The temporal stem in traumatic brain injury: preliminary findings

The temporal stem (TS) of the temporal lobe is a major white matter (WM) region containing several major pathways that connect the temporal lobe with the rest of the brain. Because of its location, it may be particularly vulnerable to shear-strain effects resulting from traumatic brain injury (TBI). A case vignette is presented in a patient with severe brain injury and focal TS pathology. Also, 12 severe TBI subjects unselected for TS pathology were compared to demographically matched, neurologically-intact controls using diffusion tensor imaging (DTI) to examine white matter tracts associated with the TS, including the inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF), arcuate fasciculus (AF), cingulum bundle (CB) and the uncinate fasciculus (UF). For each tract, fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were computed and compared between the two groups and also examined in relationship to memory performance in the TBI subjects. Significant FA and ADC differences were observed in all tracts in the TBI patients compared to controls, with several relationships with memory outcome noted in the IFOF, ILF and AF. Based on these preliminary findings, the potential role of TBI-induced WM disconnection involving the TS is discussed as well as the relationship of TS damage to neurobehavioral outcome. The need for future studies specifically examining the role of TS injury in TBI is emphasized.