Optic nerve damage in shaken baby syndrome - Detection by beta-amyloid precursor protein immunohistochemistry

Background.-Rapid acceleration-deceleration of an infant's head during inte ntional shaking should in theory exert stretch or shear forces upon the opt ic nerves sufficient to cause axonal injury. beta-Amyloid precursor protein (beta-APP) immunohistochemistry recently has been shown to be a highly eff ective method for identifying diffuse axonal injury in the brains of infant s with shaken baby syndrome. In this study, we investigated the utility of beta-APP in identifying optic nerve damage in infants who have sustained fa tal whiplash shaking. Materials and Methods.-beta-Amyloid precursor protein immunohistochemistry was performed on formalin-fixed, paraffin-embedded sections of eyes (includ ing 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 h ead trauma (3 cases), and "pure" blunt head trauma (1 case). Nontraumatic c ontrol cases included infants who died of suffocation (1 case), sudden infa nt death syndrome (1 case), and positional asphyxia (1 case) and an enuclea tion from a child with a retinoblastoma (1 case). Matched hematoxylin-eosin - and neurofilament-stained sections were used for comparison. Results.-Three of the 5 shaken baby cases and all 3 combined shaken baby/bl unt head trauma cases had optic nerve axonal injury identified by the prese nce 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. Conclusions.-Optic nerve axonal injury is a prominent feature of intentiona l fatal whiplash head trauma in infants less than 1 year of age. beta-Amylo id protein precursor immunohistochemistry appears to be the most effective method for demonstrating axonal damage in the optic nerve.