Spontaneous intracranial hypotension

Spontaneous intracranial hypotension (SIH), also known as spontaneous cerebrospinal fluid (CSF) leak or spontaneous low CSF pressure headache, is a condition characterized by reduced cerebrospinal fluid pressure due to a spontaneous leak of CSF from the spinal dural sac, occurring without any obvious precipitating cause such as trauma or lumbar puncture. The condition primarily affects the central nervous system. CSF normally surrounds and cushions the brain and spinal cord; when it leaks, the reduced volume and pressure cause the brain to sag downward within the skull, leading to characteristic symptoms. The hallmark symptom is an orthostatic headache — a headache that worsens significantly upon standing or sitting upright and improves when lying down. Other common symptoms include neck pain or stiffness, nausea, vomiting, dizziness, hearing changes (such as muffled hearing or tinnitus), visual disturbances (including double vision), and cognitive difficulties sometimes described as brain fog. In some cases, patients may develop subdural fluid collections or subdural hematomas as a complication of brain sagging. SIH most commonly affects adults, with a peak incidence in the fourth and fifth decades of life, and appears to have a slight female predominance. The underlying cause of the CSF leak is often related to dural weakness, which may be associated with underlying connective tissue disorders such as Marfan syndrome, Ehlers-Danlos syndrome, or other heritable connective tissue conditions, though in many cases no such association is identified. Structural abnormalities such as meningeal diverticula, dural tears, or CSF-venous fistulas along the spine are recognized sources of the leak. Diagnosis is typically supported by brain MRI findings, which may show diffuse pachymeningeal (dural) enhancement, brain sagging, subdural collections, engorgement of venous structures, and pituitary enlargement. Spinal imaging, including CT myelography and digital subtraction myelography, is used to localize the site of the CSF leak. Treatment of SIH follows a stepwise approach. Initial conservative management includes bed rest, hydration, and caffeine intake. If symptoms persist, an epidural blood patch (EBP) — in which a patient's own blood is injected into the epidural space to seal the leak — is the first-line procedural treatment and is effective in many patients. Some patients require multiple or targeted blood patches directed at the identified leak site. For refractory cases, particularly those with CSF-venous fistulas or large dural tears, surgical repair or transvenous embolization may be necessary. While many patients recover fully with appropriate treatment, some experience a chronic or relapsing course that can be significantly disabling.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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