What is low CSF pressure headache?
Low cerebrospinal fluid (CSF) pressure headache is caused by an internal spinal fluid leak and may range from obvious and disabling to subtle and nagging. The brain normally sits inside a “bag” filled with spinal fluid that extends down from the skull into the spine. The “bag” consists of membranes called the meninges (as in meningitis). The fluid helps to circulate waste products out of the brain and provides cushioning and support. When the pressure of this fluid is too low — typically when there is a small leak somewhere in the meninges — the brain may “sag” downward when the patient is upright, stretching the meninges and nerves lining the brain and causing pain.
What are the symptoms of low pressure headaches?
The classic symptom is a headache that becomes severe when the patient is upright and quickly disappears when the patient is lying flat. So, the headaches are typically absent first thing in the morning, and start or worsen shortly after getting out of bed. The pain is often worse at the back of the head, and may be accompanied by some neck discomfort and nausea. Rarely there are more serious neurological symptoms caused by stretching nerves or the downward displacement of the brain.
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What causes low pressure headaches?
In most cases, there is an obvious cause of the leak, such as a spinal tap, spinal surgery, or trauma to the head or neck. In cases when postural headaches develop shortly after an obvious potential cause, diagnosis is usually easy to make. Subtle cases can be trickier to diagnose. There may be no obvious precipitating event, or perhaps the leak was caused by a sneeze, a violent cough, or some other unrecognized minor trauma. Some patients — particularly those with hyperflexibility of the joints — may be born with meninges that are more susceptible to tearing with relatively small degrees of force.
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How are low pressure headaches diagnosed?
The condition may be frustrating to diagnose even when the cause is strongly suspected, particularly in the less dramatic cases.
Brain MRI with injected contrast dye may reveal “enhancement” of the meninges lining of the brain and sometimes indicate evidence of the brain “sagging” downward from the skull toward the neck. MRI of the neck and back occasionally reveals spinal fluid leaking out of its normal location.
Computed tomography (CT) myelogram (a CT scan of the back after dye is injected into the spinal fluid) may reveal the site of the leak directly.
CSF cisternogram — a procedure in which a radioactive dye is injected in the spinal fluid and detected by a special radiation-detecting camera — may reveal the leak directly, or may only show indirect evidence of the leak’s presence but not its exact location.
Lumbar puncture (spinal tap) may reveal lower than normal spinal fluid pressure, but might increase the severity of the symptoms temporarily.
Sometimes we are 100 percent sure a leak is lurking somewhere but may be unable to find it with any test.
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How are low pressure headaches treated?
Treatment usually begins conservatively — with strict bed rest, increased fluid intake, and caffeine (either in drink form or by pill). If this cautious approach fails to result in closure of the hole, an epidural “blood patch” may be performed. In this procedure, the patient’s own blood is removed from a vein with a syringe and injected into the spine, either at the exact site of the leak or at a safe location in the low back. Often a blood patch results in rapid plugging of the hole and nearly immediate relief of symptoms. This procedure may need to be repeated a few times to be successful.
If the exact site of the leak is known, an interventional radiologist can sometimes “glue” the hole using a needle under X-ray guidance. Sometimes a neurosurgeon is needed to repair larger tears found in the spine, or a neurosurgeon or otolaryngologist (ENT) must fix leaks inside the skull.
Our Johns Hopkins anesthesiologists and pain specialists can perform the epidural blood patches. We work closely with neurosurgeons and otolaryngologists who can perform surgical repairs, and we have world-class interventional neuroradiologists who can perform targeted gluing of leaks under X-ray guidance.
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