Arteriovenous Malformations

Arteriovenous malformations (AVMs) are development anomalies of the intracranial vasculature; they are not neoplastic despite their tendency to expand with time and the descriptive term 'angioma' occasionally applied.

Diminished blood flow to surrounding brain due to a 'steal' effect

_ — Enlarged feeding vessel

Saccular aneurysms occasionally develop on proximal vessels

_ — Enlarged feeding vessel

Firm tangled mass of blood vessels with small haemorrhages, areas of thrombosis and calcified nodules _ ___ within the bulk of the lesion

Dilated arterialised veins

Dilated aneurysmal segment

Diminished blood flow to surrounding brain due to a 'steal' effect

Saccular aneurysms occasionally develop on proximal vessels

Dilated arteries feed directly into a tangled mass of blood vessels of varying calibre; they bypass the capillary network and shunt oxygenated blood directly into the venous system. As a result of raised intraluminal pressure, veins may adopt an 'aneurysmal' appearance. Arteriovenous malformations may occur at any site but are commonest in the middle cerebral artery territory.

Vascular malformations vary in size and different forms exist: Capillary telangiectasis', an area of dilated capillaries, like a small petechial patch on the brain surface - especially in the pons. These lesions are often only revealed at autopsy. Cavernous malformation/angioma: plum coloured sponge-like mass composed of a collection of blood filled spaces, but without enlargement of feeding or draining vessels.

CLINICAL PRESENTATION Haemorrhage

About 40-60% of patients with an AVM present with haemorrhage - often with an intracerebral or intraventricular component. In comparison with saccular aneurysms, AVMs tend to bleed in younger patients, i.e. 20-40 years, and are less likely to have a fatal outcome. Vasospasm and delayed ischaemic complications rarely develop. Small AVMs are at greater risk of bleeding than larger lesions.

Risk of initial and recurrent bleeding: the risk of haemorrhage over a 5-year period in patients with a previously unruptured AVM is approximately 15% (i.e 2-3% per year); however, this risk increases to 50% over 5 years for lesions under 3 cm in size.

After a haemorrhage, the chance of a further bleed is slightly increased in the first year but beyond that the risk reverts to that of an unruptured AVM.

Mortality from haemorrhage: in contrast to the high mortality following aneurysm rupture, haemorrhage from an AVM carries the relatively low mortality rate of approximately 288 10%-20%.

Was this article helpful?

0 0
Peripheral Neuropathy Natural Treatment Options

Peripheral Neuropathy Natural Treatment Options

This guide will help millions of people understand this condition so that they can take control of their lives and make informed decisions. The ebook covers information on a vast number of different types of neuropathy. In addition, it will be a useful resource for their families, caregivers, and health care providers.

Get My Free Ebook


Post a comment