Topographical Disorientation in Mild Cognitive Impairment: A Voxel-Based Morphometry Study

BACKGROUND AND PURPOSE: To assess the neural substrates underlying topographical disorientation (TD) in patients affected by mild cognitive impairment (MCI), forty-one patients diagnosed with MCI and 24 healthy control individuals were recruited. METHODS: TD was assessed clinically in all participants. Neurological and neuropsychological evaluations and a volumetric-head magnetic resonance imaging scan were performed in each participant. Voxel-based morphometry was used to compare patterns of gray-matter atrophy between patients with and without TD, and a group of normal controls. RESULTS: We found TD in 17 out of the 41 MCI patients (41.4%). The functional abilities were significantly impaired in MCI patients with TD compared to in MCI patients without TD. Voxel-based morphometry analyses showed that the presence of TD in MCI patients is associated with loss of gray matter in the medial temporal regions, including the hippocampus and parahippocampal cortex, the fusiform gyrus, the inferior occipital gyrus, the amygdala, and the cerebellum. CONCLUSIONS: The findings found in this study represent the first evidence that the presence of TD in patients with MCI is associated with loss of gray matter in those brain regions that have been documented to be responsible for orientation in both neuropsychological and neuroimaging studies.

Topographical disorientation in Alzheimer's disease / Desorientação topográfica na doença de Alzheimer

Topographical disorientation (TD) has not been as extensively studied as other frequent manifestations of Alzheimer's disease (AD). OBJECTIVE: To verify the occurrence of TD and to identify the neuropsychological dysfunctions associated with TD in AD. METHOD: Thirty patients with probable AD, their caregivers and 30 subjects without dementia (controls) were interviewed with a questionnaire and evaluated with tests related to topographical orientation. RESULTS: AD patients, even those with mild dementia, differ from controls in the questionnaire on topographical orientation and in most neuropsychological tests except for tests of spatial working memory, point localization, three dimension and nonsense figure copy. When the performances in the neuropsychological tests of patients with mild or moderate dementia were compared, only landmark recognition and route description were more impaired in moderate dementia. CONCLUSION: TD occurs even in mild dementia of AD, a finding apparently not explained by the impairments of more elementary spatial functions.

Desorientação topográfica (DT) não tem sido tão exaustivamente estudada quanto outros sintomas frequentes da doença de Alzheimer (DA). OBJETIVO: Verificar a ocorrência de DT e identificar as disfunções neuropsicológicas associadas com a DT na DA. Método: Trinta pacientes com DA provável, seus cuidadores e trinta sujeitos sem demência (controles) foram entrevistados com um questionário e testes relacionados à orientação topográfica. RESULTADOS: Pacientes com DA, mesmo aqueles com demência leve, diferiram dos controles no questionário de orientação topográfica e na maioria dos testes neuropsicológicos, exceto nos testes memória operacional espacial, localização de pontos, cópia de figuras sem sentido e de figura em três dimensões. Quando os desempenhos de pacientes com demência leve ou moderada foram comparados, apenas os testes de reconhecimento de marcos e descrição de rotas foram mais comprometidos na demência moderada. CONCLUSÃO: DT ocorre mesmo na demência leve da DA, um achado aparentemente não explicado pelo comprometimento das funções espaciais mais elementares.