From the Guidelines
Ring-enhancing lesions on brain imaging are most commonly caused by brain metastases, high-grade gliomas, brain abscesses, and neurocysticercosis, as these conditions are associated with significant morbidity and mortality, and their prompt diagnosis and treatment are crucial for improving patient outcomes. The causes of ring-enhancing lesions can be categorized into:
- Infections:
- Brain abscess
- Toxoplasmosis (especially in immunocompromised patients)
- Tuberculosis
- Neurocysticercosis 1
- Tumors:
- High-grade gliomas (e.g., glioblastoma multiforme)
- Metastatic brain tumors 1
- Inflammatory conditions:
- Multiple sclerosis (acute demyelinating lesions)
- Acute disseminated encephalomyelitis (ADEM)
- Other causes:
- Subacute infarction
- Resolving hematoma The ring enhancement pattern occurs due to disruption of the blood-brain barrier, allowing contrast material to accumulate around the lesion's periphery, as noted in a study on brain metastases 1. The center often appears hypodense or non-enhancing due to necrosis or cystic changes. To differentiate between these causes, consider the patient's clinical history, immune status, and additional imaging characteristics, such as diffusion-weighted imaging, which can help distinguish abscesses (restricted diffusion) from tumors (variable diffusion) 1.
Further diagnostic workup may include additional imaging modalities (e.g., MR spectroscopy), laboratory tests, and potentially biopsy for definitive diagnosis. Prompt identification and treatment of the underlying cause are crucial for optimal patient outcomes, as delayed or inappropriate treatment can lead to increased morbidity and mortality. According to the most recent and highest quality study on brain metastases 1, a thorough diagnostic evaluation and timely treatment can significantly improve patient outcomes.
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 possible causes include:
- Infections, such as pyogenic abscess, tuberculosis, and toxoplasmosis 2, 3, 4, 5
- Tumors, including primary neoplasms like glioma and metastatic lesions 2, 4, 6
- Demyelinating diseases and immune-mediated disorders 4, 6
- Vascular diseases and treatment-related conditions 6
- Hematoma and other non-infectious, non-neoplastic conditions 6
Infectious Causes
Infectious causes of ring-enhancing lesions can occur in both immunocompetent and immunocompromised patients. Some of the infectious causes include:
- Toxoplasmosis, which is more common in immunocompromised patients 4, 5
- Pyogenic abscess and tuberculosis, which can occur in both immunocompetent and immunocompromised patients 2, 3
- Mycobacterium tuberculosis infection, which is more common in immunocompetent patients 4
Non-Infectious Causes
Non-infectious causes of ring-enhancing lesions can also occur and include:
- Primary neoplasms, such as glioma, and metastatic lesions 2, 4, 6
- Demyelinating diseases and immune-mediated disorders, which are more common in immunocompetent patients 4, 6
- Vascular diseases and treatment-related conditions, which can occur in both immunocompetent and immunocompromised patients 6
Diagnostic Challenges
Diagnosing the cause of ring-enhancing lesions can be challenging due to the non-specific clinical symptoms and the varied differential diagnosis. A combination of radiological investigations, such as MRI, and diagnostic procedures, such as brain biopsy, is often necessary to establish a definitive diagnosis 2, 4, 6.