title: Symmetric corticobasal degeneration (S-CBD).
abstract: BACKGROUND
  Corticobasal degeneration (CBD) is a neurodegenerative disease characterized pathologically by neuronal loss, gliosis and tau deposition in neocortex, basal ganglia and brainstem. Typical clinical presentation is known as corticobasal syndrome (CBS) and involves the core features of progressive asymmetric rigidity and apraxia, accompanied by other signs of cortical and extrapyramidal dysfunction. Asymmetry is also emphasized on neuroimaging.
  
  
  OBJECTIVE
  To describe a series of cases of CBD with symmetric clinical features and to compare clinical and imaging features of these symmetric CBD cases (S-CBD) to typical cases of CBS with CBD pathology.
  
  
  METHODS
  All cases of pathologically confirmed CBD from the Mayo Clinic Rochester database were identified. Clinical records were reviewed and quantitative volumetric analysis of symmetric atrophy on head MRI using atlas based parcellation was performed. Subjects were classified as S-CBD if no differences had been observed between right- and left-sided cortical or extrapyramidal signs or symptoms. S-CBD cases were compared to 10 randomly selected typical CBS cases.
  
  
  RESULTS
  Five cases (2 female) met criteria for S-CBD. None had limb dystonia, myoclonus, apraxia or alien limb phenomena. S-CBD cases had significantly less asymmetric atrophy when compared with CBS cases (p=0.009); they were also younger at onset (median 61 versus 66 years, p<0.05) and death (67 versus 73 years, p<0.05). Family history was present in 40% of S-CBD cases.
  
  
  CONCLUSIONS
  CBD can have a symmetric presentation, clinically and radiologically, in which typical features of CBS, such as limb apraxia, myoclonus, dystonia and alien limb phenomenon, may be absent.
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Anhar
authors.initials: A
authors.lastname: Hassan
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Whitwell
authors.forename: Bradley F
authors.initials: BF
authors.lastname: Boeve
authors.forename: Clifford R
authors.initials: CR
authors.lastname: Jack
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Parisi
authors.forename: Dennis W
authors.initials: DW
authors.lastname: Dickson
authors.forename: Keith A
authors.initials: KA
authors.lastname: Josephs
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001479:Basal Ganglia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000000981:diagnostic imaging / Q000503:physiopathology*; D018450:Disease Progression; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D019636:Neurodegenerative Diseases / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology; D009483:Neuropsychological Tests; D011859:Radiography; D012189:Retrospective Studies