A 3-year-old girl presents with acute onset convergent strabismus. Fundoscopy examination reveals papilloedema.
What are the next steps in the management of their daughter?
First thoughts – is this a space-occupying lesion? If you haven’t seen it already, please check out HeadSmart. It details presentations commonly associated with a brain tumour in each age group. Strabismus alone is a rare sign of a brain tumour in this age group; however, the associated papilloedema is concerning.
The fact that fundoscopy has been carried out on this child is a feat. It is often difficult to do this in an ED setting. Still, many departments have access to eye clinics or on-call ophthalmology with better equipment and a nicer setting, making getting a good view of the fundus easier. Papilloedema may be a sign of raised intracranial pressure and is worrying. This child needs imaging urgently. MRI is the modality of choice.
In this case, the MRI did not show a space-occupying lesion, and neither did it show hydrocephalus. What could be going on?
What is Idiopathic Intracranial Hypertension (IIH)?
Idiopathic intracranial hypertension (IIH) is a condition where there is increased intracranial pressure (ICP) in the absence of a space-occupying lesion, hydrocephalus and with normal cerebrospinal fluid (CSF) composition. Previously called benign intracranial hypertension, this misleading title was dropped. Many of the symptoms are not benign, including a loss in visual acuity, and the ‘idiopathic’ term helps us understand that this is a diagnosis of exclusion.
IIH is rare in children. The median age is 12 years. The estimated UK annual incidence is 0.8 per 100,000 child population (1.0 for girls and 0.5 for boys). Obese girls are the most at risk, with a higher incidence in the USA thought to be linked to an increase in rates of obesity. The cause of IIH is still unknown, with various hypotheses suggesting excess CSF production, CSF outflow reduction, an increase in cerebral blood volume or an obstruction to venous drainage.
How is IIH diagnosed?
Below are the criteria for diagnosing IIH:
If there is no papilloedema, you can still make the diagnosis if features 2-5 are present and if the patient has unilateral or bilateral abducens nerve palsy. The diagnosis can only be suggested, but not confirmed, if there is no papilloedema or sixth nerve palsy, but 2–5 from above are present, plus markers of raised ICP on imaging.
A lumbar puncture (LP) with manometry is required to diagnose IIH. However, this must only be performed once neuroimaging has been carried out. An intracranial abnormality and/or elevated ICP could risk brain herniation.
How do you perform LP manometry?
Before performing the LP, consent should be obtained, which should include highlighting any complications such as:
- post-LP headache (although reduced in those with IIH as performing an LP has therapeutic benefits of decreasing the ICP)
- pain at the site of needle insertion
- failure to obtain a sample and the need to repeat (this is the one we emphasise the most as it is the most common and can cause distress to parents)
- Potential to introduce infection (however, performing the procedure under sterile conditions limits this)
- Bleeding at the site (taking blood tests for clotting and platelets before proceeding is imperative)
- nerve root irritation (rare)
- cerebral herniation (very rare)
Ensure the equipment is assembled and ready before proceeding. The manometer has a 3-way tap; it is important to ensure this is not too tight to open after insertion. Stackable columns should be assembled under sterile conditions before starting the procedure.
Perform the lumbar puncture with the child in a lateral decubitus position, aiming for the L3-4 or L4-5 interspace.
Avoid flexing the hips too much, and keep the neck in a neutral line.
Once the needle has been inserted, remove the stylet and attach the 3-way tap on the manometer as quickly as possible once the stylet is withdrawn, with the manometer pointing upwards.
Open the 3-way tap to the patient and watch while the monometer column fills. Once the level stabilizes, take that reading as the opening CSF pressure. CSF samples can then be taken, and some excess CSF can be removed to reach a normal value.
If the open pressure is exceptionally high (e.g., 60 cmH20), aim to reduce the pressure to around 30 cmH2O to avoid significant headaches.
- Open the three-way valve to the patient and manometer. Note the manometer is orientated perpendicular to the ground in two planes.
- Close the three-way valve to the patient to drain CSF from the manometer.
- Close the three-way tap to the manometer to collect samples.
A general anaesthetic can affect the CSF pressure, increasing it by 5-10 mmHg. If you cannot avoid a general anaesthetic, monitor the end-tidal CO2 and aim for normocarbia. Hypercapnia can cause an elevation in CSF pressure.
How do we manage paediatric IIH?
Our goals are to save vision and provide symptomatic relief from the effects of raised ICP. Close follow-up with paediatric ophthalmology and neurology teams is essential.
The first-line medical management is acetazolamide, a carbonic anhydrase inhibitor, which acts by reducing CSF reduction. The success rate is between 47-67%. Acetazolamide can cause metabolic acidosis and electrolyte disorders, especially in the high doses needed in some IIH patients. Topiramate is a weak carbonic anhydrase inhibitor and is effective in adults. It can be combined with acetazolamide for an add-on effect.
Furosemide is the second-line treatment and is likely effective due to diuresis. Long-term use may lead to electrolyte imbalances; hence, some reservations about its use exist. In the short term, steroids may be combined with acetazolamide and are reserved for those with severe visual failure.
Surgery may be considered when medical treatment fails or acute visual deterioration and debilitating headaches occur. Surgical options include:
- CSF shunting
- Subtemporal decompression
- Venous sinus stenting to allow better drainage of cerebral blood
- Optic nerve fenestration. This allows CSF to leak out and decreases the pressure on the optic nerve.
No surgical technique is better, and careful MDT discussions are needed.
Archives of Disease in Childhood – Education and Practice Published Online First: 20 January 2023. doi: 10.1136/archdischild-2022-324881
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Moavero Romina, Sforza Giorgia, Papetti Laura, et al Clinical Features of Pediatric Idiopathic Intracranial Hypertension and Applicability of New ICHD-3 Criteria Frontiers in Neurology, Vol 9 2018 DOI 10.3389/fneur.2018.00819 ISSN 1664-2295