Prognostic value of histopathological findings in aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) carries a severe prognosis, which is often related to the development of cerebral vasospasm. Even though several clinical and radiological predictors of vasospasm and functional outcome have been established, the prognostic value of histopathological findings remains unclear.

Histopathological findings in resected distal aneurysm walls were examined, as were the clinical and radiological factors in a series of 91 patients who had been neurosurgically treated for aneurysmal SAH. The impact of the histological, clinical, and radiological factors on the occurrence of vasospasm and functional outcome at discharge was analyzed.

Histopathological findings frequently included lymphocytic infiltrates (60%), fibrosis (60%), and necrosis (50%) of the resected aneurysm wall. On univariate analysis, clinical (Hunt and Hess grade) and radiological (aneurysm size) factors as well as histopathological features-namely, lymphocytic infiltrates and necrosis of the aneurysm wall-were significantly associated with the occurrence of vasospasm. On multivariate analysis, lymphocytic infiltrates (OR 6.35, 95% CI 2.32-17.36, p = 0.0001) and aneurysm size (OR 1.22, 95% CI 1.05-1.42, p = 0.009) remained the only factors predicting the development of vasospasm. A poor functional outcome at discharge was significantly associated with vasospasm, other clinical factors (Hunt and Hess grade, alcohol consumption, hyperglycemia, and elevated white blood cell count [WBC] at admission), and radiological factors (Fisher grade and aneurysm size), as well as with histopathological features (lymphocytic infiltrates [p = 0.0001] and necrosis of the aneurysm wall [p = 0.0015]). On multivariate analysis taking into account all clinical, radiological, and histological factors; vasospasm (OR 9.82, 95% CI 1.83-52.82, p = 0.008), Hunt and Hess grade (OR 5.61, 95% CI 2.29-13.74, p = 0.0001), patient age (OR 1.09, 95% CI 1.02-1.16, p = 0.0013), elevated WBC (OR 1.29, 95% CI 1.01-1.64, p = 0.04), and Fisher grade (OR 4.35, 95% CI 1.25-15.07, p = 0.015) best predicted functional outcome at discharge.

The demonstration of lymphocytic infiltrates in the resected aneurysm wall is of independent prognostic value for the development of vasospasm in patients with neurosurgically treated aneurysmal SAH. Thus, histopathology might complement other clinical and radiological factors in the identification of patients at risk.