Recommended Imaging Modality for Hydrocephalus
MRI of the head without IV contrast is the optimal imaging modality for evaluating hydrocephalus, as it provides superior anatomical detail and functional information about cerebrospinal fluid dynamics compared to other imaging techniques. 1, 2
Primary Imaging Options
MRI Head Without Contrast
- First-line imaging choice for most patients with suspected hydrocephalus
- Provides superior soft tissue characterization and multiplanar capabilities
- Can identify:
- Cause of obstruction in the CSF pathway
- Ventricular size and configuration
- Presence of transependymal flow (interstitial edema)
- Associated brain parenchymal abnormalities
CT Head Without Contrast
- Alternative when MRI is contraindicated or unavailable
- Appropriate for emergency situations requiring rapid assessment
- Advantages:
- Quick acquisition time
- No sedation required
- Readily detects ventricular enlargement
- Useful for acute evaluation of complications (e.g., shunt failure)
- Limitations:
- Limited soft tissue contrast
- Exposure to ionizing radiation (particularly concerning in pediatric patients)
- Less detailed information about CSF flow dynamics
Special MRI Sequences for Hydrocephalus Evaluation
For optimal assessment of hydrocephalus, specific MRI sequences should be included 3:
- 3D CISS (Constructive Interference in Steady State): Excellent for visualizing CSF pathways and identifying obstructions
- Cine Phase Contrast (PC): Evaluates CSF flow dynamics, particularly useful in aqueductal stenosis
- T2-weighted sequences: Best for assessing ventricular size and periventricular edema
- Sagittal T1-weighted images: Evaluates midline structures including aqueduct of Sylvius
Age-Specific Considerations
Neonates and Infants
- Cranial ultrasound may be used as initial screening in infants with open fontanelles 3, 4
- Advantages: Bedside evaluation, no sedation required, no radiation
- Limitations: Limited field of view, operator-dependent, cannot reliably identify etiology
- MRI remains the definitive study even in this age group when diagnosis is uncertain
Children and Adults
- MRI without contrast is the preferred modality 1
- CT may be used in emergency situations or when MRI is contraindicated
Etiology-Specific Imaging
- Obstructive hydrocephalus: MRI with sagittal and axial T2-weighted sequences to identify site of obstruction
- Normal pressure hydrocephalus: MRI with assessment of ventricular size, periventricular changes, and CSF flow studies
- Post-hemorrhagic hydrocephalus: Initial CT to detect acute blood, followed by MRI for ongoing management
- Suspected infection: Consider MRI with contrast to evaluate for complications
Common Pitfalls to Avoid
- Relying solely on CT when MRI is available and not contraindicated
- Not including specialized MRI sequences that evaluate CSF flow dynamics
- Failing to image the entire neuraxis when Chiari malformations or spinal dysraphism are suspected
- Misinterpreting incidental findings as the cause of hydrocephalus
- Not correlating imaging with clinical presentation when determining shunt responsiveness
MRI provides the most comprehensive assessment of hydrocephalus by offering both anatomical and functional information, making it the preferred modality for initial evaluation and follow-up of patients with hydrocephalus 3, 2.