Idiopathic Intracranial Hypertension (IIH)

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Idiopathic intracranial hypertension (IIH)\: raised intracranial pressure without intracranial mass or hydrocephalus, causing
headaches and visual disturbances.
Aetiology\: unknown; highly associated with female sex and obesity.
Pathophysiology\: Increased CSF pressure compresses retinal veins, causing papilloedema; potential mechanisms include
overproduction of CSF, out
Risk factors\: obesity, female sex, medications (e.g., contraceptive pills, tetracyclines, vitamin A, retinoids, lithium, thyroxine,
nitrofurantoin).
Symptoms\: headache, pressure-like sensation behind eyes, transient visual loss, pulsatile tinnitus, visual disturbances
(peripheral
Clinical
diplopia, normal neurological examination otherwise.
Di
obstruction, malignant hypertension, obstructive sleep apnoea.
Investigations\: MRI/CT to exclude secondary causes, lumbar puncture (elevated opening pressure >250 mmH O), blood
2
pressure check, magnetic resonance venogram, perimetry, ocular coherent tomography (OCT).
Diagnosis\: based on modi
sixth cranial nerve palsies), normal CSF composition, normal neuroimaging, no other cause of increased intracranial
pressure.
Management\:
Conservative\: weight loss, discontinue causative medications.
Medical\: acetazolamide (
Therapeutic serial lumbar punctures (temporary measure).
Surgical\: CSF diversion procedures (ventriculoperitoneal shunt preferred), optic nerve sheath fenestration (ONSF).
Complications\: permanent visual loss, especially in advanced disease; urgent surgical referral for severe cases.
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Introduction

Idiopathic intracranial hypertension (IIH), also known as benign intracranial hypertension or pseudotumour cerebri, is
de
CSF volume). This causes headaches and signi
IIH is a rare condition that a1
UK, the incidence is approximately 4.7 per 100,000 people, and its growth parallels obesity.
2
In the

Aetiology

The underlying cause of IIH remains unknown. IIH in adults is highly associated with female sex and obesity.
3Pathophysiology
Cerebrospinal
system against the surrounding bones. It is secreted by the choroid plexus in the lateral, third, and fourth ventricles. CSF
absorption mainly occurs via the arachnoid granulations when pressure exceeds the venous pressure in the sinus.
The intracranial subarachnoid space extends from the optic nerve to the back of the eyes. Increased CSF pressure
compresses the thin walls of retinal veins as they cross extensions of subarachnoid spaces to enter the optic nerve.
This causes congestion of retinal veins, bulging forward of optic discs and oedema of the discs, known as papilloedema.
Persistent papilloedema can lead to optic atrophy and irreversible blindness.
Several mechanisms have been proposed to explain the increased intracranial pressure in IIH, but the pathophysiology
remains unclear\:
4,6
Overproduction of CSF
Out
Raised pressure in venous sinuses
Dysfunction in the glymphatic pathway
Hormonal alteration

Risk factors

IIH may happen to any age group or sex, but it more commonly a
4-6
Obesity (often associated with recent weight gain)
Female sex
Medications including combined contraceptive pills, tetracyclines, vitamin A, retinoids, lithium, thyroxine, nitrofurantoin

Clinical features

History
Symptoms of IIH are usually chronic and progressive and include\:
2,4-6
Headache\: the most common clinical presentation of IIH. Usually non-speci
with nausea/ vomiting and retrobulbar pain.
A pressure-like sensation behind the eyes, typically worsens on bending forward or Valsalva manoeuvres.
Transient visual loss/blurring of vision\: usually lasts \<30 seconds, followed by full vision restoration to baseline.
Pulsatile tinnitus\: a pulse-synchronous sound classically described as a unilateral “whooshing” sound exacerbated by
lying
Visual disturbance\: commonly a
obscuration.
Ocular motility disturbance\: horizontal diplopia is reported by one-third of IIH patients, and 10-20% of them are related
to cranial nerve sixth palsy (as a false localising sign)
Clinical examination
All patients with suspected IIH should undergo a comprehensive neurological examination, which includes cranial nerves
examination (particularly second, third, fourth and sixth cranial nerves), upper limb and lower limb examination to exclude
other causes of raised intracranial pressure.
A full ophthalmic examination should include visual acuity, colour vision, pupils, visual fundoscopy.
Common clinical
4-7
Papilloedema, typically bilateral and symmetrical, is the hallmark sign of IIH; the severity of papilloedema can be
graded using the Modi
Enlargement of blind spotPeripheral visual
disease
Horizontal diplopia can occur among patients with non-localising neurological sixth cranial nerve palsy
Otherwise, a normal neurological examination
Figure 1. Retinal photograph of the right
eye showing papilloedema in a patient
with IIH

