Study of the relationship between changes in functional and structural magnetic resonance imaging and memory disorders and depressive symptoms in patients with mesial temporal lobe epilepsy

Author(s)

Tamires Araujo Zanão

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Ciências Médicas
• Defense date: 2016-07-22

Examining board members

Fernando Cendes; Luiz Eduardo Betting; Rachel Paes Guimarães

• Advisor: Clarissa Lin Yasuda; Fernando Cendes

Abstract

Epilepsy is characterized by recurrent seizures associated with different etiological substrates, excluding symptomatic crises caused by acute brain injuries. The most common subtype of focal epilepsy is the mesial Temporal Lobe Epilepsy (mTLE), corresponding to about 60% of cases of ELT. Epilepsy is a brain disease that in addition to the predisposition to generate epileptic seizures, is also characterized by its neurobiological, psychological, cognitive and social consequences. Aspects of daily living of these patients are affected by comorbidities that impair cognition and social relations, including symptoms of depression. Several factors such as onset of epileptic seizure, duration and frequency of seizures, frequency of seizures and the use of anti-epileptic drugs interfere with cognitive performance. Neuropsychological deficits are prevalent in patients with TLE, especially when there is hippocampus¿ atrophy. TLE is considered focal epilepsy, but although the brain is spatially distributed it is functionally connected with the areas that continually exchange information with each other. These networks are functionally connected. They are linked to multiple sensory and cognitive processes and might be disrupted by neurological and neurophysiological disorders. These networks are called "Resting State Networks" (RSN) and can be observed during rest; in the absence of a goal-oriented task. The dysfunction of the RSN may play a role in the genesis of cognitive or psychiatric complications. This hypothesis, however, remains speculative and further clinical studies are needed to access the possible association between the severity of cognitive dysfunction and depressive symptoms with the injury of RSN. Among the various RSN, the Default Mode Network (DMN) is the one that is active during cognitive tasks, recovery of memories and future planning; it is required to engage in theory of mind and expression of moral judgments. Its activity is also increased in the absence of external stimuli and it is involved in higher mental functions. The posterior cingulate cortex is one of the most metabolically active regions in healthy subjects at rest with closed eyes and is commonly used to identify the DMN (seed method). Our objective was to investigate the relationship between absence and presence of hippocampal atrophy and DMN, cognitive (episodic memory) and depressive symptoms in patients with TLE and controls. We use functional and structural MRI and neuropsychological assessment to undertake such analyzes. As results, we obtained that patients with hippocampal atrophy had lower performance on neuropsychological assessments in relation to the group without atrophy and controls. However, there is not a significant difference between groups for depressive symptoms. Patient groups also showed higher participation of temporal areas in the controls for the analysis of DMN, suggesting that the temporal lobe is involved in the functioning of this network. Still, we analyzed the DMN according to the performance on neuropsychological evaluation (patients were classified as "normal" or "altered" to verbal memory, visual and delayed recall) and we found different patterns of activation for each of the groups, suggesting that these connectivity standards can be used as biological markers to estimate and predict performance of TLE patients in the assessed tasks (AU)

• FAPESP's process: 14/16559-0 - Study of the relationship between changes in functional and structural magnetic resonance imaging and memory disorders and depressive symptoms in patients with mesial temporal lobe epilepsy
• Grantee: Tamires Araujo Zanão Mariano
• Support Opportunities: Scholarships in Brazil - Master