Daniel Korya, MD
Raoult H, Bannier E, Maurel P, Neyton C, Ferré JC, Schmitt P, et al. Hemodynamic Quantification in Brain Arteriovenous Malformations With Time-Resolved Spin-Labeled Magnetic Resonance Angiography. Stroke. 2014
Ruptured brain arteriovenous malformations (AVMs) represent about 2% of hemorrhagic strokes, but they can be quite devastating and often affect young people. What if there was a way for us to predict which AVMs are more likely to rupture by quantifying some parameter? That would be something. Well, that is what Raoult and colleagues set out to do in this recent publication.
They used a 3T unenhanced time-resolved spin-labeled MRA (4D-SL-MRA) sequence of brain vessels to determine hemodynamic quantitative parameters in order to correlate them with progression of disease and rupture risk.
In total, there were 16 patients in the study who were divided into groups based on AVM characteristics and prior rupture history. One of the groups was considered to be the “High-Rupture-Risk” (HRR), while another was determined to be “Low-Rupture-Risk” (LRR). Patients in the HRR were those with a history of ruptures (including asymptomatic bleeding signs on MRI), or exclusively deep venous drainage on DSA, or deep location. There was another grouping that separated patients into hemorrhagic and non-hemorrhagic sub-groups.
Essentially, what was observed was that patient’s in the HRR group (a majority of which had previous hemorrhages), were significantly more likely to have lower venous-to-arterial time-to-peak (TTP) ratio values. The venous-to-arterial TTP ratio was below 2.0 in all cases that were more likely to rupture, and was thought to reflect higher velocities and exposure to higher vascular pressures within the AVM nidus.
Furthermore, by using the 4D-SL-MRA, the investigators argued that they were able to achieve temporal resolution in the range of 50-100 milliseconds, as compared with the usual 1-second times achieved by the current methods of contrast-enhanced MRA. This provided for significantly better visualization of the vessels and limited vessel superposition.
This modality allowed for accurate determination of the AVM’s main arterial feeders and draining veins as close to the nidus as possible, the nidus center, and the contralateral arteries corresponding to the main arterial feeders. The level of detail obtained in a non-invasive way is certainly commendable and may be useful in not only predicting rupture risk, but also planning for treatment.