Effects of Grating Spatial Orientation on Visual Evoked Potentials and Contrast Sensitivity in Multiple Sclerosis

1. Effects of Grating Spatial Orientation on Visual Evoked Potentials and Contrast Sensitivity in Multiple Sclerosis Presented By: Vanessa Grieco Logi, F., Pellegrinetti, A., Bonfiglio, L., Baglini, O., Siciliano, G., Iudice, A. & Sartucci, F. (2001) Effects of grating spatial orientation on visual evoked potentials and contrast sensitivity in multiple sclerosis. Acta Neurologica Scandinavica103 (2), 97-104.

2. Introduction • Multiple Sclerosis, or MS, is a disease of the brain and spinal cord • Affects 400,000 Americans at any one time • Most patients with MS can lead a normal life. However it may cause a handicap for others

3. Anatomy • Brain is command center of the body (receives information and sends order to different parts of the body) • Orders from the brain travel to the spinal cord = central nervous system

4. Orders to rest of body travel through peripheral nerves = peripheral nervous system • Different areas of brain control different functions: vision, motions, touch, hearing and thinking

5. Central Nervous and Peripheral Nervous System

6. Anatomy • Neurons = cells of brain and nerves • Axon = long fibers that are similar to electrical wires • Each neuron has a body and axon • Neurons communicate through axons

7. Myelin covers axons • Myelin improves the conduction and communication between neurons • In MS, the myelin in certain parts of the brain, spinal cord, or nervous system is destroyed • Scientist do not know why myelin is destroyed

8. Myelin

9. Multiple Sclerosis • Myelin that covers nerve cells becomes inflamed, swollen and detached • Destroyed because a scar forms over axons = sclerosis (scar) • Myelin destruction = neurons communicate less effectively, causing symptoms of MS

10. Example: If myelin of vision is destroyed, vision is affected • Some myelin destruction repairs itself, but can become inflamed again at different times

11. Sclerosis

12. Multiple Sclerosis • Mild MS: symptoms do not get worse, also known as benign Ms (occurs 15% of cases) • Severe MS: symptoms lead to disability, also known as progressive MS = no recovery or remission, symptoms get worse and new ones develop

13. Ages 20 – 40 • Women affected twice as often as men • Immune system usually attacks germs and foreign bodies • Some scientists believe that cells of the immune system attack the myelin in the central nervous system

14. Autoimmune disease = cells of immune system may attack myelin in MS because they mistake it for a foreign harmful material • MS may be partially hereditary

15. Diagnosis • Magnetic Resonance Imaging (MRI) can be done to see certain patches of destroyed myelin • If diagnosis is questionable, spinal fluid may be taken from the back to test for abnormalities

16. 2 tests aimed at measuring the speed of the brain connections : • 1) Visual Evoked Response test = measure speed of the visual pathway • 2) Brain Evoked Response test = measure speed of the auditory pathways

17. Magnetic Resonance Imaging

18. Treatment • Medications are available, since no cure has been discovered yet • Steroids are sometimes used to reduce symptoms • Anti-depressant • Eating healthy, exercising, resting and reducing stress in life

19. Effects of Grating Spatial Orientation on Visual Evoked Potentials and Contrast Sensitivity in Multiple Sclerosis

20. Rationale: Contrast Sensitivity and PVEPs • To evaluate the diagnostic value of contrast sensitivity (CS) in revealing involvement of cortical structures • Aimed to analyze the behavior of PVEPs components and CSF and compare their diagnostic value in a group of MS patients, using bars 1 and 4 c/d SF with different orientation

21. Contrast Sensitivity (CS) = reciprocal of minimal contrast necessary to perceive a given spatial frequency (SF) • CS is affected by refraction errors

22. Pattern Visual Evoked Potentials (PVEPs) • Represent an elective electrophysiological (electrical phenomena associated with a physiological process) technique in the study of visual system • Role in diagnosing multiple sclerosis is well known.

23. Diagnostic value is dependent on the characteristics of the stimulus (orientation, and field dimensions) • Previous studies suggest delay of PVEPs in MS depending on grating orientation

24. Healthy Observer

25. Material and Methods • All patients had a history of Retro bulbar optic neuritis (RBON) which represents the first symptom of the disease • MS was diagnosed (MRI, cerebrospinal fluid analysis)

26. PVEPs = evoked using a black and white grating pattern, with horizontal and vertical bars • CS = grating shown to patient and then the luminance contrast was gradually either reduced or increased

28. Data • Mean values of latencies and amplitudes of P60, N70, and P100 • Vertical bars vs. horizontal • PVEPs for : 1 degree cycle/degree (c/d) Vertical bars= Abnormal in 25% for P60 Abnormal in 32% for N70 Abnormal in 36% for P100 Horizontal bars= Alterations found in P60, P70 and P100 4 degree c/d: Vertical bars= 25% for P60 36% for N70 42% for P100 Horizontal bars= 19 % for P60 27% for N70 35% for P100

30. Pattern Visual Evoked Potentials Using Vertical and Horizontal Bars

31. CS resulted more abnormal for vertical grating, with a maximum impairment for 3.7 c/d SF • By comparing CSF of patients and controls it resulted in an evident loss of CS in MS patients for vertical bars stimuli

32. Student's t-test for vertical bars showed significant for all SFs, while horizontal stimuli only for 1, 2, 3.7, 5 c/d and with oblique only for 2 and 3.7 c/d. • RBON history had a CS with vertical stimuli abnormality in 93%

33. Percentage of Abnormalities

34. Vertical Grating

35. Horizontal Grating

36. Oblique Grating

37. Conclusion • The use of vertical grating in clinical routine is more reliable both for PVEPs and CS testing • CS can be abnormal even with normal PVEPs: this could mean an early impairment of CS and provide useful indications about a sub clinical involvement of visual cortex. • Vertical bars CS was deeply impaired in 93% of MS patients and the most sensitive to reveal CS dysfunction, with the highest percentage of abnormalities, in particular for medium SF (3.7 c/d: 71%), near to the peak of CSF.

38. Patients' mean values of vertical bars CSF showed the greatest difference when compared to controls, as shown in Fig. 4, while Figs 5 and 6 show how lower is such difference for horizontal and oblique bars.

39. References • Bodis-Wollner I & Camisa M. Contrast sensitivity measurement in clinical diagnosis. In: Jessel S, Van Dalen JIW, eds. Neuro-ophthalmology. A series of critical surveys of the International literature. Amsterdam: Elsevier, 1980;1:373 401. • Brooks EB & Chiappa KH. A comparison of clinical neuro-ophthalmological findings and pattern shift visual evoked potentials in multiple sclerosis. Adv Neurol 1982;32:453 7. • Celesia GG & Kaufman D. Pattern ERGs and visual evoked potentials in maculopathies and optic nerve disease. Invest Ophthalmol Vis Sci 1985;26(5:726 35. • Dawson WW, Maida TM, Rubin ML. Human pattern-evoked retinal responses are altered by optic atrophy. Invest Ophthalmol Vis Sci 1982;22(6:796 803. • Halliday AM & Mushin J. The visual evoked potentials in neuro-ophthalmology. In: Sokol S, ed. International Oph-thalmology Clinics. Boston: Little, Brown & Co, 1980;20:155 83. • http://www.nlm.nih.gov/medlineplus/

40. QUESTIONS?