What are the typical MRI findings in suspected intracranial hypertension?

Typical MRI Findings in Suspected Intracranial Hypertension

MRI of the head and orbits is the most useful imaging modality for evaluating suspected intracranial hypertension, with characteristic findings including empty sella, flattening of the posterior globes, distention of the perioptic subarachnoid space, and transverse sinus stenosis. 1

Primary MRI Findings

Brain Findings

• Empty sella/partially empty sella (56-66% sensitivity, high specificity) 1, 2
• Flattened pituitary gland (reduced pituitary height, 56% sensitivity, 97% specificity) 2
• Transverse venous sinus stenosis (high sensitivity in IIH, 94% sensitivity when evaluated as part of cranial venous outflow obstruction) 1, 2
• Slit-like ventricles (less common finding) 3

Orbital Findings

• Posterior globe flattening (56% sensitivity, 100% specificity) 1, 2
• Intraocular protrusion of the optic nerve (40% sensitivity, 100% specificity) 1
• Horizontal tortuosity of the optic nerve (68% sensitivity, 83% specificity) 1
• Optic nerve sheath distention/hydrops (92% sensitivity, 89% specificity) 1, 2
• Enlarged optic nerve sheath (mean 4.3 mm in IIH vs 3.2 mm in controls) 1

Additional MRI Findings

• Enlarged Meckel's caves (15.9% prevalence in patients undergoing brain MRI) 4, 5
• Widening of the foramen ovale (50% sensitivity, 81% specificity for area >30 mm²) 6
• Cerebellar tonsillar descent (less common finding) 4
• Cephaloceles (rare finding, 1.4% prevalence) 4

Diagnostic Value of Multiple Findings

• The presence of multiple MRI findings increases diagnostic confidence
• At least 2 MRI findings could be demonstrated in each IIH patient in some studies 2
• The number of positive MRI findings correlates with CSF pressure (r = 0.62) 2
• Prevalence of papilledema increases from 2.8% among patients with at least 1 MRI sign to 40% among patients with 4 or more MRI signs 4

Imaging Protocol Recommendations

• MRI head and orbits without and with IV contrast is the most useful initial imaging modality 1, 7
• Include fat-saturated T2-weighted sequences of the orbits for better evaluation of perioptic subarachnoid space 1
• Include sagittal T2-weighted sequences to evaluate for empty sella and midbrain position 7
• MR venography (MRV) should be included to evaluate for transverse sinus stenosis and to exclude cerebral venous sinus thrombosis 1

Clinical Correlation

• MRI signs of intracranial hypertension are relatively common incidental findings (49% of patients undergoing brain MRI had at least one sign) 4
• These findings rarely associate with papilledema unless multiple signs are present 4
• Incidentally detected signs without papilledema or concerning symptoms likely do not require lumbar puncture 4

Pitfalls and Considerations

• Normal MRI does not exclude intracranial hypertension
• Some findings (like empty sella) can be seen in other conditions or as normal variants
• Findings should be interpreted in clinical context with ophthalmologic examination
• CT has limited value in evaluating for intracranial hypertension compared to MRI 1, 7
• MRI findings may normalize after successful treatment of intracranial hypertension 3

MRI is the imaging modality of choice for suspected intracranial hypertension, with multiple characteristic findings that, when present in combination, strongly support the diagnosis.