Intradural dorsal arteriovenous fistula: a case report and literature review

Intradural dorsal arteriovenous fistula (AVF) is a rare spinal vascular malformation that primarily affects the blood-supplying arteries of the intradural dorsal. Its clinical manifestations are dominated by bilateral lower limb weakness and a lack of specificity in early symptoms, which can easily lead to underdiagnosis or misdiagnosis. Thus, the successful diagnosis of intradural dorsal AVF is difficult.

A 56-year-old woman presented with lower limb weakness for 3 months without significant sensory deficits. The patient has a history of hyperthyroidism, but the condition has been cured, and the patient is not currently taking any long-term medications. Upon admission, the patient reported no abnormal sensations related to urination or defecation. We performed muscle strength testing, which revealed a grade V-muscle strength in both lower limbs. Magnetic resonance imaging (MRI) of the lumbar spine showed abnormal vascular shadows in the lumbar spinal canal. Initially misdiagnosed as extradural AVF, right iliac artery angiography via digital subtraction angiography (DSA) revealed an AVF at the L3-4 segment, supplied by nerve root artery from sacral external arteries and drained through chondromalacia veins. Due to the tortuous and delicate nature of the vessels at the lesion site, the microcatheter cannot reach the affected area. Therefore, we opted for surgical treatment. During surgery, the fistula in intradural dorsal was found to be supplied by upward and downward radicular arteries, draining through a soft meningeal vein. The drainage veins were clipped using an aneurysm clip and subsequently resected by electrocoagulation. The operation was successful, with significant improvement in lower limb weakness to class V muscle strength. Postoperative MRI at 2 weeks showed disappearance of abnormal vascular shadow. During subsequent telephone follow-ups, the patient did not report any significant abnormalities.

Intradural dorsal AVF treatment aims to block arteriovenous shunts through surgical or endovascular methods. Surgical resection is the primary treatment. In this case, the long, narrow feeder arteries favored direct surgery. However, surgery risks trauma, cerebrospinal fluid leakage, infection, and neurologic injury; therefore, treatment decisions should consider fistula characteristics, vascular anatomy, and patient health status.