Research reportMemory and anatomical change in severe non missile traumatic brain injury: ∼1 vs. ∼8 years follow-up

In previous studies, we investigated a group of subjects who had suffered from a severe non missile traumatic brain injury (nmTBI) without macroscopic focal lesions and we found brain atrophy involving the hippocampus, fornix, corpus callosum, optic chiasm, and optic radiations. Memory test scores correlated mainly with fornix volumes [37,38].In the present study, we re-examined 11 of these nmTBI subjects approximately 8 yr later. High-spatial resolution T1 weighted magnetic resonance images of the brain (1 mm3) and standardised memory tests were performed once more in order to compare brain morphology and memory performance originally assessed 3-13 months after head injury (first study) and after 8-10 yr (present study). An overall improvement of memory test performance was demonstrated in the latest assessment, indicating that cognitive recovery in severe nmTBI subjects had not been completed within 3-13 months post-injury. It is notable that the volumes of the fornix and the hippocampus were reduced significantly from normal controls, but these volumes do not differ appreciatively between nmTBI subjects at first (after ∼1 yr) and at second (after ∼8 yr) scans. On the contrary, a clear reduction in the volume of the corpus callosus can be observed after ∼1 yr and a further significant reduction is evident after ∼8 yr, indicating that the neural degeneration in severe nmTBI continues long after the head trauma and relates to specific structures and not to the overall brain.

► Cognitive recovery in severe nmTBI can occur even after 1 yr post-injury. ► One year post injury, fornix and hippocampal volumes do not reduce further. ► A clear reduction of callosal volume is observed between 1 and 8 yr post injury. ► Neural degeneration continues long after trauma and relates to specific structures.