Idiopathic Intracranial Hypertension

A syndrome of raised intracranial pressure without a mass, hydrocephalus, venous sinus thrombosis, or abnormal CSF composition, in which papilloedema threatens vision. Annual incidence about 1 in 100,000 in the general population and 15 to 20 per 100,000 in obese women of reproductive age.

• Typical patient: obese woman aged 15 to 45 years (body mass index above 30); recent weight gain of 5 to 15 percent is a risk. Also occurs in men (with worse visual outcomes), children, and non-obese patients.
• Diagnostic requirements: symptoms and signs of raised intracranial pressure only (headache, papilloedema), a normal neurological examination except cranial nerve abnormalities, normal brain and venous imaging, normal CSF composition, and elevated opening pressure at lumbar puncture (above 25 cmH2O in adults, above 28 cmH2O in children, or above 25 in non-obese and non-sedated children).
• Drugs and conditions associated: tetracyclines (doxycycline, minocycline), vitamin A and retinoids (isotretinoin), lithium, growth hormone, corticosteroid withdrawal, oral contraceptive use (weak), thyroid and endocrine disorders, polycystic ovary syndrome, anaemia, sleep apnoea, renal failure, and transverse sinus stenosis (found in 70 to 90 percent).
• Pathogenesis is unclear: impaired venous outflow, CSF absorption, obesity-related hormonal and inflammatory mechanisms.

• Headache (about 90 percent; daily, generalised or retro-orbital, worse lying down and in the morning, migraine-like in half), transient visual obscurations (70 percent), pulsatile tinnitus (60 percent), diplopia (horizontal from sixth nerve palsy), blurred vision, photopsias, neck, back and radicular pain, and retrobulbar pain with eye movement.
• Papilloedema (nearly always bilateral, sometimes asymmetric): graded from mild (C-shaped halo, temporal sparing) to severe (disc elevation with obscured vessels, haemorrhages, cotton wool spots, and exudates), with chronic changes of optic atrophy and gliosis.
• Visual field defects (enlarged blind spot, then inferonasal loss and arcuate constriction); acuity is usually preserved until late; fulminant cases show rapid visual loss within days.
• Sixth nerve palsy in 10 to 20 percent.

• Visual acuity, colour vision, pupils, motility, automated visual fields (Humphrey 24-2 or 30-2), dilated fundus examination, fundus photographs, and optical coherence tomography of the retinal nerve fibre layer and ganglion cell layer.
• MRI brain with and without gadolinium plus MR venography: exclude mass, hydrocephalus and cerebral venous thrombosis; supportive features: empty or partially empty sella, flattening of the posterior globe, optic nerve sheath distension, tortuous optic nerves, and transverse sinus stenosis.
• Lumbar puncture in the lateral decubitus position with legs relaxed: opening pressure above 25 cmH2O, normal CSF cells, protein and glucose; remove CSF to reduce pressure to normal (up to 20 to 30 mL).
• Blood tests: full count, renal function, thyroid function, glucose, pregnancy test, coagulation screen, and screening for associated conditions.
• Differential: pseudopapilloedema (optic disc drusen), cerebral venous sinus thrombosis, tumour, chronic meningitis, and obstructive sleep apnoea.

• Aims: preserve vision and control headache.
• Weight loss: 5 to 15 percent of body weight (low-sodium diet, calorie restriction, bariatric surgery for body mass index above 35 to 40); disease remission is directly related to weight loss.
• Acetazolamide: 500 mg twice daily (extended release) increased by 500 mg every week as tolerated to 1 to 2 g daily in divided doses (maximum 4 g daily); adverse effects: paraesthesia, taste change, fatigue, nausea, kidney stones, metabolic acidosis (check bicarbonate); avoid or use cautiously in pregnancy (first trimester) and sulphonamide allergy.
• Alternatives: topiramate 25 to 50 mg twice daily (also helps weight and headache), furosemide 20 to 40 mg daily, and potassium supplements with diuretics.
• Stop contributing drugs (tetracyclines, vitamin A and retinoids, lithium); treat sleep apnoea, anaemia, and endocrine disease.
• Headache: migraine prophylaxis (amitriptyline 10 to 50 mg nightly, propranolol 40 to 160 mg daily, topiramate), and limit analgesic overuse (opioids, simple analgesics more than 15 days a month); repeated lumbar puncture only as a temporary measure.
• Fulminant or rapidly deteriorating vision (acuity decline, rapidly progressive field loss): admit; intravenous acetazolamide 500 mg, intravenous methylprednisolone 1 g daily for 3 to 5 days as a short bridge, and urgent surgery.
• Surgery for failing or severe disease: optic nerve sheath fenestration (protects vision, limited effect on headache), CSF diversion by lumboperitoneal or ventriculoperitoneal shunt, and venous sinus stenting for significant transverse sinus stenosis with a pressure gradient above 8 mmHg.
• Pregnancy: acetazolamide after the first trimester, weight control, and visual monitoring; no need for caesarean section.
• Monitoring: visual fields and optical coherence tomography every 1 to 3 months initially, until stable; long-term follow-up for relapse.
• Prognosis: most improve with treatment; permanent visual loss in about 10 percent and persistent headache in many.