Traumatic axonal injury in lambs: a model for paediatric axonal damage

Axonal injury (Al), an important determinant of clinical outcome after traumatic head injury in adults, has been little studied in child neurotrauma. In this experimental model, 10 anaesthetised, ventilated and physiologically monitored 4-5 week old lambs sustained a temporal impact to an unconstrained head. Examination of the brain 2 hours post-impact using amyloid precursor protein immunostaining, a sensitive marker of axonal damage, revealed widespread multifocal Al in the ipsilateral and contralateral hemispheres, brain stem and cerebellum in all cases. Impact contusions (predominantly microscopic) (8/10), contralateral contusions (2/10), parenchymal haemorrhage (10/10) and focal subarachnoid haemorrhage (10/10) were also present. Unusual multifocal cerebellar granular layer necrosis occurred in all impacted lambs. The pattern of Al in these lamb brains 2 hours post-impact was similar to that found in adult sheep using the same experimental paradigm.