MR diffusion tensor imaging applied to the spinal cord of patients with neuropatic pain secundary to Herpes Zoster infecction

Abstract

The fiber tracking obtained by magnetic resonance analyze a group of nervous fibers based on characteristics of diffusion of the water represented by a tensor, by connecting points it forms the image of a nervous pathway. It is a three-dimensional reconstruction of images obtained with the diffusion sequences in the MR studies.The use of diffusion sequences in the study of the spine is more recent when compared to its use in the studies of the brain. Problems like the occurrence of artifact secondary to movements, breathing small size of the spinal cord were partially solved and the application of these techniques in the spinal cord has contribute to complementary diagnosis. There are studies of spinal cord compression with evidence of morphological alterations and eventual functional abnormalities. To study arterio-venous malformation fiber tracking can help the surgical preparation when it is possible to visualize the shift of fibers. To study multiple sclerosis and trauma of he spine it can quantify the extension of the lesion. The functional aspect of the dti exam allows a better perspective of clinical-radiographic correlation. There is a study about siringomiely showing a correlation between characteristics of the pain of the patient and the dti results. Qualitative aspects using the FA of the fibers were used to compare anterior to posterior segments of the spinal cord and correlate it to the pain presented by the patients. The comprehension of the dysfunctions of the somato-sensory system in syringomiely was improved with this knowledge. Other parameters that were studied using the dti technique were the number of fibers and the ADC (apparent diffusion coefficient). During the acute phase of the herpes zoster infection is possible to see abnormal signal in the roots, braquial plexus, spinal cord and brain stem. When the infection is related to the trigeminal nerve it is possible to see a hyper-intense signal in T2 in the nucleus and tract of the trigeminal nerve. Transitory or permanent lesion can be clarified in the studies of the nervous system lesions caused by herpes zoster virus. There is no study about dti applied to the spinal cord of patients with post herpetic neuralgia what justify the present study. The purpose of this study is compare the clinical findings to the quantitative and qualitative values obtained by the dti studies. Comparing the results between the populations that had herpes Zoster infection with and without post herpetic neuralgia it will be possible to have a predictable value for the evolution of these infections. Objectives: To apply the technique of dti and use the fiber tracking to study normal subjects and characterize the spinal cord of these individuals using the FA, ADC and number of fiber as parameters. To study the spinal cord of the patients with post herpetic neuralgia using the FA, ADC and number of fiber parameters and correlate these data with the clinical findings. To compare the results of the dti study of the patients that developed post herpetic neuralgia with the results of the patients that presented herpes Zoster but didn't present secondary neuralgia. (AU)