Multiple Hypointense Vessels on Susceptibility-Weighted Imaging in Acute Ischemic Stroke: Surrogate Marker of Oxygen Extraction Fraction in Penumbra?

Abstract

Background: Multiple hypointense vessels (MHV) on susceptibility-weighted imaging (SWI) are frequently observed in patients with acute cerebral ischemia, but their implication has not been clearly established. To elucidate the clinical significance of MHV on SWI, we investigated the association of MHV on SWI with clinical data and other MR markers in patients with acute ischemic stroke. Methods: We enrolled acute stroke patients with internal carotid or proximal middle cerebral artery occlusion who underwent MRI including SWI within 3 days from stroke onset. Baseline clinical data were reviewed. Stroke severity was measured by the National Institutes of Health Stroke Scale (NIHSS). We graded the degree of MHV on SWI as four groups of none, subtle, relative, or extensive by the modified Alberta Stroke Program Early CT Scan (ASPECTS) system. To evaluate the degree of collateral flow, distal hyperintense vessels (DHV) on FLAIR and vessels on post-contrast time-of-flight MR angiography (TOF MRA) source images were graded respectively as 3 groups: none/subtle/prominent and poor/moderate/good. Diffusion and perfusion lesion volume and diffusion-perfusion mismatch (DPM) ratio were measured in all patients. We analyzed the association of the degree of MHV on SWI with clinical data and MR markers. Results: Eighty patients were included in the study. The mean MR time from stroke onset was 12.4 h (range 0.5-63.0). There is no difference in MR time from stroke onset between groups of MHV on SWI. MHV were observed in 68 (85%) of 80 patients: none in 12, subtle in 11, relative in 13, and extensive in 44. There were no statistically significant associations between MHV on SWI and vascular risk factors. Patients with more extensive MHV on SWI had a smaller diffusion volume (p < 0.001), larger DPM (p < 0.001), and lower initial NIHSS scores (p = 0.022). Prominent DHV was presented in 29 of 44 patients with extensive MHV (p < 0.001). Good collateral flow on TOF MRA source images was presented in 37 of 44 patients with extensive MHV (p < 0.001). Conclusions: More extensive MHV on SWI in acute ischemic stroke is associated with lower initial NIHSS scores, smaller diffusion lesion volume, better collateral flow, and larger DPM. Our results show the possibility that MHV on SWI may be a useful surrogate marker for predicting increased oxygen extraction fraction and diffusion-perfusion mismatch in acute ischemic hemisphere.

Prominent Hypointense Vessel Sign on Susceptibility-Weighted Imaging Is Associated with Clinical Outcome in Acute Ischaemic Stroke

“…PHVS was defined as numerous or larger veins with a greater hypointense sign as compared to the contralateral hemisphere on SWI [14, 16]. Cortical vessel sign (CVS) was defined as numerous or larger veins with a greater hypointense sign as compared to the contralateral hemisphere on the cortical vessel [9].…”

“…The extent of PHVS on SWI was assessed by ASPECTS [16]. The PHVS of the insular cortical vessels was recorded as I.…”

ASL and susceptibility-weighted imaging contribution to the management of acute ischaemic stroke

“…Indeed, when exposed to experimental hypoxia, the venous compartment gives a proportionally lower signal that can be detected visually [23]. During acute ischaemia, the local oxygen deprivation secondary to arterial occlusion is seen as a hypointense zone in the cortical and deep veins called the brush sign [24], as multiple hypointense vessels [25], or as prominent vessel [26]. The presence of these signs in the acute phase is associated with a less severe clinical presentation (lower initial NIHSS score), lower lesion diffusion-weighted imaging (DWI) volume, more extensive penumbra, and more pronounced collaterals [25].…”

Low thalamostriate venous quantitative susceptibility measurements correlate with higher presenting NIH stroke scale score in emergent large vessel occlusion stroke

“…[10][11][12] SWI can therefore show the presence or absence of the last physiologic response (increased oxygen extraction fraction) of ischemic tissue before cellular metabolism can no longer be maintained. [13][14][15] Furthermore, increased prominence of the cerebral veins on SWI has been associated with the presence of vigorous collateral flow. 15 These characteristics of SWI suggest that the presence or absence of prominent veins may serve as a valuable biomarker for tissue viability, and may thus indicate the potential benefit to the patient of endovascular revascularization.…”

“…[13][14][15] Furthermore, increased prominence of the cerebral veins on SWI has been associated with the presence of vigorous collateral flow. 15 These characteristics of SWI suggest that the presence or absence of prominent veins may serve as a valuable biomarker for tissue viability, and may thus indicate the potential benefit to the patient of endovascular revascularization. However, SWI is a qualitative technique and does not provide a quantitative measurement of venous oxygen saturation or deoxyhemoglobin.…”