Rapid acceleration-deceleration of an infant's head during intentional shaking should in theory exert stretch or shear forces upon the optic nerves sufficient to cause axonal injury. beta-Amyloid precursor protein (beta-APP) immunohistochemistry recently has been shown to be a highly effective method for identifying diffuse axonal injury in the brains of infants with shaken baby syndrome. In this study, we investigated the utility of beta-APP in identifying optic nerve damage in infants who have sustained fatal whiplash shaking.
beta-Amyloid precursor protein immunohistochemistry was performed on formalin-fixed, paraffin-embedded sections of eyes (including optic disc and distal optic nerve) from infants less than 1 year of age with shaken baby syndrome (5 cases), combined shaken baby syndrome/blunt head trauma (3 cases), and "pure" blunt head trauma (1 case). Nontraumatic control cases included infants who died of suffocation (1 case), sudden infant death syndrome (1 case), and positional asphyxia (1 case) and an enucleation from a child with a retinoblastoma (1 case). Matched hematoxylin-eosin-and neurofilament-stained sections were used for comparison.
Three of the 5 shaken baby cases and all 3 combined shaken baby/blunt head trauma cases had optic nerve axonal injury identified by the presence of strongly beta-APP-immunoreactive beaded or swollen axonal segments. Axonal injury could not be detected in the corresponding hematoxylin-eosin-or neurofilament-stained sections. Optic nerve axonal injury was not seen in the case involving pure blunt head trauma or in the nontraumatic control cases.
Optic nerve axonal injury is a prominent feature of intentional fatal whiplash head trauma in infants less than 1 year of age. beta-Amyloid protein precursor immunohistochemistry appears to be the most effective method for demonstrating axonal damage in the optic nerve.