Cerebellar Atrophy
Gregory L. Katzman, MD, MBA
DIFFERENTIAL DIAGNOSIS
Common
Aging Brain, Normal
Encephalomalacia, NOS
Progressive Non-Familial Adult Onset Cerebellar Degeneration
Chronic Vertebrobasilar Insufficiency
Alcoholic Encephalopathy
Phenytoin (Dilantin) Use, Chronic
Paraneoplastic Syndromes
Lithium Intoxication
Radiation and Chemotherapy
Hypothyroidism
Less Common
Cerebellitis, NOS
Rare but Important
Multiple System Atrophy
Ataxia, Hereditary, NOS
Ataxia Telangiectasia
Cerebellar Atrophy, Hereditary, NOS
Congenital Vermian Hypoplasia (Mimic)
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
Clinical history often more important in making diagnosis than imaging findings
Helpful Clues for Common Diagnoses
Aging Brain, Normal
1 Brain volume (including cerebellum) with ↑ age
Relative ↑ CSF spaces
Selective atrophy of WM (not gray matter) predominates
“Successfully aging brain”: Thin periventricular high signal rim without white matter hyperintensities
May find focal/confluent periventricular white matter hyperintensities
Encephalomalacia, NOS
All etiologies appear as CSF replacing destroyed parenchyma due to
Post-ischemic loss of tissue following parenchymal hypoxic cell death
Post-traumatic loss from parenchymal irreversible traumatic insult
Post-inflammatory loss by irreversibly injured tissue
Progressive Non-Familial Adult Onset Cerebellar Degeneration
Chronic Vertebrobasilar Insufficiency
Vertebral artery stenosis, posterior circulation ischemia
Posterior circulation ischemia of hemodynamic or embolic etiology
Atrophy w/sulcal enlargement; DWI dark
Alcoholic Encephalopathy
Primary (direct) effects of EtOH = neurotoxicity → cortical/cerebellar degeneration & atrophy
Best clue: Disproportionate superior vermian atrophy
F-18 FDG PET: Significant decrease in whole-brain metabolism
Phenytoin (Dilantin) Use, Chronic
Dilantin vs. seizures as cause of atrophy debated
Dilantin induces organic cerebellar damage & may interfere w/intestinal absorption of folate causing folate deficiency → cerebellar atrophy
Seizures can cause cerebellar atrophy as cerebellum is very sensitive to hypoxia → cerebellar atrophy
Normal orientation & anisotropy of middle cerebellar peduncle & transverse pontine fibers
Paraneoplastic Syndromes
Remote neurological effect(s) of cancer, associated with extra-CNS tumors
Most common tumor: Small cell lung carcinoma
Manifestation of paraneoplastic encephalomyelitis associated w/cerebellar degeneration
Lithium Intoxication
Lithium is a neurotoxin with a particular affinity for the cerebellum
Atrophy of internal granule and Purkinje cell layers with dentate gliosis → neuronal loss and spongiosis
Preceded by neuroleptic malignant syndrome
Radiation and Chemotherapy
Injury may be divided into acute, early delayed injury, late delayed injury
Diffuse white matter injury or necrosis
Radiation → induces cryptic vascular malformations; blood products
Hypothyroidism
Best diagnostic clue: Symmetrical pituitary enlargement reversible with thyroid hormone replacement therapy
May see generalized atrophy; alternatively focal cerebellar vermis or olivopontocerebellar atrophy
↓ Cerebral perfusion & metabolism
Helpful Clues for Less Common Diagnoses
Cerebellitis, NOS
Rare inflammatory syndrome typically occurring as primary infectious, post-infectious, post-vaccination, or idiopathic disorder
Bilateral diffuse hemispheric abnormalities are most common (73%)
Often results in moderate to severe atrophy
Helpful Clues for Rare Diagnoses
Multiple System Atrophy
Sporadic progressive neurodegenerative disorder of adult onset, unknown etiology
“Hot cross bun” sign: Cruciform pontine hyperintensity on T2WI
Impaired orientation/anisotropy of middle peduncle transverse pontine fibers
Ataxia, Hereditary, NOS
Example: Friedreich ataxia → cerebellar, spinal atrophy
Can be divided into autosomal dominant, autosomal recessive, X-linked, mitochondrial
Some etiologies (e.g., cerebrotendinous xanthomatosis) may have diffuse white matter T2 hyperintense lesions
Ataxia Telangiectasia
Progressive neurodegenerative disorder; onset in early childhood; 1 in 40,000
Multisystem disease → cerebellar ataxia, oculomucocutaneous telangiectasias, & susceptibility to certain infections and neoplastic processes
Purkinje cell loss, atrophy of dentate nuclei, diffuse spongy degeneration, multiple foci of coagulative necrosis w/calcification in white matter
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