What Threshold Defines Penumbral Brain Tissue in Patients with Symptomatic Anterior Circulation Intracranial Stenosis: An Exploratory Analysis

Abstract

BACKGROUND AND PURPOSE Impaired distal perfusion predicts neurological deterioration in large artery atherosclerosis. We aim to determine the optimal threshold of Tmax delay on perfusion imaging that is associated with neurological deterioration in patients with symptomatic proximal anterior circulation large artery stenosis. METHODS Data were abstracted from a prospective ischemic stroke database of consecutively enrolled patients with symptomatic proximal intracranial stenosis (internal carotid artery or M1 segment of the middle cerebral artery) who underwent magnetic resonance perfusion imaging within 24 hours of symptom onset during a 15‐month period. Tissue volumes of perfusion delay Tmax 0‐4 seconds, Tmax > 4 seconds, Tmax > 6 seconds, and Tmax > 8 seconds were calculated using an automated approach. A target mismatch (penumbra—core) was defined as ≥15mL of brain tissue using each of the Tmax threshold categories. The outcome was neurological deterioration at 30 days defined as new or worsening neurological deficits that are not attributed to a nonvascular etiology. RESULTS Among 52 patients with symptomatic intracranial stenosis, 26 patients met inclusion criteria. Neurological deterioration was associated with target mismatch profile defined according to Tmax > 6 seconds (66.7% [6/9] vs. 5.9% [1/17], P < .01) and Tmax >8 seconds (57.1% [4/7] vs. 15.8% [3/19], P = .05] but not according to Tmax > 4 seconds (27.3% [6/17] vs. 11.1% [1/9], P = .35]. CONCLUSIONS A target mismatch profile using Tmax > 6 seconds may define tissue at risk in patients with acute symptomatic proximal anterior circulation intracranial stenosis. More studies are needed to confirm our findings.

Peri-procedural stroke or death in stenting of symptomatic severe intracranial stenosis

“…This study, however, has major limitations including its retrospective nature, the possibility of selection bias, and a small sample size. Thus, the optimal definition of impaired distal perfusion in patients with sICAS in the anterior circulation remains controversial and requires further validation 28…”

Infarct Pattern, Perfusion Mismatch Thresholds, and Recurrent Cerebrovascular Events in Symptomatic Intracranial Stenosis

“… Brain and neck CTA was reviewed by a neuroradiologist and sICAS was defined as intracranial large artery stenosis ≥70% on CTA using a standardized method and symptoms attributable to the same intracranial stenosis . Proximal anterior circulation stenosis was defined as involving the intracranial ICA or proximal MCA. The MRP protocol was described in previous studies . Mismatch brain tissue volume of ≥15 mL (penumbra—infarct volume) was used to define a target mismatch similar to prior studies and using each of the above T max categories to define penumbra.…”

“…Proximal anterior circulation stenosis was defined as involving the intracranial ICA or proximal MCA. The MRP protocol was described in previous studies . Mismatch brain tissue volume of ≥15 mL (penumbra—infarct volume) was used to define a target mismatch similar to prior studies and using each of the above T max categories to define penumbra. As the primary predictor was infarct pattern, patients with no evidence of infarction on diffusion weighted imaging were excluded.…”

“… Brain and neck CTA was reviewed by a neuroradiologist and sICAS was defined as intracranial large artery stenosis ≥70% on CTA using a standardized method and symptoms attributable to the same intracranial stenosis . Proximal anterior circulation stenosis was defined as involving the intracranial ICA or proximal MCA. The MRP protocol was described in previous studies .…”

“…Recently, we showed that T max > 6 seconds delay best defines penumbral tissue in patients with acutely symptomatic proximal anterior intracranial circulation stenosis but the association between T max > 6 seconds delay and BZ infarcts remains unclear. In addition, there are limited data comparing recurrent event rates based on BZ infarct type (IBZ vs. CBZ)…”