Conditions

Cerebrospinal Fluid Leak

Also known as: CSF leak · Spinal fluid leak · CSF otorrhea

A cerebrospinal fluid leak occurs when the membrane containing the fluid around the brain is breached, allowing fluid to escape through the ear or nose. Because an open pathway to the brain carries a risk of meningitis, CSF leaks are treated rather than observed.

What it is

The brain and spinal cord are surrounded by cerebrospinal fluid, contained by a membrane called the dura. A cerebrospinal fluid leak occurs when both the dura and the bone that supports it are breached, allowing fluid to escape into an adjacent air-filled space.

When that breach is in the temporal bone — the bone housing the ear — fluid drains into the middle ear and mastoid. From there it either escapes through a perforated eardrum as clear drainage from the ear, or, with an intact eardrum, passes down the Eustachian tube and presents as clear watery drainage from the nose. This second pattern is a common source of diagnostic confusion, because the fluid appears at the nose while the actual defect is in the ear.

Sometimes brain covering, or brain tissue itself, herniates through the bony defect. This is called an encephalocele, and it is often found alongside the leak.

Causes

Spontaneous leaks occur without any injury or prior operation, and have been increasingly recognized over the past decade or two. They are strongly associated with chronically elevated intracranial pressure, which thins the bone of the skull base over years until a defect develops. Contributing factors include elevated body mass index, obstructive sleep apnea, and radiographic findings such as an empty sella. These leaks are frequently found at thin areas of the tegmen, the bony roof of the middle ear and mastoid.

Acquired leaks follow a specific event:

  • Surgery on the ear or lateral skull base
  • Head trauma, particularly temporal bone fractures
  • Chronic ear disease, especially cholesteatoma that has eroded through the roof of the middle ear
  • Tumors that erode the skull base

Symptoms

  • Clear, watery drainage from one ear, or from one side of the nose, sometimes worse when bending forward or straining
  • Aural fullness or a sensation of fluid in the ear
  • Hearing loss, typically conductive, from fluid filling the middle ear
  • Headache, which may be positional
  • Pulsatile tinnitus, particularly when elevated intracranial pressure is involved
  • Meningitis — fever, severe headache, neck stiffness, and light sensitivity — which is sometimes the first presentation and requires immediate care

A patient with unexplained recurrent meningitis should be evaluated for an occult skull base defect.

Diagnosis

Beta-2 transferrin testing on a sample of the fluid is the standard confirmatory test. The protein is essentially unique to cerebrospinal fluid, so a positive result establishes the diagnosis.

High-resolution CT of the temporal bone identifies the bony defect and its precise location, which is essential for surgical planning. MRI demonstrates whether soft tissue — meninges or brain — has herniated through the defect, and distinguishes an encephalocele from simple fluid.

Because spontaneous leaks are associated with raised intracranial pressure, evaluation often extends to that question, and may include assessment for sleep apnea and, in some cases, measurement of the pressure itself.

Treatment

Surgical repair is the definitive treatment for spontaneous leaks and for acquired leaks that do not close with conservative measures. The defect is sealed using a multilayer reconstruction, and any herniated tissue is addressed. The approach depends on the location and size of the defect:

  • Transmastoid, working through the mastoid bone behind the ear
  • Middle cranial fossa, approaching from above the ear to expose the roof of the temporal bone directly
  • A combined approach, for large or multiple defects

Multiple defects are common in spontaneous cases, since the same process that thinned the bone in one place has usually thinned it elsewhere. Surgical planning accounts for this.

Managing the underlying pressure matters for durability. When elevated intracranial pressure is contributing, addressing it — through weight management, treatment of sleep apnea, medication, or in some cases a shunt — reduces the likelihood of a repair failing or a new leak developing at another thin spot.

Common questions

How do I know whether the fluid is spinal fluid and not just ear drainage?

Cerebrospinal fluid is typically clear, thin, and watery rather than thick or discolored, and the drainage may increase when you lean forward or strain. It cannot be confirmed by appearance alone. A sample can be tested for beta-2 transferrin, a protein found in cerebrospinal fluid and almost nowhere else, which makes the diagnosis definitively.

Why is a CSF leak considered serious?

A leak means there is an open channel between the space around the brain and the ear or nose, which normally has bacteria in it. That pathway allows bacteria to travel inward, creating an ongoing risk of meningitis. Repairing the leak closes the pathway.

Can a CSF leak heal on its own?

Some leaks following trauma or surgery close with conservative measures such as bed rest, head elevation, and sometimes temporary drainage of spinal fluid. Spontaneous leaks — those arising without an obvious injury — rarely resolve permanently on their own and usually require surgical repair.

Is a CSF leak related to my weight or headaches?

It can be. Spontaneous leaks are frequently associated with chronically elevated intracranial pressure, which is itself associated with elevated body mass index and can cause headaches and pulsatile tinnitus. When that underlying pressure is present, addressing it is part of preventing the leak from recurring after repair.

Where can I be evaluated for a CSF leak in Colorado?

Cerebrospinal fluid leaks of the temporal bone and lateral skull base are evaluated and repaired by Dr. Ashley Nassiri at UCHealth University of Colorado Hospital, on the University of Colorado Anschutz Medical Campus in Aurora, Colorado, in the Denver metropolitan area. She is a fellowship-trained neurotologist and skull base surgeon, and appointments are arranged through UCHealth.

Related

Cholesteatoma Temporal Bone & Lateral Skull Base Tumors Hearing Loss

Where this care is provided

Dr. Ashley Nassiri is a fellowship-trained neurotologist and skull base surgeon at UCHealth University of Colorado Hospital, on the University of Colorado Anschutz Medical Campus in Aurora, Colorado, in the Denver metropolitan area. Patients seeking evaluation for a cerebrospinal fluid leak can schedule by calling the clinic below or through UCHealth. There is also an overview of what a neurotologist treats and when to ask for a referral.

Call 720-848-2820 UCHealth provider page

UCHealth Ear, Nose and Throat Clinic – Anschutz Outpatient Pavilion, Aurora, Colorado

This page provides general information about a medical condition or procedure and is not medical advice. It is not a substitute for evaluation by a qualified clinician, and it cannot account for the specifics of any individual case. If you have symptoms that concern you, seek care directly.