What is intracranial hypotension?
Intracranial hypotension is a condition caused by reduced cerebrospinal fluid (CSF) volume, most commonly due to a spinal CSF leak. This leads to downward displacement of intracranial structures and characteristic positional symptoms.
It is classified into:
- Spontaneous intracranial hypotension (SIH): occurring without preceding procedure or trauma, often due to spontaneous dural tears or spinal CSF-venous fistulas.
- Secondary intracranial hypotension: following procedures such as lumbar puncture, spinal or epidural anaesthesia, spinal surgery, or trauma.
Prognosis of intracranial hypotension
The prognosis is generally good when appropriately diagnosed and treated. Many patients respond to conservative measures or epidural blood patching. However, symptoms may persist or recur if the CSF leak is not identified or adequately sealed.
Complications can include subdural haematomas and, less commonly, cerebral venous thrombosis. Following successful treatment, some patients may develop rebound intracranial hypertension, which may require temporary medical management.
Symptoms of intracranial hypotension
The most typical symptom is an orthostatic headache, which worsens on standing and improves on lying down.
Associated symptoms may include:
- Neck stiffness or pain.
- Nausea and vomiting.
- Dizziness or imbalance.
- Tinnitus or hearing changes.
- Visual disturbance (blurred vision or diplopia).
- Cognitive slowing or “brain fog”.
- Fatigue.
In severe cases, altered consciousness or cranial nerve palsies may occur.
Diagnosis of intracranial hypotension
Diagnosis is based on clinical history supported by imaging.
- Brain MRI may show signs such as brain sagging, enhancement of the meninges, or subdural fluid collections.
- Spinal MRI can help identify a possible CSF leak.
- CT myelography or digital subtraction myelography (DSM) may be used to locate difficult-to-detect leaks.
Causes of intracranial hypotension
The main cause is leakage of cerebrospinal fluid through a tear in the dura mater. This may occur spontaneously or following medical procedures such as lumbar puncture, spinal anaesthesia, or spinal surgery. Less commonly, it may be associated with connective tissue disorders that weaken the meninges.
Prevention of intracranial hypotension
Not all cases are preventable. Risk reduction is mainly relevant to iatrogenic cases, where careful technique during spinal procedures reduces the likelihood of dural puncture. Early recognition of post-procedural positional headache is important to avoid delayed treatment.
Treatments for intracranial hypotension
Management follows a stepwise approach:
- Conservative treatment: bed rest, hydration, oral caffeine, and simple analgesia. Often used initially in mild or recent cases.
- Epidural blood patch (EBP): first-line interventional treatment. This may be non-targeted or targeted depending on leak localisation.
- Targeted interventions: CT- or fluoroscopy-guided blood patching or fibrin sealant injection at the identified leak site.
- Surgical repair: reserved for persistent or clearly localised leaks, including dural tears or CSF-venous fistulas, and may involve minimally invasive spinal surgery.
Medications for intracranial hypotension
Medication is supportive rather than curative. Options include analgesics, antiemetics, and caffeine-based therapy. In cases of rebound intracranial hypertension after treatment, acetazolamide may occasionally be required under specialist supervision.
Which specialist should you see for intracranial hypotension?
Initial assessment is usually by a neurologist, particularly a headache specialist. In cases requiring intervention, a neurosurgeon or interventional neuroradiologist may be involved.
