Why is an MRI indicated in a patient with sickle cell disease, IgM (Immunoglobulin M) dengue positive, seizure disorder, and micro hemorrhage with surrounding perilesional edema on non-contrast computed tomography (NCCT) head, and what findings can be expected on MRI?

MRI Indications in a Patient with Sickle Cell Disease, Dengue Infection, Seizures, and Microhemorrhage

MRI is strongly indicated in this patient with sickle cell disease, IgM dengue positivity, seizure disorder, and microhemorrhage with perilesional edema on NCCT to better characterize the extent of cerebrovascular involvement, detect additional lesions, and guide management decisions. 1, 2

Rationale for MRI in This Complex Case

• MRI is significantly more sensitive than NCCT for detecting subacute and chronic hemorrhage, which is crucial for evaluating the microhemorrhage already identified on NCCT 1
• MRI is indicated when NCCT results are normal or inconclusive but there are persistent unexplained neurological findings, such as seizures in this case 1, 2
• The combination of sickle cell disease and dengue infection creates a high-risk scenario for cerebrovascular complications requiring detailed evaluation 3, 4
• Susceptibility-weighted imaging (SWI) is 3-6 times more sensitive than conventional T2* gradient-echo sequences in detecting hemorrhagic lesions, making it essential for complete evaluation 1

Expected MRI Findings in This Patient

Sickle Cell Disease-Related Findings:

• Evidence of vasculopathy and focal hypoperfusion, which are factors in the development of sickle cell disease-associated seizures 3
• Possible small ischemic infarcts that may be missed on CT but detected on MRI, as 70% of missed ischemic stroke diagnoses present with altered mental status 1, 2
• Potential moyamoya-like changes, as up to 40% of children with sickle cell disease may show these vascular abnormalities 1

Hemorrhage-Related Findings:

• Better characterization of the microhemorrhage already identified on NCCT, including precise location, extent, and age 1
• Detection of additional microhemorrhages not visible on NCCT, as SWI is extremely sensitive for depicting intracranial blood products of various stages 1
• Evaluation of surrounding perilesional edema with greater sensitivity than NCCT 1

Seizure-Related Findings:

• Potential areas of cortical or subcortical injury that may serve as seizure foci 1
• Possible underlying structural abnormalities contributing to seizures that weren't apparent on NCCT 2
• Correlation between areas of perfusion abnormality and seizure activity, as these are often ipsilateral 3

Optimal MRI Protocol for This Patient

• MRI head without IV contrast as the initial study to evaluate brain parenchyma and detect hemorrhage 1
• T2* gradient-echo (GRE) and susceptibility-weighted imaging (SWI) sequences to optimally detect microhemorrhages 1
• Diffusion-weighted imaging (DWI) to identify acute ischemic changes and axonal injuries 1
• T2-weighted FLAIR imaging to detect high signal in the sulci (ivy sign), which may indicate slow flow in affected vascular territories 1
• MR angiography (MRA) of the head and neck to evaluate for vasculopathy, which is common in sickle cell disease 1, 5

Clinical Significance in This Patient

• The combination of sickle cell disease and dengue infection creates a high risk for vaso-occlusive crisis and cerebrovascular complications 4
• Cerebrovascular accident (CVA) is associated with a 5.7-fold increased risk of developing seizures in patients with sickle cell disease 6
• MRI findings will help guide management decisions, including the need for transfusion therapy to lower hemoglobin S levels below 30% 4
• Detailed characterization of vascular abnormalities is essential for long-term management of this patient's neurological complications 7

Potential Pitfalls and Considerations

• Gadolinium-based contrast agents are generally not necessary for initial evaluation of traumatic or hemorrhagic lesions 1
• Patient stability must be considered, as MRI may not be feasible in unstable patients or those requiring continuous monitoring 2
• If the patient cannot undergo MRI due to contraindications or instability, CTA of the head and neck with IV contrast could be an alternative, though less sensitive for microhemorrhages 1
• Timing is crucial - MRI should be performed as soon as clinically feasible to guide management decisions 2