Is MRV (Magnetic Resonance Venography) with or without contrast best for diagnosing hydrocephalus?

MRV for Hydrocephalus: Contrast is NOT Needed

For diagnosing hydrocephalus, MRI without IV contrast is the appropriate imaging modality; MRV (Magnetic Resonance Venography) is not indicated for routine hydrocephalus evaluation, and when venous imaging is needed, it should be performed without contrast. 1, 2

Why MRV is Not the Primary Imaging Tool for Hydrocephalus

Standard MRI Without Contrast is Optimal

• The American College of Radiology explicitly states that MRI head without IV contrast is usually appropriate for initial imaging of suspected normal pressure hydrocephalus (NPH), and the diagnostic findings are optimally visualized on noncontrast MRI sequences. 1, 2
• MRI without contrast can identify all key diagnostic features of hydrocephalus including ventricular enlargement (Evans index >0.3), temporal horn enlargement, callosal angle <90 degrees, transependymal CSF flow, and aqueductal flow void. 1
• MRI is superior to CT for detecting periventricular white matter changes and cerebral aqueduct flow void, which cannot be visualized on CT and is associated with good response to shunt surgery. 2, 3

When MRV Might Be Considered (Rare Scenarios)

• MRV without contrast may be obtained if there is specific concern for venous sinus thrombosis as a cause of hydrocephalus or if evaluating a mass near the sagittal sinus. 4
• The ACR Appropriateness Criteria rate MR venography head without IV contrast as a rating of 4 (may be appropriate) for general cerebrovascular disease evaluation, indicating it is not a primary modality. 4
• If venous imaging is needed, noncontrast MRV can be performed when contrast cannot be administered. 4

Critical Distinction: MRV vs. Standard MRI

MRV is Vascular Imaging, Not Hydrocephalus Imaging

• MRV specifically images venous structures (dural sinuses, cortical veins), not the ventricular system or CSF spaces that are the focus of hydrocephalus evaluation. 4
• Standard MRI sequences (T1, T2, FLAIR) provide the anatomic detail needed for hydrocephalus diagnosis without requiring specialized vascular imaging. 1, 2

Specialized CSF Flow Imaging (When Needed)

• For complex cases requiring CSF flow assessment, phase-contrast MRI (PC-MRI) or cine MRI showing ventricular flow rates can identify shunt-responsive NPH patients with high positive predictive value. 2, 5
• Gadolinium-enhanced MR ventriculography (off-label intrathecal gadolinium) may be used in select cases of multiloculated hydrocephalus to assess CSF flow obstruction sites, but this is invasive and reserved for complex cases. 6, 7, 8

When IV Contrast Might Be Added (Limited Utility)

Specific Clinical Scenarios Only

• The ACR suggests IV contrast could have limited utility when infectious or inflammatory conditions (such as meningitis, ventriculitis, or carcinomatosis) are among the differential diagnoses being considered. 1
• Contrast may help identify underlying enhancing masses or vascular malformations if these are suspected causes of obstructive hydrocephalus. 4

Avoid Reflexive Contrast Ordering

• The ACR recommends avoiding ordering MRI with contrast reflexively for NPH evaluation, as this adds unnecessary cost, time, and potential contrast-related risks without improving diagnostic accuracy for hydrocephalus itself. 1

Practical Algorithm for Imaging Selection

Initial Evaluation

1. Order MRI head without IV contrast for suspected hydrocephalus of any type (communicating, obstructive, or NPH). 1, 2
2. Ensure sequences include T1, T2, FLAIR, and sagittal views to assess callosal angle and aqueductal flow void. 1, 2

If MRI is Contraindicated

• Use CT head without IV contrast as an alternative, recognizing it has lower sensitivity for periventricular changes and cannot detect aqueductal flow void. 2

Add Contrast Only If:

• Infectious/inflammatory etiology is suspected (meningitis, ventriculitis). 1
• Underlying mass lesion needs characterization. 4
• Vascular malformation is in the differential. 4

Consider MRV (Without Contrast) Only If:

• Venous sinus thrombosis is suspected as the cause of hydrocephalus. 4
• Evaluating mass proximity to dural venous sinuses. 4

Common Pitfalls to Avoid

• Do not confuse MRV (venous imaging) with standard MRI for hydrocephalus evaluation—they serve different purposes. 4, 1
• Do not order contrast-enhanced MRI routinely for hydrocephalus—the diagnostic features are visible without contrast. 1
• Do not use MRV as a substitute for standard MRI sequences when evaluating ventricular size and morphology. 1, 2
• Be aware that intrathecal gadolinium for MR ventriculography is off-label and should be reserved for complex multiloculated cases where standard imaging is insufficient. 6, 7, 8