Adam de Havenon, MD
The gold standard for diagnosing and characterizing intracranial aneurysms is digital subtraction angiography (DSA), but it’s an expensive and potentially dangerous procedure that isn’t available at many smaller medical centers. In its stead, computed tomography angiography (CTA) is the test of choice, particularly in the acute setting. However, it is widely accepted that any ionizing radiation is harmful regardless of dose and some patients will not tolerate iodinated contrast. Magnetic resonance angiography (MRA) helps fill this void, but historically has been considered significantly less sensitive and specific than either DSA or CTA.
This review and meta-analysis by Anna Sailer and colleagues is the first to revisit the topic in a systematic way since 2000 and includes data from 12 studies comparing MRA to DSA for the detection of ruptured and unruptured intracranial aneurysms dating from 1999 to 2012 with 960 patients and 772 aneurysms. During that time period, MRA technique has changed considerably, from contrast-enhanced MRA to time-of-flight (TOF), 1.5T field strength to 3T, and hardcopy films to digital images with 3D multiplanar reconstructions.
The pooled sensitivity and specificity of MRA in these studies was 95% and 89% with false negative and false positive aneurysms located primarily at the skull base and middle cerebral artery. The use of digital images, in particular freehand 3D reconstruction performed by the radiologist, improved detection, while the increase in field strength from 1.5 to 3T showed a trend towards higher performance, but did not reach statistical significance, and MRA TOF was not superior to contrast-enhanced MRA. The prior meta-analysis on MRA from 2000 reported a pooled sensitivity and specificity of 95% and 89%. It’s not exactly a compelling evolution, and given that a recent meta-analysis of CTA suggests sensitivity and specificity of 95% and 96%, it will remain the non-invasive diagnostic test of choice when reliable and rapid result are needed. This study reinforces the utility of MRA for sub-acute and serial evaluation, and of the newer techniques such as 3D reconstruction and TOF.