Cerebellar Mass

Gregory L. Katzman, MD, MBA

DIFFERENTIAL DIAGNOSIS

Common

Cerebral Ischemia-Infarction, Acute
Hypertensive Intracranial Hemorrhage
Neoplasms
- Medulloblastoma (PNET-MB)
- Pilocytic Astrocytoma
- Hemangioblastoma
- Metastases, Parenchymal

Less Common

Enlarged Perivascular Spaces
“Tumefactive” Demyelinating Disease
- Multiple Sclerosis
- ADEM
Abscess
Cerebellitis, NOS
Vascular Malformation, with/without Hemorrhage
- Cavernous Malformation
- Arteriovenous Malformation
- Dural A-V Fistula

Rare but Important

Tuberculosis
Glioblastoma Multiforme
Dysplastic Cerebellar Gangliocytoma
Oligodendroglioma
Ganglioglioma
Remote Cerebellar Hemorrhage

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Child vs. adult
- Child: Neoplasm > infection, demyelinating disease
- Adult: Ischemia, hypertensive hemorrhage > neoplasm

Helpful Clues for Common Diagnoses

Cerebral Ischemia-Infarction, Acute
- PICA distribution most common
  - DWI restriction w/correlating ADC map
  - Early cortical swelling
  - “Hemorrhagic transformation” in 15-45%
Hypertensive Intracranial Hemorrhage
- Round/elliptical high density mass
- 10% occur in pons, cerebellum
Medulloblastoma (PNET-MB)
- 4th ventricle > cerebellum
- Desmoplastic variant
Pilocytic Astrocytoma
- Best clue: Cystic mass + enhancing mural nodule
- Childhood (not adult) tumor
Hemangioblastoma
- Adult with intra-axial posterior fossa mass with cyst, enhancing mural nodule abutting pia
- May be associated with von Hippel-Lindau syndrome
Metastases, Parenchymal
- Intra-axial posterior fossa mass in middle-aged/older adult? Think metastasis!
- Can be solitary but look for other lesions

Helpful Clues for Less Common Diagnoses

Enlarged Perivascular Spaces
- Fluid-filled spaces that look like CSF, surround/accompany penetrating arteries
- No diffusion; may have FLAIR hyperintense parenchymal rim
Multiple Sclerosis
- Fulminant acute plaque or conglomeration of acute plaques forming mass lesion(s)
- May display ring enhancement simulating tumor or abscess
- Most common disabling CNS disease of young adults; 1:1000 in developed countries
ADEM
- Lesions 10-14 days following infection/vaccination
- Large flocculent FLAIR hyperintensity but with less mass effect than that expected
- Punctate, ring, incomplete ring, peripheral enhancement
Abscess
- Especially in children
- Ring-enhancing lesion
  - High signal on DWI, low ADC
  - T2 hypointense rim with surrounding edema
- Central necrotic area may show presence of acetate, lactate, alanine, succinate, pyruvate, amino acids on MRS
Cerebellitis, NOS
- Typically occurs as a primary infectious, post-infectious, post-vaccination, or idiopathic disorder
- Variable enhancement → none to intense; meningeal enhancement can be seen
- Abnormal T2 hyperintensity & swelling
- Bilateral diffuse hemispheric abnormalities are most common (73%)
Cavernous Malformation
- “Popcorn ball” appearance with complete hypointense hemosiderin rim on T2WI MR
- NECT: 40-60% Ca++
Arteriovenous Malformation
- “Bag of black worms” (flow voids) on MR with minimal/no mass effect
- Flow-related aneurysm on feeding artery 10-15%; intranidal “aneurysm” > 50%
Dural A-V Fistula
- Best imaging tool: DSA with superselective catheterization of feeders
- Dural AVF involving the region of the foramen magnum, tentorium, torcula Herophili, or posterior fossa veins (e.g., inferior vermian vein) may affect cerebellum
- Most often presents with hemorrhage

Helpful Clues for Rare Diagnoses

Tuberculosis
- CECT: “Target sign” → central Ca++ or enhancement surrounded by enhancing rim
- T1 C+: Solid homogeneous to rim enhancement; ± central necrosis
- MRS: Prominent lipid, lactate but no amino acid resonances
Glioblastoma Multiforme
- Thick irregular enhancing rind of neoplastic tissue surrounding necrotic core
- Characterized by necrosis and neovascularity
- Viable tumor extends far beyond signal abnormalities
Dysplastic Cerebellar Gangliocytoma
- Widened cerebellar folia with a striated appearance on MR
- Thinning of skull may be apparent
- a.k.a., Lhermitte-Duclos disease, associated with Cowden syndrome
Oligodendroglioma
- Partially Ca++ subcortical/cortical mass in middle-aged adult
- Majority calcify → nodular or clumped Ca++ (70-90%)
- May expand, remodel, erode calvarium
Ganglioglioma
- Partially cystic, enhancing, cortically based mass in child or young adult
- Ca++ common → 35-50%
- Cortical dysplasia is commonly associated
Remote Cerebellar Hemorrhage
- Occurs after supratentorial craniotomy
- Superior cerebellar folia
  - Bilateral (33%)
  - Contralateral to side of surgery (29%)
  - Ipsilateral (22%); isolated vermian (9%)