Damage to intracranial optic pathways in fatal closed head injury in man

Head injury is a leading cause of visual impairment. This is partly due to direct trauma to the eye and optic nerve hut much of the damage involves th e intracranial optic pathways. We have studied the frequency, distribution and nature of the intracranial lesions of the optic pathways at autopsy in 45 cases of severe closed head injury, and examined the correlation between these post-mortem lesions and the ante-mortem clinical findings. Twenty-fo ur of the patients had been involved in road traffic accidents. The ages ra nge fern 9 to 88 years (mean 46.4). the Glasgow Coma Score (GCS) on admissi on ranged from 3 to 15 (mean 5), and the survival time after injury from 2. 5 h to 15 days (mean 3.3 days). Skull fractures were present in 75.6% of th e cases. Histological assessment included the use of immunohistochemistry f ur beta -amyloid precursor protein (beta -APP) and the microglial marker CD 68. Axonal injury of varying severity was demonstrable in all cases, and in 39 (87%) the optic chiasm, tracts or radiations were involved, usually in more than one region. The severity of axonal injury was mild in 11 (24%), m oderate in 9 (20%) and severe in 19 (42%) cases. The optic radiation at the level of the trigone of the lateral ventricle was particularly frequently and severely affected. The least affected parts of the intracranial optic p athways were the optic chiasm and the posterior segment of the optic nerve. The severity of injury to the optic pathways did not always reflect severi ty of axonal injury elsewhere in the brain and correlated poorly with the t ype of trauma (high- or low-velocity), presence of skull fractures or evide nce of raised intracranial pressure (ICP). Of the 39 patients who survived more than 6 h, histological evidence of ischaemic injury to the primary opt ic cortex was present in 26 (67%) and was severe in 12. We conclude that th e visual pathways are affected in a high proportion of patients with fatal closed head injury, nerve fibres in the optic radiations being particularly vulnerable. The findings suggest that damage to the posterior parts of the optic pathways may be under-diagnosed among patients with head injury. (C) 2001 Elsevier Science B.V. All rights reserved.