Disclosed are methods and devices for navigating a subarachnoid space in a vertebrate organism including percutaneously introducing a device into the spinal subarachnoid space at an entry location. Navigation of the spinal subarachnoid space is disclosed for the purpose of reaching a desired location in the subarachnoid space or the intracranial space, including areas in and around the spinal cord and brain. Once a desired location is reached, methods and devices for cooling or heating the desired location to cause physiologic changes are suggested.