RESUMO
Material-specific memory dysfunction is a feature of mesial temporal lobe epilepsy (mTLE) and has lateralizing potential. We used voxel-based morphometry (VBM) and partial regression analysis of whole-brain tissue class volumes to test if there are correlations between material-specific cognitive dysfunction and localized gray matter loss. In a cohort of 89 patients with mTLE and hippocampal sclerosis (HS), we found correlations between global gray matter and cerebrospinal fluid volume and cognitive test scores in the group with left HS. These findings, however, were poorly anatomically localized; no global changes were detected in the group with right HS. Thus, correlations between gray matter loss and cognitive dysfunction were present and suggested the involvement of widespread neural networks.
Assuntos
Cognição/fisiologia , Hipocampo/patologia , Imageamento por Ressonância Magnética/métodos , Esclerose , Adolescente , Adulto , Idoso , Mapeamento Encefálico , Epilepsia do Lobo Temporal/patologia , Epilepsia do Lobo Temporal/fisiopatologia , Feminino , Lateralidade Funcional , Humanos , Imageamento Tridimensional/métodos , Masculino , Pessoa de Meia-Idade , Testes Neuropsicológicos , Análise de Regressão , Esclerose/patologia , Esclerose/fisiopatologiaRESUMO
PURPOSE: Patients with temporal lobe epilepsy (TLE) due to hippocampal sclerosis (HS) often suffer from material-specific memory impairments. The purpose of this study was to use functional magnetic resonance imaging (fMRI) to study the organization of specific memory functions in these patients. METHODS: We report 14 patients with unilateral TLE and HS, and 10 controls, performing an fMRI memory paradigm of word, picture, and face encoding. RESULTS: Compared with controls, patients with left TLE demonstrated less left MTL and greater right MTL activation and patients with right TLE demonstrated less right MTL and greater left MTL activation. Correlations between fMRI activation and memory performance revealed greater activation in the damaged left hippocampus to be correlated with better verbal memory performance in left TLE patients and greater right hippocampal activation to be correlated with better nonverbal memory in right TLE patients. Conversely, greater fMRI activation in the contralateral hippocampus correlated with worse memory performance. CONCLUSIONS: Our findings suggest that memory function in unilateral TLE is better when it is sustained by activation within the damaged hippocampus and that reorganization to the undamaged MTL is an inefficient process, incapable of preserving memory function.
Assuntos
Epilepsia do Lobo Temporal/fisiopatologia , Lateralidade Funcional/fisiologia , Hipocampo/fisiopatologia , Transtornos da Memória/fisiopatologia , Comunicação não Verbal/fisiologia , Comportamento Verbal/fisiologia , Adulto , Mapeamento Encefálico , Epilepsia do Lobo Temporal/diagnóstico , Epilepsia do Lobo Temporal/patologia , Feminino , Hipocampo/patologia , Hipocampo/fisiologia , Humanos , Imageamento por Ressonância Magnética , Masculino , Memória/fisiologia , Rememoração Mental/fisiologia , Pessoa de Meia-Idade , Testes Neuropsicológicos , Cuidados Pré-Operatórios , Reconhecimento Psicológico/fisiologia , Esclerose , Percepção Visual/fisiologiaRESUMO
Functional MRI (fMRI) is a useful tool for noninvasively localizing areas in the brain involved in specific cognitive functions. Since its introduction, there has been considerable speculation regarding the role it may play in the presurgical assessment of temporal lobe epilepsy (TLE). This review considers the progress made to date in using fMRI to investigate memory processing in the medial temporal lobe in normal subjects and in those with TLE. Results so far suggest that fMRI will be incorporated into the presurgical assessment of TLE in the coming years to improve definition of eloquent cerebral areas, with the objective of minimizing the adverse cognitive sequelae of anterior temporal lobe resection.