The medial loop of the V2 segment of the vertebral artery and the importance of this variation in correlation with the resection safe zone and technical characteristics of spinal cages during anterior cervical approaches

Abstract

Dear Editor, Reviewing the literature, the incidence of anatomic variations of the V2 segment of the vertebral artery (VA), is relatively high. Furthermore, ignoring a medial loop of the V2 segment can potentially lead to severe complications during anterior approaches to the cervical spine. We studied the course of 400 vertebral arteries on 190 magnetic resonance imaging and ten contrast-enhanced computed tomography scans from our archive between May 2011 and June 2012. In our study, patients with MRI or CT axial sections from C3 to C7 were included regardless of the underlying pathology. In nine patients (4, 5 %), the V2 segment of the vertebral artery formed a medial loop with distance to the midline 8 mm and 8 mm except in one level (one in 360 cervical levels) [4]. Furthermore, anterior cervical diskectomy 8–10 mm from the midline and width of cervical corpectomy 16–18 mm centered on the midline have been suggested in the literature as safe resection zones [3]. The width and adequacy of cervical corpectomy remains a controversial topic, especially in cases of an unusual medial loop of the V2 segment. It could be technically challenging to avoid the injury of VA and achieve an adequate anterior decompression. Careful choice of cages regarding their width is a prerequisite for anterior cervical diskectomy and corpectomy procedures. According to our study, during drilling for anterior cervical approaches, this variation is likely to be encountered at 7–11 mm depth of vertebral body or intervertebral disk space. In such cases, the application of intraoperative Doppler could be invaluable. Knowledge of the aforementioned anatomic variation of the V2 segment is important for the avoidance of inadvertent injury of the vertebral artery during anterior cervical spine approaches [2], with potentially catastrophic complications for the patient. Given the relatively high incidence of a V2 N. Gkekas (*) :N. Georgakoulias Department of Neurosurgery, Athens General Hospital, G. Gennimatas, Mesogeion 154, Athens, Greece 11526 e-mail: nikolaosgkekasdr@yahoo.gr