of improved magnetic resonance sequences such as gradient echo and susceptibility weighted imaging, the diagnosis of amyloid has been more prevalent and can be made with more certainty. The usual next step after diagnosis is to look for indicators of prognosis and the group cited out of Austria looked to identify mechanisms for why those patients with superficial siderosis present on the cortex had poorer outcome.
The authors performed a longitudinal analysis of clinical and neuroimaging data over a 9 year period and collected data for 38 patients found to have convexal subarachnoid hemorrhage. Out of these, they found that 29 or 76% where found to have imaging features consistent with CAA and 26 or 68% had imaging findings consistent with superficial siderosis. After a mean follow up time of approximately 24 months it was found that 15 of the patients (39%) suffered recurrent of their convexal subarachnoid hemorrhages and additionally 14 patients (37%) had suffered lobar intracranial hemorrhages. Interestingly, the group was able to obtain pathology for one of the patients in their cohort which showed leakage of meningeal vessels affected by CAA. They found that there may be some connection with convexity subarachnoid hemorrhages expanding into the brain parenchyma causing lobar intracerebral hemorrhages.
The data points toward recurrent subarachnoid hemorrhages being a poor predictive factor of outcome in patients with CAA as previously unrelated links of lobar ICH in patients with previous subarachnoid hemorrhages are now being connected given the improved knowledge of CAA, however the authors have provided further evidence that this link exists. The future of the area of research will likely be developing strict preventative measures in those with convexity subarachnoid hemorrhages to prevent ICH, especially if they meet criteria for CAA.