Abstract

In vivo imaging techniques have indicated for many years that there is loss of white matter after human traumatic
brain injury (TBI) and that the loss is inversely related to cognitive outcome. However, correlated, quantitative evidence
for loss of neurons from either the cerebral cortex or the diencephalon is largely lacking. There is some evidence
in models of TBI that neuronal loss occurs within the thalamus, but no systematic studies of such loss have been
undertaken in the thalamus of humans after blunt head injury. We have undertaken a stereological analysis of
changes in numbers of neurons within the dorsomedial, ventral posterior and lateral posterior thalamic nuclei in
patients assessed by the Glasgow Outcome Scale as moderately disabled (n = 9), severely disabled (n = 12) and vegetative
(n = 10) head-injured patients who survived between 6 h and 3 years, and controls (n = 9). In histological sections
at the level of the lateral geniculate body, the cross-sectional area of each nucleus and the number and the mean size of
neurons within each nucleus was quantified. A statistically significant loss of cross-sectional area and number of neurons
occurred in the dorsomedial nucleus in moderately disabled, and both the dorsomedial and ventral posterior
thalamic nuclei in severely disabled and vegetative head injured patients.However, there was no change in neuronal
cell size. In the lateral posterior nucleus, despite a reduction in mean cell size, there was not a significant change in either
nuclear area or number of neurons in cases of moderately disabled, severely disabled or vegetative patients. We posit,
although detailed neuropsychological outcome for the patients included within this study was not available, that
neuronal loss in the dorsomedial thalamus in moderately and severely disabled and vegetative patients may be the
structural basis for the clinical assessment in the Glasgow Outcome Scale. In severely disabled and vegetative patients,
loss of neurons from the ventral posterior thalamic nucleus may also reflect loss of response to afferent stimuli.