Idiopathic Intracranial Hypertension (IIH) is a rare disease, primarily affecting overweight females of child-bearing age. Patients suffer from increased intracranial pressure (ICP), typically resulting in headaches, visual disturbances and bilateral papilledema, pulsatile tinnitus and cognitive deficits. The disease is difficult to diagnose, treat and monitor. The only current method of measuring the ICP in day-to-day clinical practice is by lumbar puncture. This procedure is invasive, and often painful for the patient. There is an unmet need of methods that can reliable measure or estimate ICP in a non-invasive manner. Ultrasound is one such potential method, and the aim of this study is to investigate the use of ocular ultrasound and transcranial doppler to measure or estimate ICP.

This study is a prospective cohort study. Investigators plan to include 50 patients in whom the IIH-diagnosis is suspected. Patients are referred from general practitioners, neurologists or ophthalmologists to the Danish Headache Center or admitted to the Neurology ward when the IIH diagnosis is suspected.

As part of an established routine clinical work-up to establish the diagnosis of IIH, all patients will undergo (according to the Friedman criteria) the following examinations:

A)

1. An interview (history taking) and clinical examination
2. Routine laboratory tests (blood tests)
3. Ophthalmological examination
4. Lumbar puncture with measurement of the ICP
5. Magnetic resonance imaging (MRI) of the brain

Additionally the following investigations will be performed at baseline (before and after lumbar puncture):

B) Transorbital sonography (TOS) C) Transcranial Doppler When the patient is seen at the clinic for their regular follow-up visits the same measurements will be done.

A control group of healthy participants (NR=25) will be included in whom TOS (B) and TCD (C) will be performed in order to compare the values between the patient group (IIH) and control group. Controls will be included to match the patients according to BMI, age and gender.

All ultrasound images- and films will be saved, and evaluated by a blinded investigator.

PATIENT GROUP (ARM 1):

Inclusion Criteria:

• Age 18-65
• Patients in whom the IIH diagnosis is suspected/or confirmed
• The diagnosis of migraine with or without aura or tension-type headache is allowed as a comorbid headache type.
• Participants must read and understand the Danish language, or have an official interpreter present to be able to understand the work-up and sign the participation consent for the study

Exclusion Criteria:

• Pregnant or breastfeeding females
• Patients who do not need a diagnostic lumbar puncture at the time of evaluation
• Patients treated with acetazolamide, topiramate or furosemide for IIH or suspected IIH before inclusion in the study (baseline)
• Any other primary or secondary headache diagnosis than migraine with or without aura or tension type headache as a comorbid disorder
• Patients in whom the examination cannot be performed due to anatomical reasons such as severe head dysmorphia or severe ophthalmological diseases
• Participants with secondary causes of raised intracranial pressure, or patients that have been treated for such (e.g. brain tumor, hydrocephalus, stroke or severe head injury)
• Participants with known atherosclerotic disease or known heart disease

CONTROL GROUP (ARM 2):

Inclusion criteria:

• Age 18-65
• Healthy persons who do not suffer from any form of primary headache except infrequent tension-type headache
• Participants must read and understand the Danish language or have an official interpreter present to be able to sign the participation consent for the study.

Exclusion criteria:

• Pregnant or breastfeeding females
• Participants in whom the examination cannot be performed due to anatomical reasons such as severe head dysmorphia or severe ophthalmological diseases