A spinal headache, formally known as a Post-Dural Puncture Headache (PDPH), is a distinct and often severe type of head pain that develops following certain medical interventions. This condition is not a typical tension headache or migraine but rather a direct consequence of an event near the central nervous system.
The Underlying Cause: Cerebrospinal Fluid Leakage
The direct cause of a spinal headache is the sustained leakage of cerebrospinal fluid (CSF) from the protective sac surrounding the brain and spinal cord. CSF is a clear fluid that cushions the brain, providing buoyancy and mechanical support. This fluid is contained by three layers of membranes called the meninges, the outermost and toughest of which is the dura mater.
When a needle punctures the dura mater, an opening is created through which the CSF can escape into the surrounding tissue faster than the body can produce new fluid. This continuous loss results in a measurable drop in CSF volume and pressure, a condition known as intracranial hypotension. Because the brain is no longer adequately supported by its fluid cushion, it begins to descend slightly when a person assumes an upright position.
This downward shift of the brain causes traction, or stretching, on pain-sensitive structures like the meninges and the blood vessels that bridge the brain and skull base. The mechanical stress generates the intense pain characteristic of a spinal headache. The reduction in pressure can also lead to a compensatory dilation of intracranial blood vessels, which contributes to the throbbing sensation experienced by the patient.
Medical Procedures That Trigger Spinal Headaches
Spinal headaches are precipitated by any procedure that requires a needle to enter the subarachnoid space where the CSF is located. The most common trigger is a lumbar puncture (spinal tap), a diagnostic procedure used to collect CSF samples or administer medications. Spinal anesthesia, a single injection used to numb a region for surgery, also carries the risk of puncturing the dura mater and causing a leak.
Epidural anesthesia, commonly administered during childbirth, is another frequent source, even though it is intended to place medication outside the dura mater. The headache occurs when the needle accidentally passes through the epidural space and punctures the dura, leading to an unintentional dural puncture. Diagnostic procedures like myelograms, which use contrast dye injected into the spinal canal, similarly require dural puncture and may result in the complication.
The physical characteristics of the needle used play a significant role in determining the risk of a leak. Larger-gauge needles and those with a cutting point create a larger, more persistent hole in the dura, increasing the incidence of PDPH. Conversely, using finer-gauge needles with a non-cutting, pencil-point tip significantly lowers the risk because the dural fibers are spread apart rather than cut, allowing for faster closure.
Distinguishing Symptoms and Duration
The most telling characteristic that sets a spinal headache apart is its positional nature, which is directly linked to the mechanics of the CSF leak. The pain is almost always moderate to severe and is dramatically worsened within minutes of sitting or standing upright. This orthostatic pain is often described as a throbbing or pressure sensation that may radiate to the neck.
Conversely, the pain is typically relieved significantly, or vanishes entirely, within a short time of lying completely flat. This rapid improvement upon recumbency is a highly specific diagnostic sign that separates the PDPH from most other headache types. Associated symptoms can include neck stiffness, nausea, vomiting, and sensitivity to light (photophobia).
Other neurological symptoms sometimes accompany the pain, such as ringing in the ears (tinnitus), hearing impairment, dizziness, or visual changes like double vision. The onset of the headache typically occurs within 24 to 48 hours following the causative procedure, though it can occasionally be delayed by up to five days. Without intervention, a spinal headache often resolves spontaneously, with about two-thirds of cases improving within one to two weeks as the puncture site heals naturally.