"Innumerable" lesion burden on brain MRI ‒ a diagnostic approach

Area of Science:

• Neuroradiology
• Neuroimaging
• Diagnostic Radiology

Background:

• The term "innumerable" on brain MRI signifies a rare and diagnostically challenging lesion burden.
• Systematic studies on brain MR imaging findings described as "innumerable" are lacking.

Purpose of the Study:

• To determine risk factors associated with innumerable brain lesions on MRI.
• To identify helpful MR imaging sequences for a diagnostic algorithm in cases of innumerable brain lesions.

Main Methods:

• A retrospective review of 12,495 brain MR imaging studies was conducted.
• Studies with 50 or more parenchymal lesions and the term "innumerable" were included.
• Patients were categorized into active and chronic groups based on MR and clinical features.

Main Results:

• Thirty-one studies met inclusion criteria, with 19 active and 12 chronic processes.
• The active group primarily comprised metastasis (9), infarction (6), and microbleeds (2).
• Malignancy and immunosuppression were identified as key risk factors.

Conclusions:

• Active innumerable brain lesions on MRI occur in 0.25% of studies.
• Metastasis and infarction were the most common causes in the active group, identified by specific MRI sequences.
• A diagnostic algorithm incorporating MR features and risk factors can guide brain biopsy decisions.