Chapter 9: Acalculia & Body Schema Disorders

Acalculia refers to the acquired loss of mathematical ability following brain injury, categorized into primary forms—where the math deficit exists in isolation—and secondary forms, which stem from broader impairments in language, memory, or attention. Clinical research identifies specific manifestations such as spatial acalculia, often linked to right hemisphere damage affecting numerical alignment, and anarithmetria, characterized by fundamental computational failures typically associated with left parietal lesions. The text highlights fascinating dissociations where patients might retain mathematical facts while losing the ability to perform procedures, or show specific deficits in reading operation symbols or naming digits. Beyond mathematics, the chapter delves into body schema disturbances, focusing on autotopagnosia, finger agnosia, and right-left disorientation. Autotopagnosia involves an inability to localize body parts on oneself or others, often revealing a split between semantic knowledge of what a body part is and the spatial understanding of where it is located. Finger agnosia and right-left disorientation are discussed both as independent symptoms and as core components of the Gerstmann syndrome tetrad. Neuroanatomically, the left inferior parietal lobule is emphasized as a critical hub for these functions, though the chapter also notes the roles of the right hemisphere in visuospatial aspects and subcortical structures in rote retrieval. Finally, the authors emphasize the necessity of comprehensive diagnostic assessment using standardized batteries to distinguish acquired deficits from premorbid weaknesses, ensuring that factors like language proficiency and educational history are carefully considered in a clinical setting.