Removing the bone with a trochlea bipes, after trephination, 1527. Trepanning is a surgical intervention in which a hole is drilled or scraped into the human skull, exposing the dura mater to treat health problems related to intracranial diseases. Cave paintings indicate that people believed the practice would cure epileptic seizures, migraines, mental disorders and the bone that was trepanned was kept as a charm to keep evil spirits away. Trepanation was also practiced in the classical and Renaissance periods.