Cerebral amyloid angiopathy (CAA) is emerging as a rather common cerebral small vessel disease and a major cause of spontaneous ICH. Diverse etiologies have been suggested for the occurrence of convexal subarachnoid hemorrhage, including cerebral amyloid angiopathy (CAA).1 The authors of this study looked at a 9-year-period of patients with spontaneous convexal subarachnoid hemorrhage (cSAH) and performed longitudinal analysis of clinical and neuroimaging data with the assumption that CAA is associated with cortical subarachnoid hemorrhage, cortical superficial siderosis and lobar ICH.

The authors identified 1178 patients diagnosed with SAH. Two-hundred-forty-nine (21%) had nontraumatic, non-aneurysmal SAH and 45 (3.8%) fulfilled the criteria of cSAH. Out of the 45 patients, seven had to be excluded due to lack of imaging and they found that 76% of the remaining (38 patients) had imaging features consistent with CAA at baseline. Post-contrast MRI was performed on 16 patients and extravasation of gadolinium at the site of the acute cSAH was seen on all post-contrast scans. During follow up for a period of 24±22 (range 1-78) months, 15 (39%) had experienced recurrent cSAHs and 14 (37%) had suffered lobar ICHs. Interestingly, of the 22 new ICHs, 17 occurred at sites of previous cSAHs or cSS. Another interesting finding was that follow-up imaging revealed that there was cortical SAH expansion into the nearby brain parenchyma and evolution of a lobar ICH in 4 patients.

The authors postulate through observational data that frequent recurrence of CAA-related cortical SAH was associated with substantial risk for future symptomatic ICH; while they believe intracerebral bleeding can occur from extension of cortical SAH and leakage of meningeal vessels the exact pathophysiological mechanism still eludes us. In order to confirm the observations from this study a much larger set of patients would have to be analyzed to make any definitive conclusions. Perhaps with better imaging techniques and more sensitive sequencing in MRI, we will be able to pick up asymptomatic cSAH in patients more often which may help in predicting future risk of a lobar ICH.

Reference:
1. Katoh M, Yoshino M, Asaoka K, et al. A restricted subarachnoid hemorrhage in the cortical sulcus in cerebral amyloid angiopathy: could it be a warning sign? Surg Neurol 2007;68:457– 460.