Nerve Fiber Layer and Optic Nerve Expression of Amyloid Precursor Protein in Non–Accidental vs. Accidental Injury of the Infant.

Abstract

Abstract: : Purpose: Amyloid Precursor Protein (APP) has been demonstrated to be a sensitive marker for axonal damage due to traumatic injury in the central nervous system. In this study, we investigate cases of non–accidental injury (NAI), formerly known as Shaken Baby Syndrome, to determine if APP is expressed as a result of hypothesized local tractional forces on the optic nerve and retina. Methods: 35 cases of autopsy eyes were selected for study from the archives of the F.C. Blodi Eye Pathology Laboratory at the University of Iowa between the years of 1995–2004. The ages of the patients ranged from <1.0–72.0 months. The eyes were categorized into three groups determined by cause of death, Non–accidental Injury (NAI) 17 cases; Accidental Injury (AI) 2 cases; and 16 Normal (N) cases in which acceleration deceleration forces did not contribute to cause of death. The eyes were evaluated for retinal hemorrhages, optic nerve sheath hemorrhages, perimacular folds, and vitreous hemorrhage. The eyes were sectioned and submitted for immunohistochemical staining for Amyloid Precursor Protein using an immunoperoxidase method. The tissue was stained with mouse anti–Alzheimer precursor protein A4 monoclonal antibody. Slides were then evaluated by two masked observers; one being an ocular pathologist and the other a neuropathologist. Results:Evaluation of the slides revealed that the specimens of the Normal group did not express APP overall. Accidental Injury expressed APP. One third of the Non–Accidental Injury group were overall negative for APP. The remaining two thirds of the group were found to be strongly positive in either the posterior retina, optic disc or the optic nerve itself. The inter–observer agreement in evaluating the slides was good overall. Conclusions: Both Accidental Injury cases and the Non–Accidental Injury cases demonstrated focal expression of APP in the retinal nerve fiber layer and the optic nerve when compared with eyes from the Normal group. These findings support the theory that local tractional forces play a role in the etiology of the retinal /optic nerve hemorrhages in cases of infantile trauma without direct ocular injury.

Keywords: pathology: human • immunohistochemistry • trauma