Spontaneous resolution of syringohydromyelia in a case of spinal Perimedullary Arteriovenous fistula (Type IVA) associated with low lying tethered cord

Introduction: Perimedullary arteriovenous fistulas (PMAVF) are defined as direct fistulous connections located on the pial surface of the spinal cord, between the anterior and/or posterior spinal arteries and the medullary veins, without any intervening nidus. PMAVFs constitute about 4% to 38% of all SCAVMs and are rare in children. The association of syringohydromyelia with low lying tethered cord in a case of PMAVF with spontaneous resolution of the syrinx has not been previously described in literature. Case report: Here we report the case of a 6 year old male child who presented with rapidly progressive weakness of both the lower limbs without any obvious sensory loss or bladder/bowel dysfunction. MRI of the spine revealed low lying tethered cord (lower border ending at the level of S3) with cord expansion and long segment septated syrinx (extending from lower border of D7 to S3). Long segment non-enhancing T2 hyper intensity was also noted in the upper dorsal cord. Multiple tortuous flow voids were seen on the surface of the cord, predominantly at its ventral aspect. Digital subtraction angiography (DSA) revealed a PMAVF (Type IVA SCAVM) with a single arterial feeder from left D9 intercostal artery. Repeat MRI done two months later showed marked spontaneous resolution of the syrinx in the dorsal region with persistence of the perimedullary flow voids. Clinically there was symptomatic improvement with resolution of the paraparesis and increased power in both the lower limbs. Conclusion: The association of syringohydromyelia in a case of type IVA PMAVF with low lying tethered cord in a child and its spontaneous resolution with clinical and radiological improvement has not been previously described in literature. The constellation of all these findings prompted us to report this rare entity. Correspondence to: Vivek Singh, Department of Radiology, Sanjay Gandhi Post Graduate Institute of Medical Sciences (SGPGIMS), Rae Bareli Road, Lucknow-226014, Uttar Pradesh, India, Tel: 8004904503, E-mail: singhvivek79@ rediffmail.com