Raised Intracranial Pressure and the Eye

Elevated pressure within the skull (normal adult lumbar puncture opening pressure 10 to 25 cmH2O; intracranial pressure about 5 to 15 mmHg supine, below 20 mmHg) transmitted along the optic nerve sheath to the optic nerve head, producing papilloedema, and affecting ocular motor nerves and visual pathways.

• Causes: space-occupying lesions (tumour, abscess, haematoma, large infarct), hydrocephalus (obstructive or communicating), cerebral venous sinus thrombosis, meningitis and encephalitis, idiopathic intracranial hypertension, traumatic brain injury, subarachnoid haemorrhage, hypertensive encephalopathy, hepatic encephalopathy, medications and toxins (tetracyclines, vitamin A, retinoids, corticosteroid withdrawal, lithium, nalidixic acid), obstructive sleep apnoea, craniosynostosis in children, and high altitude.
• Mechanisms in the eye: axoplasmic flow stasis at the lamina cribrosa, venous congestion, and mechanical compression of the optic nerve and its blood supply.

• Headache (worse in the morning, lying down, coughing, and straining), nausea, vomiting, drowsiness, pulsatile tinnitus, and transient visual obscurations lasting seconds on standing or bending.
• Papilloedema: bilateral disc hyperaemia and swelling, blurred margins, obscured vessels at the disc, loss of spontaneous venous pulsation, peripapillary haemorrhages and cotton wool spots, Paton folds, and later pallor with gliosis (chronic atrophic papilloedema).
• Visual function: normal acuity early, enlarged blind spot, arcuate defects and constriction of peripheral fields later, and loss of acuity in advanced or fulminant disease.
• Ocular motor signs: abducens (sixth nerve) palsy, unilateral or bilateral (false localising sign); upgaze palsy (Parinaud syndrome) with hydrocephalus; setting-sun sign in infants; skew deviation.
• Pupillary signs in acute rises: unilateral dilated pupil with ptosis (third nerve compression by uncal herniation), a neurological emergency; bilateral fixed pupils indicate brainstem failure.
• Cushing triad (hypertension, bradycardia, irregular breathing) signals impending herniation.

• Dilated fundus examination, fundus photographs, optical coherence tomography (retinal nerve fibre layer thickness, disc volume), visual fields (Humphrey 24-2 or 30-2), colour vision, and motility.
• Urgent imaging: MRI brain with gadolinium plus MR venography (or CT with CT venography when MRI is unavailable) to detect mass, hydrocephalus, sinus thrombosis, and signs of raised pressure (flattening of the posterior globe, enhancement and distension of the optic nerve sheath, empty sella, transverse sinus stenosis).
• Lumbar puncture with opening pressure (lateral decubitus, legs extended; adult normal 10 to 25 cmH2O, above 25 cmH2O is elevated; children above 28 cmH2O) and CSF analysis (cells, protein, glucose, culture) once imaging excludes a mass.
• Ocular ultrasound measurement of the optic nerve sheath diameter (above 5.0 to 5.7 mm suggests raised pressure) as a bedside screening tool; transcranial Doppler and invasive intracranial pressure monitoring in neurocritical care.
• Blood pressure, renal function, thrombophilia screen, and medication review.

• Neurological emergency with impending herniation: head elevation to 30 degrees, airway and ventilation (target PaCO2 of 35 to 40 mmHg; short-term hyperventilation to 30 to 35 mmHg as a bridge), mannitol 20 percent 0.25 to 1 g/kg IV over 15 to 30 minutes (maximum osmolality 320 mOsm/kg), or hypertonic saline 3 percent 2 to 5 mL/kg over 10 to 20 minutes (23.4 percent 30 mL via central line), dexamethasone 10 mg IV then 4 mg every 6 hours for vasogenic oedema from tumour or abscess (avoid in head trauma), urgent neurosurgical review for decompressive craniectomy, haematoma evacuation, or external ventricular drainage.
• Treat the cause: tumour resection or radiotherapy, antibiotics and drainage for abscess and meningitis (ceftriaxone 2 g IV twice daily, vancomycin, dexamethasone 10 mg before or with the first antibiotic dose in suspected bacterial meningitis), anticoagulation for venous sinus thrombosis (enoxaparin 1 mg/kg twice daily, then warfarin or a direct anticoagulant for 3 to 12 months), CSF shunting for hydrocephalus (ventriculoperitoneal shunt), withdrawal of offending drugs, and weight loss for obesity-related disease.
• Chronic or non-mass pressure elevation: acetazolamide 250 mg twice daily increased up to 1 to 2 g daily (maximum 4 g) to reduce CSF production, topiramate 25 to 100 mg twice daily, and repeated lumbar puncture as a bridge.
• Vision-threatening papilloedema not controlled medically: optic nerve sheath fenestration, CSF diversion (lumboperitoneal or ventriculoperitoneal shunt), or venous sinus stenting for demonstrated stenosis with a pressure gradient.
• Monitor visual fields and optical coherence tomography every 1 to 4 weeks until stable; urgent escalation for falling acuity or field constriction.
• Counselling and education about symptoms of progression and about driving and field loss.