Wihasto Suryaningtyas1, Muhammad Arifin2, Abdul Hafid Bajamal2. 1. Department of Neurosurgery, Airlangga University Faculty of Medicine - Dr. Soetomo General Hospital, Gedung Pusat Diagnostik Terpadu (GDC) Lantai 5, RSUD Dr. Soetomo, Jl. Mayjen, Prof Moestopo 6-8, Surabaya, Indonesia. w_hasto@yahoo.co.uk. 2. Department of Neurosurgery, Airlangga University Faculty of Medicine - Dr. Soetomo General Hospital, Gedung Pusat Diagnostik Terpadu (GDC) Lantai 5, RSUD Dr. Soetomo, Jl. Mayjen, Prof Moestopo 6-8, Surabaya, Indonesia.