Objective:

To determine whether atypical presentations of corticobasal degeneration (CBD) exist, and if so, examine such presentations and identify neuroanatomic and histopathologic features that could account for such presentations.

Background:

CBD is a rare, progressive neurodegenerative disease associated with a variety of cognitive and motor features. International consensus criteria define five clinical phenotypes of CBD. It is unknown whether there are other “atypical” presentations of CBD and whether these atypical presentations have unique neuroanatomic and/or neuropathologic features. 

Design/Methods:

We identified all patients evaluated at Mayo Clinic with a pathological diagnosis of CBD. Medical records were screened to determine if clinical presentations were consistent with one of the five criteria phenotypes. Statistical parametric mapping (SPM) was used to compare grey/white matter volume loss in atypical CBD to CBD patients who had a classic corticobasal syndrome (CBS) presentation. Phosphorylated tau deposition was assessed using digital pathology in cortical and basal ganglia regions in atypical CBD and CBD-CBS.

Results:

Of 100 CBD patients, seven could not be classified (4 females, mean age at death = 71.1 years, mean disease duration = 6.3 years, like the other 93 CBD patients). Presenting features of the atypical patients included unclassified aphasia, apperceptive agnosia, Gerstmann syndrome, and topographagnosia. Over time, limb apraxia developed in three, but none met probable CBS criteria before death. SPM analysis showed greater temporal lobe, but less motor cortex, volume loss compared to CBD-CBS. Average tau immunoreactive lesion size was greater in all cortical regions, but not basal ganglia, in atypical CBD. Number of dystrophic neurites and their burden was greater in atypical CBD. 

Conclusions:

We have identified unique presentations of CBD not captured by the current consensus criteria. Such presentations were related to a transference of neurodegeneration away from motor cortex and towards temporal lobe, as well as tau lesion differences.