The Cushing reflex in the absence of intracranial hypertension.

A case is presented in which the left frontoparietal scalp, skull and dura were excised during removal of a massive squamous cell carcinoma. The exposed and relaxed brain was protected only with split-thickness skin grafts for 23 days before successful rotation of a full thickness scalp flap. During the first postoperative day following tumor removal, lumbar cerebrospinal fluid drainage by indwelling catheter was instituted. Transient cardiovascular signs of the classical Cushing reflex and an ipsilateral pupillary dilation rapidly ensued. This phenomenon lends further support to one of the theories regarding the pathogenesis of the Cushing reflex being a pressure gradient (not high intracranial pressure per se) causing axial distortion of the brain stem. In addition, this case is an example of brain herniation in the absence of clinical intracranial hypertension.