A STUDY TO ASSESS THE USEFULNESS OF VISUAL EVOKED POTENTIAL [VEP] IN TRAUMATIC OPTIC NEUROPATHY

Dr. P. Magesh; Dr. K. Prabhuraman; Dr. N. Raghunathan

Volume : IX, Issue : III, March - 2019

A STUDY TO ASSESS THE USEFULNESS OF VISUAL EVOKED POTENTIAL [VEP] IN TRAUMATIC OPTIC NEUROPATHY

Dr. P. Magesh, Dr. K. Prabhuraman, Dr. N. Raghunathan

Abstract :

Introduction: Traumatic Optic Neuropathy (TON) is a devastating potential complication of closed head injury. Indirect traumatic optic neuropathy is seen in up to 5% of closed head trauma in Indian population. The diagnosis of TON is often missed in emergency room unless viewed with a high index of suspicion in patients with unilateral/bilateral Periorbital Ecchymosis. Visual evoked Potential (VEP) can be helpful to document the presence of TON in unresponsive patients or in cases with concomitant ocular injuries. Patients can also be followed with serial VEP examinations to document recovery of function when clinical parameters are equivocal. Aim: To evaluate the usefulness of VEP in prognostigating the outcome in Traumatic Optic Neuropathy and to analyze the clinical parameters useful in predicting the final visual outcome. Methodology: This study was conducted at the Institute of Neurology, Madras Medical College and Rajiv Gandhi Government General Hospital, Chennai over a 3 year period. 65 patients of closed head injury with indirect traumatic optic neuropathy were enrolled in the study. Patients were subjected to complete physical examination including tests for visual acuity and Swinging torch light test to detect Relative Afferent Pupillary Defect (RAPD). CT scan of the ain and orbits were done. Visual Evoked Potentials were recorded using the Checker–Board pattern Full–field stimulation method. All patients received intravenous methylprednisolone 1gm daily in divided doses for three consecutive days. Results were subjected to Student’s t test and Chi–square test and their prognostic significances were analysed. Results and conclusion: 44 patients in the study with persistant absent VEPs had no visual recovery till end of 4 to 6 months.11 out of 65 patients had improvement in the waveforms over 3 weeks and consequently, improvement in vision at the end of second month. Among clinical features, RAPD grading on admission was predictive of poor visual outcome. Among imaging findings, posterior ethmoid hemmosinus is found to be a negative prognostic sign in patients affected by traumatic optic neuropathy. Thus the present study concludes that VEP can be an useful tool to prognosticate visual outcome in patients with traumatic optic neuropathy.