The article represents information about the Kimmerle anomaly, is it an anomaly or is it a kind of defense mechanism? Bone as well as arterial abnormalities or a combination of both can reduce cerebral blood flow leading to early disability.

Purpose. To assess the frequency of occurrence and type of Kimmerle’s anomaly by radiological research methods.

Materials and methods. A CT scan of the upper segment of vertebra column was performed in 230 patients aged from 21 to 85 years. Kimmerle's anomaly was identified in 41 patients. The average age in the male section was 46.9 years, in the female section – 52.8 years. These patients underwent ultrasound duplex scanning of the V3 section and ultrasound transcranial Doppler ultrasound and magnetic resonance angiography of the vessels of the craniovertebral zone.

Results. The frequency of the anomaly was 17.8%. In patients with confirmed Kimmerle's anomaly CT of the brain in most cases revealed signs of vascular encephalopathy, cerebellar atrophy and single cysts in various variations as well as degenerative-dystrophic changes in the cervical spine. In most cases Kimmerle anomaly was bilateral. With a one-sided arrangement the atlas bone jumper was more often found on the left. Ponticulus posticus located on the right in a quarter of cases was open.  The calcification of the posterior atlanto-occipital membrane of the atlas above the left arch was overwhelmingly closed. In young patients with unilateral open Kimmerle's anomaly hemodynamically significant changes in blood flow velocity were not observed, in the remaining groups, there was a decrease in blood flow in the vertebral artery within the lower limit of normal. All patients with a closed form of Kimmerle's anomaly showed a decrease in blood flow on this side. Closed bone ring C1 on both sides led to a slowdown in blood flow through the basilar artery. According to the results of the study in more than half of the cases changes in the structure of the cerebral arterial circle represented by aplasia of one or both of the posterior communicating arteries were noted. A hypoplastic vertebral artery, according to magnetic resonance angiography at the V3-V4 level, was more often noted on the side where a closed form of Kimmerle's anomaly was detected.

Conclusion. A spondylogenic factor in the form of a vaulted opening can be the cause of the development of disorders of the craniovertebral circulation.