Vascular malformations are an abnormal vessel or vessels that form a direct connection between arteries and veins without the normal capillary mesh to facilitate blood flow between them. In the spine, vascular malformations can involve: the spinal cord, the tissues around the spinal cord within the spinal canal, the bones of the spine, the tissues around the spine, or a combination of these. Spinal and paraspinal (surrounding the spine) vascular malformations can pose serious medical issues, in particular areas they can result in weakness and in severe cases, paralysis, of some or all limbs.
Some malformations in the spine are present at birth while others develop later in life. Symptoms can be caused by decreased blood supply to the spine and nerves, by pressure from the abnormal vessels, or by rupture of the vessels resulting in hemorrhage. Spinal and paraspinal vascular malformations are divided into three broad classifications: neoplastic tumors with prominent vascular supply, spinal aneurysms, and spinal arteriovenous lesions.
- Neoplastic tumors with prominent vascular supply are relatively rare within the spinal cord and or paraspinal tissues. Patients usually present because the mass effect upon the spinal cord produces low back pain; pain radiating down the legs; numbness and or tingling in the legs; loss of bladder or bowel control, and progressive lower extremity weakness. Examples of typical neoplastic tumors with prominent blood supply include: hemangioblastoma and cavernous malformations.
- Spinal aneurysms are a very rare condition. Patients usually experience a spinal cord stroke or sub-arachnoid hemorrhage. Aneurysms can occur within the arterial supply or venous outflow connections of the spinal cord. They are usually identified by their location, i.e. radicular artery aneurysm.
- Spinal arteriovenous lesions are rare and complex. Arteriovenous lesions are further divided into fistulas (AVF’s) or more extensive malformations (AVM’s). Each of these lesions is then broken down into their location intradural (inside the outer covering of the brain called the "dura") or extradural ( between the inside of the skull and the outer covering of the brain) . Additional classification of AVM’s includes nidal size and further location criteria.
Prior to any treatment of a spinal or paraspinal vascular malformation it is necessary to perform a spinal angiogram to provide a roadmap of the blood vessels of the spine.
- Neoplastic tumors with prominent blood supply can be treated with tumor embolization.
- Spinal aneurysms can be treated with aneurysm embolization.
If there are no symptoms or almost none, or if an AVF is in an area of the brain that cannot be easily treated, conservative medical management may be indicated. If possible, a person with an AVF should avoid any activities that may excessively elevate blood pressure, such as heavy lifting or straining, and they should avoid blood thinners like warfarin. A person with an AVF should have regular checkups with his or her doctor.
It may be possible to treat part or all of the AVF by placing a small catheter inside the blood vessels that supply the AVF and blocking off the abnormal blood vessels with a variety of different materials. These include liquid tissue adhesives (glues), micro-coils, particles and other materials used to stop blood flowing to the AVF. Endovascular therapy is usually performed prior to surgery or stereotactic radiosurgery.
If an AVF has bled and/or is in an area that can be easily operated upon, then surgical removal may be recommend. The patient is put to sleep with anesthesia, a portion of the skull is removed, and the AVF is surgically removed. When the AVF is completely taken out, the possibility of any further bleeding should be eliminated.
An AVF that is not too large, but is in an area that is difficult to reach by regular surgery, may be treated by performing stereotactic radiosurgery. In this procedure a cerebral angiogram is done to localize the AVF. Focused-beam high energy sources are then concentrated on the dural AVF to produce direct damage to the vessels that will cause a scar and allow the AVF to “clot off”.
Left: Lateral T2 weighted image of the cervical spine showing flow voids within the lower cervical spine consitent with an AVM
Right: Lateral image of a left vertebral angiogram showing an abnormal tangle of vessels within the lower cervical spine with
dilated spinal veins
Left: AP plain radiograph showing a glue injection into a branch of the left vertebral artery feeding a spinal cord AVM
Right: Lateral angiogram after the first embolization showing minimal filling of the spinal cord AVM
Lateral CT spinal angiogram showing a glue cast in a portion of the spinal intramedullary AVM