Comparative study on the characteristics of the high site visual field injuries and the visual nerve injuries after the head trauma / 中国法医学杂志

ABSTRACT

Objective To Study the characteristics of the high site visual field injury and the LED-VEP after the head trauma for the purpose of the medico-legal appraisals. Methods 11 cases with cortical blindness resulted from the head injury were studied and then compared with 20 cases suffered from optical nerve injuries with respect to the clinical manifestations and characteristics of the visual field injury and LED-VEP. Results As compared with the characteristics of the optical nerve injuries, besides the subjective complain of lowering the visual field, there were not any positive findings in pupil reflex of light and retina examination in case of the high site visual field injuries. The electrical visual field test revealed the homony-mous hemianopia while the internal segment optical nerve injury manifested unilateral visual field defect. 8 out of 11 cases with cortical blindness, occipital cortex were injured and the flash VEP demonstrated the slight prolongation of the latent period of the PI wave of both eyes, while the PI amplitudes were normal. 3 out of 11 cases were suffered from the subcortical injuries and were manifested with the prolongation of the latent period of the PI wave and the amplitude of the PI wave were significantly reduced. Conclusion Bilateral homonymous hemianopia were the characteristics of the high site visual field injury while the abnormal rate of the flash VEP of the high site visual field was quite low. So that, homonymous hemianopia may be helpful for the diagnosis of cortical blindness. At the same time CT scanning and the electroen-cephalography (EEG) also must be considered comprehensively in the medico-legal appraisals.