Spontaneous Intracranial Hypotension

Overview

Spontaneous intracranial hypotension (SIH) is a condition in which the pressure of the cerebrospinal fluid (CSF) that surrounds and cushions the brain and spinal cord becomes too low. The most common cause is a spontaneous leak of this fluid through a small tear or weak spot in the membrane that holds it, usually somewhere along the spine. As fluid escapes, the brain loses some of its cushioning and sags slightly, which produces characteristic symptoms.

The hallmark of SIH is a headache that is much worse when standing or sitting up and improves when lying down. The condition is often underrecognized and can be mistaken for other types of headache, leading to delays in diagnosis. Although it can be debilitating, SIH is not usually life-threatening, and many people improve with rest or specific treatments that seal the leak.

Symptoms

The most recognizable feature is a position-related headache, but other symptoms can occur as well.

• A headache that develops or worsens within minutes to hours of standing or sitting up and eases when lying flat (an orthostatic headache)
• Neck pain or stiffness
• Nausea and vomiting
• Ringing in the ears, muffled hearing, or a sense of fullness in the ears
• Dizziness and balance problems
• Sensitivity to light and sound
• Blurred or double vision in some cases

Over time, the positional pattern of the headache may become less obvious. Rarely, significant low pressure can lead to more serious complications, so worsening or new neurological symptoms should be evaluated promptly.

Causes

SIH is caused by a leak of cerebrospinal fluid, most often from the spine. Recognized causes include:

• Spontaneous dural tears: Small tears in the tough membrane around the spinal cord, sometimes triggered by minor strain.
• Bony spurs: Small calcified spurs from the spine that can puncture the membrane.
• Weak spots or cysts: Areas where the membrane is naturally thin or where fluid-filled cysts form.
• CSF-venous fistulas: Abnormal connections that allow fluid to drain into nearby veins.

Connective tissue disorders that make membranes more fragile can increase the likelihood of a leak. Importantly, SIH is distinct from low pressure caused by a known procedure such as a spinal tap, which has an obvious trigger.

Risk Factors

• Connective tissue disorders that weaken membranes
• Bony spurs or disc problems in the spine
• Minor physical strain or trauma in some cases
• Female sex and middle age, in which it is more commonly recognized

Diagnosis

Diagnosis can be challenging and often relies on the typical headache pattern plus imaging. Tests may include:

• Brain MRI with contrast: Can show characteristic changes such as brain sagging and thickening of the membranes
• Spine MRI: To look for collections of leaked fluid along the spine
• Specialized imaging: CT or MRI myelography, in which contrast is used to pinpoint the exact site of the leak
• Pressure measurement: Occasionally, the CSF pressure is measured directly

Treatment

Treatment ranges from conservative measures to procedures that seal the leak. Care is usually guided by a neurologist and, when needed, specialists in spine or interventional procedures.

• Conservative care: Bed rest, good fluid intake, and sometimes caffeine, which can help some leaks settle on their own.
• Epidural blood patch: A common treatment in which a small amount of the person's own blood is injected near the leak to seal it; it may need to be repeated.
• Targeted patching or sealants: Injection of fibrin sealant or precise patching when the leak site is known.
• Surgery: To repair a tear, remove a bony spur, or close a fistula when other treatments fail.

Many people improve significantly once the leak is sealed, though it can sometimes take more than one attempt to find and fix the source.

When to See a Doctor

See a doctor if you develop a new headache that is clearly worse when you stand or sit up and better when you lie down, especially if it is accompanied by neck pain, ringing in the ears, or nausea. Seek prompt medical attention for any sudden, severe headache, or for a headache combined with confusion, weakness, difficulty speaking, vision loss, or a stiff neck and fever, as these can indicate a more serious or emergency condition that needs urgent evaluation.

Related Topics

Frequently Asked Questions

References

1. Cleveland Clinic. Spontaneous Intracranial Hypotension.
2. American Migraine Foundation. Spontaneous Intracranial Hypotension.
3. National Organization for Rare Disorders (NORD). Spontaneous Intracranial Hypotension.
4. MedlinePlus, U.S. National Library of Medicine. Cerebrospinal fluid.