Vessel Wall Enhancement in Unruptured Intracranial Aneurysms: An Indicator for Higher Risk of Rupture? High-Resolution MR Imaging and Correlated Histologic Findings.

BACKGROUND AND PURPOSE: Recent studies have suggested that wall enhancement of unruptured intracranial aneurysms in high-resolution MR imaging might serve as an imaging biomarker for higher risk of rupture. Histologic studies have revealed a possible association among inflammatory processes, degeneration, and destabilization of the aneurysm wall preceding rupture. Understanding the histologic condition underlying aneurysm wall enhancement could be an important step toward assessing the value of this method for risk stratification. We present our observations of aneurysm wall enhancement in MR vessel wall imaging and underlying histologic changes. MATERIALS AND METHODS: We reviewed records of patients with an unruptured middle cerebral artery aneurysm who underwent MR vessel wall imaging before aneurysm clipping. Contrast enhancement of the aneurysm wall was dichotomized into either none/faint or strong. Histologic analysis included myeloperoxidase stain for detection of inflammatory cell invasion and CD34 stain for assessment of neovascularization and vasa vasorum. RESULTS: Thirteen aneurysms were included. Five aneurysms showed strong wall enhancement. Among these, myeloperoxidase staining revealed inflammatory cell infiltration in 4. Three showed neovascularization. In 2 aneurysms, vasa vasorum were present. Seven aneurysms did not show wall enhancement; 1 had only mild enhancement. None of these bore evidence of inflammatory cell invasion or neovascularization, and they all lacked vasa vasorum. CONCLUSIONS: Wall enhancement in MR vessel wall imaging is associated with inflammatory cell invasion, neovascularization, and the presence of vasa vasorum. Enhancement does not occur when histologic signs of inflammation are absent. Our results support the hypothesis that MR vessel wall imaging could provide valuable information for risk stratification.

The subpetrous carotid wall hematoma: a sign of spontaneous dissection of the internal carotid artery on non-enhanced computed tomography - a retrospective study.

PURPOSE: Spontaneous dissection of the internal carotid artery (CAD) is an increasingly recognized cause for stroke especially in young and middle-aged patients. We hypothesized that non-enhanced cranial computed tomography (NECCT) can visualize the subpetrous carotid wall hematoma and thus enable identification of patients with CAD. MATERIALS AND METHODS: We retrospectively reviewed patients with confirmed CAD (n = 21) and a control group with ischemic symptoms but without CAD (n = 42) who received NECCT at admission. Two independent neuroradiologists rated the presence and shape of SPH, density and diameter of the subpetrous internal carotid artery. Additionally, we correlated the shape of the subpetrous carotid wall hematoma with the grade of stenosis on subsequent angiographic imaging. RESULTS: The subpetrous carotid wall hematoma was present in 14 of 21 patients (Cohen's κ = 0.67). Mean diameter was 6.95 ±â€Š1.05 mm in dissected vessels and 5.71 ±â€Š1.52 mm in the contralateral vessel (p < 0.05). Mean difference in vessel density was 15.05 ±â€Š8.01 HU (p < 0.01). Median grade of stenosis was significantly higher in patients with a full moon- shaped (n = 11) than crescent-shaped (n = 3) subpetrous carotid wall hematoma (21 % vs. 80 %, p < 0.05). CONCLUSION: Two-thirds of patients with CAD  were correctly identified on NECCT. The extracranial carotid artery should be evaluated in patients with symptoms of cerebral ischemia.