Spontaneous intracranial hypotension
Spontaneous intracranial hypotension is low cerebrospinal fluid volume and pressure from a spontaneous, usually spinal, CSF leak, presenting with an orthostatic headache that worsens within seconds of sitting or standing and eases lying flat. Contrast-enhanced brain MRI showing diffuse smooth pachymeningeal enhancement (in nearly 80%) with signs of brain sagging makes the diagnosis, an opening pressure below 60 mm H2O confirms it, and an epidural blood patch, blind lumbar or targeted to an identified leak, is the treatment.
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What this article covers
- Overview
Definition: spontaneous intracranial hypotension (SIH) is a secondary headache disorder caused by leakage of cerebrospinal fluid (CSF) without a preceding dural puncture, lowering CSF volume and pressure.
- Epidemiology
Relative frequency: leakage after lumbar puncture is the most common source of intracranial hypotension; the spontaneous form is less common.
- Risk factors
Spinal CSF leak: the defining cause; leaks are typically spinal rather than cranial.
- Pathophysiology
CSF loss lowers intracranial pressure: a leak drains CSF faster than it is replaced, reducing the volume and pressure that buoy the brain.
- Clinical features
Orthostatic headache is the cardinal feature: headache that worsens within 20 seconds of sitting or standing and eases lying down; a patient may wake pain-free and develop headache within 30 minutes…
- Differential diagnosis
Subarachnoid hemorrhage: the most common cause of thunderclap headache, found in nearly 25% of such patients, with blood on noncontrast head CT or in the CSF.
- Diagnosis
Diagnosis is established by a compatible orthostatic headache plus objective evidence of low CSF volume: contrast-enhanced brain MRI showing diffuse smooth (nonnodular) pachymeningeal enhancement…
- Management
First, identify which leak you are treating: if the headache began after a lumbar puncture or epidural, treat it as post-dural-puncture headache; if no dural puncture preceded it, proceed directly to an epidural blood patch for SIH.
- Complications
Subdural fluid collections: a direct imaging consequence of low CSF volume that can be mistaken for a primary subdural hematoma.
- Prognosis
Blood patching is effective: the epidural blood patch is the most appropriate treatment and resolves symptoms in 80% to 90% of post-lumbar-puncture leaks.
- Prevention
Use a small-caliber atraumatic needle for every lumbar puncture: it reduces the risk of a post-dural-puncture leak, whereas bed rest after the procedure does not.
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