Table 2.

Definitions of the terms used in the guidance

Term	Definition
Adult	All patients above the age of 16 years old for the purpose of this statement.
Idiopathic intracranial hypertension (IIH)	Patients with raised ICP of unknown aetiology fulfilling the criteria set out in figure 1.
Fulminant IIH	Patients meeting the criteria for a precipitous decline in visual function within 4 weeks of diagnosis of IIH.14
Typical IIH	Patients who are female, of childbearing age and who have a body mass index (BMI) greater than 30 kg/m2.
Atypical IIH	Patients who are not female, or not of childbearing age or who have a BMI below 30 kg/m2. These patients require more in-depth investigation to ensure no other underlying causes (table 2).15 25
IIH without papilloedema	A rare subtype of IIH16 17 and is seen in patients who meet all the criteria of definite IIH,4 seen in figure 1, in the absence of papilloedema. The criteria have highlighted the importance of a pressure greater than 25 cm CSF and the necessity for additional features, which suggest pathologically raised ICP. Features such as sixth nerve palsy and MRI imaging features indicating raised ICP should be sought (box 1).
IIH in ocular remission	Patients that have been diagnosed as IIH, and the papilloedema has resolved. These patients may have ongoing morbidity from headache, but their vision is no longer at risk while there is no papilloedema.
Experienced clinician	Refers to any clinician, in the context of this guidance, who has confidence in their own experience of managing IIH.