Dr Melody Bacon and Dr Louise Hartley
“Dear General Paediatric Colleague, I would be grateful if you could urgently review Sam, a 14 year old boy who has been complaining of blurred vision and headaches. His headache tends to get worse when he bends over and is not relieved by over the counter analgesia. He has been reviewed by a local optician who is concerned he may have papilloedema. He is otherwise healthy.”
You review Sam in clinic. He is completely well and has no other symptoms. He weighs 100kg. His neurological examination is normal except you are unsure whether you can identify papilloedema. You arrange an urgent MRI, which is normal, and refer Sam to paediatric ophthalmology, who confirms papilloedema. Routine bloods: FBC, U&E, LFT, Bone profile, CRP are normal.
What are the causes of raised intracranial pressure?
- Space occupying lesion – red flags for brain tumour can be found here
- Cerebral oedema
- Pseudotumor cerebri (PTCS)
- Secondary (e.g. venous thrombosis)
What is Idiopathic Intracranial Hypertension?
Idiopathic Intracranial Hypertension (IIH), also known as Benign Intracranial Hypertension (BIH) or Pseudotumour Cerebri (PTCS), is a condition where there is increased intracranial pressure (ICP) without a space-occupying lesion or hydrocephalus and with a normal cerebrospinal fluid (CSF) composition. IIH is a very rare disorder and frequently misdiagnosed. It occurs in about 0.71 per 100,000 per year in those under 16 years old, mostly affects children between ages 10 – 16 years old, and obesity is a major risk factor. Pre-puberty, boys and girls are equally affected but post-puberty, it is more common in females.
Why does it happen?
Why it happens is, like a lot of neurological conditions, largely unknown. There are theories based on neuroradiological and/or CSF hydrodynamic studies done on humans and animals. Some of these theories suggest it may be related to too much CSF being produced, or not enough CFS being absorbed, or that the blood flow to the brain is increased or not draining properly.
How does it present?
The most common features are headache and visual disturbance. Headaches are often described as frontal, throbbing, worse with supine posture, bending over, coughing/straining. The visual disturbances they get is often transient visual loss, blurred vision, or seeing double. Papilloedema will invariably be present. Don’t get caught out though because it can be bilateral as it can be unilateral. Sometimes patients will also complain of pulsatile tinnitus: “throbbing in my ear”. Rarely it can also present with back pain, dizziness, neck pain, cognitive disturbances, radicular pain, or even VI nerve palsy (occasional III or IV nerve paresis).
How do we make a diagnosis?
The full diagnostic criteria can be found here. Below is a brief summary:
- Normal neurological examination (except VI nerve palsy)
- Neuroimaging: normal brain parenchyma (no hydrocephalus, mass, structural lesion, or meningeal enhancement) and venous thrombosis excluded in all
- Normal CSF constituents
- Elevated LP pressure ≥ 25cmCSF in non-obese and un-sedated, ≥ 28 cmCSF in obese and/or sedated
- IIH without papilloedema (IIHWOP) diagnostic criteria
- Presence of criteria 2-5 for IIH + unilateral or bilateral VI cranial nerve palsy
MRI or CT head for IIH are essentially normal but below are some typical features you might see.
Back to our patient Sam: you decide to call the paediatric neurology team, who advises you do a lumbar puncture with opening pressure as unfortunately there are no services in the area that can do CSF studies.
CSF in IIH
CSF opening pressure
- Measure CSF opening pressures in the left lateral decubitus position. However, in some instances you may find that the only way to be successful is to insert the needle whilst they are sitting forward and then place them in the left lateral decubitus position.
- When lumbar puncture opening pressure is measured under general anaesthetic, it is important to record a normal end‐tidal pCO2.
