Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Recognise cerebrospinal-fluid volume loss, distinguish post-dural-puncture headache from spontaneous intracranial hypotension, and arrange safe imaging and definitive leak-directed care without relying on opening pressure alone.
Intracranial hypotension is better understood as inadequate cerebrospinal-fluid volume and buoyancy than as a numerical pressure disorder. Loss of buoyancy permits pain-sensitive meninges and bridging veins to stretch while intracranial veins enlarge to preserve total intracranial volume. A dural tear, leaking meningeal diverticulum or direct fistula into a paraspinal vein may be responsible. A leak following a lumbar puncture or neuraxial anaesthetic has an identifiable precipitant; spontaneous intracranial hypotension often begins without major trauma and may be delayed in reaching diagnosis.
Orthostatic headache is diagnostically useful but not uniform. Some people deteriorate within seconds of standing, others after hours, and improvement after recumbency may be slow. Migraine, postural tachycardia, cervicogenic pain and Chiari malformation can also vary with posture. Conversely, a long-standing cerebrospinal-fluid leak may become non-postural. The whole phenotype, procedural history, neurological examination and imaging must therefore be integrated rather than applying a single timing rule.
Lumbar puncture, spinal or epidural procedures and spinal surgery can create a dural hole through which cerebrospinal fluid continues to escape.
A ventral dural tear, ruptured meningeal diverticulum or less obvious defect may arise spontaneously or after minor mechanical strain.
An abnormal connection can drain cerebrospinal fluid directly into a paraspinal vein without a conventional extradural fluid collection.
Underlying meningeal fragility and spinal structural abnormalities increase leak risk in some people, although no systemic disorder is identified in many cases.
Persistent spinal leakage or venous drainage reduces the intracranial cerebrospinal-fluid cushion even when a lumbar opening-pressure measurement remains normal.
Reduced buoyancy permits downward displacement when upright, stretching meninges, bridging veins and cranial nerves and producing orthostatic pain.
Intracranial veins enlarge to preserve total cranial volume, contributing to diffuse pachymeningeal enhancement, pituitary enlargement and headache.
Traction can tear bridging veins or split dural layers, allowing subdural fluid or blood to accumulate.
Head pain is absent or mild on waking, increases after sitting or standing and improves when supine; record the delay to onset and recovery rather than merely writing postural headache.
Headache within days of lumbar puncture, epidural placement or spinal intervention, often with neck stiffness, auditory symptoms or nausea, supports a procedure-related dural leak.
Horizontal diplopia, tinnitus, altered hearing, facial sensory symptoms or imbalance can result from cranial-nerve and posterior-fossa traction and strengthen the syndrome.
Abrupt onset after trivial twisting, coughing or exercise, meningeal diverticula, hypermobility or other connective-tissue features should prompt a specialist spontaneous intracranial-hypotension pathway.
New focal deficit, seizure, somnolence or a changing non-postural headache may reflect subdural haematoma, venous thrombosis or marked brain sag and needs urgent neuroimaging.
Nausea, photophobia and movement sensitivity overlap, but a reproducible posture–symptom relationship and brain-sag imaging favour low-volume headache.
Progressive headache, papilloedema, seizure or prothrombotic risk requires venous imaging because venous thrombosis may mimic or complicate pressure disorders.
Tonsillar descent can resemble brain sag, but congenital posterior-fossa anatomy and absence of diffuse low-pressure features support primary Chiari disease.
Postural tachycardia, hypotension and upper-cervical pain can worsen upright without cerebrospinal-fluid loss; measured physiology and targeted imaging distinguish them.
Prominent tachycardia without leak features, migrainous episodicity independent of posture, fever or a thunderclap onset should broaden assessment before attributing everything to cerebrospinal-fluid loss.
Stretched bridging veins can rupture, producing blood collections, mass effect, seizure or altered consciousness during ongoing cerebrospinal-fluid loss.
Traction commonly affects ocular-motor or auditory pathways, causing diplopia, tinnitus, hearing change and disabling disequilibrium during persistent low pressure.
Severe brain sag can distort diencephalic and brainstem structures, causing cognitive change, movement disorder or rarely profound reduced consciousness.
Persistent leakage can prevent upright activity and work, while repeated patches, imaging and surgery carry infection, bleeding and further-puncture risks.
The disorder's historical name is misleading: only a minority of imaging-confirmed spontaneous cases have a markedly low lumbar opening pressure.
As disease persists, the headache may take longer to appear or become continuous, so earlier history is often more discriminating than today's pattern.
An extradural cerebrospinal-fluid collection points toward a dural tear, whereas its absence raises the possibility of a venous fistula and different myelography positioning.
Draining a collection without treating the driving leak can permit recurrence; neurosurgical and leak specialists should coordinate sequencing unless mass effect demands emergency action.
A new frontal, morning or recumbent-worse headache after successful sealing may reflect raised pressure rather than treatment failure, changing the appropriate response.
Excluding the diagnosis because one opening pressure is normal.
Ordering lumbar puncture solely to prove low pressure despite supportive imaging.
Assuming every postural headache is a cerebrospinal-fluid leak without checking mimics.
Using prolonged bed rest as definitive treatment for disabling spontaneous disease.
Repeating blind procedures indefinitely without specialist leak-localisation review.
Missing a subdural haematoma or cerebral venous thrombosis when symptoms change.
Calling rebound intracranial hypertension recurrent low pressure after a successful patch.
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A 36-year-old has a three-week headache that worsens within fifteen minutes of standing and improves after lying flat. Contrast brain MRI shows smooth pachymeningeal enhancement and brain sag, but lumbar opening pressure is within the laboratory reference range. What is the best interpretation?
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
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Check combination products and total daily exposure; analgesia must not delay assessment of neurological deterioration or replace definitive treatment of a persistent leak.
Benefit is short lived and evidence is limited; consider pregnancy or breastfeeding, arrhythmia, anxiety, insomnia and toxicity from repeated or concentrated preparations.