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| MRI helps identify ischaemic stroke patients likely to benefit from t-PA |
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05 May 2006
Defects in the blood-brain barrier can raise the risk of intracranial haemorrhage in patients who have experienced an ischaemic stroke. A new study demonstrates that contrast-enhanced MRI findings can identify patients more likely to experience intracranial haemorrhage and are therefore at far greater risk from tissue plasminogen activator (t-PA) treatment.
"Early endothelial ischaemic damage is followed by the loss of microvascular permeability barriers. Therefore, small molecules such as Gd-DTPA can extravasate and become visible on contrast-enhanced MR images" in the parenchyma, Dr Guo explained. On the other hand, he continued, "the hyperintense middle cerebral artery sign was related to increased diameter of the vessel compared with contralateral vessel diameter, and showed blurred margins with intense signal. This likely represents vascular distention at or proximal to the obstructing clot." Hypertension may also contribute to this finding because of exudation of RBCs and gadolinium, leading the affected middle cerebral artery to become thickened and blurred with increased T1 signal."
None of the 14 patients who did not develop intracranial bleeding had either sign.
Three of five patients treated with t-PA developed haemorrhagic transformation, and all three patients had a hyperintense middle cerebral artery sign, and two had early parenchymal enhancement.
Based on these findings, Dr Guo recommends that "acute stroke imaging protocols that usually include gadolinium administration for perfusion imaging and or magnetic resonance angiography be followed with T1-weighted spin echo imaging to screen for parenchymal enhancement and the hyperintense middle cerebral artery sign."
"This could lead to an extension of the treatment window beyond current time constraints of 3 hours in those patients who have a stable blood-brain barrier."
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