A spinal fistula is a rare condition characterized by an abnormal connection between blood vessels located in or around the spinal cord. This bypasses the normal capillary network, leading to neurological issues. Early recognition and effective treatment are important.
What is a Spinal Fistula?
A spinal fistula involves an atypical direct connection between an artery and a vein within the spinal region, bypassing the capillary beds that normally regulate blood flow and pressure. Arteries typically carry high-pressure, oxygenated blood away from the heart, while veins return lower-pressure, deoxygenated blood. In a fistula, high-pressure arterial blood flows directly into the lower-pressure venous system. This shunting causes veins to swell and become congested, increasing pressure within the veins that drain the spinal cord.
This elevated venous pressure impairs the normal drainage of blood from the spinal cord, leading to venous hypertension. The spinal cord tissue can then experience a lack of oxygen (ischemia) and swelling (edema), progressively damaging its function. The most common type is a spinal dural arteriovenous fistula (SDAVF), which occurs in the dura mater, the protective outer covering of the spinal cord. Another type, the perimedullary arteriovenous fistula (PMAVF), is less common and involves an abnormal connection directly on the surface of the spinal cord itself.
Recognizing the Symptoms
Symptoms of a spinal fistula develop gradually and vary, making early diagnosis challenging. Patients commonly experience progressive weakness or numbness in their legs, leading to difficulty walking and balance problems. These symptoms may worsen over time, sometimes fluctuating in severity.
Lower back pain is also a frequent complaint, and a sensation of “pins and needles” or other abnormal sensations in limbs. As the condition progresses, it can affect bowel and bladder function, causing incontinence or difficulty with urination. The gradual and nonspecific nature of these symptoms can lead to misdiagnosis, as they may mimic common spinal conditions like degenerative disc disease.
How Spinal Fistulas are Diagnosed
Diagnosis begins with a comprehensive neurological examination and a detailed review of a patient’s medical history. The physician assesses neurological function, including strength, sensation, and reflexes, to identify patterns indicative of spinal cord involvement. This assessment guides further diagnostic steps.
Magnetic Resonance Imaging (MRI) of the spine is an imaging tool for initial detection. MRI scans can reveal signs of spinal cord swelling (T2 hyperintensity) and dilated, tortuous veins, appearing as “flow voids” on images. While MRI can suggest the presence of a fistula, a spinal angiogram, also known as digital subtraction angiography (DSA), is considered the definitive diagnostic test. This invasive procedure involves injecting a contrast dye into spinal arteries and taking X-ray images, allowing precise visualization of the abnormal connection and its exact location. Magnetic Resonance Angiography (MRA) is a non-invasive alternative that can aid in detecting and localizing fistulas, potentially expediting confirmatory studies.
Treatment Options
Treatment for spinal fistulas aims to close the abnormal connection and restore normal blood flow to the spinal cord, preventing further neurological damage and potentially improving symptoms. Two primary approaches are used: endovascular embolization and surgical disconnection.
Endovascular embolization is a minimally invasive procedure where a catheter is guided through blood vessels to the site of the fistula. A liquid embolic agent, such as a glue-like material or tiny particles, is then injected to block the abnormal connection. The goal is to occlude the fistula and normalize venous pressure. Surgical disconnection involves an open surgical procedure where the fistula is directly clipped or removed, interrupting the abnormal arterial-venous shunt. Both treatments alleviate venous congestion that damages the spinal cord, and timely intervention leads to better outcomes.