Intracranial pathology is frequently associated with cardiac dysrhythmias, which are sometimes lethal. Stroke, subarachnoid hemorrhage, seizures and head trauma with or without increased intracranial pressure are observed to be accompanied by myocardial damage and by ECG abnormalities, including Twave changes, shortened P-R interval, prolonged Q-T interval, premature ventricular contractions, ventricular ectopy, sinus bradycardia, ventricular and supraventricular tachycardias. Derangements of autonomic function have been shown to be responsible for these disturbances of rate, rhythm and conduction. The autonomic nervous system receives neural input from various parts of the cerebral cortex, the hypothalamus and the brainstem which are extensively interconnected. Although unequivocal data supporting associations between specific neuropathological conditions or damage to specific structures and the observed dysrhythmias do not exist, some evidence for laterality of function does exist in humans. Tachycardia and pressor responses are more common after stimulation of the right insular cortex and after experimental stimulation of the left vagus which innervates the atrioventricular node and the cardiac conduction system. Bradycardia seems to be more common after stimulation of the left insular cortex or the right vagus nerve which innervate the sinoatrial node.