**7.2 Magnetic resonance imaging (MRI) of the brain**

MRI of the brain is highly sensitive for the location of the cAVM nidus and an associated draining vein; it also has a unique sensitivity in demonstrating remote bleeding related to these lesions. MRI of the brain is particularly valuable in follow-up patients after treatment. After radiosurgery MRI is important for the regression of the nidal volume. Whereas the MR angiography techniques can characterize the venous drainage and other vascular features, the surrounding tissue that is subjected to the radiation field can be accurately monitored for post-therapy oedema or radiation necrosis [18].

### **7.3 Cerebral angiography**

It is the gold standard for the diagnosis, treatment planning and follow-up after treatment of cAVMs. The anatomical and physiological information of the cAVM nidus, its relationship to surrounding vessels and localization of the draining or efferent portion of the cAVM are readily obtained with this cerebral angiography. It will also help in demonstration of associated aneurysm suggesting a lesion at higher risk for subsequent hemorrhage. The contrast transit times provide additional useful information regarding (**Figure 4**).
