Year : 1991 | Volume
: 39 | Issue : 1 | Page : 20--21
Visual evoked potentials in optic nerve injury--does it merit to be mentioned?
Dept. of Neurosurgery, Neurosciences Centre, All Institute of Medical Sciences, New Delhi, India
A K Mahapatra
Dept. of Neurosurgery, Neurosciences Centre, All Institute of Medical Sciences, New Delhi
The value of Visual Evoked Potentials (VEP) in the management of indirect optic nerve injury was prospectively studied in 78 patients. The initial VEPs were normal in 10, abnormal in 29 and absent in 39 patients. All 10 patients with normal VEP showed visual recovery. Amongst 29 patients with abnormal VEP, 26 (86.6%) showed improvement. In 39 patients initial VEPs showed no wave, however, subsequent VEP recordings demonstrated wave formation. Thus in 31 patients repeated VEP recordings failed to demonstrate wave formation, and none of them improved. This study, thus brings out the high predictive value of both positive and negative VEPs.
|How to cite this article:|
Mahapatra A K. Visual evoked potentials in optic nerve injury--does it merit to be mentioned?.Indian J Ophthalmol 1991;39:20-21
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Mahapatra A K. Visual evoked potentials in optic nerve injury--does it merit to be mentioned?. Indian J Ophthalmol [serial online] 1991 [cited 2022 May 17 ];39:20-21
Available from: https://www.ijo.in/text.asp?1991/39/1/20/24489
Optic nerve injury is a rare complication of closed head injury. Except for an isolated series by Fukado , no other large series is available ,,. The recent studies reported over the last two years consisted of fewer than 50 cases ,,,sub .The present report prospectively analyses the VEP findings in 78 patients with optic nerve injury and justifies it's role in predicting the outcome.
MATERIAL AND METHODS
Over a 41/~ year period (Jan. 1984 through July 1988) 78 patients with optic nerve injury were managed at the neurosurgery department of AIIMS. They entered into a prospective study with an aim to evaluate the role of VEP in the management of optic nerve injury. VEPs were performed routinely by using the Nicolet 1170 model or Nicolet Compact four model. VEPs were recorded either by using Pattern reversal method or by Light Emitting Diodes (LED). LED was used in unconscious or uncooperative patients and helped in establishing the diagnosis in those in whom visual loss was suspected. VEPs were performed within 48 hours of initial evaluation and were repeated within 7 to 10 days to assess the electrophysiological improvement. VEPs were categorised as normal, abnormal or absent [Figure 1] a & b depending upon their wave formation and latencies. Latencies longer than 2 SD of the control value were considered as abnormal. Initial VEPs were normal in 10, abnormal in 29 and absent in 39 patients. Overall improvement occurred in 29 (56%) patients. All the 10 patients with normal VEP recovered. Among 29 patients with abnormal VEP, 26 (86.6%) showed visual improvement. Thus 6 out of 39 patients (92.2%) with a positive VEP wave had visual improvement ultimately. Thirty-nine patients with initial absent VEPs 31 of whom had repeated absent VEP waves had no subsequent improvement [Table 1.
Optic nerve injury is a rare condition and except for the series by Mahapatra & Bhatia  no other prospective study is available. The pathogenesis is not clear and the ideal management is yet to be established. These days VEPs are routinely performed to assess the integrity of the anterior visual pathways. However, not much literature is available on the role of VEP in the management of optic nerve injury. ,, Recent reports published in the literature do not even mention the role of such a valuable investigation ,, Shaken et al in 1982  reported a patient in whom repeated VEPs were performed. Mahapatra and Bhatia  in a recent study of 45 patients with optic nerve injury established the predictive value of VEPs in patients with traumatic unilateral blindness. They reported improvement in 90% of patients with positive P 100 waves. Nau et al in 1987  reported 14 patients in whom VEPs were performed. Surprisingly enough they did not find out the importance of a positive VEP, however, they concluded the role of negative VEPs as an indicator of poor prognosis. In the present study 44 patients had visual improvement (56%). All the 10 patients with normal VEP had good recovery. Thirty-six out of 39 patients with a positive P 100 wave had significant visual improvement and none of the 31 patients with repeatedly absent VEP had shown visual recovery. Thus the present study established the role of both positive and negative VEPs in the diagnosis and in predicting the outcome. In unconscious patients VEPs did help in establishing the diagnosis of optic nerve injury.
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