| 1. Signs and symptoms of raised intracranial pressure. |
| 2. Absence of localising findings on neurological examination (except sixth nerve palsies or rarely other false localising signs.) |
| 3. Normal neuroimaging with no evidence of venous sinus obstruction. (empy sella and dilated optic nerve sheaths are acceptable.) |
| 4. A CSF opening pressure greater than 250mm H2O. |
| 5. Normal CSF constituents. |