Intracranial hypotension is a condition where the volume of cerebrospinal fluid (CSF) surrounding your brain drops too low, typically because of a leak somewhere along the spine. The hallmark symptom is a headache that gets significantly worse when you stand up and improves when you lie down. With an estimated incidence of about 4 cases per 100,000 people per year, it’s considered rare, though experts at the National Organization for Rare Disorders believe this is likely an undercount.
What Happens Inside Your Skull
Your brain floats in cerebrospinal fluid, a clear liquid that acts as a cushion and shock absorber. When that fluid leaks out through a tear or weak spot in the membrane surrounding the spinal cord (called the dura), the total volume of fluid around your brain decreases. The name “intracranial hypotension” suggests low pressure is the problem, but research now points to low fluid volume as the more important factor. Patients can have completely normal CSF pressure measurements and still have the full syndrome.
Your skull holds a fixed amount of space shared between brain tissue, blood vessels, and cerebrospinal fluid. When fluid volume drops, something else has to expand to fill the gap. Veins inside the skull, which have more flexible walls than arteries, stretch and engorge to compensate. The brain itself can sag downward under gravity without its usual fluid support. One research group found that brain tissue volume actually decreases slightly (by about 0.85%) during active CSF leakage, overturning the long-held assumption that brain volume stays constant.
What Causes the Leak
In spontaneous intracranial hypotension, the CSF leak occurs without an obvious trigger like surgery or a spinal tap. The exact causes aren’t fully understood, but the condition is thought to develop when a relatively minor event, sometimes as small as a cough, sneeze, or awkward twist, tears a dura that already has a slight weakness. Bony spurs along the spine (osteophytes) can press against and eventually puncture the dura. Small outpouchings of the spinal membrane, called meningeal diverticula, are another common site of vulnerability.
People with underlying connective tissue disorders may be more prone to these leaks because their dural membrane is inherently weaker. In many cases, though, no clear predisposing factor is ever identified.
Symptoms Beyond the Headache
The classic presentation is an orthostatic headache: pain that worsens within minutes of standing or sitting upright and eases when you lie flat. Early in the condition, this positional pattern can be dramatic and unmistakable. Over time, though, the headache may lose its clear positional quality and become more constant, which makes diagnosis harder.
The headache is often accompanied by a cluster of other symptoms driven by the brain sagging and veins engorging inside the skull. These can include neck pain or stiffness, nausea, changes in hearing (muffled sounds or ringing), a sense of pressure in the ears, dizziness, and cognitive fog. Some people describe feeling like they’re thinking through mud. The combination of these symptoms with a headache that responds to position is the strongest clinical clue.
How It’s Diagnosed
Diagnosis relies on a combination of symptoms, brain imaging, and sometimes spinal imaging to locate the leak itself. On an MRI of the brain, doctors look for a recognizable pattern of changes. The most telling signs include thickening and enhancement of the membranes covering the brain (called pachymeningeal enhancement), engorged venous sinuses, fluid collections beneath the skull’s inner lining, and downward displacement of brain structures. The pituitary gland can appear swollen, and the cerebellar tonsils may descend below their normal position, sometimes mimicking a Chiari malformation.
A validated scoring system called the Bern score assigns points based on these MRI findings to help standardize the diagnosis. For example, diffuse dural enhancement, a narrowed space above the pituitary, and engorged venous sinuses each earn 2 points, while subdural fluid collections and measurements of brain sagging earn 1 point each.
Importantly, a normal MRI doesn’t completely rule out the condition. The formal diagnostic criteria from the International Headache Society require that the headache develops in connection with low CSF pressure or evidence of a CSF leak, and that no procedure or trauma explains it. But because CSF pressure can be normal even during active leakage, some patients fall outside strict diagnostic criteria yet still respond to treatment.
First-Line Treatment: Conservative Measures
Initial management focuses on simple, noninvasive strategies. Bed rest is the most immediately effective, since lying flat takes gravity out of the equation and reduces the headache. Oral hydration, caffeine, and abdominal binders (which increase pressure in the abdomen and may help support CSF pressure) round out the conservative approach. Many patients improve with these measures initially, especially if the leak is small enough to seal on its own.
For some people, a few days to weeks of strict bed rest is enough. Others find that symptoms return every time they try to resume normal activity, signaling that the leak hasn’t closed.
Epidural Blood Patch
When conservative treatment isn’t enough, the next step is an epidural blood patch. In this procedure, a small amount of your own blood (or sometimes a fibrin sealant) is injected into the epidural space of the spine near the suspected leak site. The injected material forms a clot that seals the tear in the dura.
The procedure is targeted whenever possible to the specific location of the leak, identified through spinal imaging. When no visible leak is found, doctors target areas that show features associated with higher leak risk, such as prominent diverticula, distended nerve roots, or disc spurs pressing on the dura. In one study, patients received an average of 3.6 blood patches over the course of their treatment, each covering about 2 to 3 spinal levels, reflecting the reality that a single patch doesn’t always achieve a permanent seal.
Even among patients who didn’t meet the strictest diagnostic criteria for intracranial hypotension, 64% experienced clinically meaningful improvement in either physical health or headache severity after epidural patching. About 54% saw significant gains in overall physical health scores, and 45% had meaningful reductions in headache impact. These improvements held up at an average follow-up of roughly a year and a half.
Potential Complications
Most cases of intracranial hypotension are uncomfortable but not dangerous. However, the condition can lead to serious complications if left untreated. Subdural fluid collections (thin layers of fluid beneath the skull lining) are relatively common and often resolve once the leak is fixed. In rare cases, though, these collections can progress to subdural hematomas, which are pockets of blood that form when the brain’s downward displacement stretches and eventually tears small bridging veins along the skull’s inner surface.
A growing subdural hematoma can press on brain tissue and cause severe neurological symptoms, including weakness, confusion, or altered consciousness. This is the main reason persistent intracranial hypotension symptoms warrant proper evaluation rather than indefinite conservative management. When both the hematoma and the underlying CSF leak are addressed, outcomes are generally good.