Diffuse Axonal Injury in Infants With Nonaccidental Craniocerebral Trauma

Abstract

Abstract Objective.—Accurate identification of diffuse axonal injury is important in the forensic investigation of infants who have died from traumatic brain injury. β-Amyloid precursor protein (β-APP) immunohistochemical staining is highly sensitive in identifying diffuse axonal injury. However, the effectiveness of this method in brain-injured infants has not been well established. The present study was undertaken to assess the utility of β-APP immunohistochemistry in detecting diffuse axonal injury in infants with either shaken baby syndrome or blunt head trauma. Materials and Methods.—Archival formalin-fixed, paraffin-embedded blocks from infants (<1 year old) with shaken baby syndrome (7 cases) and blunt head trauma (3) and blocks from 7 control cases that included nontraumatic cerebral edema (1), acute hypoxic-ischemic encephalopathy (1), and normal brain (5) were immunostained for β-APP. A semiquantitative assessment of the severity of axonal staining was made. Corresponding hematoxylin-eosin–stained sections were examined for the presence of axonal swellings. Results.—Immunostaining for β-APP identified diffuse axonal injury in 5 of 7 infants with shaken baby syndrome and 2 of 3 infants with blunt head trauma. Immunoreactive axons were easily identified and were present in the majority of the sections examined. By contrast, hematoxylin-eosin staining revealed axonal swellings in only 3 of 7 infants with shaken baby syndrome and 1 of 3 infants with blunt head trauma. Most of these sections had few if any visible axonal swellings, which were often overlooked on initial review of the slides. No β-APP immunoreactivity was observed in any of the 7 control cases. Conclusions.—Immunostaining for β-APP can easily and reliably identify diffuse axonal injury in infants younger than 1 year and is considerably more sensitive than routine hematoxylin-eosin staining. We recommend its use in the forensic evaluation of infants with fatal craniocerebral trauma.