MRI Features of the Spine in Sickle Cell Disease
MRI of the spine in sickle cell disease shows characteristic findings of marrow hyperplasia, bone infarction, and potential ischemic complications that require specific imaging protocols for optimal evaluation.
Key MRI Features
Bone Marrow Changes
- Diffuse marrow hyperplasia: Appears as diffusely decreased signal intensity on T1-weighted images throughout the axial and peripheral skeleton due to hematopoietic marrow expansion 1
- Iron deposition: In patients receiving chronic transfusion therapy, appears as extremely low signal intensity on T2-weighted fast spin echo images with fat suppression 2
Infarction Patterns
- Acute bone marrow infarcts:
- Low signal intensity on T1-weighted images
- High signal intensity on T2-weighted images due to edema 1
- Chronic infarcts:
- Low signal intensity on both T1 and T2-weighted images, suggesting fibrosis 1
Structural Changes
- Vertebral body changes: Structural alterations due to marrow hyperplasia occur in approximately 44% of patients 3
- Vertebral collapse: Avascular necrosis leading to collapse of vertebral bodies seen in about 27% of patients 3
Complications
- Spinal cord ischemia: MRI without and with IV contrast is useful for evaluation when spinal cord ischemia is suspected in sickle cell disease 4
- Infective spondylitis: Most serious complication occurring in approximately 24% of patients 3
Optimal MRI Protocol for Sickle Cell Spine Evaluation
Essential Sequences
- T1-weighted spin-echo sequences (sagittal and axial)
- T2-weighted sequences with fat suppression or STIR (Short Tau Inversion Recovery)
- Diffusion-weighted imaging (particularly important for early detection of ischemic changes) 4
- Contrast-enhanced T1-weighted sequences with fat suppression when infection or ischemia is suspected
Importance of Diffusion-Weighted Imaging
- Diffusion-weighted imaging can show signal alteration in the spinal cord earlier after symptom onset compared with T2-weighted images 4
- Should be included whenever there is concern for spinal cord ischemia 4
Distinguishing Features from Other Conditions
Red Flags for Alternative Diagnoses
- Longitudinally extensive lesions extending over three or more vertebral segments (suggests neuromyelitis optica spectrum disorders rather than sickle cell disease) 4
- Prominent involvement of the central gray matter with spinal cord swelling (suggests inflammatory disorders) 4
- Leptomeningeal or nerve root involvement (suggests neurosarcoidosis or infectious disease) 4
Differentiating from Multiple Sclerosis
- MS spinal cord lesions are typically small, covering less than two vertebral segments 4
- MS lesions are usually located in the periphery of the spinal cord, mainly in lateral or dorsal columns 4
- Sickle cell disease typically shows more diffuse marrow signal changes rather than discrete focal lesions 1
Clinical Correlation and Monitoring
- MRI findings should be correlated with clinical symptoms, particularly in painful crisis
- MRI can differentiate between acute and chronic marrow infarcts, serving as a guide for monitoring and directing therapy 1
- Follow-up imaging may be necessary to assess treatment response, especially in cases of infection
Common Pitfalls and Caveats
- Iron deposition from repeated transfusions may be misinterpreted as marrow hyperplasia; T2-weighted fast spin echo images with fat suppression help distinguish between these entities 2
- Infection may mimic infarction; contrast enhancement patterns and diffusion-weighted imaging help differentiate
- Vertebral collapse in sickle cell disease may be confused with other causes of vertebral compression; clinical history and pattern of marrow signal changes are important for correct diagnosis
By understanding these characteristic MRI features, radiologists and clinicians can better diagnose and manage spinal complications in patients with sickle cell disease, potentially improving morbidity and mortality outcomes.