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Imaging
Findings reveal a classic arterio-venous malformation in the left parietal
region, with areas of flow void and hemorrhage and mass effect.
Discussion
There are four main types of AVMs in the brain and spinal cord: the
classic arteriovenous malformation, the cavernous angioma, venous angioma
and the capillary telangectasia. The most common is the classic AVM.
As
the name implies, arteriovenous malformations (AVMs) are a conglomeration
of abnormal vascular channels, which shunt blood from arteries to veins
without an intervening capillary network. AVMs have been likened to a
vascular "bag of worms" which can cause a steal phenomena
leading to ischemia and atrophy of adjacent brain.
Clinical
Features
The majority of AVMs are assymptomatic until adulthood, presenting as a
progressive neurologic deficit, seizure or acute intracranial hemorrhage
between the ages of 20 and 40 years. One fourth of all AVMs hemorrhage
within the first 15 years of life. The annual risk of intracranial
hemorrhage is believed to be 2-4%, with each episode of hemorrhage
carrying a 30% risk of death and 25% likelihood of long-term morbidity.
The majority of AVMs are solitary, but a small number, roughly 2%, are
multiple and usually associated with neurocutaneous disorders such as
Osler-Weber-Rendu or Wyburn-Mason Syndromes. Their typical location is
within the cerebral hemispheres. A minority (15%) occur in the posterior
fossa.
Symptoms
The most common symptoms of an AVM are headache similar to migraine,
seizures, progressive neurological deficits and hemorrhage or brain
attack. Over time as the AVM steals blood from surrounding
tissues, this causes a lack of blood flow or ischemia to the surrounding
brain. Progressive neurological deficits means a slow loss of specific
functions (motor, sensory, vision, etc.) that is often insidious and
not appreciated by the patient until the symptoms are severe.
MR
Findings
MRI shows the majority of vessels as signal-void, and is capable of
providing information regarding the vascular supply and venous drainage,
as well as the nidus. In addition, PC technique may be helpful in
determining blood flow velocities in arteries and veins involved with the
AVM.
Treatment
Options
include microscopic surgical excision of the entire nidus, endovascular
occlusion of feeding vessels and if possible the nidus itself with
embolization, and stereotatic surgery.
Contribution
Dr.
Ashok Raghavan, Manipal Hospital, Bangalore
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