The headache of low cerebrospinal fluid (CSF) pressure can be very severe. Its main feature is that it gets worse on sitting or standing and improves upon lying down. Sometimes, this change is quick but occasionally the headache slowly gets worse as the day goes on and is mildest or absent upon awakening in the morning.
Low CSF pressure often results from the needle going in too far during an epidural steroid injection for low back pain or epidural anesthesia during delivery or surgery. This results in the spinal fluid leaking into the soft tissues of the back. The loss of fluid causes sagging of the brain which normally floats in a thin layer of CSF. Spinal fluid leaks usually seal on their own but sometimes require a “blood patch”– injecting the patient’s blood into the area of the leak. The injected blood clots and seals the leak.
If a CSF leak happens after a diagnostic spinal tap or an epidural procedure, it is better to have the blood patch sooner rather than later. I recommend doing it if the headache persists for more than a couple of days.
Rarely, a spinal fluid leak occurs spontaneously after straining or without an obvious trigger. This condition is called spontaneous intracranial hypotension (SIH). A review of scientific reports of SIH involving over 2,000 patients by a British physician Dr. Manjit Matharu and his colleagues provides a good description of this condition. Headache was present in 99% of patients. In 2% the headache did not change with the change of position and 1% had no headache but only other symptoms.
The five most common symptoms of SIH besides headaches, were nausea, neck pain or stiffness, tinnitus (ringing in the ears), dizziness, and hearing problems.
The diagnosis can be made by an MRI scan with an intravenous injection of gadolinium, which is a contrast dye. According to Dr. Matharu’s review, however, MRI was normal in 19% of patients. A spinal tap to measure the pressure can be a useful test, although it was normal in one-third of patients. This is explained by the fact that intracranial pressure often fluctuates. In some patients, a spinal tap can make headaches worse. Another test is an MRI of the spine to detect an accumulation of the leaking CSF. This test was helpful only in a little more than half of the patients. A more advanced test done when other tests are negative and a blood patch is ineffective is a digital subtraction myelogram. So even when SIH is suspected – and often it is not – it may be difficult to prove the diagnosis.
In 28% of patients, bed rest and hydration were sufficient to heal the leak. A single or repeated blood patch was effective in 64% of patients. When the site of the leak is not found, most specialists do a blind patch at the lumbar level. A larger volume of blood, 20-30 ml is more effective than smaller volumes. In a small proportion of patients, surgical repair of the leak is necessary and it is done by a neurosurgeon.
