Endovascular treatment of a sacral dural arteriovenous fistula

Background

Spinal dural arteriovenous fistulas (SDAVFs) are rare pathological conditions presenting with 5–10 cases per year per 1 million individuals in the population.1 This inappropriate arteriovenous communication causes venous hypertension and congestion in the spinal cord, leading to sensory disturbances and further progressing to myelopathy.2 The combination of rarity, non-specific symptoms and difficult imaging often leads to missed diagnoses.3 SDAVFs most often present in the thoracolumbar region. This report describes a rare pelvic presentation of an SDAVF which was further complicated by imaging challenges. Awareness of less common fistula locations and difficulties in the diagnostic process is important to provide timely treatment to reduce the degree of irreversible deterioration by early intervention.

Case presentation

An adult male (age 60–70) with history of diabetes and chronic kidney disease presented to establish care with a primary care provider. He had problem of progressive lower limb weakness and myelopathy. The patient described that he initially had sensory disturbances, which progressed to motor weakness in the lower limbs over the preceding 3 months. He was able to ambulate independently but had difficulty running. Diabetic polyneuropathy was suspected given the patient’s presentation and history; however, referral to neurology was requested for further workup.

During the neurology visit, the patient reported several recent falls and heaviness in both lower limbs. Additionally, he experienced burning sensations from the waist down including the rectum and perineal region. MRI scan of the brain, cervical, thoracic and lumbar spine demonstrated increased T2 signal intensity within the caudal thoracic cord from the level of T9 to the conus which enhanced with contrast. These findings raised suspicion for a dural arteriovenous malformation; therefore, consultation to neurosurgery was initiated.

The patient presented to the neurosurgery clinic reporting a particularly sharp decline in functioning over the prior months. Examination was compatible with upper motor neuron distribution of bilateral lower limb weakness with 4/5 power. Given the patients age, clinical presentation and referral history, additional MRI imaging was requested since a spinal dural fistula was suspected.

The new spinal cord MRI was suspicious for a spinal dural fistula, revealing oedema of the lower thoracic spinal cord and conus with degenerative canal stenosis and serpiginous intradural extramedullary veins (figure 1). Although the level of the fistula was not clear at this point, magnetic resonance angiography (MRA) of the spine demonstrated a prominent tortuous vessel along the left T8–T9 level (figure 2). Given this evidence, we decided to perform a digital spinal angiogram to locate and potentially treat the fistula.

A spinal angiogram was performed under general anaesthesia, using predominantly hand injection technique for the intercostal and pelvic vasculature. An obvious spinal fistula was not identified initially, but on further inspection of the angiographic images, there was a suspicion of an abnormal pelvic vessel along the midline. Additionally, we had not been able to identify the right-sided L5 intercostal artery. We therefore decided to repeat the spinal angiogram, focusing on the pelvis and with a view to perform a cranial angiogram, should this be unremarkable. In conjunction with interventional radiology, repeat angiography was performed of the lower aorta and left-sided internal iliac artery using a power injection technique on this occasion. Glucagon was used to reduce peristaltic bowel shadows which had been noticed during the first angiogram. Resultingly, a pelvic dural arterial venous fistula arising from the left sacral artery, leading to a venous pouch and then radicular vein, was identified. Figure 3 presents the results of the two angiograms, showing the radicular draining vein on the second angiogram.

Treatment

Using a coaxial access system, a microcatheter was advanced into the lateral sacral artery, and selective angiography performed (figure 4). Embolisation of the fistula was successfully performed using onyx (ethylene vinyl alcohol) glue to close the fistula (figure 5).

Outcome and follow-up

The patient was seen 3 months after the embolisation of his fistula with significant recovery in his lower extremity weakness. Additionally, MRI of the spine showed significant improvement of oedema. Occupational therapy notes that the patient met all goals following treatment and is being discharged with continued home exercise programmes. Physical therapy notes significant improvements in ambulation; however, there are still some functional deficits. They are satisfied with the progress and anticipate he will be discharged within the next few weeks. Delayed catheter angiography by neurosurgery is planned for 6 months following his treatment for monitoring.