Diagnostic Approach to T1 Hyperintense Cortical Lesions

Introduction to Diagnostic Considerations

• The American Academy of Neurology recommends considering hemorrhagic metastases, subacute cortical infarction with laminar necrosis, focal cortical dysplasia type IIb, melanin-containing lesions, and proteinaceous lesions in the differential diagnosis for T1 hyperintense cortical lesions, with the specific diagnosis determined by clinical context, lesion morphology, and additional MRI sequences 1, 2

Hemorrhagic Lesions

• Hemorrhagic metastases are the most common cause of T1 hyperintense cortical lesions in patients with known malignancy, particularly from melanoma, renal cell carcinoma, thyroid carcinoma, and ovarian cancer 1
• The presence of multiple lesions strongly favors metastatic disease over other etiologies 1

Developmental and Epileptogenic Lesions

• Focal cortical dysplasia (FCD) type IIb characteristically shows T1 hyperintensity in unmyelinated infant brains, appearing opposite to the expected signal in the involved cortical region 2
• Clinical presentation with medically refractory focal seizures strongly suggests FCD 2

Diagnostic Algorithm

• The American College of Radiology recommends obtaining T2*/SWI sequences to distinguish hemorrhagic from non-hemorrhagic causes, with blooming present indicating hemorrhagic lesion 1
• Assessing lesion morphology, such as curvilinear following cortical ribbon for laminar necrosis or focal mass with enhancement at gray-white junction for metastasis, is crucial for diagnosis 1, 2

Common Pitfalls and Considerations

• The National Institute of Neurological Disorders and Stroke advises against assuming all T1 hyperintense cortical lesions are hemorrhagic and recommends correlating with clinical history, such as known malignancy favoring metastases or acute stroke favoring laminar necrosis 1, 2
• Multiple sclerosis cortical lesions are typically NOT T1 hyperintense, appearing as T1 hypointense or isointense lesions best seen on DIR sequences 3, 4, 5