gms | German Medical Science

Objective: Rotational provoked occlusion of the vertebral artery (VA), also named bow hunter's syndrome, is a rare but surgical treatable cause of vertebrobasilar insufficiency. Pathological findings are dynamic stenoses of the VA during neck-rotations or -extensions caused by osteophytes, fibrous bands, disc herniations or developmental anomalies. Options for treatment are decompression of the narrow point, cranio-cervical fusion in cases of instability or interventional vascular management.

Methods: We are presenting the rare case of a 19-year-old female patient admitted to our hospital with recurrent symptoms of cerebellar dysfunction (vertigo, impaired vision, gait difficulties). Imaging diagnostics (CT, CT-A, MRI) ruled out signs of cerebellar insults, a C1-assimilation anomaly with instability of the C1/2-segment and a Klippel-Feil-syndrome at level C4/5. Angiography demonstrated during head rotation a right side blood-flow reduction at the V3/4-segment. Because of C1/2-instability and C1-assimilation single decompression of the V3/4-segment was not possible. Indication for occipital-cervical-fusion was seen. 1 week before surgery patient was fixed in a halo vest to evaluate in final fixation position vertebrobasilar insufficiency. Surgery was performed over a dorsal occipito-cervical midline incision. Because of C1-assimilation and dysplastic changing a right C2 lateral mass screw and C2-lamina screw were inserted under navigational assistance. Lateral mass screws were placed at left C3- and C4-level and right C4- and C5-level. Screws were connected with bended rods and fixed to an occipital plate. For supportive boney fusion, material from patients iliac crest and ceramic bone gaft was prepared and placed in occipital-suboccipital region and down to C5.

Results: After surgery the patient showed no new neurological deficits or signs of vertebro-basilar insufficiency. 3-month follow up CT-scans demonstrated regular placed fixation material with good fusion results of the occipital-suboccipital region.

Conclusion: Rotational provoked occlusion of the VA caused by dynamic stenosis in case of C1-assimilation with instability of the C1/2-segment is a rare entity. Vascular imaging diagnostics of the occipital-cervical-region are important for planning adequate therapy strategies. In cases of C1/C2-instability, options for single decompression are limited and fusion is indicated. If reasons for the dynamic stenosis are resolved patients can expect a good outcome.