This axial (cross sectional) proton density weighted MRI image through the posterior fossa demonstrates the very typical appearance of a cavernous malformation within the pons, which has also been called a cavernous angioma. This represents a slow flow type vascular malformation, which has also been referred to as an OCVM (occult vascular malformation) because they are generally angiographically invisible. These lesions represent dilated capillary spaces with no intervening normal brain. They can expand, however they are not usually associated with significant acute hemorrhages.