Abstract Body (Do not enter title and authors here):
Introduction
Vasovagal syncope occurs when an overwhelming parasympathetic tone is triggered by causes including emotion, pain, or baroreceptor stimulation. We present a rare case of vasovagal syncope mediated by locally invasive tonsillar squamous cell carcinoma (SCC).

Case
A 66 year old man with untreated L tonsillar SCC presented with recurrent syncope, hypotension, sinus bradycardia and sinus arrest up to 6 seconds as observed on telemetry (figure 1, bottom). Symptoms were atropine responsive and reliably reproduced with head turning to the L or palpation. CT neck (figure 1A-B) showed extension of the tumor into the L carotid body and adjacent vagal sheath. Echocardiogram revealed no structural heart disease. Pacemaker implantation was deferred due to suspected reversible vasovagal mechanism. He received a course of steroids, targeted cancer therapy with weekly Cetuximab infusion and daily radiation to the neck mass. After treatment initiation, the patient remained hospitalized for 3 days with no recurrent syncope or bradycardia observed. He continued outpatient treatments with resolution of his neck mass (figure 1C-D) and had no syncopal episodes over the next year.

Discussion
We highlight this case as an example of locally invasive tumor causing mechanical disruption of the carotid body and neural reflex stimulation via the vagal sheath. When associated with vasovagal syncope, this phenomenon has been previously named carotid body syndrome. Although vasovagal mechanism remains the most common cause of syncope, diagnosis and treatment can prove challenging, particularly due to variable demonstration of vasodepressor and cardioinhibitory reflexes amongst individual patients. Treatment of vasovagal syncope focuses on trigger avoidance and treatment for predisposing conditions. Pacemaker implantation remains controversial and may be offered to patients with predominantly cardioinhibitory reflex and high-risk recurrent syncope, with a possible role for implantable cardiac monitoring. In this case, the management strategy was guided by association of symptoms with head turning, and treatment of the culprit neoplastic process yielded resolution of vasovagal syncope with avoidance of device implantation.