Rotational Vertebral Artery Dissection Secondary to Anomalous Entrance into Transverse Foramen.

Background: Rotational vertebral artery occlusion is a rare syndrome characterized by vertebrobasilar insufficiency secondary to position-dependent occlusion of the vertebral artery. Most cases reported in the literature have been attributed to osteophytic compression, either from the occipital condyle or within the transverse foramen. However, vertebral artery dissection secondary to motion in the setting of anomalous anatomy has not been reported.

Case Description: To the authors' knowledge, rotational vertebral artery occlusion and dissection secondary to anomalous entrance into the transverse foramen have never been reported. The authors describe the case of a 42-year-old male who presented with multiple posterior circulation transient ischemic attacks. Standard digital subtraction cerebral angiography demonstrated a non-flow-limiting right vertebral artery dissection, while dynamic digital subtraction cerebral angiography was remarkable for right vertebral artery stenosis that worsened with neck rotation. Computed tomography angiography of the neck revealed an anomalous course of the right vertebral artery, which entered the transverse foramen at C4 with preforaminal compression by the anterior tubercle of the C5 transverse process. The patient had no further symptomatic events after decompression of the vertebral artery by resecting the anterior C5 tubercle.

Conclusions: In the setting of codominant vertebral circulation and unilateral bony compression, the authors propose that neck rotation led to vertebral artery trauma, causing dissection complicated by thromboembolism. This is a novel and unusual entity that is different from Bowhunter's syndrome.