Spinal Vascular Malformations

Vascular malformations, or blood vessel abnormalities, can affect different parts of the body, including the spine and spinal cord. Spinal vascular malformations comprise several different conditions, including arteriovenous malformations (AVMs), dural arteriovenous fistulae (DAVFs) and cavernomas. Both AVMs and AVFs are characterised by abnormal, direct connections (or ‘shunts’) between feeding arteries and draining veins without normal capillaries in between. The difference between the two is the presence of a nidus (or ‘tangle of vessels’) within the spinal cord in AVMs. AVFs, on the other hand, are much more common, and the abnormal connection (i.e. ‘fistula’) between artery and vein occurs within the dura (i.e. covering of the nerves and spinal cord). Cavernomas (also known as cavernous malformations) are abnormal clusters of thin-walled capillaries (‘mulberry-like’) within the spinal cord. They, along with AVMs, are generally considered to be congenital (i.e. people are born with them), while DAVFs may be acquired, e.g. through trauma. Spinal vascular malformations may create problems if they bleed (i.e. haemorrhage) or cause build up of pressure in draining veins and spinal cord (especially in the case of DAVFs). Large AVMs can even cause direct compression of, or ‘steal’ blood away from, the spinal cord itself.

Symptoms

• Back or neck pain
• Leg or arm pain, numbness, pins and needles, or weakness
• Balance problems, or difficulties with walking, due to spinal cord dysfunction
• Clumsy hands, or problems with dexterity and fine motor movements, due to spinal cord dysfunction
• Bladder and bowel issues, due to spinal cord dysfunction
• It should be noted that many spinal vascular malformations do not cause any symptoms at all, and may have been found ‘incidentally’ (i.e. on scans done for unrelated issues)

Diagnosis

• MRI
• DSA (Digital Subtraction Angiogram), where a small catheter is placed, usually through the groin, into the blood vessels supplying the spinal cord, and special dye (i.e. contrast) injected to characterise AVMs and DAVFs

Treatment

Not all spinal vascular malformations require treatment, especially asymptomatic ones. Unfortunately, there are no effective medications for these conditions, and radiotherapy has not been proven to be effective (in contrast to certain AVMs in the brain, for example). On the other hand, surgery on the spinal cord is considered very high risk, especially for AVMs, and is usually only considered if absolutely necessary. In contrast, surgery to ‘disconnect’ DAVFs, where the fistulous connection is in the dura (and not in the spinal cord itself), can usually be safely performed and is effective is preventing neurological deterioration in the majority of cases, even reversing symptoms in some. Embolisation, done with DSA using specialised ‘glues’ to ‘block off’ abnormal connections in DAVFs, and certain AVMs (often combined with surgery), can also be effective sometimes.

Figure. Intraoperative photo taken under the microscope of a DAVF, showing the ‘arterialised’ draining vein next to the nerve just inside the dura.