Stereology of cerebral cortex after traumatic brain injury matched to the Glasgow outcome score.

Magnetic resonance imaging provides evidence for loss of both white and grey matter, in terms of tissue volume, from the cerebral hemispheres after traumatic brain injury. However, quantitative histopathological data are lacking. From the archive of the Department of Neuropathology at Glasgow, the cerebral cortex of 48 patients was investigated using stereology. Patients had survived 3 months after traumatic brain injury and were classified using the Glasgow Outcome Scale as follows: moderately disabled (n = 13), severely disabled (n = 12) and vegetative state (n = 12); and controls. Some patients from the archive were diagnosed with diffuse axonal injury post-mortem. Comparisons of changes in cortical neuron population across Glasgow Outcome Scale groups between diffuse axonal injury and non-diffuse axonal injury patients were undertaken using effect size analyses. The hypotheses tested were that (i) thinning of the cerebral cortex occurred after traumatic brain injury; (ii) changes in thickness of cortical layers in Brodmann areas 11, 10, 24a and 4 differed; and (iii) different changes occurred for neuronal number, their size and nearest neighbour index across Glasgow Outcome Scale groups. There was a greater loss of large pyramidal and large non-pyramidal neurons with a more severe score on the Glasgow Outcome Scale from all four cortical regions, with the greatest loss of neurons from the prefrontal cortex of patients with diffuse axonal injury. There were differences in the changes of number of medium and small pyramidal and non-pyramidal neurons between different cortical regions, and between patients with and without diffuse axonal injury. Generally, a decrease in the somatic diameter of pyramidal and non-pyramidal neurons was associated with a more severe clinical outcome. However, in the motor cortex a more severe Glasgow Outcome Scale was associated with an increased diameter of medium pyramidal neurons and small non-pyramidal cells. Pyramidal and non-pyramidal neurons did not follow a Poisson distribution within the neuropil of control patients. Pyramidal neurons were usually scattered while medium and small non-pyramidal neurons were clustered. An increased spacing between remaining neurons usually occurred across Glasgow Outcome Scale groups. It is concluded that loss of neurons resulted in reduced executive and integrative capability in patients after traumatic head injury.

Thalamic nuclei after human blunt head injury.

Paraffin-embedded blocks from the thalamus of 9 control patients, 9 moderately disabled, 12 severely disabled, and 10 vegetative head-injured patients assessed using the Glasgow Outcome Scale and identified from the Department of Neuropathology archive. Neurons, astrocytes, macrophages, and activated microglia were differentiated by Luxol fast blue/cresyl violet, GFAP, CD68, and CR3/43 staining and stereological techniques used to estimate cell number in a 28-microm-thick coronal section. Counts were made in subnuclei of the mediodorsal, lateral posterior, and ventral posterior nuclei, the intralaminar nuclei, and the related internal lamina. Neuronal loss occurred from mediodorsal parvocellularis, rostral center medial, central lateral and paracentral nuclei in moderately disabled patients; and from mediodorsal magnocellularis, caudal center medial, rhomboid, and parafascicular nuclei in severely disabled patients; and all of the above and the centre median nucleus in vegetative patients. Neuronal loss occurred primarily from cognitive and executive function nuclei, a lesser loss from somatosensory nuclei and the least loss from limbic motor nuclei. There was an increase in the number of reactive astrocytes, activated microglia, and macrophages with increasing severity of injury. The study provides novel quantitative evidence for differential neuronal loss, with survival after human head injury, from thalamic nuclei associated with different aspects of cortical activation.

Differential responses in three thalamic nuclei in moderately disabled, severely disabled and vegetative patients after blunt head injury.

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.

Continued in situ DNA fragmentation of microglia/macrophages in white matter weeks and months after traumatic brain injury.

Paraffin-embedded material from the pons of head-injured patients whose disability could be attributed to diffuse traumatic axonal injury, and controls, was identified from the department's archive. The cases were divided into three groups based on survival, viz Group 1 (n = 5) who survived for between 4 and 8 weeks, Group 2 (n = 5) for between 3 and 9 months, and Group 3 (n = 5) who survived for more that 12 months. Sections were stained by the TUNEL (TdT-mediated UTP nick end labelling) technique, and by H&E, LFB/CV and immunohistochemically for astrocytes (GFAP) and microglia/macrophages (CD68). Microscopic abnormalities were mapped onto line diagrams of two levels of the pons and quantitation of the response determined by an eye-piece graticule placed over the medial lemmisci, cortico-spinal and transverse fiber tracts. Data were pooled by region of interest. In the H&E and LFB/CV stained sections, there was variable pallor of staining in ascending and descending fiber tracts due to loss of myelin: within these same tracts there was an astrocytosis and increased numbers of microglia/macrophages compared with controls. In the white matter tracts of the controls, there was on average 1-2 TUNEL+ cells per unit area. In contrast, there were on average 2-16 TUNEL+ cells in the cortico-spinal tracts and in the medial lemnisci of all groups of head-injured patients. CD68+ cells co-located with the TUNEL+, and their number mirrored the TUNEL + staining with on average 16-30 cells per unit area in Group 1, 14-27 cells per unit area in Group 2, and 12-14 cells per unit area in Group 3. There was a statistical association between the TUNEL+ and CD68+ cells. Few changes were seen in the transverse fiber tracts of the pons. These findings indicate that most of the in situ DNA fragmentation occurred in microglia/macrophages in ascending and descending fiber tracts of the brain stem in which by conventional light microscopy there is Wallerian degeneration. However, in addition, a few TUNEL+ oligodendrocyte-like cells were also seen.