Venous Angioma, Cavernous Angioma, and Hemorrhage

In this issue of AJNR, Wilms et al ( 1) add to the ongoing debate whether the venous angioma, more recently called developmental venous anomaly (2), can be symptomatic, whether it alone can bleed, or whether such hemorrhage occurs because of the concomitant occurrence of a cavernous angioma . This debate is not just semantic. It is essential to pathophysiologic understanding of a given lesion so that risks of sequelae can be determined. Therapeutic options can then be considered once those risk factors are known. The venous angioma is a slow-flow venous anomaly consisting of a number of dilated medullary veins converging into a central hilum to produce the classic caput medusae. This venous complex then drains into an even more dilated transparenchymal vein that leads to a major venous outflow track such as a dural sinus. The venous angioma is frequently found incidentally on computed tomography (CT), magnetic resonance (MR), or cerebral angiography performed to evaluate a specific lesion such as a brain tumor, demyelinating disease , or carotid stenosis , but it also may be found in a patient having vague neurologic symptoms such as headache or dizziness. Since the introduction of MR imaging, and particularly the development of contrast-enhanced MR, the venous angioma is seen much more commonly than in the past (3-6). Moreover, venous angioma is frequently discovered in areas unrelated to the symptoms prompting the imaging procedure . This would suggest that the venous angioma is usually a normal variant and not productive of symptoms or hemorrhagic/ischemic . sequelae. However, various series in the litera ture suggest that the venous angioma may produce the presenting symptoms in as many as 40% of patients (7, 8). We have seen an exampie of a fourth-ventricular hemorrhage secondary to bilateral cerebellar venous angioma in a young gymnast who probably raised her venous pressure during exercise (9); we have seen patients who have had a venous angioma and parenchymal hemorrhage and who have undergone surgery without the pathologic findings of a cavernoma or other vascular malformation other than the venous angioma. We have also seen cases of venous ischemia in the region of a venous angioma (10) . Reports in the literature, albeit on the basis of a small number of cases, suggest that posterior fossa venous angiomas may produce symptoms and hemorrhagic sequelae more commonly than supratentorial lesions ( 11). These reports invariably refer to papers in the CT era at which time posterior fossa venous angioma was only detected when accompanied by hemorrhage. Even with this caveat, our observations and the literature suggest that the venous angioma may not be totally benign. Increased systemic venous pressure, or increased local venous pressure secondary to stenosis of the draining transparenchymal vein or other venous obstruction, might lead to hemorrhagic or ischemic complications (6 , 9) (Dillon WP, Hieshima GB, Halbach VV, Dowd CF, A New Observation on the Association of Venous Angioma , Hemorrhage and 'Cryptic Vascular Malformation,' presented at American Society of Neuroradiology, Washington , DC, 1991). With the increased use of MR, observers have identified lesions containing chronic blood products consisting of mixed low (hemosiderin), and high (methemoglobin) intensity on T2weighted studies in the vicinity of venous angi omas, with or without evidence of more recent hemorrhage (12). The terminology for these le sions of mixed MR intensity can be confusing. Cavernomas, or cavernous angiomas, a re s low-