Cardiac Arrhythmias and Sudden Death in Subarachnoid Hemorrhage• Life-threatening cardiac arrhythmias can occur in patients with subarachnoid hemorrhage secondary to rupture of intracranial aneurysms. The arrhythmias are secondary to acute dysfunction of the central nervous system and possibly to sudden increase in intracranial pressure. The autonomic nervous system is the mediator in the production of these disorders. The clinical significance of these rhythm disorders is discussed, particularly in regard to the sudden, unexpected death seen in this type of patient. The possible mechanisms of production are analyzed and their therapeutic implications are stressed.

Apraxia of gait in patients with communicating hydrocephalus appears in the context of a generalised motor disorder that includes defective righting reflexes, generalised increased tone to passive movements, grasp reflexes, difficulty with serial movements of the hands and defective smooth pursuit eye movements. The inability to walk does not appear to be due to a motor disorder but to release of proprioceptive supporting reactions. This mechanism is triggered by proprioceptive stimuli.

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SUMMARY Experimental subarachnoid hemorrhage (SAH) in dogs was produced by introducing blood into the subarachnoid space through a catheter connected to an artery of the animal. The intact animals and those with preserved vagi and heart sympathetic innervation, developed arrhythmias with short latencies which correlated with the sudden increase in the intracranial pressure. The animals with sections of both vagi and heart sympathetic innervation, but with an intact spinal cord, developed arrhythmias that were delayed and did not correlate with the changes in intracranial pressure. These arrhythmias were preceded by changes in the QT interval, T wave and ST segment. It was concluded that the arrhythmias could be produced either by direct autonomic discharges to the heart or by increased circulating and tissue catecholamines. The clinical implications of these findings are discussed.