Spinal Arteriovenous Malformations
Spinal arteriovenous malformations (AVMs, or angiomatous malformations) are congenital (from birth) abnormalities of blood vessels. Arteries that directly communicate with veins bypass the capillary network (which has not yet developed) and thus creates a shunt. AVMs appear as a mass of convoluted, dilated vessels. In regards to the spinal cord, they are usually located in the thoracolumbar region (between the thoracic and lumbar regions, 60% of the time), as opposed to the upper thoracic (20%) and cervical regions (approximately 15%). Cervical malformations arise from the anterior spinal artery and lie within the cord, whereas thoracolumbar malformations can be internal, external or encompass both areas of the cord.
Malformations can be recognised as part of an acute illness or gradual onset disease. In diseases such as subarachnoid hemorrhage, signs and symptoms include headache, neck stiffness and back and leg pain. Extradural, subdural and intramedullary hematomas are all signs of acute cord compression. Gradual onset diseases are more common (85-90% of all diseases leading to a diagnosis of malformation) and are usually due to an increased venous pressure. Other factors such as thrombosis or arachnoiditis can be involved. A bruit (unusual blood sounds) may be heard overlying the spinal arteriovenous malformation. Very occasionally, nevus (moles) or angiolipomas are found.
Myelography is used to confirm the diagnosis of AVMs and it shows 'snake-like' vessels on the cord's surface. If the myelogram is positive, angiography is required to show the extent of malformation and the exact site of the shunt. Magnetic resonance imaging (MRI) may show the appropriate area. If AVMs are left untreated, 50% of patients with gradual symptoms will be unable to walk within 3 years of onset. Operations can prevent progression and may improve any gait or incontinence.
Read more about this topic: Vascular Myelopathy