V3 Vertebrovertebral Arteriovenous Fistula in a Patient with Bilateral Kimmerle's Anomaly: A Case Illustration and Treatment Decision-Making

Kimmerle’s anomaly, also known as ponticulus posticus or arcuate foramen, is an osseous variant of the atlas that may affect the V3 segment of the vertebral artery. Although it has been associated with vertebrobasilar insufficiency, tinnitus, headache, Bow Hunter syndrome, vertebral artery dissection, and surgical risk during upper cervical instrumentation, an arteriovenous fistula associated with this anomaly has not been clearly documented. A 33-year-old man presented with a two-year history of left-sided pulsatile tinnitus, occipital pulsation, a posterior cervical bruit, and dizziness induced by neck extension. Lateral cervical radiography and three-dimensional computed tomography demonstrated Kimmerle’s anomaly bilaterally, incomplete on the left and complete on the right. Computed tomography angiography revealed dilated venous structures around the left vertebral artery. Digital subtraction angiography showed a high-flow fistula at the left V3 segment with early venous drainage into the vertebral/spinal venous plexus and poor antegrade visualization of the distal left vertebral artery. Right vertebral artery injection demonstrated retrograde filling of the distal left vertebral artery, consistent with a steal phenomenon. Segmental coil embolization was performed, after which the patient’s symptoms resolved completely. Six-month follow-up angiography confirmed complete obliteration of the fistula with preserved posterior circulation filling. This case suggests that incomplete Kimmerle’s anomaly may rarely predispose the V3 vertebral artery to repetitive mechanical injury and arteriovenous fistula formation. Endovascular coil occlusion may provide definitive treatment when contralateral vertebral artery circulation is adequate. During nine years of clinical follow-up, the patient remained asymptomatic without neurological deterioration or recurrent vertebrobasilar symptoms.

Arcuate foramen Coil embolization Kimmerle’s anomaly Ponticulus posticus Vertebral artery Arteriovenous fistula