Idiopathic intracranial hypertension, formerly known as benign intracranial hypertension, is defined by increased cerebro-spinal fluid pressure without any known cause. Symptoms are typical for other types of hydrocephalus - headache, nausea and vomiting, usually combined with tinnitus. However, unlike most cases of hydrocephalus, no blockage of CSF can be seen. Diagnosis starts with a lumbar puncture to confirm high fluid pressure, and a head scan to rule out other conditions.