The Mechanism of Postpuncture Headache
Postpuncture headache occurs in perhaps 20 per cent of patients who have had a diagnostic lumbar puncture. It usually begins within 12 hours of the lumbar puncture. The headache is occipital, or occasionally frontal, and appears within a short time after the patient assumes the erect position. Associated symptoms may be nausea or stiffness of the neck. The headache is very distressing and usually incapacitating but is relieved almost immediately by lying down.
The condition is usually ascribed to a loss of cerebrospinal fluid through the needle puncture wound in the dura which removes the fluid cushion supporting the brain, and allows the brain to settle in the cranial cavity causing traction on the nerves, blood vessels, and dura. The headache appears shortly after the patient assumes the erect posture because with this change in position the lumbar fluid pressure is approximately trebled, thus greatly increasing the rate of fluid loss through the puncture wound.
It is a fact that postpuncture headache is accompanied by a decreased volume of cerebrospinal fluid. This can be proved by measuring the quantity of fluid after removing it and replacing it with air as in encephalography. In patients with a postpuncture headache, the spinal pressure is abnormally low, and the volume of cerebrospinal fluid recoverable at encephalography is always greatly reduced. In some cases I have found it to measure as little as 30 cc. as compared with a normal of perhaps 120 cc. This, however, does not prove that the lost cerebrospinal fluid. . .