CSF leak types (spontaneous intracranial hypotension)

Schievink 2016 · Bern score 2019MRICT myelographyDSM

Spinal CSF leaks fall into four types by mechanism. Brain MRI sets the pre-test probability (Bern score); spine imaging then decides between a fast leak (extradural fluid: types 1 and 2) and a slow leak without extradural fluid (CSF-venous fistula, type 3).

Spinal CSF leaks: Schievink classification

Type	Lesion	Extradural CSF on spine MRI / CTM	Typical imaging and work-up
1a	Ventral dural tear, usually from a calcified disc-osteophyte spicule, mostly thoracic	Yes, often long-segment	Look for a calcified ventral spicule on CT. Prone dynamic myelography (DSM or dynamic CTM) localizes the tear
1b	Posterolateral (lateral) dural tear, often near the nerve root sleeve	Yes	Lateral decubitus dynamic myelography on the side of the extradural collection
2a	Simple meningeal diverticulum (nerve root sleeve)	Yes	Leaking diverticulum, usually thoracic
2b	Complex meningeal diverticulum or dural ectasia	Yes	Often seen in connective tissue disorders
3	CSF-venous fistula: direct communication between the subarachnoid space and a paraspinal or epidural vein	No	Lateral decubitus CTM or DSM, ideally with high temporal and spatial resolution (photon-counting CT where available). Signs: hyperdense paraspinal vein, opacified epidural or foraminal vein; often next to a nerve root diverticulum, most often lower thoracic, more often right-sided
4	Indeterminate: SIH with no leak found	No	Repeat targeted myelography; consider an empiric epidural blood patch

Fast leak (types 1–2): extradural CSF on fat-saturated T2 spine MRI or CTM. The collection can extend far from the leak site, so it does not localize the leak by itself.
Slow leak (type 3): no extradural CSF. Use decubitus positioning, image immediately after injection, and use bone-subtracted or thin-section CT.
A normal brain MRI does not exclude SIH, and a normal opening pressure does not exclude a leak.

Bern SIH score (brain MRI)

Finding	Threshold	Points
Pachymeningeal enhancement	Diffuse, smooth dural enhancement	2
Venous sinus engorgement	Convex inferior margin of the dominant transverse sinus	2
Suprasellar cistern effacement	≤ 4.0 mm	2
Subdural fluid collection	Hygroma or haematoma	1
Prepontine cistern effacement	≤ 5.0 mm	1
Mamillopontine distance	≤ 6.5 mm	1

Total (0–9)	Probability of a spinal CSF leak
≤ 2	Low
3–4	Intermediate
≥ 5	High

Cranial (skull base) CSF leaks

Site	Clinical presentation	Best imaging
Cribriform plate / fovea ethmoidalis	CSF rhinorrhea, recurrent meningitis	Thin-section CT of the skull base for the bony defect; CT or MR cisternography if there are several candidate defects
Lateral recess of the sphenoid sinus	CSF rhinorrhea, often with obesity and idiopathic intracranial hypertension	Thin-section CT; look for arachnoid pits and meningoencephalocele
Tegmen tympani / mastoideum	CSF otorrhea or middle-ear effusion (rhinorrhea through the Eustachian tube)	Temporal bone CT, with MRI for encephalocele
Post-traumatic or post-operative	Fracture or surgical defect	CT; CT cisternography for an active leak

Skull base leaks cause rhinorrhea or otorrhea and usually do not cause orthostatic headache. Spinal leaks cause SIH. Associated idiopathic intracranial hypertension is common in spontaneous skull base leaks and can unmask after repair.

Sources

Schievink WI, Maya MM, Jean-Pierre S, Nuño M, Prasad RS, Moser FG. A classification system of spontaneous spinal CSF leaks. Neurology. 2016;87:673–679.PubMed ↗
Dobrocky T, Grunder L, Breiding PS, et al. Assessing spinal cerebrospinal fluid leaks in spontaneous intracranial hypotension with a scoring system based on brain magnetic resonance imaging findings. JAMA Neurol. 2019;76:580–587.PubMed ↗
Schievink WI, Maya MM, Tay ASS, et al. Lateral spinal CSF leaks in patients with spontaneous intracranial hypotension: radiologic-anatomic study of different variants. AJNR Am J Neuroradiol. 2024;45:951–956.PubMed ↗
Kranz PG, Gray L, Malinzak MD, Houk JL, Kim DK, Amrhein TJ. CSF-venous fistulas: anatomy and diagnostic imaging. AJR Am J Roentgenol. 2021;217:1418–1429.PubMed ↗

Radessential summarizes published classification systems for practicing radiologists. Summaries are condensed; confirm details against the cited source before relying on them for patient care.