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Spontaneous Intracranial Hypotension: The Leak Is in the Spine

Fellowship-level neuroradiology teaching by E. Brooke Schrickel, MD. Open this topic in the interactive reading room →

Watch · concise explainerVisual summary

Core clinical idea

The brain findings are the consequence; the leak is in the spine — treat the spinal CSF leak, not the brain. The most dangerous miss is the patient with subdural collections: fix the leak, don't operate on the subdurals.

Bottom line

Brain shows it, spine causes it — fix the leak, not the subdural, and don't be fooled by the Chiari/meningitis/SAH mimics.

Core workstation questions

  • Does this brain show the SIH constellation (subdurals + smooth dural enhancement + sag + pituitary engorgement)?
  • Is the patient's headache orthostatic — does the clinical picture support SIH before I call meningitis/Chiari/SAH?
  • If there are subdurals, am I steering toward leak treatment rather than subdural evacuation?
  • Conventional myelography negative but brain looks like SIH — is this a CSF-venous fistula needing dynamic/decubitus technique?

What changes reporting / management

  • When the SIH constellation is present, recommend spine imaging for a CSF leak and flag subdurals as secondary to the leak.
  • In SIH with subdural hematomas, steer management to leak treatment (most resolve) rather than subdural evacuation.
  • Match the study to the leak: MR myelography often first, CT myelography the workhorse, dynamic/digital subtraction myelography for fast/ventral leaks and CSF-venous fistula.
  • Treatment ladder: conservative measures, then epidural blood patch (first-line intervention, repeatable), then targeted fibrin glue, then surgical repair.

Practical traps

  • Calling smooth diffuse dural enhancement meningitis/neoplasm when it is venous engorgement from hypotension.
  • Recommending posterior fossa decompression for a pseudo-Chiari caused by brain sag.
  • Triggering an SAH/aneurysm pathway off pseudo-subarachnoid hemorrhage on CT.
  • Excluding SIH because head CT is normal (it usually is).
  • Missing a CSF-venous fistula when there is no CSF collection but the brain looks low-pressure.

Teaching pearls

  • The findings are intracranial; the leak is spinal — image the spine.
  • In SIH with subdural hematomas, treat the leak, not the subdurals.
  • Smooth dural enhancement here is venous engorgement, not meningitis.
  • Brain sag mimics Chiari — don't decompress a sagging brain.
  • No collection but the brain looks low-pressure? Hunt the CSF-venous fistula.

Teaching visuals

Spontaneous intracranial hypotension — the sag constellationSagittal · the brain slumps; the cause is a leak in the spine12345THE CONSTELLATIONsigns of brain sag1Pachymeningeal enhancementsmooth, diffuse, non-nodulardural thickening2Brain sageffaced supra/prepontinecisterns, flattened pons3Low cerebellar tonsilsslumping toward the foramenmagnum (pseudo-Chiari)4Venous engorgementdistended dural sinuses, plumppituitary, SDH/effusions5The cause: spinal leakfind and treat the CSF leak inthe SPINEThe clinical hingeLow CSF volume lets the brain slump: smooth pachymeningeal enhancement, effaced basal cisterns, a flattened pons, lowtonsils (pseudo-Chiari) and engorged veins / plump pituitary. The brain MRI tells you it's happening......but the leak is in the SPINE. Don't stop at the head — go look for the spinal CSF leak (CT/MR myelography) so itcan be targeted.
SIH Brain-MRI Constellation (Monro-Kellie)
Brain shows the consequence → the leak is in the SPINESIH work-up: stop reading the brain as the target; hunt the spinal CSF leak.SIH — from consequence back to the leakMonro–Kellie: low CSF volume forces compensation; the brain signs are downstreamBrain MRIsag + smooth dural enhancement + engorged sinuses + subduralsRecognize intracranial hypotensionNOT Chiari · NOT meningitis · NOT primary subdural hematomaGo to the SPINE for the leakCT myelographyworkhorse — localizes most dural leaksDynamic / digital-subtractionmyelographyfor fast / ventral leaksConventionalmyelogram negative?No → leak foundYesLateral decubitusdynamic myelographyhunt the CSF–venousfistulaTreat the leak: epidural blood patch → glue → surgeryfix the leak, NOT the subdurals
Brain Shows the Consequence, the Leak Is in the Spine
⚠ TRAPPseudo-Chiari ≠ Chiari Ibrain sag mimics a tonsillar pegPseudo-Chiari (BRAIN SAG)low tonsils because the whole brain has droppedwhole brain sagsCisterns effaced · dural enhancement · tonsil descends WITH brainTrue Chiari Iisolated tonsillar peg, brain otherwise normalopen cisternsIsolated peg-like tonsils · normal cisterns · no dural enhancementLow tonsils + dural enhancement + sag = treat the leakdo NOT decompress
Trap: Pseudo-Chiari Is Not Chiari I

Source lectures

  • Spontaneous Intracranial Hypotension

Educational material for radiology residents and neuroradiology fellows. Nothing here drives individual patient care, and it contains no patient data.