Predicting Unilateral Postlaminectomy C5 Palsy by Measuring C5 Exit Foramen Area on Preoperative Computed Tomography

Background. Postoperative C5 motor palsy is known as a common complication not only after cervical laminectomy but also after anterior discectomy. There is no consensus to verify any of the proposed mechanisms of C5 palsy following posterior cervical decompression. The authors of this article have found that C5 palsy is more common among patients with smaller C5 root exit foramen area. The purpose of this study was to define a cutoff value for C4-C5 foraminal area on preoperative computed tomography images to predict postlaminectomy C5 palsy. Methods. In this prospective clinical study, C4-C5 foraminal area of 119 patients with cervical spondylotic Myelopathy calculated on reformatted pure sagittal computed tomography images by measuring maximal height and transverse diameter of foramina and a cutoff value was defined in which with lesser amounts, postlaminectomy C5 palsy was more common. Results. Of 119 patients with spondylotic myelopathy undergoing cervical laminectomy, 23 experienced postoperative C5 palsy with mean C4-C5 foraminal area of 44.54±0.72 mm2; Mean C5 root exit foraminal area in patients with intact postoperative root function calculated 56.78±5.48 mm2 and the difference between these two groups was statistically significant (P< 0.05). No patient with C5 exit foraminal area more than 46 mm2 have had C5 palsy after laminectomy. Conclusions. The incidence of postlaminectomy C5 palsy is significantly higher in patients with C5 exit foraminal area less than 46 mm2. Prophylactic C4-C5 foraminotomy in this group may significantly reduce risk of postoperative C5 nerve motor palsy although there is still debate about the effect of this procedure. Keywords: Cervical Nerve Palsies; Laminectomy; Spinal Cord Disease; Spinal Osteophytosis; Cervical Vertebrae