MRI Sequences for Detecting Demyelination
For detecting demyelination in the brain and spinal cord, use T2-weighted sequences, FLAIR (Fluid-Attenuated Inversion Recovery), and T1-weighted sequences with gadolinium contrast as your core protocol. 1
Brain Imaging Protocol for Demyelination
The standardized brain MRI protocol for suspected demyelinating disease should include:
- T2-weighted sequences (dual-echo, axial and coronal, 3mm slices) - these are fundamental for visualizing demyelinated lesions as hyperintense areas 1
- FLAIR sequences (preferably 3D with thin slices ≤1mm for triplanar reformatting) - superior for detecting periventricular and juxtacortical lesions while suppressing CSF signal 1
- T1-weighted sequences (thin slice 3D, ≤1mm) - useful for identifying "black holes" which represent severe demyelination and axonal loss 1
- Gadolinium-enhanced T1-weighted sequences - essential for detecting active demyelination (enhancing lesions indicate blood-brain barrier breakdown) 1
Spinal Cord Imaging Protocol for Demyelination
For spinal cord demyelination, the protocol differs slightly:
- T2-weighted Fast Spin Echo (FSE) sequences in sagittal and axial planes (3mm slices) - primary sequence for detecting spinal cord lesions 1, 2
- STIR (Short T1 Inversion Recovery) sequences in sagittal plane - significantly superior to conventional T2-weighted sequences for both lesion detection and conspicuity, detecting lesions missed on T2 in up to 24% of cases 3
- T1-weighted sequences with gadolinium - identifies active inflammatory demyelination 1
- Diffusion-weighted imaging (DWI) - should be included when spinal cord ischemia is in the differential, as it shows signal changes earlier than T2-weighted images 1
Advanced Sequences for Improved Detection
Several specialized sequences enhance demyelination detection:
- Susceptibility-Weighted Imaging (SWI) at 3.0T or higher - detects the perivenular distribution pattern characteristic of MS lesions and iron deposition from demyelination 1
- Double Inversion Recovery (DIR) - selectively depicts grey matter by suppressing white matter and CSF signals, improving cortical lesion detection 1
- Magnetization Transfer Ratio (MTR) - sensitive to cortical and spinal cord demyelination with 78% sensitivity, though specificity is modest at 29% 4, 5
- T1/T2-weighted ratio (T1T2R) - shows 75% sensitivity for cortical demyelination 4
Critical Technical Considerations
Use 3T scanners over 1.5T whenever available, as higher field strengths significantly improve detection of demyelinating lesions, particularly for perivenular patterns and iron deposition 1
The timing of imaging matters significantly in pediatric cases: a "T2 isointense stage" occurs at 8-12 months of age during normal myelination, which can obscure malformations and demyelinating lesions. Repeat MRI after completion of myelination (third year of life) may be necessary 1
Practical Imaging Strategy
For suspected demyelinating disease:
- Start with conventional sequences: T2-weighted, FLAIR, and gadolinium-enhanced T1-weighted imaging of brain and spinal cord 1
- Add STIR sequences for spinal cord imaging - this significantly improves lesion detection over T2 alone 3
- Include DWI if spinal cord ischemia is a consideration 1
- Consider advanced sequences (SWI, DIR) at specialized centers for difficult cases or when conventional MRI is negative but clinical suspicion remains high 1
A common pitfall is relying solely on axial T2-weighted sequences for spinal cord imaging - sagittal imaging is essential, and STIR sequences detect lesions missed on conventional T2 in a substantial proportion of cases 3. Another critical error is imaging during the T2 isointense period in infants without follow-up imaging 1.
The cervical spinal cord is most frequently involved in MS (80-90% of cases), and typical demyelinating lesions appear as focal, clearly demarcated, cigar-shaped lesions on sagittal images and wedge-shaped on axial images, usually located peripherally in lateral or dorsal columns 6, 7.