ABSTRACT
The case of a 20-year-old woman with a carotid body tumor of Shamblin class III is reported. Ten hours after preoperative direct intralesional embolization with 20 mL Onyx (ethylene-vinyl alcohol copolymer; Micro Therapeutics, Irvine, Calif), the patient showed symptoms of Horner syndrome and deficits of the hypoglossal and glossopharyngeal nerves. Intraoperative examination 12 hours after Onyx embolization revealed a massive swelling of the hypoglossal and glossopharyngeal nerves. The patient's tongue motility and glossopharyngeal function improved after surgery, but Horner syndrome was still present. Owing to the delayed occurrence of these adverse effects, the optimal time of surgical intervention after Onyx embolization should be discussed and perhaps expedited.