t2 hyperintensity symptomst2 prolongation mrit2 hyperintense lesionsubcortical t2 hyperintensitiesabnormal t2 hyperintensityperiventricular t2 hyperintensityscattered t2 hyperintensitiespunctate t2 hyperintensitieshyperintense t2 signalfocal t2 hyperintensityt2 prolongation brain mrihyperintensity on mri