The occurrence of syncope and convulsions due to a hyperactive carotid sinus reflex has been receiving deserved emphasis lately.1 The carotid sinus is the bulbous dilatation at the bifurcation of the common carotid artery. Normally an increase in intrasinal pressure reflexly produces a moderate decrease in arterial tension, cardiac rate and output of epinephrine, while respiration and peristalsis are increased. In a patient with a hypersensitive carotid sinus, stimulation of the sinus by pressure will often induce syncope or convulsions as well as other manifestations.
The three dominant sinal responses are: (1) the vagal type, with the efferent impulse traveling over the vagus nerve to produce sinoauricular or auriculoventricular block, with resultant asystole and syncope; (2) the depressor type, the efferent arc of which over the aortic depressor nerves accounts for vasodilatation and hypotension unassociated with bradycardia, and (3) the cerebral type, in which syncope occurs without cardiovascular changes.
ROBINSON LJ. SYNCOPE, CONVULSIONS AND THE UNCONSCIOUS STATERELATION TO THE HYPERACTIVE CAROTID SINUS REFLEX. Arch NeurPsych. 1939;41(2):290–297. doi:10.1001/archneurpsyc.1939.02270140076006