A. Ring Enhancing Brain Lesions (Table 1, Ref [1])

1. Infections
   1. Pyogenic brain abscess
   2. Toxoplasmosis
   3. Cysticercosis
   4. Necrotic fungal infection
2. Neoplasms
   1. Primary brain tumors - usually aggressive
   2. Primary central nervous system lymphoma
3. Demyelinating Disease
   1. Resolving infarction
   2. Hematoma - mid stage to late
   3. Thrombosed giant aneurysm
4. Other
   1. Radiation necrosis
   2. Postoperative necrosis

B. Non-Ringed Brain Lesions

1. Early Cerebral hemorrhage
2. Early Thromboembolic Stroke
3. Primary brain tumor - usually slow growing
4. Metastatic disease

References

1. Friedlander RM, Gonzolez RG, Afridi NA, Pfannl R. 2003. NEJM. 348(21):2125 (Case Record)