The notion that pre-treatment imaging can improve a stroke patient's prognosis has been widely accepted; however, questions remain about which modality to use, according to data presented at the 2009 European College of Radiology (ECR) this week in Vienna, Austria.

Most patients are examined with CT, explained Professor Rüdiger von Kummer, MD, from Dresden University Hospital in Dresden, Germany, who will take part in the session. CT scanners are more widely available than MRI systems, and, because of their rapidity, are easier for sick patients to tolerate. CT angiography and perfusion measurement are also more robust techniques than MR angiography or MR perfusion imaging, von Kummer said.

On the other hand, MRI with diffusion-weighted imaging is a highly sensitive technique for detecting small lesions caused by embolic events, which can be missed by CT, according to researchers.  MRI is as sensitive as CT in the detection of acute brain hemorrhages, but has a higher sensitivity for old brain hemorrhages.

Based on randomized trials, systemic thrombolysis is approved for the first three hours after stroke only. But the studies have used brain hemorrhage and major infarction alone as contra-indications to drug therapy. A recent study demonstrated the efficacy of recombinant tissue plasminogen activator, the only approved treatment for acute ischemic stroke so far, up to 4.5 hours. The researchers reported that identification of patients with small ischemic damage, despite arterial occlusion and extended perfusion impairment, may allow effective reperfusion treatment beyond currently accepted time windows.

Because intra-veinous thrombolytics may fail to recanalize arterial obstructions, von Kummer suggested that the angiography suite is prepared for endovascular intervention when drug-based stroke treatments are to be used. Intra-arterial recanalization can then begin immediately if the treatment fails, and may thus significantly improve the patient's prognosis.

Endovascular recanalization can be carried out up to six hours after onset of acute stroke, with a good outcome, explained Gerhard Schroth, MD, director of diagnostic and interventional neuroradiology at Bern University Hospital in Bern, Switzerland. Recanalization rates now approach 80 percent, and one in every three procedures saves a patient from severe impairment, he said.

The procedure consists of injecting a clot-busting drug directly into the thrombus, and no longer just in front of the occlusion site as it used to be performed a few years ago, Schroth said. Recanalization can be achieved for the majority of patients by this means and is associated with improved outcome. Additionally, other mechanical recanalisation techniques (retriever devices, percutaneous transluminal angioplasty or stenting) can be employed by interventional radiologists if vessel occlusion persists after thrombolysis. Referrals for endovascular treatment can come at any time, and the faster interventional radiologists can respond, the more likely is a successful outcome.

"Endovascular treatment is one of the most cost-effective treatments in healthcare, given the high rates of handicap associated with stroke," Schroth said.