RESUMO
Toe walking refers to the lack of heel strike during the stance phase of the gait cycle. It is a common variation of normal gait development in children. Persistent toe walking past 2-3 years of age warrants further evaluation as toe walking can be associated with cerebral palsy, muscular dystrophy, and autism spectrum disorders. The diagnosis of idiopathic toe walking is a diagnosis of exclusion used for children with persistent toe walking and no associated medical condition. Despite variable pathophysiology, the treatment of toe walking has similarities across diagnoses as it is focused on the maintenance of range of motion through the ankle.
Assuntos
Transtornos Neurológicos da Marcha/etiologia , Dedos do Pé , Articulação do Tornozelo/fisiopatologia , Transtorno Autístico/complicações , Transtorno Autístico/diagnóstico , Paralisia Cerebral/complicações , Paralisia Cerebral/diagnóstico , Pré-Escolar , Marcha/fisiologia , Transtornos Neurológicos da Marcha/fisiopatologia , Transtornos Neurológicos da Marcha/terapia , Humanos , Masculino , Distrofias Musculares/complicações , Distrofias Musculares/diagnóstico , Amplitude de Movimento ArticularRESUMO
PURPOSE: To report the visual resolution of multiple cell and vascular "layers" in the cat retina using MRI. MATERIALS AND METHODS: T2- and diffusion-weighted MRI at 4.7 Tesla was performed. Layer-specific thickness, T2, spin density, apparent diffusion coefficient perpendicular (ADC(perpendicular)) and parallel (ADC(parallel)) to the retinal surface were tabulated. T1-weighted MRI was acquired before and after intravenous administration of Gd-DTPA and subtraction images were obtained. Histology was performed for validation. RESULTS: Three distinct "layers" were observed. The inner strip nearest to the vitreous (exhibiting large T2, ADC, spin density with Gd-DTPA enhancement) overlapped the ganglion cell layer, bipolar cell layer, and the embedded retinal vascular layer. The middle strip (exhibiting small T2, ADC, spin density without Gd-DTPA enhancement) overlapped the photoreceptor cell layer and the inner and outer segments. The outer strip (exhibiting large T2, ADC, spin density with Gd-DTPA enhancement) overlapped the tapetum and choroidal vascular layer. T2, spin density, ADC(perpendicular) and ADC(parallel) of different "layers" were tabulated. The inner strip was slightly thicker than the other two strips. The total thickness, including neural and nonneural retina, was 358 +/- 13 microm (N = 6) by MRI and 319 +/- 77 microm (N = 5) by histology. CONCLUSION: MRI provides a noninvasive tool to study the retina with laminar specificity without depth limitation.