- Lumbar puncture is a single-point measurement and hence it may not be a reliable evaluation of intracranial pressure. Opening pressures are variable over time:
- LP opening pressures are raised if
- Crying / struggling
- Hypoventilating (raised pCO2)
- Sedated or under general anaesthetic
- Measured in the sitting position
- LP opening pressures are lowered if
- Hyperventilating (lowers pCO2)
- LP opening pressures are raised if
- There are conflicting data on the normal CSF opening pressures in children.
- In adults, a pressure > 25 cm H2O (∼18 mm Hg) is considered high.
- In a recent study of children <18 years of age, the 90th centile for CSF opening pressure was 28 cm H2O (∼21 mm Hg) in obese or sedated children, and 25 cm H2O for non-obese non-sedated children.
CSF infusion studies
- A CSF infusion study helps to assess hydromechanical properties of the CSF system.
- During the infusion test, a LP is performed with CSF pressure (CSFp) monitoring, with measurement of a baseline, longer term CSFp. If the pressure is below ~30 mmHg, sterile CSF like fluid is infused via the spinal needle.
- Lumbar puncture
- Infusion pump
- Pressure is read by pressure monitor
- Computer with specific software
Image from: https://www.nice.org.uk/guidance/ipg263
- In adults and children, the assessment of average CSF pressure over more than 20 minutes, ‘steady state’, is reported to be more reliable than a single opening pressure measurement using the height of a fluid column.
- The resultant pressure-volume data can be analysed to give the CSF dynamics and variables such as the pulse amplitude of ICP, the compensatory reserve, and the magnitude of slow waves of CSFp as shown below:
The paediatric neurology team kindly accept to do this under ketamine sedation. The lumbar puncture opening pressure is 54cm, enough CSF is removed to bring the pressure to 20cm. CSF MC&S is normal. Almost immediately Sam says he feels much better but still has a mild headache.
How do we manage IIH?
- The 2015 Cochrane review concluded that there is no current consensus on the best management strategy for IIH.
- There are 2 main goals for management
- Preserve visual function
- Alleviate symptoms of raised ICP
- The best approach to manage IIH in children is through a MDT that includes a paediatrician, paediatric neurologist, ophthalmologist, orthoptist, and neurosurgeon.
If a child remains symptomatic after diagnostic lumbar puncture the following are the treatment options:
|CSF shunting – ventriculoperitoneal shunt |
or lumbo-peritoneal shunt
Venous sinus stenting
Optic nerve fenestration
- The length of treatment varies and may last, in some cases, 9–14 months.
- Weaning should be considered as soon as improvement is evident.
- A detailed description of each treatment, including mode of action, dose, and side effects can be found here.
In all cases, whether asymptomatic or symptomatic, paediatric ophthalmology and neurology follow up is essential.
If medical therapy fails, is not tolerated, or there is fulminant IIH, more aggressive measures should be considered. The decision regarding the choice of surgical procedure often depends on local expertise and the patient’s morbidity. Interventional radiology is also an option and there is increasing experience in children as well as in adults, of endovascular stenting of a stenosed or narrowed transverse sinus.
The neurology team decide to start Sam on Acetazolamide 500mg BD. However the parents ask you will this happen again ?
What is the outlook?
The outlook tends to be good with complete resolution of symptoms in most children with mild to moderate visual disturbance. The more severe the papilloedema, the higher the risk of visual loss or blindness.
3 months later, Sam is reviewed in the neurology and ophthalmology clinic. He feels much better with no headache or visual symptoms. The papilloedema has resolved. The decision is to wean the acetazolamide and on further review he gets discharged.
Take Home Messages
- IIH is a rare condition without a space-occupying lesion or hydrocephalus and with a normal cerebrospinal fluid (CSF) composition.
- It is often misdiagnosed, however early diagnosis and treatment are imperative to prevent permanent visual loss.
- Where possible, it is better to do CSF dynamic studies over a single lumbar puncture opening pressure reading.
Dr Melody Bacon is a paediatric registrar with special interest in Neurology at the Royal London Hospital, consultant review by Dr Louise Hartley, consultant in Paediatric Neurology at the Royal London Hospital
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