Diagnosing a Cerebrospinal Fluid (CSF) Leak

What is a CSF leak?

The brain and spinal cord are protected by three membranes (meninges). When the outermost layer of the meninges, the dura, is injured or punctured — often as a result of a head injury, certain medical procedures, or an increase of pressure in the skull — a cerebrospinal fluid (CSF) leak may occur. Cerebrospinal fluid is a clear liquid that flows in and around the brain and spinal cord to protect from injury and transfer nutrients.

Cerebrospinal fluid leaks are categorized according to the location of the leak: Spinal CSF leaks originate from the dura around the spinal column, whereas cranial CSF leaks originate from the dura around the skull. Symptoms of a CSF leak vary and may include headache, tinnitus, nasal drainage, ear drainage, dizziness, nausea, and/or behavioral changes.

Diagnosing a CSF leak

The diagnostic process for a CSF leak typically begins with a physical examination and medical history. If a CSF leak is suspected, certain diagnostic tests may be ordered, including the following:

Cranial CSF leak diagnostic tests

• Nasal fluid analysis
  Beta-2 transferrin is a protein found almost exclusively in cerebrospinal fluid. Diagnosis of CSF can be confirmed if a nasal fluid analysis tests positive for this protein.
• Magnetic resonance imaging (MRI) with contrast
  An MRI scan uses strong magnetic fields and radiofrequency currents to create detailed images of tissues, organs, bones, and nerves. An MRI of the brain with contrast involves the injection of a contrast agent (gadolinium) before the scan is done. The contrast agent helps show irregularities in the brain and determine the location of a CSF leak.
• CT cisternogram/cisternography
  A cisternogram, or citernography, may be ordered to determine the precise location of a cranial CSF leak in the skull base. Contrast is injected into the spinal column via a spinal tap, and a CT scan is performed.
• Pledget study
  A pledget study can be performed to determine whether CSF is leaking into the nose or mastoid through a break in the bone at the base of the skull. This test involves the injection of a radioactive tracer into the spinal fluid via a spinal tap. Small cotton pads (pledgers) are placed in the nose to collect fluid. After several hours, they are extracted and tested for the presence of radionuclide. A positive test indicates a cranial CSF leak.
• Tympanometry
  A tympanomety involves inserting a tympanometer (a handheld device with a probe) into the ear to determine if fluid is present and to measure middle ear function. Clear fluid in the ear may indicate a cranial CSF leak.

Spinal CSF leak diagnostic tests

• Radioisotope cisternogram
  Similar to a CT cisternogram, a radioisotope cisternogram measures the CSF pressure before injecting a chemical into the space around the spinal cord via a spinal tap. In the next 24 hours, several images are taken to monitor any changes in the flow of CSF, which may indicate the presence of a leak.
• Magnetic resonance imaging (MRI) with contrast
  An MRI scan uses strong magnetic fields and radiofrequency currents to create detailed images of tissues, organs, bones, and nerves. An MRI of the spine with contrast involves the injection of a contrast agent (gadolinium) before the scan is done. The contrast highlights tissues and shows changes in the spine in greater detail, which helps determine the location and severity of a CSF leak.
• Myelogram/myelography
  A myelogram, or myelography, involves the injection of a contrast agent into the spinal column via a spinal tap before detailed images via X-rays or CT scan are obtained. This can detect the precise location of a CSF leak.