The test is performed by placing the patient in the lateral decubitus position, thereafter the clinician performs a lumbar puncture. The opening pressure is measured. Then, the clinician's assistant compresses both jugular veins (if increased intracranial pressure is not suspected then one may exert pressure on both external jugular veins but usually pressure is first exerted on the abdomen, this pressure causes an engorgement of spinal veins and in turn rapidly increases cerebrospinal fluid pressure), which leads to a rise in the intracranial pressure.