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• OPTIC NEURITIS AND VISUAL ELECTROPHYSIOLOGY
  Fabio Bandini
  Published on: 22 March 2016

• Published on: 22 March 2016

  OPTIC NEURITIS AND VISUAL ELECTROPHYSIOLOGY

  • Fabio Bandini, Director

  Sir, I read with much interest the review by Weerasinghe and Lueck on the diagnosis of optic neuritis. The authors provide an extensive and detailed analysis on the differential diagnoses and the management of the disease. The importance of retinal electrophysiology is also acknowledged when differentiating retinal disorders that can mimic optic neuritis. Surprisingly, however, the diagnostic role of pattern-reversal Visua...

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  Sir, I read with much interest the review by Weerasinghe and Lueck on the diagnosis of optic neuritis. The authors provide an extensive and detailed analysis on the differential diagnoses and the management of the disease. The importance of retinal electrophysiology is also acknowledged when differentiating retinal disorders that can mimic optic neuritis. Surprisingly, however, the diagnostic role of pattern-reversal Visual Evoked Potentials (VEPs) is not discussed, not even mentioned. VEPs can assess visual pathway function at a millisecond time scale and no other visual function measure shares this temporal sensitivity. More than 40 years ago Martin Halliday demonstrated a delay in the VEPs after an attack of optic neuritis. Since then, a huge number of studies have provided converging evidence about the importance of VEPs recording in optic neuritis and Multiple Sclerosis (MS). Doubtless, the clinical use of VEPs has changed over time and the advent of magnetic resonance imaging (MRI) have reduced the use of VEPs in clinical practice. However, even in the MRI era, an abnormal VEP in unaffected eyes of patients with MS provides evidence for clinically silent demyelinating lesions in the optic pathway. This, in turn, is extremely useful in identifying dissemination in space and, therefore, in establishing the diagnosis of MS. In their review, the authors also fail to mention another important electrophysiological test, i.e. the Pattern Electroretinogram (PERG). The PERG is generated by the activity of the retinal ganglion cells. Taken together, PERG and VEPs are useful to identify the site(s) of dysfunction along the retinocortical pathway. In a typical case of optic neuritis PERG and VEP recordings might not be necessary. However, these techniques can still retain many roles: first, to show the magnitude of conduction block of the optic nerve fibres in the acute stage of the disease. Secondly, to demonstrate the optic nerve conduction delay due to demyelination. Third, to follow remyelination, which is seldom correlated to an improvement in visual acuity, through the shortening of VEP latency. Finally, to define the eventual retrograde degeneration of ganglion cells, which is reflected by an amplitude reduction of the PERG N95 peak. Moreover, when diagnosing atypical optic neuritis, these neurophysiologic techniques should be implemented as a part of a comprehensive assessment. Of note, the visual pathway can now be more precisely evaluated in detail by means of new neurophysiological tests (multifocal VEPs and ERG). These techniques provides higher sensitivity and specificity in detecting abnormalities in visual function in optic neuritis and MS

  Conflict of Interest:

  None declared

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  Conflict of Interest:
  None declared.

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