Aneurysmal subarachnoid hemorrhage is a serious medical and social problem. The main physiological mechanisms that determine secondary brain damage in this patients are intracranial hypertension, cerebral vasospasm, dysfunction of autoregulation mechanisms, violation of liquorodynamics and delayed cerebral ischemia. The multimodal neuromonitoring for prevention and timely correction ofsecondary brain injury factors has become routine practice in neuroICU. Measurement of oxygen tension in the brain parenchyma is one of neuromonitoring options. During the years of intensive use of this method in clinical practice the reasons for reducing the oxygen tension in the brain parenchyma were revealed, as well as developed and clinically validated algorithms for correction of such conditions. However, there are clinical situations that are difficult to interpret and even more difficult to make the right tactical and therapeutic solutions. We present the clinical observation of the patient with aneurysmal subarachnoid hemorrhage, who had dramatically reduced brain intraparenchymal oxygen pressure although prolonged hypothermia were used. Despite this, the outcome was favorable. The analysis allowed to assume that the reason for this decrease in oxygen tension in the brain parenchyma could be hypothermia itself