The brain and spinal cord are bathed in fluid known as cerebrospinal fluid (CSF). This fluid is held inside layers of connective tissue called the meninges which surround the brain and spinal cord. There are three meningeal layers: pia mater; arachnoid mater; dura mater. The outermost layer of the meninges is called the dura mater or simply dura. The dura is normally a tough connective tissue. The CSF is in the subarachnoid space, between the arachnoid mater and the pia mater layers.
This image shows the basic anatomy of the spinal cord with meningeal layers.
When the spinal dura has a hole or tear, the cerebrospinal fluid (CSF) leaks out of this enclosed space. These defects can be small or large and often result in a low volume of CSF remaining around the brain and spinal cord.
This image shows the brain, spinal cord, dura and that the cerebrospinal fluid flows around both the brain and the spinal cord in one compartment.
These dural holes or tears can be:
1. Iatrogenic – caused by a medical procedure intentionally or inadvertently. These occur at the time of a spinal tap (lumbar puncture) which is a diagnostic sampling of CSF or at the time of lumbar puncture for injection of contrast for a type of spinal imaging known as myelography. Most often these holes heal over quickly, but in some cases, they do not. Dural tears may occur inadvertently at the time of epidural (space in spinal canal outside of dura and spinal cord) injections. They may also occur at the time of surgery.
2. Traumatic – caused as a result of an injury.
3. Spontaneous – occurring with minimal or no clear precipitant. These spontaneous leaks are often associated with thinner dura than normal as is seen with a number of heritable disorders of connective tissue. A calcified intervertebral disc or bone spur may also be the cause of a dural tear.
The loss of volume of CSF around the brain and spinal cord can result in a range of symptoms with severe positional headache being the most common. Symptoms can be mild to very disabling. Often, a patient may have very limited ability to function in the upright position. A wide range of neurologic signs and symptoms may occur, and rarely, dementia, stroke, coma and even death have been reported.
The diagnosis may be suspected on the basis of symptoms. MRI of the head without and with contrast is the diagnostic imaging that should be performed in most cases. There are several typical findings seen in 80 % of cases although normal imaging does not rule out the diagnosis.
Spinal imaging including myelography is used to locate the CSF leak. This can be done using magnetic resonance imaging (MRI), computed tomography (CT) or digital subtraction imaging. Spinal imaging fails to identify leaks in about half of suspected cases due to limited sensitivity which impacts treatment options.
Initial treatment may be conservative if the symptoms are not severe. This might include bedrest, oral and IV fluids, oral and IV caffeine. Some cases resolve without any further treatment. For those that require treatment, epidural patching with autologous blood (the patient’s own blood) is the mainstay of treatment. This can be repeated a number of times. Epidural patching with fibrin glue can be directed at specific leak locations. A percentage of patients will require surgical repair by a spinal neurosurgeon.
Misdiagnosis or delayed diagnosis of spontaneous spinal CSF leak is common and is largely related to a lack of familiarity among physicians. Unfortunately, the degree of disablity may also be underestimated, contributing to a delay in appropriate diagnostic testing and treatment.
Overall, the prognosis is good for the majority of patients with appropriate diagnostics and treatments although some patients continue to have persistent symptoms despite several procedures.
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