BACKGROUND: The carotid sinus syndrome (CSS) is characterized by syncope and hypotension due to a hypersensitive carotid sinus located in the carotid bifurcation. Some patients ultimately require surgical sinus denervation, possibly by transection of its afferent nerve (carotid sinus nerve [CSN]). The aim of this study was to investigate the anatomy of the CSN and its branches. METHODS: Twelve human carotid bifurcations were microdissected. Acetylcholinesterase (ACHE) staining was used to identify location, side branches, and connections of the CSN. RESULTS: A distinct CSN originating from the glossopharyngeal (IX) nerve was identified in all specimens. A duplicate CSN was incidentally present (2/12). Mean CSN length measured from the hypoglossal (XII) nerve to the carotid sinus was 29 +/- 4 mm (range, 15-50 mm). The CSN was frequently located on anterior portions of the internal carotid artery, either laterally (5/12) or medially (6/12). Separate connections to pharyngeal branches of the vagus (X) nerve (6/12), vagus nerve itself (3/12), sympathetic trunk (2/12), as well as the superior cervical ganglion (2/12) were commonly observed. The CSN always ended in a network of small separate branches innervating both carotid sinus and carotid body. CONCLUSION: Anatomical position of the CSN and its side branches and communications is diverse. From a microanatomical standpoint, CSN transection as a single treatment option for patients with CSS is suboptimal. Surgical denervation at the carotid sinus level is probably more effective in CSS. CLINICAL RELEVANCE: Some patients suffering from CSS ultimately require surgical carotid sinus denervation, possibly by transection of its afferent nerve (CSN). This study was performed to investigate the anatomy of the CSN using a nerve-specific ACHE staining technique. Microdissection demonstrated a great variability of the CSN and its branches. Simple high transection of the CSN may lead to an incomplete sinus denervation in patients with CSS. Surgical denervation at the level of the carotid sinus itself may be more effective in CSS.
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