Pediatric emergency medicine trisk 4004 4004

Arteriovenous
Malformation.
Current
Evidence.
Arteriovenous
malformations (AVMs) are vascular abnormalities composed of a fistulous
connection of arteries and veins without a normal intervening capillary bed.
In the cerebral hemispheres, they frequently occur as cone-shaped lesions
with the apex of the cone reaching toward the ventricles. Nearly all AVMs
are thought to be congenital. Supratentorial location is the most common
(90%). The most common presentation of an AVM is intracerebral
hemorrhage (ICH). AVMs are responsible for 30% to 50% of hemorrhagic
strokes in children. After ICH, seizure is the second most common
presentation. Other presentations of AVMs include headache and focal
neurologic deficits which, including seizure, may be related to steal
phenomena or other alterations in perfusion in the tissue adjacent to the
AVM.
Size of AVM. In a series of 168 patients followed after presentation
without a prior hemorrhage, the size of the AVM was not found to be
predictive of future hemorrhage. However, other studies have found AVMs
of small size to be at higher risk of hemorrhage.
AVMs and Aneurysms. Prevalence of the association of AVMs with
aneurysms varies from 2.7% to 22.7%. This association seems to be
correlated with a higher risk of hemorrhage. Brown et al. studied 91
patients with unruptured AVMs and found the risk of ICH in patients with
coexisting aneurysm to be 7% at 1 year compared with 3% among those
with AVM alone. At 5 years, the risk persisted at 7% per year, while it
decreased to 1.7% per year in those with an AVM not associated with
aneurysms.
Diagnostic Imaging. A CT scan may be used as an initial screening tool
for patients presenting with neurologic sequelae related to unruptured or

ruptured AVMs. This study can be used quickly to determine location of the
lesion, acute hemorrhage, hydrocephalus, or areas of encephalomalacia
from previous surgery or rupture. A nonenhanced CT may show irregular
hyperdense areas frequently associated with calcifications in unruptured
AVMs or acute hemorrhage with ruptured AVMs ( Fig. 122.2 ). A contrastenhanced CT can demonstrate the nidus, feeding vessels, or dilated draining
veins.
MRI is superior to CT scan in delineating details of the macro
architecture of the AVM, except in the case of acute hemorrhage. These