Cerebrospinal Fluid Leak

A cerebrospinal fluid leak is an escape of cerebrospinal fluid through a defect in the dura and skull base or spinal canal. Cranial leaks present with clear rhinorrhoea or otorrhoea and a risk of meningitis. Spinal leaks cause intracranial hypotension.

Traumatic cranial leaks follow 1 to 3% of head injuries and up to 30% of basal skull fractures. Spontaneous cranial leaks occur in about 1 in 100,000 people each year, usually in middle aged women with obesity and raised intracranial pressure.

Causes. Head trauma, skull base or sinus surgery, tumour, congenital defects, lumbar puncture and spinal procedures, idiopathic intracranial hypertension (spontaneous leaks) and erosive infection.

Course. Traumatic leaks stop spontaneously in 70% within a week; persistent or recurrent leaks risk meningitis in 10 to 25% of untreated cases for each year of leak. Spontaneous leaks seldom close without repair.

Pathophysiology.

A defect in the dura and bone, often at the cribriform plate, ethmoid roof, sphenoid or temporal bone, allows fluid to pass along a pressure gradient.

Raised intracranial pressure causes thinning of bone and arachnoid herniation (meningoencephalocele) and sustains a spontaneous leak.

• Clear, watery, salty fluid from the nose (increasing when leaning forward) or ear, often unilateral.
• Salty taste, reduced smell, headache, and a "halo" sign of staining on linen.
• Orthostatic headache and features of low pressure with spinal leaks.
• Recurrent meningitis, especially with pneumococcus, fever and neck stiffness.
• Hearing loss, a middle ear effusion or a pulsatile tinnitus with temporal bone defects.

Red flags.

• Fever, neck stiffness or confusion (meningitis).
• Pneumocephalus after trauma or surgery.
• Recurrent meningitis or a persistent leak after trauma.

• Test for beta-2 transferrin (or beta trace protein) in the fluid; glucose testing is unreliable.
• High resolution CT of the skull base to find bone defects, and MRI cisternography or heavily T2-weighted MRI to show fluid tracts and encephaloceles.
• CT or MR cisternography, or intrathecal fluorescein (specialist use), when the site is unclear.
• Lumbar puncture opening pressure in spontaneous leaks (to detect raised pressure), and assessment for idiopathic intracranial hypertension with fundoscopy and visual fields.
• Spinal imaging (MRI of the whole spine, CT myelography) for suspected spinal leaks.

Differential diagnosis. Allergic or vasomotor rhinitis, sinusitis, nasal discharge from tears, serous otitis media, otorrhoea from external otitis, spontaneous intracranial hypotension and halo of other fluid.

• Conservative care for traumatic leaks in the first week: head of bed raised 30 degrees, avoid straining, nose blowing and sneezing, and stool softeners; most close spontaneously.
• Surgical repair (endoscopic endonasal repair for rhinorrhoea, middle fossa or transmastoid repair for otorrhoea) for leaks persisting over 7 days to 2 weeks, recurrent leaks, large defects or meningitis; success is over 90%.
• Spontaneous leaks with raised pressure: weight loss, and acetazolamide 250 mg orally twice daily, increased by 250 mg every 1 to 2 weeks to a maximum of 1000 mg daily in divided doses. Monitor electrolytes, bicarbonate, renal function and kidney stones. Avoid in severe renal or hepatic impairment, hyponatraemia and sulphonamide allergy; avoid in pregnancy unless benefit outweighs risk.
• Temporary lumbar drain, or ventriculoperitoneal shunt for raised pressure, by neurosurgery.
• Meningitis: ceftriaxone 2 g intravenously every 12 hours for 10 to 14 days, with additional cover for resistant pneumococcus directed by local microbiology, plus dexamethasone 10 mg intravenously every 6 hours for 4 days started before or with the first antibiotic dose. Maximum 4 g ceftriaxone daily. Monitor renal and liver function, and neurological state. Avoid in cephalosporin anaphylaxis; reduce dose in severe renal and hepatic impairment together.
• Prophylactic antibiotics are not routinely used; give pneumococcal vaccination to patients with persistent leaks.
• Spinal leak: epidural blood patch (20 mL of autologous blood, up to 30 mL as tolerated, under imaging), or surgical repair at a specialist centre when patches fail.

Monitoring. Review at 1 week and 6 weeks after treatment; repeat imaging for recurrence; monitor weight and visual fields in raised pressure.

Referral and escalation. ENT, neurosurgery and neuroradiology for localisation and repair; urgent admission for meningitis.

Special groups. Obesity: weight loss reduces recurrence. Pregnancy: avoid acetazolamide where possible.