Efeitos da neuromodulação nas funções visuais básicas em pacientes após acidente vascular cerebral

Abstract

Stroke is one of the leading causes of death worldwide and its occurrence can generate disabling sequelae that affect the quality of life of individuals and their families. Among the main sequelae caused by stroke, we can mention motor, cognitive and sensorial deficits, the latter often neglected by its subclinical character. Thus, alternative therapies have often been studied and improved in order to reduce the functional damages caused by stroke. In this context, transcranial direct current stimulation (tDCS) may be an auxiliary tool to the process of rehabilitation of several sensory functions such as basic visual functions in patients suffering from stroke. In this sense, the main objective of the present study is to characterize basic visual functions before and after the anodic tDCS in post-stroke patients. For this, we counted with 10 participants, five healthy and five who were in the chronic phase of the stroke.This work was divided into two stages. In study 1, characterized as double-blind, placebo-controlled and cross-over, we sought to compare the effects of a single session of anodic and sham tDCS on healthy and stroke participants. In order to evaluate visual color perception, the Cambridge Color Test (CCT) was used. For the evaluation of the contrast sensitivity, were used vertical sinusoidal grids of spatial frequencies .3; .6; 2.0; 4.0; 11.3; 15.9 cpg. The normality of the data was confirmed using the Shapiro-Wilk test. Once normality was measured, repeated measurements was performed for all variables, considering the tests performed. For comparisons between pairs, the Bonferroni correction was used. The results showed that tDCS significantly altered the chromatic perception on the green and blue axis in the group of healthy participants. In the stroke group, no perceptual threshold was changed. No significant results were found at any spatial contrast sensitivity frequency in either group. In Study 2, a protocol of 20 minutes of stimulation with daily anodic tDCS for five consecutive days was performed in five patients in the chronic phase of stroke. After the protocol was completed, the participants were reassessed. The same visual assessment instruments used in Study 1 were used. The normality of the data was confirmed by the Shapiro-Wilk test. After this step, we performed t-tests for paired samples to compare the results of the first test and after five days of stimulation. Significance was not reached in any variable measured. In both studies, although many results did not present adequate significance, the data behaved in the expected direction, which allowed us to make some inferences regarding the effectiveness of the tDCS. Thus, it can be concluded that tDCS may be an adequate technique in modulating specific basic visual functions in healthy individuals and possibly in patients who have suffered stroke and that further studies should be developed in order to resolve the issues presented in the present study.