Ring-Enhancing Lesion, Solitary

Yoshimi Anzai, MD, MPH

Judy Tan, MD

DIFFERENTIAL DIAGNOSIS

Common

Metastases, Parenchymal
Glioblastoma Multiforme
Abscess
Intracerebral Hematoma (Subacute)
Cerebral Infarction, Subacute
Radiation Necrosis

Less Common

Tumefactive Demyelinating Lesion
Neurocysticercosis
Lymphoma, Primary CNS
Toxoplasmosis, Acquired
Tuberculoma
Aneurysm (Thrombosed)
Arteriovenous Malformation (Thrombosed)
Ganglioglioma
Pilocytic Astrocytoma

Rare but Important

Lacunar Infarction (Subacute)
Fungal Diseases
Parasites, Miscellaneous

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Solitary ring-enhancing lesions most often related to tumor, infection, or demyelination
Location of lesion often helpful for diagnosis
Metastatic lesions are typically subcortical, while primary tumors are often deep
Smooth rim enhancement suggests abscess
Irregular, thick rim suggests tumor

Helpful Clues for Common Diagnoses

Metastases, Parenchymal
- Often significant vasogenic edema
- Gray-white matter junction typical
- Generally does not restrict on DWI
- Multiple > single lesion
Glioblastoma Multiforme
- 95% of primary GBMs have central necrosis, rim enhancement, DWI negative
- Heterogeneous white matter (WM) tumor with irregular, thick rim enhancement
- Strong tendency to infiltrate widely
Abscess
- Can be pyogenic, fungal, or granulomatous
- T2 hypointense rim & thin enhancing rim
- DWI + in pyogenic abscess
- Look for other signs of infection & source in mastoids & paranasal sinuses
- Proton MR spectroscopy (MRS) within pyogenic abscess cavity shows elevated cytosolic amino acids (0.9 ppm), acetate (1.92 ppm), and succinate (2.4 ppm)
Intracerebral Hematoma (Subacute)
- History of trauma, coagulopathy, amyloid angiopathy
- Ring enhancement common subacutely
- Look for blood products on MR (especially on GRE/T2*/SWI sequence)
Cerebral Infarction, Subacute
- Signal changes in a vascular territory
- May see gyriform T1 hyperintensity
- Enhancement: Ring-like &/or gyriform
- At this stage, DWI has normalized
Radiation Necrosis
- Occurs months after radiotherapy in site of radiation portal
- Perfusion MR may discriminate between radiation necrosis & tumor
  - Radiation necrosis: Hypoperfusion
  - Tumor: Hyperperfusion

Helpful Clues for Less Common Diagnoses

Tumefactive Demyelinating Lesion
- Seen in multiple sclerosis & ADEM
- Often incomplete ring enhancement, little mass effect or vasogenic edema; resolves with steroid therapy
- Often mimics neoplasm
Neurocysticercosis
- Cyst with a scolex is pathognomonic
- Ring enhancement seen in colloidal vesicular & granular nodular stage
Lymphoma, Primary CNS
- Ring-enhancing pattern seen in immunocompromised patients
- Typical locations: Periventricular, corpus callosum, basal ganglia (BG)
- Hyperdense on CT, hypointense on T2 MR due to hypercellularity
- MRS may differentiate from toxo
- Lymphoma: Elevated choline level
Toxoplasmosis, Acquired
- Solitary or multiple lesions with nodular or ring enhancement
- Occurs in immunocompromised, especially HIV+ patients
Tuberculoma
- Associated with TB meningitis in 50%
- Can be solitary or multiple
Aneurysm (Thrombosed)
- May be partially or completely thrombosed
- Laminated appearance of thrombus
- May see pulsation artifact on MR
Arteriovenous Malformation (Thrombosed)
- May be partially or completely thrombosed
- Blood products, calcium are common
- Serpiginous nidus seen as flow voids on MR, large draining veins
Ganglioglioma
- May be solid, cystic, or mixed solid-cystic
- 1/3 have calcifications
- Temporal lobes & cerebellar hemispheres most common locations
- Temporal lobe lesions present with seizures
Pilocytic Astrocytoma
- Common locations: Cerebellum, hypothalamus, optic pathway
- 4 predominant imaging patterns
  - Mass with enhancing cyst wall & intensely enhancing mural nodule (46%)
  - Mass with a nonenhancing cyst & intensely enhancing mural nodule (21%)
  - Necrotic mass with central nonenhancing zone (16%)
  - Predominantly solid mass with minimal cyst-like component (17%)
- Associated with neurofibromatosis type 1

Helpful Clues for Rare Diagnoses

Lacunar Infarction (Subacute)
- Typically in BG, thalamus, or deep white matter
- May enhance subacutely
Fungal Diseases
- Rare infections that occur primarily in immunosuppressed patients
- Includes nocardia, blastomycosis, coccidioidomycosis, histoplasmosis, candidiasis
- Multiple lesions > single lesion
Parasites, Miscellaneous
- Rare infections occur at all ages, most common in children & young adults
- Patient’s travel history important
- May cause solitary or multiple ring-enhancing lesions
- Amebic encephalitis: Single or multiple nodular or ring-enhancing masses
- Paragonimiasis: Hemorrhage or infarct with granuloma formation; ring enhancement

SELECTED REFERENCES

1. Smirniotopoulos JG et al: Patterns of contrast enhancement in the brain and meninges. Radiographics. 27(2):525-51, 2007

Image Gallery

Axial T1 C+ FS MR shows a solitary, thick-walled mass in the right cerebellum

. A thick enhancing rim suggests tumor. Biopsy proved metastatic melanoma.

Coronal T1 C+ MR shows a cystic mass with large mural nodule in the cerebellum

. While this lesion resembles hemangioblastoma, the wall of most cystic hemangioblastomas rarely enhances.

(Left) Axial T1 C+ MR shows a histologically proven glioblastoma multiforme in the left thalamus

. Note irregular wall & central necrosis. GBMs tend to occur in the deep white matter or deep nuclei & infiltrate widely beyond the enhancing margins. (Right) Axial T1 C+ MR shows a large glioblastoma multiforme