Category: Clinical Sciences/Health Conditions
Case Diagnosis: Thoracic Dural Arteriovenous Fistula
A 68-year-old woman, previously independent, presented with acute-onset lower-extremity weakness. She was unable to walk. Contrast-enhanced T-spine MRI showed central cord hyperintensity from T7-L1, with conus/cauda equina involvement. Laboratory studies including LP, aquaporin-4-IgG, and paraneoplastic/rheumatologic/infectious panels were negative. She was diagnosed with longitudinal-extensive transverse myelitis. Her strength/gait improved with steroids and inpatient rehabilitation. However, she experienced frequent lower-extremity weakness “flares” with three subsequent acute-hospital readmissions, each time prompting steroids and/or plasmapheresis plus inpatient rehabilitation. Her disease course also included varying signal level (highest was T4), lower-extremity hypoesthesia, neurogenic bladder, and recurrent UTIs. Physical exertion was noted to transiently exacerbate her weakness. Repeat contrast-enhanced T-spine MRI showed small, previously-unseen serpentine flow-voids posterior to the cord at T9-T12; angiogram confirmed dural arteriovenous fistula. L1-L3 laminectomy and surgical clipping was performed, followed by inpatient rehabilitation. She has since experienced significant improvement and has been an independent community ambulator with rollator for several weeks.
Spinal dural arteriovenous fistulas are abnormal connections between an artery and a vein in the subdural space. When blood from the high-pressure arterial system enters the low-pressure venous system, blood supply is compromised and venous congestion/swelling occurs, leading to potentially irreversible damage. Symptoms include weakness, numbness, paresthesia, pain, bowel/bladder incontinence, and even paraplegia; however, many are asymptomatic. MRI is frequently nondiagnostic, so strong clinical vigilance and access to spinal angiography is required. Radiographic embolization is first-line therapy, but in this case surgery was necessary due to microvascular collateral circulation. Once repaired, spinal cord blood flow improves but damage may not reverse.
Spinal arteriovenous fistulas should be suspected in any case of paraparesis of non-definitive etiology, especially when there is exertion-associated weakness. As early management portends a better prognosis, we hope that this case educates physiatrists on this clinical pathology and leads to improved patient care/outcomes.