Conditions That Can Require Brain Surgery /Craniotomy Brain surgery is performed to correct a variety of neurological disorders, or conditions. This information focuses on different conditions that may require brain surgery- brain tumors, acoustic neuromas, aneurysms and arteriovenous malformations. Because the brain fits so compactly within the skull, an increase in tissue size caused by any kind of tumor (benign or malignant) can result in increased pressure within the skull. This condition, known as increased intracranial pressure, usually requires surgery to be corrected. Q C 15 What is increased ICP? How is it monitored? Normal Intracranial pressure (adult) ranges from 10-20 mm Hg. To measure: a catheter is placed in the ventricle, then either a manometer is used to manually measure the pressure, or the catheter is hooked up to a transducer and a machine that will provide a digital readout of the measurement.