Acalculia in Autopsy-Proven Corticobasal Degeneration

Corticobasal degeneration (CBD) is a neurodegenerative condition presenting with an asymmetric extrapyramidal disorder, cortical sensory loss, and apraxia. While the original case descriptions mentioned acalculia,1 few studies have investigated this,2,3 and reports of acalculia in autopsy-proven CBD are very rare. We detail 2 autopsy-defined CBD cases with acalculia to emphasize that CBD compromises cognitive functioning due to disease that includes parietal cortex. ### Case 1. A 72-year-old right-handed woman with hypertension and hypothyroidism was evaluated for progressive cognitive and motor difficulties over 3 years. She first noted writing difficulty. Her right hand began performing involuntary, semi-purposeful movements. She required increasing assistance dressing and cutting food. She misjudged spatial relationships while driving and cooking. She had several falls. Examination revealed Mini-Mental State Examination (MMSE) score of 27. She had ideomotor apraxia, slowed writing, and difficulty copying geometric designs. Number knowledge was impaired, including miscounting “X” marks on a paper and erring during oral and written calculations (e.g., given “9 + 12,” she responded “20”). Memory, digit span, reading, comprehension, and speech were intact. She had axial rigidity and decreased right arm swing, but no other involuntary movements. Neuropsychological evaluation ( z scores relative to 25 demographically matched controls) revealed deficits on spatial tasks (e.g., geometric figure copy z = −7.74), mild executive dysfunction (e.g., animal category naming fluency z = −1.90), and preserved language (e.g., Boston Naming test z = −0.86) and memory (delayed recall of a 10-word list z = 0.02). MRI showed parietal atrophy. Over the next 18 months, ideomotor apraxia worsened, and she …