Our patient is a 50-year-old woman admitted to the hospitalist service with a presumptive diagnosis of syncope. The day prior to admission, she developed intermittent pre-syncopal episodes without clear inciting factors. Symptoms were recurrent, non-positional, and not associated with any chest discomfort. Further review of her history was notable for a relatively recent diagnosis of squamous cell carcinoma of the base of her tongue for which she underwent radical neck dissection one month prior to admission with an uncomplicated post-operative recovery.
Following admission, she was witnessed to have spontaneous sinus bradycardia to a heart rate of 30. Her bradycardia was treated successfully with intravenous atropine. These episodes were recurrent and associated with relative hypotension to a systolic blood pressure of 80 mmHg. A CT of her head and neck was performed which revealed a phlegmon between the branches of her carotid artery concerning for an abscess. Given her history, consideration was given that this could represent a malignant mass or inflammatory process. She was admitted to the intensive care unit for temporary transvenous pacer placement as well as antibiotic treatment.
Discussion:
Carotid sinus syndrome often presents with episodes of syncope and is caused by stimulation of the carotid sinus. The carotid sinus is a collection of nerves that sits at the base of the internal carotid artery superior to the bifurcation of the internal and external carotid arteries. In a normal baroreflex, pressure changes to the internal carotid wall stimulates the carotid sinus, signaling through the glossopharyngeal nerve to the nucleus tractus soleus in the brainstem. The efferent limb of the reflex is carried via sympathetic and parasympathetic nerves to the heart and blood vessels decreasing contractility, heart rate, and peripheral resistance.
Abnormalities of the baroreflex may result from an adjacent mass or collection of fluid compressing on the carotid sinus. Pertinent to our patient, squamous cell carcinoma can metastasize to the retropharyngeal or parapharyngeal spaces and the resulting tumor may press on the carotid sinus causing syncope. Risk of metastasis of squamous cell carcinoma to the carotid sinus is increased when a patient has undergone a radical neck dissection. The carotid sheath serves as a good barrier against invasion by squamous cell carcinoma and disruption of this barrier allows tumors to form around the carotid sinus. Post-surgical phlegmon or abscess in the area of the carotid sinus would present similarly to a tumor caused by metastasis of squamous cell carcinoma.
Conclusions:
In a differential of syncope or near syncope for patients admitted to the hospital, carotid sinus syndrome should be considered. In addition to the more common diagnosis of carotid sinus hypersensitivity, mass-effect compression of the carotid sheath may lead to carotid sinus syndrome. In the case of our patient, there was a high level of concern for recurrent squamous cell carcinoma, and she was referred for radiation treatment in consultation with her surgical oncologist. In addition, an abscess could not be confidently ruled out, as the location of her phlegmon precluded a biopsy, thus she was presumptively treated with broad-spectrum antibiotics. After initiation of antibiotic treatment, she had no further episodes of bradycardia. However, given concern for recurrence, she was referred for pacemaker placement prior to hospital discharge.