Idiopathic intracranial hypertension (IIH), often referred to as pseudotumor cerebri or benign intracranial hypertension, is a condition of unknown etiology that manifests with chronically elevated intracranial pressure (ICP). It predominantly affects obese women, especially such who have gained significant weight over a short period of time, but certain drugs (growth hormones, tetracyclines, excessive vitamin A) are also associated with the condition. The most common symptoms are diffuse headaches, although various visual symptoms and pulsatile tinnitus are also common. Ophthalmologic examination is crucial for confirming the diagnosis and usually reveals bilateral papilledema and possibly loss of vision. MRI is often done to rule out other causes of increased ICP. Lumbar puncture typically shows an elevated opening pressure. Acetazolamide is the first-line therapy, whereas surgery is only used as a last resort. Even with treatment, the condition often worsens over the course of months to years, and permanent symptoms are common.
- Predominantly affects obese women aged 15–44 years 
Epidemiological data refers to the US, unless otherwise specified.
- Risk factors 
Modified Dandy criteria: used to diagnose idiopathic intracranial hypertension 
- Symptoms of increased ICP (e.g., headache, visual changes, pulsatile tinnitus, papilledema)
- Absence of localizing neurologic findings on neurologic examination
- The absence of deformity, displacement, or obstruction of the ventricular system with otherwise normal neurodiagnostic studies
- Awake and alert
- No other apparent cause of intracranial hypertension
- A mismatch between production and resorption of CSF (cause unknown) → ↑ ICP → damage to structures of the CNS and especially to the optical nerve fibers
- Orthograde axoplasmic flow stasis at the optic nerve head leads to bilateral papilledema.
- Diffuse headaches
- Visual symptoms
- Pulsatile tinnitus (swishing sound)
- Cranial nerve disorders (especially CN VI → diplopia)
- Back pain 
- No cognitive impairment
The following tests should always be performed: 
- Ophthalmologic examination
MRI: with contrast and MR venography (MRV)
- To rule out other causes of increased ICP
- Unremarkable brain parenchyma
- Possible abnormalities of the sclera and/or optic nerve (e.g., scleral flattening)
- Empty sella: an empty appearing sella turcica in cross-sectional imaging as a result of CSF displacing cerebral tissue (mainly due to shrinkage of the pituitary gland)
- Possible cerebral venous sinus stenosis (especially transverse sinus)
Lumbar puncture (LP)
- Routinely performed for diagnostic and therapeutic purposes, despite increased intracranial pressure 
- Exclusion of an intracerebral mass or obstructive hydrocephalus prior to LP
- May show
- Temporary headache relief may be reported by the patient after LP.
In communicating hydrocephalus (e.g., in IIH), there is no pressure difference between the ventricles and subarachnoid space. Therefore, a decrease in intracranial pressure poses little risk of herniation. Unlike in meningitis, papilledema and other signs of increased intracranial pressure are not a contraindication for LP in IIH.
- Discontinue any offending agents.
- Weight loss
- Medical therapy (first-line)
- Surgery: if conservative measures fail
- IIH typically worsens over months to years, until the condition stabilizes.
- Even with treatment, many patients will have persistent symptoms (up to 79%). 
- Severe loss of vision (or even blindness) occurs in up to 24% of patients.