MRI Brain: Sickle Cell Vasculopathy

MRI of the brain characterises the cerebrovascular consequences of sickle cell disease, including overt and silent infarcts, haemorrhage and large-vessel vasculopathy such as moyamoya. Unlike TCD, which estimates stroke risk, MRI with MRA depicts established parenchymal injury and vessel anatomy to guide transfusion and surgical revascularisation decisions. It is the study of choice for neurological symptoms, stroke evaluation and surveillance of silent cerebral infarction.

Indications

Acute neurological deficit or suspected stroke in sickle cell disease
Seizures, cognitive decline or headache warranting infarct assessment
Surveillance for silent cerebral infarction guiding therapy
Abnormal or low TCD velocities requiring vessel characterisation
Suspected moyamoya vasculopathy or progressive large-vessel stenosis
Pre-operative or pre-transplant neurological assessment and monitoring of therapy response

Contraindications & Cautions

Standard MRI contraindications: incompatible pacemakers, certain implants, ferromagnetic foreign bodies
Gadolinium: avoid or use macrocyclic agents cautiously in significant renal impairment (nephrogenic systemic fibrosis risk); most vasculopathy assessment uses non-contrast MRA and is achievable without gadolinium
Sedation risk in young children with cardiorespiratory compromise - involve anaesthesia and optimise hydration/oxygenation to avoid provoking sickling
Claustrophobia may require sedation or open-bore systems

Patient Preparation

Ensure adequate hydration, oxygenation and warmth to reduce the risk of sickling during the study
Screen thoroughly for MRI-incompatible implants and complete a safety checklist
Young or uncooperative children may need sedation or general anaesthesia with appropriate monitoring
Explain the procedure and obtain informed consent/assent
Review haemoglobin, recent transfusion and TCD history to contextualise findings
3T is preferred where available for higher-resolution vessel imaging

Technique & Parameters

Core sequences: axial T1, T2, FLAIR, DWI with ADC, and susceptibility-weighted imaging or GRE for haemorrhage/microbleeds
3D time-of-flight MRA of the circle of Willis for stenosis, occlusion and moyamoya
FLAIR for chronic infarcts and periventricular white matter disease; DWI for acute ischaemia
Consider perfusion imaging (ASL avoids gadolinium) to assess haemodynamic reserve
Slice thickness around 3-5 mm for structural sequences; thin overlapping slabs for MRA
Add MR venography if venous thrombosis is a consideration; contrast reserved for specific vascular/inflammatory questions

Systematic Review

Screen frontal and parietal deep white matter and watershed zones for silent infarcts on FLAIR
Assess DWI/ADC for acute infarction and its arterial territory
Evaluate SWI/GRE for microbleeds, prior haemorrhage or haemosiderin
Review MRA for stenosis, occlusion and the distal ICA/proximal MCA-ACA moyamoya pattern
Look for basal collateral vessels and the ivy sign of leptomeningeal collateralisation
Assess for subarachnoid or parenchymal haemorrhage and aneurysms
Correlate parenchymal injury with vascular territory and TCD data

Key Findings & Significance

Silent cerebral infarcts: small FLAIR hyperintensities in frontal/parietal white matter and watershed zones without acute deficit
Acute infarct: restricted diffusion in a territorial or borderzone distribution
Intracranial haemorrhage: parenchymal or subarachnoid, sometimes from associated aneurysms or moyamoya collaterals
Moyamoya pattern: progressive supraclinoid ICA and proximal MCA/ACA stenosis with basal collaterals
Cerebral microbleeds on SWI reflecting chronic vasculopathy
Vessel stenosis/occlusion on MRA identifying territory at risk and guiding transfusion or revascularisation

Differential Considerations

White matter FLAIR foci: silent sickle infarcts versus non-specific gliosis, demyelination or migraine-related lesions
Territorial infarct: large-vessel sickle vasculopathy, embolism, moyamoya collateral failure
Progressive ICA/MCA stenosis: sickle moyamoya versus idiopathic moyamoya or vasculitis
Parenchymal haemorrhage: ruptured moyamoya collateral, aneurysm, hypertensive bleed
Microbleeds: chronic sickle vasculopathy versus hypertensive or amyloid angiopathy (age-dependent)
Watershed injury: chronic anaemic hypoperfusion versus acute hypotensive event

Pearls & Pitfalls

Silent infarcts are common, associated with cognitive impairment and predict future overt stroke
Non-contrast TOF MRA usually suffices - avoid gadolinium where renal function is impaired
Optimise oxygenation and hydration around sedation to prevent iatrogenic sickling
Watershed distribution reflects the chronic anaemic, hyperdynamic circulation
Correlate MRA vasculopathy with TCD; low TCD velocities can reflect severe stenosis rather than reassurance
Look specifically for moyamoya collaterals and the ivy sign, which change management

Structured Report

List sequences performed and whether MRA/contrast were used
Describe acute and chronic infarcts with location, territory and diffusion characteristics
Report haemorrhage, microbleeds and any aneurysm
Detail MRA findings: stenosis, occlusion, moyamoya pattern and collaterals
Compare with prior imaging to assess progression
Impression: integrate parenchymal and vascular findings with TCD and clinical status; advise on transfusion/revascularisation referral and follow-up interval

References

DeBaun MR et al., SIT Trial: Silent Cerebral Infarcts and Transfusion (NEJM 2014)
American Society of Hematology Guidelines: Cerebrovascular Disease in Sickle Cell Disease
ACR Appropriateness Criteria: Cerebrovascular Disease
RadioGraphics: Neuroimaging of Sickle Cell Disease

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.

MRI Brain: Sickle Cell Vasculopathy

📋 Indications

⛔ Contraindications & Cautions

🧑‍⚕️ Patient Preparation

⚙️ Technique & Parameters

🔎 Systematic Review

🩻 Key Findings & Significance

🧠 Differential Considerations

💡 Pearls & Pitfalls

📝 Structured Report

📚 References