Effect of impact on different regions of the head of lambs

The heads of anaesthetized lambs aged 4-5 weeks were subjected to impact (temporal, frontal or occipital) of constant strength with a humane stunner. Two hours later, the brains were perfusion-fixed with 4% paraformaldehyde and serial whole coronal slices processed by routine methods. Sections were stained with haematoxylin and eosin or labelled with a monoclonal antibody to amyloid precursor protein, a sensitive marker of axonal injury and neuronal reaction. Microscopical evaluation of axonal, neuronal and vascular damage was performed with a quantitative grid system. Frontal impact produced the greatest damage, followed by occipital then temporal impact. An unusual lesion found in the majority of lambs subjected to impact was multifocal necrosis of the cerebellar granular layer. The findings should assist clinicians in evaluating the probable outcome of traumatic head injury in domestic animals.