Page 52 - Inaugural Lecture Prof Dr Ahmad Sobri Muda

Neurointervention

via the obstructive lesion and retrograde circulation around the
lesion via collateral channels. The three major cerebral collateral
networks that may be recruited during vascular blockage in acute
stroke are the Circle of Willis, leptomeningeal collaterals, and
extracranial-intracranial connection.
Patients with ischemic stroke can have their cerebral collateral
circulation evaluated using a variety of imaging techniques,
including magnetic resonance angiography (MRA), computed
tomography angiography (CTA), Doppler ,and digital subtraction
angiography (DSA). But there are disparities in how much each of
these modalities are being used. Although the conventional DSA
with CBCT appears to be the best method to assess the quantity and
quality of collateral expansion, grading still rely on CTA or MRA.
Large clinical trials on collateral flow show strong inter-observer
reliability and a positive correlation with clinical outcome.
At 90 days after a stroke, patient with grade 2 or lower on the
modified Rankin Scale (mRS) associated with a higher collateral
score. In the analysis, patients who had significant regional
leptomeningeal collateral also had excellent clinical outcomes in
more than half of the cases. In a more recent analysis, presence
of collateral was reported to have a more significant impact
on ischemic progression and penumbral recovery than stroke
symptoms at onset. Therefore, besides the time to revascularization
within the 6-hour window period requirement for re-establishing
arterial flow, the collateral score should be recognized as one of
the core aspects in effective treatment. A more complete collateral
classification or grade should be used to determine the collateral
assessment objectively. Furthermore, the most recent DAWN trial
data suggest extending the time window for reperfusion therapy up
to 24 hours for patients with clinical-infarct mismatch expected to
be treated with endovascular thrombectomy.

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