Idiopathic intracranial hypertension (paediatric)

What it is

IIH is raised intracranial pressure with no detectable structural, infectious, vascular or neoplastic cause. The underlying pathophysiology is incompletely understood but likely involves impaired CSF absorption at the arachnoid villi, possibly together with cerebral-venous-sinus narrowing in some patients. The clinical importance is that the resulting papilloedema can damage the optic nerve permanently if not treated — making IIH primarily a sight-preservation problem rather than just a headache problem.

How it presents

The classic picture in an adolescent girl is a daily, dull, pressure-type headache (often worse on waking, on coughing or bending forward), brief 'greying-out' visual obscurations lasting a few seconds and provoked by posture, intermittent diplopia (often from a sixth nerve palsy), and pulsatile tinnitus. Younger pre-pubertal children may present with more non-specific irritability, poor school performance, behaviour change and intermittent headaches — they often lack the typical adolescent risk factors.

Diagnosis

Examination of the fundus is the single most important step. Papilloedema is the cardinal sign — bilateral disc swelling with blurred disc margins, hyperaemia, venous engorgement, peripapillary haemorrhages and loss of spontaneous venous pulsation. Optical coherence tomography (OCT) of the retinal nerve fibre layer provides reproducible quantification.

MRI of the brain with venography is needed to exclude structural causes (mass, hydrocephalus) and cerebral venous sinus thrombosis (a key mimic). Supportive MRI features of IIH include empty sella, flattening of the posterior globe, distension of the perioptic subarachnoid spaces and partial transverse sinus stenosis — although these are not specific.

Lumbar puncture in the lateral decubitus position measures opening pressure. The 2019 Friedman paediatric criteria require opening pressure ≥28 cm H2O in children (relaxed to ≥25 cm H2O if the child is sedated, non-obese, and not Valsalva-ing). CSF composition must be normal.

Treatment

Treatment has three goals — relieve symptoms, reduce CSF pressure, and protect the optic nerves. The choice depends on the severity at presentation.

• Weight management — for adolescents with obesity, structured weight loss (5–10% body weight) often produces symptomatic and biochemical remission. Dietitian and family-centred support are essential. Avoid extreme rapid weight-loss diets, which can themselves trigger IIH
• Acetazolamide — carbonic anhydrase inhibitor that reduces CSF production. Start 250–500 mg twice daily and titrate up to 2 g/day in adolescents (paediatric dose 25 mg/kg/day in 3 divided doses, max 4 g). Side effects: paraesthesiae, taste changes, fatigue; less commonly metabolic acidosis, renal stones. Pregnancy-safety profile is reasonable
• Topiramate — second-line, useful when acetazolamide is not tolerated; has the advantage of also reducing headache; titrate slowly to 100–200 mg/day in adolescents
• Furosemide — adjunct or alternative when acetazolamide is contraindicated
• Avoid tetracyclines, vitamin A excess, lithium and growth hormone, which can precipitate or worsen IIH
• Surgical CSF diversion (ventriculoperitoneal or lumboperitoneal shunt) — for sight-threatening IIH unresponsive to medical treatment, or for severe headache. Shunt revision is common (30–50% over 5 years)
• Optic nerve sheath fenestration (ONSF) — preserves vision in sight-threatening IIH; performed by neuro-ophthalmology
• Venous sinus stenting — increasingly used in carefully selected patients with a focal venous-sinus stenosis and a measurable pressure gradient

Monitoring

Children need regular ophthalmology review for the first 6–12 months: visual acuity, formal visual fields (or pattern visual-evoked potentials if too young), and OCT of the retinal nerve fibre layer. Worsening visual function is the trigger for escalation. After remission, follow-up tapers but rarely fully stops, because relapse is recognised — particularly with weight regain.

Prognosis

With prompt diagnosis and treatment, most children retain good vision and become asymptomatic within months. Permanent visual field loss occurs in 10–25% — the strongest predictor is the severity of papilloedema at presentation. Headache may persist as a chronic post-IIH phenotype that responds to standard migraine treatments.

How an educational review can help

Families seeing daily headache, blurred vision and the prospect of a lumbar puncture are often anxious. An educational review can place the picture in the Friedman 2019 framework, explain the relative roles of acetazolamide, topiramate, weight management and surgery, and help prepare focused questions for your treating team — especially around the ophthalmology surveillance plan.

It is an educational second opinion — not a diagnosis, treatment or prescription — and it does not replace the care of your child's own clinicians.