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

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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 Scandinavica  103 (2), 97-104.

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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

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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

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• 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

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Central Nervous and Peripheral Nervous System
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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

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• 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

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Myelin
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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

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

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Sclerosis
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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

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• 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

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• 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

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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

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• 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

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Magnetic Resonance Imaging
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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

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

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

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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.

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• 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

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Healthy Observer
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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)

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• 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

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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

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Pattern Visual Evoked Potentials Using Vertical
and Horizontal Bars
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• 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

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• 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

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Percentage of Abnormalities
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Vertical Grating
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Horizontal Grating
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Oblique Grating
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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.

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• 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.

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References

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• http//www.nlm.nih.gov/medlineplus/

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• QUESTIONS?