Visual Impairment Following Shaking/Impact Injury in Infancy: A Clinical and Electrophysiological Study

Abstract

Abstract: : Purpose: To evaluate the binocular flash visual evoked potential (VEP) as a tool for the assessment of infants with shaken baby syndrome (SBS) and to relate the findings to fundus appearance, intracranial pathology and visual impairment. Methods: Cases admitted with suspected SBS and referred to the ophthalmology service were studied. All had dilated indirect ophthalmoscopy performed. As soon as the childs condition permitted, binocular flash VEPs were elicited using a Ganzfeld Bowl stimulator, the strength of a stimulus being 1 Standard Flash and proportionate background illumination (ISCEV 94). The stimulus repetition rate was set to 1 per second. At least two averages were obtained to check for consistency, and quantitative analysis was performed on the average of these two. Latency of the most consistent positive component of the VEPs elicited, i.e. component PIV was measured and compared to age matched controls. Those with abnormal flash VEPs had a follow up VEP performed. Results: 10 cases with a final diagnosis of SBS were included in the study. 9/10 had abnormal VEPs at presentation, including 5 with absent retinal haemorrhages. 6/8 who had initially abnormal VEPs had normal VEPs at follow up (3 – 22 months following admission.) The 2 remaining abnormal VEPs showed significant improvement. One child failed to attend for a follow up VEP and the child whose VEP was initially normal did not have the test repeated. At final follow up (range 2 1/2 – 50 months) 5 had decreased visual acuity including the child with the initially normal VEP. 8/10 had subdural haematomas. The two with normal neuroimaging were scanned 5 months and 21 months later than the time of suspected injury Conclusion: The flash VEP can be a marker for optic nerve, visual pathway and visual cortex damage in SBS and may provide additional information to fundoscopy.

Keywords: electrophysiology: clinical • trauma