Spontaneous Intracranial Hypotension (SIH)

Spontaneous intracranial hypotension (SIH) is a neurologic condition caused by a leak of cerebrospinal fluid (CSF) from around the spine. Loss of CSF reduces the pressure around the brain, leading to a characteristic pattern of symptoms—most notably headache that is worse when upright and improves when lying down.

SIH is frequently underrecognized or misdiagnosed as migraine, another headache disorder, or POTS. With appropriate evaluation and treatment, many patients experience meaningful or complete improvement.

CSF is a clear fluid that:

• Cushions the brain and spinal cord

• Maintains normal pressure inside the skull

• Supports normal neurologic function

In SIH, CSF escapes through a defect in the spinal covering (the dura), resulting in low CSF volume and pressure.

In SIH, the leak typically occurs without a major injury or medical procedure.

Contributing factors may include:

• Fragility or weakness of the spinal dura

• Small dural tears or holes

• Spinal bone spurs

• Disc disease

• Underlying connective tissue disorders

Many people do not recall a specific trigger. Minor strain, coughing, bending, or stretching may precede symptoms, but SIH can occur without any clear cause.

Orthostatic (positional) headache

The hallmark feature of SIH is a headache that:

• Is worse when upright

• Improves when lying flat

• Often develops within minutes to hours of standing

Early in the condition, the positional pattern can be very clear. Over time, the headache may become less obviously positional, which can make diagnosis more challenging.

Other common symptoms

SIH can cause a wide range of symptoms, including:

• Neck pain or stiffness

• Nausea or vomiting

• Hearing changes (muffled hearing, tinnitus)

• Dizziness or imbalance

• Visual symptoms

• Brain fog or slowed thinking

• Fatigue

• Sensitivity to light or sound

Symptoms often fluctuate and can be significantly disabling.

SIH can resemble migraine, but important clues include:

• Positional worsening (upright worse, headache-free when flat)

• New daily or near-daily headache onset

• Poor or inconsistent response to typical migraine treatments

• Prominent neck pain, hearing changes, or balance symptoms

Some patients have both SIH and migraine, which can further complicate the picture.

Diagnosing SIH requires a high index of suspicion and targeted testing.

Brain MRI

A brain MRI with contrast is usually the first imaging study.

Importantly, a normal MRI does not rule out SIH, especially early in the condition.

Spine imaging

If SIH is suspected, additional imaging may include:

• MRI of the spine

• CT myelography

• Digital subtraction myelography

These tests aim to localize the CSF leak, but a leak is not always visible even with advanced imaging.

Lumbar puncture

Lumbar puncture is not routinely required to diagnose SIH and may worsen symptoms. CSF opening pressure can be low, normal, or misleading.

What is the 48-hour supine test?

The 48-hour supine test is a simple, non-invasive observation period where a patient remains lying flat (supine) for approximately 48 hours, avoiding prolonged upright activity.

Why is this helpful?

In SIH, symptoms—especially headache—often improve significantly when lying flat. The supine test can:

• Demonstrate positional dependence of symptoms

• Provide useful clinical information when imaging is inconclusive

• Help support or refute suspicion of SIH

• Give treating clinicians clearer diagnostic context

How is the test done?

• Remain lying flat as much as possible for ~48 hours

• Limit sitting or standing to brief bathroom breaks

• Keep a simple symptom log before, during, and after the test

How should results be interpreted?

• Clear improvement while supine, followed by worsening when upright, supports SIH

• Lack of improvement does not completely rule out SIH, but makes it less likely

This test does not replace imaging, but can be a valuable adjunct and discussion point with your doctor.

The BERN score is a brain MRI–based scoring system used to estimate the likelihood that a person’s symptoms are due to spontaneous intracranial hypotension (SIH) from a CSF leak.

It does not diagnose SIH on its own, but helps clinicians interpret MRI findings in a structured, standardized way.

Why is the BERN score used?

SIH can be challenging to diagnose because:

• Symptoms can overlap with migraine and other headache disorders

• Brain MRI findings may be subtle or incomplete

• Some patients have normal imaging early in the condition

The BERN score helps by:

• Quantifying MRI features associated with low CSF pressure

• Improving diagnostic consistency between clinicians

• Helping guide decisions about further testing or treatment, such as targeted spine imaging or blood patch therapy

What MRI features are included in the BERN score?

The score is based on specific changes seen on brain MRI with contrast, such as:

• Brain sagging

• Thickened or enhanced meninges

• Enlargement of venous structures

• Subdural fluid collections

Each feature contributes points to the total score.

What does the score mean?

• Higher BERN scores suggest a greater likelihood of SIH

• Lower scores make SIH less likely, but do not fully exclude it

Importantly:

• A low or normal BERN score does not rule out SIH

• Some patients with confirmed CSF leaks have minimal or absent MRI findings

The BERN score is best interpreted in the context of symptoms and clinical history, not in isolation.

How does the BERN score fit into care?

Clinicians may use the BERN score to:

• Support suspicion of SIH when symptoms fit

• Decide whether advanced spine imaging is warranted

• Guide urgency and type of treatment

• Communicate findings clearly across care teams

It is one piece of a larger diagnostic puzzle that includes symptom pattern, exam findings, response to positional changes, and treatment response.

Patients with SIH should be managed by an expert multi-disciplinary team.

