DOI: http://dx.doi.org/10.18203/2320-6012.ijrms20150263

Study of voluntary alteration of visual evoked potentials: Evaluating role in functional visual loss

Sangeeta Gupta, Gaurav Gupta, Surjit Singh

Abstract


Background: Pattern reversal visual evoked potentials (PRVEP) are one of the recommended tests for detection of functional visual loss. However, voluntary alterations producing abnormal records have been reported in the normal subjects limiting the role of the test. Hence, this study aimed to record voluntarily altered PRVEP responses and to study the role of various modifications in the technique for detection of the condition.

Methods: 20 normal subjects in the age-group of 18-25 years were studied. PRVEP records were obtained in the normal perceiving states and then with voluntary alterations in different stimulus conditions and the changes in the mean P100 latency and N75-P100 amplitude were compared and analysed using paired t-test.

Results: 15 out of 20 subjects could voluntarily alter their PRVEP records with 26 out of 30 eyes demonstrating statistically significant abnormal records in terms of latency delay or amplitude reduction or both. Modifications in the technique with increased check size, field size and binocular stimulation reduced the number of abnormal records. But, mean P100 latency and N75-P100 amplitude recorded from the above stimulus conditions in voluntarily altered states were still statistically significantly altered from those in the normal perceiving conditions (p<0.05).

Conclusion: Normal subjects can voluntarily produce abnormal PRVEP responses. Various modifications in the technique like increase in the check-size, field size and binocular stimulation should be employed if voluntary alteration is suspected, but interpretation should be made carefully in the context of clinical findings of the subject.

 


Keywords


Visual evoked potentials, Voluntary alteration

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References


American Psychiatric Association. Diagnostic and statistical manual of mental disorders: DSM-IV-TR. 4. Washington, DC: American Psychiatric Association; 2000.

Smith CH, Beck RW, Mills RP. Functional disease in neuro-ophthalmology. Neurol Clin. 1983;1(4):955–71.

Xu S, Meyer D, Yoser S, Mathews D, Elfervig JL. Pattern visual evoked potential in the diagnosis of functional visual loss. Ophthalmol. 2001;108(1):76-80.

Suppiej A, Gaspa G, Cappellari A, Toldo I, Battistella PA. The role of visual evoked potentials in the differential diagnosis of functional visual loss and optic neuritis in children. J Child Neurol. 2011;26(1):58-64.

Galloway NR, Odom JV, Anastasi M, et al. Visual electrodiagnostics: A guide to procedures. Nottingham: ISCEV Publications; 1997: 2–5.

Halliday AM, McDonald WI: Visual evoked potentials, in Stalberg E, Young RR (eds): Neurology J. Clinical Neurophysiology. London, Butterworths; 1981: 228-258.

Bumgartner J, Epstein CM. Voluntary alteration of visual evoked potentials. Ann Neurol. 1982;12(5):475-8.

Morgan RK, Nugent B, Harrison JM, O'Connor

PS. Voluntary Alteration of Pattern Visual Evoked Responses. Ophthalmol. 1985;92(10):1356-63.

Tan CT, Murray NM, Sawyers D, Leonard TJ. Deliberate alteration of the visual evoked potential. J Neurol Neurosurg Psychiatry. 1984;47(5):518–23.

Chiappa KH, Yiannikas C. Voluntary alteration of evoked potentials. Ann Neurol. 1982;12:496.

Lentz KE, Chiappa KH. Non-pathologic (voluntary) alteration of pattern shift visual evoked potentials. Electro-encephalogr Clin Neurophysiol. 1985;61:30.

American Clinical Neurophysiology society Guidelin 9 B: Guidelines on Visual evoked potentials. J Clin Neurophysiol. 2006;23(2):138-56.

Halliday AM, McDonald WI, Mushin J. Delayed pattern evoked responses in optic neuritis in relation to visual acuity. Trans Opthalmol Soc UK. 1973;93:315-25.

Cant BR, Hume AL, Shaw NA. Effects of luminance on the pattern visual evoked potential in multiple sclerosis. Electroencephalogr Ciln Neurophysiol. 1978;45:496-504.