Spinal Cord Vascular Malformation
What is a Spinal Cord Vascular Malformation?
The spinal cord is made up of neuronal pathways, glial tissue, and interwoven vascular structures. Spinal cord vascular malformations (arterial and venous) represent a divergent group of blood vessel disorders that affect the spinal cord either directly or indirectly. This group consists of spinal AVMs, dural arteriovenous fistulas (AVF), spinal hemangiomas, cavernous angiomas, and aneurysms. Spinal Cord Vascular Malformations occur much less frequently than cranial vascular malformations.
The most common spinal vascular malformations are AVMs and AVFs. They are rare disorders that are thought to cause neurologic deterioration. An accurate diagnosis is important because these lesions may represent a reversible cause of spinal cord injury.
Spinal cord vascular malformations have the same diagnosis and treatment protocol as AVMs. Please see AVM section for more information on diagnosis and treatment. However, the symptoms for a spinal cord vascular malformation are much different than symptoms for an AVM.
The 4 Categories of Spinal Cord Vascular Malformations
Spinal cord vascular malformations have been classified into the following 4 categories.
Type One: Dural AVF
This is the most common type of malformation, accounting for 70% of all spinal vascular malformations. Spinal DAVFs are most commonly found in the thoracolumbar region. Patients with type one malformations become symptomatic because the AVF creates venous congestion and hypertension, resulting in ischemia, and edema of the spinal cord. Due to the slow-flow nature of type 1 AVFs, hemorrhage rarely occurs. Type I lesions are most frequently found in men from 50-80 years old. Symptoms increase over an extended period of months to years and include progressive weakness of the legs and concurrent bowel or bladder difficulties. Activity may intensify symptoms in the thoracic or lumbar region and can result in thoracic spinal cord venous congestion and lower-extremity weakness.
Type 2: Glomus AVM
Type 2 malformations consist of a tightly compacted group of arterial and venous vessels (nidus) inside a short segment of the spinal cord. Multiple feeding vessels from the anterior spinal artery and/or the posterior spinal circulation typically supply these AVMs. Type 2 AVMs are the most commonly encountered intramedullary vascular malformations, accounting for about 20% of all spinal vascular malformations. The typical patient is younger than 30 years and presents with a subarachnoid or intraparenchymal hemorrhage, vascular steal phenomenon, and, rarely, mass effect on the spinal cord.
Type 3: Arteriovenous Malformations
Type 3 malformations consist of abnormalities of the spinal cord fed by multiple vessels. These juvenile malformations are extensive lesions with abnormal vessels that can be both intramedullary and extramedullary in location. These lesions are typically found in young adults and children.
Type 4: Pial AVFs
These malformations are intradural extramedullary AVFs on the surface of the spinal cord that result from a direct communication between a spinal artery and a spinal vein without an interposed vascular network. They are usually seen in patients who are between 30-60 years old.
Patients with subarachnoid hemorrhage may experience sudden onset of a severe headache, neck stiffness, intolerance of bright lights, and at times, excruciating back pain.
Patients with intradural lesions can present with mass effect caused by growth of the AVM. The enlargement of the vascular malformation compresses the surrounding neural tissue, impairing neurologic function.
These intradural spinal vascular malformations (types 2-4) develop during embryogenesis and, therefore, are present in an even distribution throughout the spinal cord. Therefore, patients with intradural AVMs may present with upper- or lower-extremity difficulties, as opposed to patients with dural AVFs, who typically have only lower-limb-extremity involvement.
Physical examination findings and the type of spinal malformation are as follows:
- Bruit (vascular murmur or sound) over spinal cord- Intradural AVM
- Overactive or overresponsive reflexes- Dural AVF and intradural AVM
- Upper motor signs – Dural AVF and intradural AVM
- Weakness – Dural AVF and intradural AVM
- Increased tone – Dural AVF and intradural AVM
- Sensory disturbance of the buttocks – Dural AVF