The first (Chapters 1-51) of two companion volumes covering all major new advances in the field of Neurosurgery since the 1985 publication of the three-volume Neurosurgery. Update I emphasizes changes in diagnostic methodologies and advances in surgical techniques, particularly relating to tumors (i.e. Magnetic Resonance Imaging, and techniques in the management of tumors involving the base of the skull). Update II will be available December 1990.