Venous angiomas & others:

Venous angiomas

Venous angiomas are also known as "Developmental venous anomalies" (DVAs) to emphasize their frequency and their be­nign nature and low incidence of sequelae. They are the most common vascular malformation found at postmortem.

They are most commonly located in the following descending order of frequency frontal lobe, parietal lobe, and cerebellar hemisphere. They may also be found in the region of the vein of Galen 

They are sporadic in nature with no genetic predisposition

They occur due to arrest of normal venous development with retention of primitive medullary veins draining blood into a large anomalous draining vein is the presumed etiology

Pathology

They are mostly seen as a small single lesion of low flow and low pressure. They represent the venous drainage of the area. There is anomalous venous drainage of otherwise normal brain tissue. It consists of radially arranged anomalous medullary veins that converge on a larger central draining vein that, in turn, drains into deep or superficial venous system.

The "crown" of veins that converge onto the connecting trunk are "collecting veins" that drain the capillaries from the affected volume.

The veins are slightly thickened and hyalinized with large amounts of smooth muscle and elastic tissue. Venous radicles are separated by normal/ gliotic intervening brain tissue.

No abnormal arteries are found. They may be associated with a cavernous angioma in 20%.

Clinical features

They are most commonly detected incidentally. However they may present with headache and focal deficit. Seizures occur rarely and may be due to chronic ischemia, encephalomalacia and calcification .

Bleeding in a venous angioma is seen less commonly than seizures.

Hemorrhage, however, may be more frequent in those venous angiomas with concurrent stenosis of the draining vein and or concurrent cavernous angioma. Even in these cases the bleed is mostly at the sites of the cavernoma and not the venous angioma

Investigations

CT SCAN

Non contrast scan is normal unless there is calcification or acute hemorrhage

Contrast enhanced scan reveals a tuft of small vessels draining into a dilated, subependymal or subpial vein may be seen with contrast.

MRI

It reveals transmedullary flow voids or as paired transmedullary lines of increased and decreased signal representing spatial misregistration of the vessel wall and lumen because of the Doppler shift in frequency as­sociated with flow. The draining trunks are substantially larger than adjacent veins, per­haps because they serve as collateral drainage pathways for adjacent regions in which veins failed to develop (or later thrombose).

Gadolinium enhancement improves display of slow flow and may be required to detect venous angio­mas not otherwise seen. It reveals the characteristic medusa head draining into a larger vein.

Stenosis of the large central vein as it enters the dural sinus and concurrent cavernous angiomas must be sought out and described, if possible, since they may signify increased risk of bleeding.

ANGIOGRAPHY

Occasionally may be angiographically occult, however, they classically produce distinct caput medusae (other descriptive terms include: a hydra, spokes of a wheel, a spider, an umbrella, a mushroom or a starburst pattern or "medusa head")

It really looks more like a hydra or a palm tree - the dominant transcortical vein is the trunk; and the radiating crowns of feeding veins are the leaves.

Post contrast MRI-T1-cor	Rt.carotid angio-AP	Temp ICH-CT	Temporal venous angioma-angio

Management:

Because of the following reasons Rx is rarely indicated.

Surgery is reserved for the following situations

-         Documented bleeding

-         Intractable seizures attributed to the lesion

Radiosurgery is still debatable. It is not accessible via an endovascular approach

Prognosis:

Excellent unless there is associated venous stenosis or cavernoma

Capillary telangiectases:

These lesions consist of groups of abnormally swollen capillaries and usually measure less than an inch in diameter. Capillaries are the smallest of all blood vessels, with diameters smaller than that of a human hair; they have the capacity to transport only small quantities of blood, and blood flows through these vessels very slowly. Because of these factors, telangiectases rarely cause extensive damage to surrounding brain or spinal cord tissues. Any isolated hemorrhages that occur are microscopic in size. Thus, the lesions are usually benign. However, in some inherited disorders in which people develop large numbers of these lesions, telangiectases can contribute to the development of nonspecific neurological symptoms such as headaches or seizures

AOVMs:

Purists claim that angiograpically occult venous malformation (AOVM) is a heterogenous group of malformations (AVMs, cavernomas and others) that are not detected by angiography and diagnosed by CT or MRI. They do not group them with the Capillary telangiectasis and Cryptic AVMs, which are a separate histopathological entity, encountered during haematoma evacuation. For all practical purposes they are considered as one group by most. Surgical intervention is indicated only when there is a large haematoma, requiring evacuation.