Longitudial observation of dynamic changes in cortical function and white matter fibrous structure of patients with visual pathway lesions by blood oxygenation level dependent-functional magnetic resonance imaging combined with diffusion tensor imaging

Abstract

Background Functional magnetic resonance imaging (fMRI) is initially used for visual cortex location. However, the application of fMRI in investigating the development of visual pathway lesions needs to be further observed. Objective This study is to longitudially observe the dynamic changes in cortical function and white matter fibrous structure of patients with visual pathway lesions by blood oxygenation level dependent-functional magnetic resonance imaging (BOLD-fMRI) combined with diffusion tensor imaging (DTI), and to analyze the characteristics of brain function and structural recombination at convalescent period of lesions. Design Randomized controlled observation. Setting Department of Radiology, the General Hospital of Nanjing Military Area Command of Chinese PLA. Participants Eight patients with unilateral or bilateral visual disorder caused by visual pathway lesions, who admitted to Department of Radiology, the General Hospital of Nanjing Military Area Command of Chinese PLA from January to September 2006 were involved, and served as experimental subjects. The patients, 6 males and 2 females, were aged 16–67 years. They had visual disorder confirmed by clinical examination, i.e. visual pathway lesion, which was further diagnosed by MR or CT. Another 12 subjects generally matching to those patients of experimental group in gender, age and sight, who received health examination in synchronization were involved and served as controls. The subjects had no history of eye diseases. Their binocular visual acuity (or corrected visual acuity) was over 1.0. Both routine examination of ophthalmology and examination of fundus were normal. Informed consents of detected items were obtained from all the subjects. Methods Signa Excite HD 1.5T magnetic resonance imaging system with 16 passages (GE Company, USA) and coil with 8 passages were used; brain functional stimulus apparatus (SAV-8800. Meide Company) was used for showing experimental mission. At the early stage and convalescent period of lesions, the patients with visual pathway lesion were examined by BOLD-fMRI combined with DTI, respectively, and brain activation volume, optic radiation anatomical structure and fractional anisotropy (FA) value were compared before and after symptomatic treatment under the stimulation to both eyes. The above-mentioned indexes were observed and compared between experimental and control groups. Main outcome measures BOLD-fMRI and DTI manifestations before and after treatment in the experimental group and control group. Results All the 8 patients and 12 healthy subjects participated in the final analysis. ▪BOLD-fMRI manifestation: Bilateral occipital lobes and calcarine gyri of control subjects were obviously activated. The activation volume of striate cortex under the stimulation to two eyes was obviously reduced in the experimental subjects than in the control subjects ( P < 0.05). After treatment, the amount of activated pixel in the stimulated cortex was increased, and the activation area was expanded. ▪ DTI results: Bilateral optic radiation of healthy controls could be traced in the subcortex. Complete optic radiation of patients with visual pathway lesion could be shown. There was no significant difference in optic radiation between experimental subjects and healthy controls. No significant difference in optic radiation was found before and after observation, either ( P > 0.05). In 4 patients with occipital lobe and optical center lesions, optic radial fiber was partially interrupted and tenuous, displacement could be found, and FA value was obviously decreased; After treatment, optic radial fiber bundle recovered to some extent, and FA value was also increased. Conclusion BOLD-fMRI and DTI explain the development of lesion from the aspect of cortical function and fibrous anatomy. It has important significance for investigating the recombination of cortical function area following visual pathway lesion.