Mild-to-Moderate Traumatic Brain Injury: A Review with Focus on the Visual System

Abstract

Traumatic Brain Injury (TBI) is a major global public health problem. Neurological damage from TBI may be mild, moderate, or severe and occurs both immediately at the time of impact (primary injury) and continues to evolve afterwards (secondary injury). In mild (m)TBI, common symptoms are headaches, dizziness and fatigue. Visual impairment is especially prevalent. Insomnia, attentional deficits and memory problems often occur. Neuroimaging methods for the management of TBI include computed tomography and magnetic resonance imaging. The location and the extent of injuries determine the motor and/or sensory deficits that result. Parietal lobe damage can lead to deficits in sensorimotor function, memory, and attention span. The processing of visual information may be disrupted, with consequences such as poor hand-eye coordination and balance. TBI may cause lesions in the occipital or parietal lobe that leave the TBI patient with incomplete homonymous hemianopia. Overall, TBI can interfere with everyday life by compromising the ability to work, sleep, drive, read, communicate and perform numerous activities previously taken for granted. Treatment and rehabilitation options available to TBI sufferers are inadequate and there is a pressing need for new ways to help these patients to optimize their functioning and maintain productivity and participation in life activities, family and community.

Keywords: head injury; prognosis; retina; traumatic brain injury; vision.

Figure 1

Coup contrecoup traumatic brain injury. The coup portion of the injury occurs when the movement of the head stops abruptly and the brain continues to move in the forward direction so that it hits the skull. The contrecoup portion further compounds the damage as the brain bounces off the skull and hits the side of the skull opposite the side of initial impact.

Figure 2

The visual pathway. The optic nerves from each eye partially cross at the optic chiasm so that fibers from the nasal half of each retina cross over to the contralateral optic tract. Fibers from the temporal portion of each retina remain ipsilateral. As a result, the left optic tract contains fibers originating from the left temporal retina, and the right nasal retina while the right optic tract contains fibers originating from the right temporal retina, and the left nasal retina.