Treatment depends on symptom severity, duration, and response to initial measures.

Conservative measures

Early or mild cases may improve with:

• Bed rest

• Increased oral fluids

• Short-term caffeine use (evidence is no longer supporting caffeine, but it is still commonly trialed)

However, conservative treatment alone is often insufficient for most patients with SIH, those with severe symptoms, and those with persistent SIH.

Epidural blood patch (EBP)

An epidural blood patch is the most commonly used treatment for SIH.

What is a blood patch?

• A small amount of the patient’s own blood is injected into the epidural space

• The blood seals the leak and helps restore normal CSF pressure

Blood patches may be:

• Non-targeted (lumbar)

• Targeted to a known leak site

Some patients require more than one blood patch.

Additional treatments

In selected cases:

• Fibrin glue patching

• Embolization

• Surgical repair for confirmed, persistent leaks

• Referral to specialized CSF leak centres

An epidural blood patch is the most commonly used treatment for SIH.

What is a blood patch?

• A small amount of the patient’s own blood is injected into the epidural space

• The blood seals the leak and helps restore normal CSF pressure

Blood patches may be:

• Non-targeted (lumbar)

• Targeted to a known leak site

Some patients require more than one blood patch.

An epidural blood patch (EBP) is a commonly used and effective treatment for spontaneous intracranial hypotension (SIH). Understanding what is normal afterward can help reduce anxiety and guide recovery.

Common and expected effects

Many people experience temporary symptoms after a blood patch. These are usually mild to moderate and improve over days.

Common experiences include:

• Back soreness or stiffness at the injection site

• Neck tightness or pressure

• Headache that feels different from the original SIH headache

• A sensation of pressure or fullness in the head

• Fatigue or a “washed-out” feeling

These symptoms often reflect restoration of CSF pressure and tissue healing.

Rebound headache or “high-pressure” symptoms

Some people develop symptoms that feel opposite to SIH after a blood patch, sometimes called rebound intracranial hypertension.

This may include:

• Headache that is worse when lying flat

• Headache on waking in the morning

• Pressure behind the eyes

• Nausea

This is usually temporary and often improves with time and conservative measures. Your clinician can help guide management if this occurs.

Changes in headache pattern

It is common for headache to:

• Improve gradually rather than immediately

• Fluctuate from day to day

• Change in character as pressure normalizes

Improvement may take days to weeks, especially if symptoms were present for a long time before treatment.

Activity and recovery after a blood patch

General recommendations often include:

• Rest for the first 24 hours

• Avoid heavy lifting, straining, or vigorous activity for several days

• Gradual return to normal activity as tolerated

Specific instructions may vary depending on the type of blood patch performed.

When to contact your care team

Seek medical advice if you experience:

• Severe or worsening back pain

• New weakness, numbness, or bladder/bowel changes

• Fever or signs of infection

• Headache that becomes progressively severe or different from expected recovery

Will one blood patch be enough?

Some people improve after a single blood patch, while others may require:

• More than one blood patch

• A targeted blood patch if a leak site is identified

• Targeted definitive intervention (embolization or surgery)

Some patients experience a new or different headache after an epidural blood patch. This is commonly called rebound headache or rebound intracranial hypertension.

This does not mean the blood patch failed.

What causes rebound headache?

In SIH, symptoms are caused by low pressure around the brain due to a CSF leak.
A blood patch works by sealing the leak and restoring pressure.

In some people, pressure:

• Normalizes quickly, or

• Temporarily overshoots above normal

This temporary shift can lead to high-pressure–type symptoms, which feel different from the original SIH headache.

What does rebound headache feel like?

Rebound headache often has features that are the opposite of SIH:

Common symptoms include:

• Headache that is worse when lying flat

• Headache that is worse in the morning

• Pressure behind the eyes or forehead

• Head fullness or tightness

• Nausea

• Sensitivity to light

Some people describe it as a new headache, rather than a return of the original one.

How long does rebound headache last?

• Often temporary

• May improve over days to a few weeks

• Can fluctuate day to day

Most cases resolve as the body re-equilibrates CSF pressure.

Not everyone with rebound headache needs medication.

Conservative measures

Initial management may include:

• Gradual return to upright activity

• Avoiding excessive fluid loading

• Time and reassurance

Medical treatment: acetazolamide

In some cases, we may prescribe acetazolamide, a medication that:

• Reduces CSF production

• Helps lower intracranial pressure

This is used:

• Short-term

• In selected patients

• When symptoms are clearly consistent with rebound high pressure

Consider SIH if you have:

• New daily headache with positional features

• Headache that disappears when lying flat

• Headache after minimal strain with no clear trigger

• Poor response to standard migraine treatment

• Associated neck pain, hearing changes, or cognitive symptoms

Early recognition improves outcomes.

Preparing in advance can help make your visit more productive and ensure important details are not missed.

If possible, we recommend bringing or tracking:

• Headache pattern over time

  • How did your headache start? What did it feel like at the beginning?

• Positional features (how symptoms change when upright versus lying flat)

• A headache diary, even if brief or informal

• Reports or images from prior tests, such as:

  • Brain or spine MRI

  • CT scans or myelography

  • Previous lumbar puncture reports

• A list of treatments already tried, including medications, caffeine, or prior blood patches

Even partial information is helpful. You do not need to have everything figured out before your visit.