“¿Qué es una tortuga?neuropsicología de la demencia semántica”

Abstract

Semantic dementia (SD) is characterized by the loss of semantic knowledge. Patients present a fluent language with single-word comprehension deficit and anomia. Neuropsychiatric disorders often appear. The overlap of cognitive and neuropsychiatric symptoms with other diseases often makes their diagnosis complex. In addition, their evaluation usually requires spoken language and many times patients with DS present alteration in this area. The objectives were: 1) to know the main cognitive and neuropsychiatric markers that allow differentiating DS from Alzheimer's disease (AD) and behavioral variant Frontotemporal dementia (vbFTD) as well as left DS from right DS; 2) to design a simple and brief drawing task as a screening test to evaluate semantic knowledge; 3) to verify the retrogenesis hypothesis, comparing the knowledge acquisition that takes place in children and the loss objectified in patients with DS by means of a brief drawing task. We recruited a sample of 87 patients (35 SD, 32 AE and 20 VFTD), and 104 children aged between 40 and 96 months. The patients underwent a complete neuropsychological evaluation and an interview about the presence of neuropsychiatric symptoms. In addition, were administered a drawing task designed by our group. The group of children was evaluated through the same drawing task. Results: the 4 cognitive tests that most helped the differential diagnosis were: a) an episodic memory test that included semantic clues, b) a task that evaluates prosopagnosia, c) a naming test and d) a test that measures visuospatial ability. Aggresion, personal care, eating habits, especially specifically over-eating and altered food preference, were the most powerful items for group categorization. Our proposal of "a brief drawing task" allows to estimate the semantic knowledge and could be a good tool for the differential diagnosis of SD. Finally, it was observed that the items that younger children drew with a higher level of detail were those that patients with more advanced DS drew more completely and vice versa. Conclusions: Despite the latest advances in biomarkers and neuroimaging techniques, this work demonstrates the significant contribution of a comprehensive and detailed cognitive assessment in the differential diagnosis. Our study suggests the potential usefulness of a brief drawing task as a screening test for semantic knowledge. Finally, the acquisition and loss of semantic knowledge in children and patients with DS through a drawing task supports the theory of retrogenesis.