Thick Clot in the Inferior Limiting Sulcus on Computed Tomography Image As an Indicator of Sylvian Subpial Hematoma in Patients with Aneurysmal Subarachnoid Hemorrhage

OBJECTIVE: Sylvian subpial hematoma (SSH) is occasionally observed in aneurysm subarachnoid hemorrhage (aSAH) when accompanied with the thick clot in the inferior limiting sulcus (ILS). We aimed to determine whether the thickness of the clot in the ILS (TCILS) was an indicator of SSH. METHODS: Data from 150 consecutive patients with aSAH were retrospectively analyzed. The relationship between TCILS on axial computed tomography (CT) image and intraoperatively confirmed SSH was reviewed. In patients without SSH, the average of the clot thickness in the bilateral ILS was used. The primary outcome was SSH. RESULTS: The median TCILS of the SSH group (n = 18, 12%) was larger than that of the non-SSH group (n = 132, 88%) (21 vs. 2.1 mm, respectively; P < 0.001). The intraclass correlation coefficients for clot thickness in the right and left ILS between 2 observers were 0.97 (P < 0.001) and 0.85 (P < 0.001). The TCILS threshold of >= 6.0 mm was associated with SSH, with a sensitivity of 89% and specificity of 99%. The unadjusted and adjusted odds ratios of the SSH of clot thickness in the affected ILS >= 6 mm relative to clot thickness in the affected ILS <6 mm were 263 (95% confidence interval [CI], 46-5063) and 137 (95% CI, 19-3029), respectively. CONCLUSIONS: The clot thickness in the ILS on CT image was easily measured and could be a marker of SSH. SSH assessment could be useful in helping us predict the clinical course in patients with aSAH.