Vasileios-Arsenios Lioutas, MD
It is well known that presence of blood products in the subarachnoid space in cases of intracranial aneurysm rupture leads to activation of several pathological processes leading to brain injury. In this well performed study, Maas et al prospectively enrolled patients with ICH, seeking to test whether radiographic extension of hemorrhage into the subarachnoid space (by CT criteria) contributed to functional outcome and mortality. 14-day mortality and modified Rankin Scale at 28 and 90 days (after correction for the ICH score) were the primary outcomes.
Subarachnoid hemorrhage was convexal and ipsilateral to the intracerebral hematoma in the majority of cases, largely different from the more widely investigated aneurysmal SAH with diffuse, thick subarachnoid clot.
Univariate comparison analysis revealed that patients with subarachnoid hemorrhage extension were older, with larger intracerebral hematoma volumes, lower Glasgow Coma Scale score and more frequently associated with lobar locations. Rate of death at 14 days as well mRS score at 28 and 90 months was significantly higher in that group.
Adjusting for ICH score, (which, as a reminder includes most of the characteristics identified as more frequent in the SAH extension group), revealed a significant association between subarachnoid extension and 14-day mortality and 28-day unfavorable outcome. A similar but weaker association with unfavourable 90-day outcome was identified.
A secondary multivariate analysis using significant variables identified in the univariate analysis showed unambiguously that SAH extension is a strong independent predictor of death by day 14 (OR 7.58, CI 1.5-36.7 p=0.012).
Why this occurs is not known with certainty, although there are a number of postulated mechanisms (mostly from the aneurysmal SAH literature) attempting to explain the harmful effect of presence of blood in the subarachnoid space.
Potential shortfalls of the study, identified by the authors as well, include the single-center character of the study, limiting the generalizability of the findings, as well as the qualitative nature of determining SAH extension and use of CT scan as detecting method. Adding quantitative measures of SAH volume and using imaging methods more sensitive than CT scan could offer additional accuracy. It would also be interesting to perform the secondary analysis using functional outcome and not only 14-day mortality as outcome measure.
Regardless, this is a well performed study that sheds light into a heretofore scarcely investigated issue, and offers objective evidence to support the intuitive suspicion that extension of hemorrhage into the subarachnoid space has a detrimental effect.