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Why Does C5 Palsy Occur after Prophylactic Bilateral C4-5 Foraminotomy in Open-Door Cervical Laminoplasty? A Risk Factor Analysis

Introduction Prophylactic bilateral foraminotomy has been shown to reduce the risk of C5 palsy after open-door laminoplasty surgery. However, it does not totally eliminate it. Other factors such as inherent cord pathology may play a role in its development. Material and Methods A retrospective review to evaluate the efficacy of bilateral C4–5 foraminotomy in preventing occurrence of postoperative C5 palsy and to identify possible risk factors for its development was performed. A total of 70 consecutive patients who underwent open-door laminoplasty with bilateral C4–5 foraminotomy were included. Clinical, radiographic, and operative data were reviewed. Development of postoperative C5 palsy was analyzed. Results Fifty-four males and 16 females were reviewed. Mean age was 56 years (range, 30–86 years). The primary pathology was spondylosis in 76% of cases and ossified posterior longitudinal ligament in 21%. Radiographic evidence of C4–5 foraminal stenosis was seen in 81% of the patients. The mean duration of preoperative symptoms was 7 ± 19 months. Four (5.7%) out of 70 patients developed C5 palsy after open-door laminoplasty with bilateral C4–5 foraminotomy. Multivariate analysis showed that a long duration of preoperative symptoms (> 12 months) and the presence of preoperative C4–5 T2-MRI cord signal change were statistically significant risk factors for the development of C5 palsy even after bilateral C4–5 foraminotomy in open-door laminoplasty (p < 0.0001 and P 0.036 respectively). Conclusion While bilateral C4–5 foraminotomy may reduce post-laminoplasty C5 palsy when compared with the historical cohort, foraminotomies do not eliminate C5 palsy occurrence. Prolonged duration of symptoms and presence of preoperative T2-MRI cord signal change increased the risk for developing postoperative C5 palsy in laminoplasty patients who underwent bilateral C4–5 foraminotomy.