Transient Horner's Syndrome following Posterior Cervical Spine Instrumentation: A Postoperative Dilemma

Horner ’ s syndrome is a rare phenomenon associated with a wide variety of medical and surgical conditions. Ipsilateral ptosis and miosis occur in Horner ’ s syndrome due to the sympathetic disruption at any point along the pathway from the posterolateral hypothalamus to the cervical sympathetic trunk. 1 It is awell-recognized but infrequententity following cervical spine instrumentation through the anterior approach with an incidence ranging from 0.02% to 3.8% during the anterior cervical discectomy and fusion (ACDF) proce-dure. 2,3 We report a rare case of transient Horner ’ ssyndrome following posterior cervical spine instrumentation for congenital atlantoaxial dislocation (AAD). A 13-year-old male patient presented with neck pain and weakness in all four limbs for the past 6 months. Neurologi-cal examination revealed a motor power of grade 3 in all four limbs with a normal pupillary size and reactivity. A diagnosis of reducible AAD was considered based on the dynamic computed tomographic (CT) imaging without radiological evidence of basilar invagination or Arnold Chiari malforma-tion. The patient was planned for C1-C2 fusion under general anesthesia in the prone position. After induction of anesthesia, the patient was placed in the prone position, the head was fi xed with the May fi eld clamp, and the eyes were