The use of flash visual evoked potentials in the early diagnosis of suspected optic nerve lesions due to craniofacial trauma

Abstract

Craniofacial trauma encroaching on the orbital apex and optic canal can result in direct or indirect optic nerve lesions, leading to visual impairment or blindness. Early diagnosis of a visual loss and immediate therapy are generally considered crucial for a successful restoration of vision in indirect trauma. However, in comatose or sedated patients the assessment of optic nerve function by testing pupillary reactivity may be severely compromised or impossible because of tensely swollen eyelids, conjunctival oedema, concussion of the ciliary muscle or pharmacological effects. In the event that clinical ophthalmic examination, computer tomography or nuclear magnetic resonance scanning fail to clarify the state of the optic nerve, visual evoked potentials (VEPs) to flash stimulation appear to provide reliable information on function within the visual pathway. On this basis, treatment with corticosteroids and/or surgical decompression can be rapidly initiated. Our results in a preliminary patient series confirm the value of acutely monitored VEPs as an objective test of optic nerve function in cases of suspected optic nerve injury immediately after admission to the emergency care unit. The imaging techniques usually applied may be complemented by VEPs to show the functional significance of structural abnormalities found in the vicinity of the optic nerve.