Diffusion Tensor Imaging of the Perforant Pathway Zone and Its Relation to Memory Function in Patients with Severe Traumatic Brain Injury

Abstract

Based on the importance of the perforant pathway (PP) for normal hippocampal function, the vulnerability of temporal structures, and significant memory impairment in patients with traumatic brain injury (TBI), we investigated in vivo changes in the PP zone, hippocampus, and temporal lobe white and gray matter using diffusion tensor imaging (DTI) and volumetric analysis, and any specific relations with memory performance (Verbal Selective Reminding Test, Rey-Osterrieth Complex Figure Test), in 14 patients with severe TBI. Compared to a demographically-similar control group, our patients had significantly decreased fractional anisotropy (FA) and higher apparent diffusion coefficient (ADC) for the PP zone bilaterally, and higher ADC bilaterally in the hippocampus. Volumetric analysis revealed significantly decreased volumes in both hippocampi and temporal gray matter bilaterally. Consistent long-term retrieval (CLTR) and delayed recall were significantly related to (1) right and left PP zone ADC, (2) left hippocampus ADC, and (3) left hippocampal volume. Nonverbal memory (immediate and delayed recall) was significantly associated with (1) right and left PP zone ADC, (2) left hippocampal volume, and (3) gray (immediate recall) and white (immediate recall, bilaterally; delayed recall, left) matter temporal volumes. Advanced neuroimaging analysis can detect in vivo changes in the PP zone and temporal structures in patients with severe TBI, with these changes being highly associated with memory impairment.

Selective Cognitive Dysfunction Is Related to a Specific Pattern of Cerebral Damage in Persons With Severe Traumatic Brain Injury

“…[30][31][32] Our data are in line with these findings. The patients in the dys-episodic group showed substantial hippocampal atrophy compared with the healthy controls and the patients in the dys-executive group.…”

“…30,[35][36][37] Other structures we were unable to investigate include the frontal pathways, whose changes can cause executive problems, such as microstructural alterations at the level of the anterior corona radiata, the superior longitudinal fasciculus, or the forceps major, which have been demonstrated to be related to executive problems in TBI. 38,39 Indeed, microstructural changes and alterations in the function (structural and functional disconnection) of white matter frontal tracts can explain the data of 2 of our dys-executive patients who presented no focal frontal lesions.…”

A Pilot Study Evaluating Presurgery Neuroanatomical Biomarkers for Postoperative Cognitive Decline After Total Knee Arthroplasty in Older Adults

“…Rather, our reliable change analyses showed a marked decline on a delay recall index that is a characteristic of individuals with amnestic disorders (84,85) and functional changes to the entorhinal cortex (8). The greatest rate of decline was also observed on a story recall test, which more closely resembles the everyday memory demands for interpersonal discourse, radio and television programs, as well as material that has been read, such as newspapers (32).…”

Exercise-induced improvement in cognitive performance after fimbria-fornix transection depends on the timing of exercise administration

“…Although the presently addressed model only represents a partial model of brain injury with limited clinical correspondence, fornix and hippocampal atrophies are frequently part of the neuropathological profile of traumatic brain injury (Bigler et al, 1997;Christidi et al, 2011;Gale et al, 1993;Tate and Bigler, 2000;Yallampalli et al, 2013). It is important that preclinical studies that address interventions potentially promoting posttraumatic functional recovery evaluate the effects of varying dosage and temporal distributions of such interventions.…”