Di

IIH is usually a diagnosis of exclusion. Therefore, in the assessment of a patient with raised intracranial pressure,
secondary causes of intracranial hypertension should be considered\:
4-6
Intracranial mass lesions (e.g. space-occupying lesions, tumours, abscesses)
Increased CSF production (e.g. choroid plexus papilloma)
Reduced CSF absorption (e.g. arachnoid granulation adhesions post-meningitis, subarachnoid haemorrhage)
Obstruction of venous out
Malignant hypertension
Obstructive sleep apnoea

Investigations

Relevant investigations include\:
4-7
MRI/CT\: to exclude secondary causes of raised intracranial pressure
Lumbar puncture\: to assess CSF opening pressure taken with the patient lying in a lateral decubitus position. The
diagnosis is based on an elevated opening pressure greater than 250 mmH O and a normal CSF constituent.
2
Other investigations to exclude other secondary causes of raised intracranial pressure include\:
Blood pressure\: to exclude malignant hypertension, which is de
blood pressure >= 120mmHg
Magnetic resonance venogram of head\: to rule out venous thrombosis
Perimetry\: to assess visual
Ocular coherent tomography (OCT)\: to measure the thickness of the retinal nerve
of papilloedema

Diagnosis

The diagnosis of IIH can be made using the modi
4
Signs and symptoms of raised intracranial pressure
Absence of localising
Normal cerebrospinal
Absence of deformity, displacement or obstruction of the ventricular system and otherwise normal neuroimaging
studies
No other cause of increased intracranial pressure presentManagement
The management of IIH focuses on treating underlying disease, preserving vision, and reducing headache morbidity.
7
Conservative management
Weight loss is disease-modifying and reduces intracranial pressure and papilloedema in IIH patients.
Any causal factor that causes raised intracranial pressure should be eliminated or treated appropriately. For example,
medications which increase the risk of IIH, as listed above, should be discontinued.
Medical management
Pharmacotherapy is usually considered for patients with mild to moderate symptoms. Acetazolamide, a carbonic
anhydrase inhibitor, is believed to reduce the rate of CSF production and is the
4,7
If acetazolamide is ine
Topiramate acts as a weak carbonic anhydrase inhibitor and can suppress appetite, causing weight loss. However,
women patients should be counselled regarding the side e
teratogenetic risks.
1,4,7
Furosemide, a loop diuretic, appears to work by producing diuresis and reducing sodium transport in the brain, thereby
reducing CSF secretion. It can be given as an adjunct alongside acetazolamide in refractory cases.
4,5,6
Therapeutic serial lumbar punctures may have a role as a temporising measure to preserve vision in patients with
fulminant IIH awaiting an imminent surgical procedure. However, they are not used as a long-term treatment strategy for IIH
due to short-lived e
7,8
Surgical management
Surgical management is essential for IIH patients with rapidly declining visual function or those who failed medical
therapy to prevent permanent loss of vision. Surgical options include\:
8
CSF diversion procedures (ventriculoperitoneal is usually preferred over lumbo-peritoneal, and is the preferred surgical
procedure in the UK)
Optic nerve sheath fenestration (ONSF)
Figure 2. Diagram of a VP shunt

Complications

Permanent visual loss is the main complication, especially in advanced disease presentation. Symptomatic patients with
extensive visual

Reference

1. Raoof N, Ho
[LINK]
2. Wakerley BR, Mollan SP, Sinclair AJ. Idiopathic intracranial hypertension\: Update on diagnosis and management. Published
July 2020. Available from\: [LINK]
3. Durcan FJ, Corbett JJ, Wall M. The incidence of pseudotumor cerebri\: population studies in Iowa and Louisiana. Published
Aug 1988. Available from\: [LINK]
4. BMJ Best Practice. Idiopathic intracranial hypertension. [LINK]
5. EyeWiki. Pseudotumor cerebri (idiopathic intracranial hypertension). [LINK]6. Wall M. Idiopathic intracranial hypertension. Published Aug 2010. Available from\: [LINK]
7. European Headache Federation. Guideline on idiopathic intracranial hypertension. Published Oct 2018. Available from\:
[LINK]
8. J Neurol Neurosurg Psychiatry. Idiopathic intracranial hypertension\: consensus guidelines on management. Published Jun
2018. Available from\: [LINK]
Image references
Figure 1. DocSee04. H u m a n R i g h t E y e R e t i n a P h o t o w i t h s e v e r e P a p i l l e d e m a . License\: [CC BY]
Figure 2. Cancer Research UK. D i a g r a m s h o w i n g a b r a i n s h u n t . License\: [CC BY-SA]

Reviewer

Dr Mounika Yelisetti
ST3 Neurology

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Contents

Introduction
Aetiology
Risk factors
Clinical features
Di
Investigations
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