Brain
CSF Pressure & Headache: Reading What You Can't Measure
Fellowship-level neuroradiology teaching by E. Brooke Schrickel, MD. Open this topic in the interactive reading room →
Core clinical idea
You usually can't read the pressure off the scan — with equal pressure across CSF spaces (as in IIH) the brain can look near-normal at very high ICP. The job is to recognize the subtle IIH constellation that should trigger an LP, and to exclude a secondary cause before accepting 'idiopathic.'
Bottom line
You can't see the pressure — read the IIH constellation to trigger the LP, treat transverse sinus stenosis as dynamic, and exclude the secondary causes before 'idiopathic.'
Core workstation questions
- Does this headache patient have the IIH constellation (globe flattening, optic sheath distension/tortuosity, empty sella, transverse sinus stenosis) that warrants an LP/opening pressure?
- Is transverse/sigmoid sinus stenosis present — and am I treating a dynamic finding as if fixed off one supine venogram?
- Have I excluded dural venous sinus thrombosis, a dural AV fistula, and an obstructing mass at the torcula/sagittal sinus before calling it idiopathic?
- Are the low tonsils real Chiari or just nonspecific pressure-related ectopia?
What changes reporting / management
- Report the IIH constellation and recommend correlation with lumbar puncture/opening pressure — the read may be what protects vision.
- Read transverse sinus stenosis as dynamic and treatable (venous stenting now a mainstay, largely supplanting optic nerve fenestration); it likely drives pulsatile tinnitus.
- Naming a secondary cause (sinus thrombosis, dural fistula, obstructing mass) changes management entirely versus the IIH pathway.
- Do not reassure off a near-normal scan in the at-risk patient (young, overweight woman with headache and visual obscurations).
Practical traps
- Reassuring off a 'normal' scan that misses vision-threatening IIH.
- Labeling 'IIH' when it is actually venous sinus thrombosis, a dural AV fistula, or an obstructing mass.
- Anchoring on nonspecific low tonsils as if diagnostic.
- Calling fixed transverse sinus stenosis off a single supine venogram.
Teaching pearls
- A normal-looking scan doesn't exclude high ICP — pressure can be equal everywhere.
- Globe flattening + optic sheath distension + empty sella + transverse sinus stenosis = look harder, recommend LP.
- IIH is a diagnosis of exclusion — clear thrombosis, dural fistula, and obstructing mass first.
- Transverse sinus stenosis is dynamic and treatable (stenting) — don't call it fixed off one supine venogram.
- Low tonsils are nonspecific; the feared endpoint of IIH is blindness.
Source lectures
- Headaches and Disorders of CSF Pressure
Educational material for radiology residents and neuroradiology fellows. Nothing here drives individual patient care, and it contains no patient data.