Motor palsy after posterior cervical foraminotomy: Anatomical consideration

Background: Motor palsy is a serious complication that can result from cervical surgery. We introduced cases of motor palsy after posterior cervical foraminotomy (PCF) and consider cervical anatomy. Methods: Between January 2007 and August 2010, 133 PCFs were performed on 106 consecutive patients with radiculopathy caused by foraminal stenosis or posterolateral disc herniation. Results: Three of 133 (2.3%) levels that underwent PCF developed a motor palsy. Two cases involved the C5 nerve root, and one case involved the C6 nerve root. The cause of the C5 palsy may have been excessive retraction, whereas the cause of the C6 palsy may have been thermal damage caused by drilling. The rate of C5 palsy (22.2%) was much higher than that seen with other nerves. Anatomically, the C5 nerve root is thinner and covers the entire intervertebral disc at a relatively sharper angle than the other nerve roots. The removal of an extruded disc at C4-5 forces more excessive retraction of the C5 nerve root. Conclusions: Although PCF is a good alternative treatment with minimal morbidity for cervical radiculopathy, surgeons should keep in mind the possibility of motor palsy, especially at C4-5.