Yes, You Should Still Be Tested for IIH Despite Normal MRI and MRV
Normal MRI and MRV imaging do not exclude idiopathic intracranial hypertension (IIH), and you should proceed with lumbar puncture to measure opening CSF pressure, as elevated intracranial pressure documented by lumbar puncture is the fundamental diagnostic criterion for IIH. 1
Why Normal Imaging Doesn't Rule Out IIH
Your symptom constellation—chronic headaches, facial pressure, balance issues, pulsatile tinnitus, and motion sensitivity—is highly suggestive of IIH, particularly the pulsatile tinnitus, which is a strong predictor of this condition. 2
Key Diagnostic Principles
MRI and MRV have significant limitations: Many patients with confirmed IIH have completely normal imaging studies, and normal neuroimaging (absence of mass, hydrocephalus, or abnormal meningeal enhancement) is actually part of the diagnostic criteria for IIH. 1, 3
MRV sensitivity is poor for IIH: Studies show MRV has less than 50% sensitivity in detecting significant venous stenosis associated with pressure gradients in IIH patients. 4
Pressure gradients can exist without visible stenosis: It is possible to find elevated intracranial pressure and physiologic venous pressure gradients even when MRV shows no anatomical stenosis. 4
The Critical Next Step: Lumbar Puncture
You must undergo lumbar puncture with opening pressure measurement to confirm or exclude IIH. 1
Diagnostic Threshold
Opening pressure ≥25 cm H₂O (≥250 mm H₂O) measured in the lateral decubitus position is required to meet diagnostic criteria for IIH. 1
Proper technique is essential: You must be in lateral decubitus position, legs extended, relaxed, breathing normally, with measurement taken after pressure stabilizes. 1
Important Caveat About Pressure Fluctuation
- If your first lumbar puncture shows borderline or normal pressure but symptoms persist, repeat lumbar puncture at 2 weeks is recommended, as intracranial pressure can fluctuate and may become elevated on subsequent measurements. 1
Your Symptom Profile Strongly Suggests IIH
High-Risk Symptoms You're Experiencing
Pulsatile tinnitus: This symptom has an odds ratio of 13.0 for predicting IIH and is one of the most specific symptoms for this condition. 2
Chronic progressive headaches: Present in 92% of IIH patients, though the phenotype is highly variable and can mimic other primary headache disorders. 5
Balance issues and motion sensitivity: These are recognized symptoms of IIH, though less specific. 1
Clinical Context Matters
- If you are female, of childbearing age, and have BMI >30 kg/m², you fit the typical demographic profile for IIH, further increasing the likelihood of this diagnosis. 1, 3
What Happens If IIH Is Left Undiagnosed
Untreated IIH can cause progressive irreversible visual loss and optic atrophy, even if you don't currently have obvious visual symptoms. 6
Visual loss can be insidious and may not be noticed by patients until it becomes severe. 7
Formal visual field testing should be performed as part of your evaluation, as visual field defects may be present even without subjective visual complaints. 6
The Diagnostic Algorithm You Should Follow
Proceed with lumbar puncture immediately to measure opening CSF pressure (your most critical next step). 1
Undergo formal ophthalmologic examination with fundoscopy to assess for papilledema, though note that IIH without papilledema is a recognized subtype. 1, 2
Complete formal visual field testing to document baseline visual function. 6
If opening pressure is ≥25 cm H₂O with normal CSF composition, IIH diagnosis is confirmed. 1, 3
If opening pressure is borderline (20-24 cm H₂O) but symptoms persist, repeat lumbar puncture in 2 weeks. 1
Common Pitfall to Avoid
Do not accept reassurance based solely on normal MRI/MRV. The absence of imaging findings does not exclude IIH, and relying on imaging alone will miss many cases of this potentially vision-threatening condition. 1, 3 The diagnosis ultimately rests on demonstrating elevated CSF pressure via lumbar puncture, not on imaging findings. 1