From the Guidelines
Ring-enhancing lesions on brain imaging are most commonly caused by brain metastases, primary CNS neoplasms, abscesses, and inflammatory processes.
Causes of Ring-Enhancing Lesions
- Brain Metastases: The presence of multiple, enhancing intracranial lesions in a patient with a preceding cancer diagnosis should raise concern for brain metastases 1.
- Primary CNS Neoplasms: Primary CNS neoplasms such as gliomas, primary CNS lymphomas, and meningiomas can also present as ring-enhancing lesions 1.
- Abscesses: Abscesses can present as ring-enhancing lesions, and the central, nonenhancing, necrotic portion of abscesses tends to restrict diffusion 1.
- Inflammatory Processes: Inflammatory processes such as multiple sclerosis, acute disseminated encephalomyelitis, or sarcoidosis can also cause ring-enhancing lesions 1.
Diagnostic Considerations
- Imaging Characteristics: The imaging characteristics of the lesion, such as its location, shape, and enhancement pattern, can help narrow down the differential diagnosis 1.
- Clinical History and Exam: A thorough clinical history and exam can also help distinguish between different etiologies of ring-enhancing lesions 1.
- Biopsy: In some cases, a biopsy may be necessary to confirm the diagnosis, especially if the lesion cannot be distinguished from other pathologies with certainty 1.
- MRI with DWI and ADC Sequences: MRI with diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) sequences can help diagnose brain abscesses, which typically show restricted diffusion 1.
From the Research
Causes of Ring-Enhancing Lesions
The causes of ring-enhancing lesions on brain imaging are diverse and can be attributed to various cerebral pathologies. Some of the common causes include:
- Infectious diseases such as pyogenic abscess and tuberculosis 2, 3
- Neoplastic diseases such as primary neoplasm (glioma) and metastasis 2, 4
- Inflammatory diseases such as neurocysticercosis 2
- Demyelinating diseases such as multiple sclerosis 4
- Vascular diseases such as hematoma 5
Characteristics of Ring-Enhancing Lesions
The characteristics of ring-enhancing lesions can vary depending on the underlying pathology. Some common characteristics include:
- Central hypointensity and peripheral contrast enhancement on MRI 5
- Hypointense rims or arcs on T2-weighted images 4
- Signal on diffusion-weighted images, central homogeneity on T2, and multiplicity of lesions 4
Diagnostic Approach
Diagnosing ring-enhancing lesions requires a combination of clinical evaluation, imaging studies, and laboratory tests. Some of the diagnostic approaches include: