The mechanism for carotid sinus hypersensitivity is unclear. Research suggests that the problem may lie within the sternomastoid muscle. This muscle overlies the carotid sinus. In normal individuals simultaneous pressure of the sternomastoid muscle and the carotid sinus - caused by turning the head for example - is correctly interpreted by the brain as external pressure, and is therefore ignored. If, however, there are defective impulses from stretch receptors in the sternomastoid muscle the changes may be interpreted as a rise in intraluminal carotid sinus pressure warranting action.
