(A581) Neck Masses Originating from the Carotid Sheath: Challenges in Diagnosis

Introduction: Carotid body tumors (CBT) and vagal schwannomas (VS) arise from glomus cells of the carotid body and vagal myelin, respectively, and present similarly (dysphagia, dysphonia, neck mass, stridor). Angiography can determine tumor blood supply, but highly vascularized VS present similarly to CBT. Treatment options include surgery and/or radiation. Embolization, which is controversial, may be indicated to reduce tumor blood supply and can provide a diagnostic clue for VS versus CBT.

Methods: A 38 year old female complaining of neck mass underwent MRI, revealing a 4.9 cm mass at the bifurcation of the right common carotid artery (CCA), with splaying of internal and external carotid arteries. Flexible laryngoscopy showed a pulsatile, submucosal mass with hypopharynx extension.

Preoperatively, embolization of the right CCA was performed. When dimethyl sulfoxide was injected the CCA branch supplying the tumor, the patient experienced temporary asystole that resolved after glycopyrrolate administration. The patient was monitored after successful embolization, then underwent right neck exploration revealing a large tumor on the right vagal nerve with extension to the skull base; not the carotid body as suspected. The vagus nerve and branches of the common carotid were dissected from the mass. The mass was successfully removed and the patient recovered fully. Frozen pathology revealed vagal schwannoma.

Results: CBT and VS remain difficult to diagnose preoperatively. Both conditions present as a neck mass and tumor origin is only confirmed intraoperatively. Fine needle aspiration and open biopsy have been used to obtain diagnosis before resection but are not standard practice due to risk of iatrogenic damage. In this case, asystole during embolization was instrumental in making the diagnosis of VS over CBT. Embolization induced ischemia of the nerve, increasing parasympathetic output, which suppressed cardiac pacemaker cells.

Conclusions: A multidisciplinary approach with ENT, neurosurgery, and vascular surgery is key when treating neck masses with broad differential diagnoses to enhance patient outcomes.