Between September 2005 and October 2011, 32 patients aged 6 to 75 years with moderate to severe TBI with NHL on brain MRI were enrolled. Brain MRI was carried out 1 to 78 days (average 12 days) after trauma, and included T1, T2, T2 flair axial images, susceptibility weighted imaging (SWI), T1 sagittal and T2 coronal images. MRI was performed using a 3.0T Achieva Philips imaging system. The protocols of axial spin echo T1-weighted imaging are 25 slices, slice thickness 5 mm, TR 450.0 msec, TE 10.0 msec, FOV 220×220 mm, reconstructed voxel size 0.430 mm, axial turbo spin echo T2-weighted imaging 25 slices, slice thickness 5 mm, TR 3000.0 msec, TE 80.0 msec, FOV 220×220 mm, reconstructed voxel size 0.449 mm, maximum/minimum intensity projection SWI 25 slices, slice thickness 5 mm, TR 25.5 msec, TE 36.2 msec, FOV 220×220 mm, reconstructed voxel size 0.371 mm, coronal turbo spin echo T2-weighted imaging 25 slices, slice thickness 5 mm, TR 3000.0 msec, TE 80.0 msec, FOV 220×220 mm, reconstructed voxel size 0.449 mm, and sagittal T1-weighted imaging 23 slices, slice thickness 5 mm, TR 430.0 msec, TE 10.0 msec, FOV 220×220 mm, reconstructed voxel size 0.430 mm.
Imaging analysis - the definition, classification, and grading of NHL
NHL is defined as demonstration of low signal at T1, and hyperintense signal change at T2 and T2 flair image but without hypointense signal change at SWI, which is most sensitive for hemorrhages10,27)
Peri-lesional edema due to hemorrhagic lesion was excluded, as well as old lacunae infarction or degenerative white matter lesions thought to be present before the trauma.
These NHLs in our patient sample were classified by location into 4 major districts and 13 detail locations including cortical and subcortical, corpus callosum, deep nuclei and adjacent area and brainstem. Cortical and subcortical were further divided into cortical, mesial temporal (hippocampus or parahippocampal gyrus), and subcortical. Lesions in the corpus callosum were divided into splenium, splenium and body. There were no lesions of the rostrum or genu of the corpus callosum. The deep nuclei and adjacent area included internal capsule, thalamus, basal ganglia and cerebellum, and the brainstem were divided into ventral, dorsal, dorso-ventral, and cerebellar peduncle.
The severity of NHL was graded from 1 to 4, according to the number of districts involved. If limited to one district, regardless of the number of NHL, it was assigned as Grade 1. The same system was applied for Grades 2 and 3. Grade 4 indicates that NHLs were present in all 4 districts. We investigated the relativity of the grading of NHL to the Glasgow coma scale score (GCS) of the patient upon admission, and the prognosis as calculated by the Glasgow outcome scale score (GOS) system.
We also investigated hemorrhagic lesions accompanying the NHL. The presence of traumatic subarachnoid hemorrhage (T-SAH), intraventricular hemorrhage (IVH) and the location of hemorrhagic contusion (H-contusion) were taken into consideration while subdural hematoma and epidural hematoma were excluded because they are extra-axial lesions.
Fourteen patients with NHL were available for MRI follow-up and investigations of the changes in the original NHLs were conducted. The initial evaluation of patients included sex, age, type of trauma, and GCS score upon admission. The prognosis was recorded by GOS taken during the last visit to the hospital, and GOS analyses of patients who were not available for in-hospital follow-up were conducted by telephone.