Raffaele Ornello, MD

Vagal A, Aviv R, Sucharew H, Reddy M, Hou Q, Michel P, et al. Collateral clock is more important than time clock for tissue fate – A natural history study of acute ischemic strokes. Stroke. 2018

The endovascular treatment of ischemic stroke is beneficial up to 24 hours from symptom onset, provided that neuroimaging studies show the presence of ischemic penumbra, i.e., the hypoperfused brain region which has not progressed to infarction. Over time, the ischemic penumbra progresses to infarction, thus limiting the possibility of treating ischemic stroke; however, current literature suggests that the presence of robust collateral vessels delays that progression.

In the present study, the authors aimed to retrospectively assess the influence of collaterals over the progression of untreated brain ischemia in a cohort of 94 untreated patients with ischemic stroke with available brain perfusion imaging. The authors found that the time from baseline to follow-up imaging was not correlated with either penumbral salvage or infarct growth, while the presence of good collaterals was associated with a smaller amount of salvaged penumbra and a higher infarct growth compared with poor collateral status.

Although limited by its retrospective design and small sample size, the present study adds important evidence to the hypothesis that the presence of good collaterals strongly delays the progression of ischemic penumbra to infarction. The greater importance of the ‘collateral clock’ over the ‘time clock’ for the progression of brain infarction will have a strong impact on ischemic stroke treatment.