Idiopathic Intracranial Hypertension
Introduction
Idiopathic Intracranial Hypertension (IIH) a.k.a. Pseudotumor Cerebri is a disorder characterised by increased ICP, papilloedema, normal CSF and normal CT/MRI. Patients generally present with complaints of headache, nausea/vomiting +/- visual disturbances. It is a condition that primarily affects overweight females of child bearing age. The pathogenesis of IIH is unknown.
Clinical Features
Symptoms
Non-specific Headache is the most common symptoms
May be retro-orbital, lateralizing or throbbing, Intermittent or persistent, often daily, maybe exacerbated by changes in posture
Nausea or vomiting asctd with headache
Ophthalmalgia
Visual Disturbance
Transient obscurations or brief flashes of light are most common. Lasts seconds at a time. Can be uni or bilateral. May be precipitated by change in position, eye movements, bright lights or valsalva
Vision loss in severe cases. Can be insidious or rapid in onset
Horizontal diplopia due to unilateral of bilateral CN VI palsy secondary to elevated ICP
Pulsatile Tinnitus
Signs
Papilloedema
Hallmark of IIH. Usually bilateral and symmetric but not always.
Vision Loss
Visual field loss occurs first (nasal loss or temporal loss). Decrease in visual acuity
CN VI Palsy
may be unilateral or bilateral. Occurs secondary to elevated ICP affect on the abducens nerve which has as long intracranial course before it exits the skull.
Other CN palsies are rare but have been reported.
Differential Diagnosis
The presence of papilloedema indicates the presence of increased intracranial pressure. Elevated ICP may be idiopathic but other causes need to be outruled prior to this diagnosis being made. There are also several causes of unilateral or bilateral swollen optic discs, which has a similar appearance to papilloedema
Secondary Intracranial Hypertension
Intracranial mass - Tumour, blood, abscess, cerebral oedema
Obstruction of Venous Outflow
e.g. venous sinus thrombosis, jugular vein pathology or compression.
Obstruction of CSF outflow i.e. Hydrocephalous
Decrease CSF absorption e.g. infectious meningitis, SAH
Increased CSF production e.g. choroid plexus papilloma
CVS disease
Hypertension, RVF, Pulmonary htn
Resp Disease
sleep apnoea, COPD
Papilloedema
Papilloedema occurs when raised ICP is transmitted to the optic nerve sheath.
Other causes of bilateral optic disc abnormalities
congenital anomalies, malignant hypertension, diabetes, hypoptension, toxic optic neuropathies e.g. methanol toxicity, severe thyroid eye disease
Causes of unilateral optic disc abnormalities
Ischaemic - Anterior ischaemic optic neuropathy e.g. giant cell arteritis, CRVO
Inflammatory - Optic Neuritis
Infiltrative - e.g. Sarcoidosis
Clinical Investigations
When a patient presents with symptoms or signs of increased ICP, our initial priority in the ED is to out-rule any potential life threatening causes.
Bedside
ECG
ECG changes due to raised ICP most commonly seen in massive ICH
Most common changes are widespread TWI and QT prolongation.
BHCG in women of child bearing age
VBG - Assess for metabolic, electrolyte, glucose disturbances
Laboratory
FBC - exclude anaemia as a contributory cause
U&E - if concerned for hypertension as cause of sx assess for evidence of hypertensive nephropathy
LFT - ? hepatic encephalopathy
TFTs - exclude hypothyroidism as contributory cause
Lumbar Puncture
Elevated opening pressure > 25cm H20 is an essential element of diagnosis. Otherwise CSF analysis is normal
Radiology
CT/MRI Brain
Neuroimaging is primarily used to out-rule central cause of secondary intracranial hypertension
Brain and ventricles appear normal in patient with IIH but there may be some nonspecific signs on CT or MRI that can favour the diagnosis
Visual Field testing
Formal visual testing should be arranged to assess the severity of optic disc involvement
Management & Dispostion
Resuscitation
Patients conscious state remains normal. If a patient presents with a decreased GCS it should prompt urgent investigation for alternative cause of raised ICP
Symptomatic Management
Simple analgesia - be cognitive of analgesic overuse headache
Headache prophylaxis
Anti-emetics PRN
Specific Treatment
A small subset of patients may present with rapidly progressing vision loss. Permanent vision loss is the main cause of significant morbidity. It’s presence should lead to aggressive interventions and early specialist involvement
Carbonic anhydrase inhibitors i.e. Acetazolamide
are believed to reduce rate of CSF production
Loop Diuretics e.g. furosemide, may be necessary if CAI alone not sufficient.
Address risk factors and co-morbidities
weight loss, treat anaemia, hypothyroidism. OCP may contribute
Severe or advanced cases may require surgical intervention
e.g. CSF shunting, optic nerve sheath fenestration
Serial lumbar punctures and lumbar drains no longer routinely recommended
Dispostion
All patients with vision loss should be admitted under Medicine/Neurology for urgent treatment and stabilisation
If the diagnosis is unclear patients should be admitted until more sinister pathology is outruled
Will need regular Ophthalmology follow up
Will need follow up with neurology +/- headache clinic
References
https://commons.wikimedia.org/w/index.php?curid=16115920 By Jonathan Trobe, M.D. - University of Michigan Kellogg Eye Center - The Eyes Have It, CC BY 3.0
Lee AG, Wall M. Idiopathic Intracranial hypertension (pseudotumor cerebri): Clinical features and diagnosis. www.uptodate.com
Case courtesy of Dr Sajoscha A. Sorrentino, Radiopaedia.org, rID: 16023
Dunn et al. The Emergency Medicine Manual, 5th Edition, Vol 1.
This blog was written by Dr Deirdre Glynn and was last updated in June 2022
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