Idiopathic intracranial hypertension, also known as pseudotumor cerebri and benign intracranial hypertension, is a syndrome characterized by increased intracranial pressure and papilledema in patients without focal neurologic findings, except for an occasional sixth nerve palsy.

 It is a diagnosis of exclusion, and radiologic examinations are used to help exclude lesions that produce intracranial hypertension, such as obstructive hydrocephalus, tumor,chronic meningitis, and dural sinus thrombosis.Opening lumbar CSF pressure is elevated but CSF composition is normal.

The pathophysiology of this syndrome is still uncertain; however, an increase in resistance to CSF absorption at the level of the arachnoid villi, resulting in interstitial brain edema, is suspected.

Most frequent in obese female subjects between the ages of 10 and 40 years.

Radiological findings:

A number of CT and MR imaging findings have been reported in association with idiopathic intracranial hypertension, including an enlarged optic nerve sheath, reversal of the optic nerve head, small ventricles, enlarged or small extraventricular CSF spaces, increased T2 signal within the white matter on MR images, and empty sella . The term empty sella refers to a condition in which the sella turcica is filled mainly with CSF. The mechanism by which an empty sella develops in patients with idiopathic intracranial hypertension is intrasellar herniation of CSF and arachnoid membrane through an absent or open diaphragma sellae in association with increased intracranial pressure. The pituitary gland is flattened and distorted.The infundibulum is midline and extends down to the floor of the sella turcica.

 

Modified Dandy criteria for the diagnosis of idiopathic intracranial hypertension :

1. Signs and symptoms of increased intracranial pressure.

2. Awake and alert patient.

3. No abnormal neurological findings except papilloedema or a sixth nerve palsy.

4. Normal CT/MRI except for empty sella syndrome or small ventricles.

5. Documented increased CSF opening pressure (>200 mm of water in non-obese and >250 mm of water in obese patient), with normal CSF composition.

6. No other known cause of raised intracranial pressure.