Demyelinating Diseases

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Demyelinating Diseases
Done by
Mohd Sulaiman Al-Houqani Mohd Ali Al-Ali
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Introduction
Demyelinating disorders of the CNS affect
myelin
and/or oligodendroglia
with relative sparing of axons.
Oligodendrocytes, like Schwann cells in the
peripheral nervous system, are responsible for
the formation of myelin around CNS axons.
One Schwann cell myelinates one axons but one
oligodendrocyte may myelinate several contiguous
axons, and the close proximity of cell to axon
may not be obvious by light microscopy.
Oligodendrocyte are present in gray matter near
neural cell bodies and in white matter near
axons.
Myelin is composed of protein 20 lipids.
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Classification of the Demyelinating diseases
Multiple sclerosis A-  Chronic relapsing
encephalomyelopathic form. B-   Acute multiple
sclerosis. C-  Neuromyelitis optica.
Diffuse cerebral sclerosis (encephalitis
periaxalis diffuse) or Schilder and concentric
sclerosis of Balo.
Acute disseminated encephalomyelitis. A- 
Following measles, rubella influenza. B-  
Following rabies or smallpox vaccination.
Acute and subacute necrotizing hemorrhagic
encephalitis. A-  Acute encephalopathic form
(hemorrhagic leukoencephalitis of Hurst) B-  
Subacute necrotic myelopathy C-  Acute brain
purpura(acute pericapillary encephalorrhagia)
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Multiple Sclerosis
MS referred by the British as disseminated
sclerosis by French as Sclerose en plaques.
MS is a common demyelinating disease,
characterized by focal disturbance of function
and a relapsing and remitting course.
Higher incidence of the disease found in the
northern most latitude of the northern southern
hemispheres compared to southernmost latitudes.
MS usually occur in young adults with a peak age
incidence of 20-40 years.
more female than males are affected.
The risk of MS in relative patients increases 20
folds.
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Pathology

• Scattered lesions with a greyish color.
• 1mm to several cm in size.
• Are present in the white matter of the brain and
  spinal cord and are referred to as plaques.

• perivenous distribution.

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RECENT LESIONS
LATER
OLD LESION

• Myelin destruction
• Relative axon sparing
• Perivenous infiltration with MNP
• Breakdown of BBB

Astrocyte proliferation

• Relatively acellular
• More clearly demarcated.
• Bare axons are surrounded by astrocytes.

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Pathology
These lesions have a predilection for the
following sites within the brain SC.

• Optic nerves
• Periventricular region
• Brainstem
• Cervical SC. (CS. Tract PC.)

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Pathogenesis
Genetic predisposition
Environmental Exposure (Virus)
Autoimmune attack by CD4 T-cell
Demyelination
Multiple Sclerosis
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Clinical Features

• Sensory Symptoms
• Numbness Paraesthesia
• Impaired vibration Joint position sensation
• Lhermittes Sign ( Shock-like sensation in the
  limb)
• Dysaesthesia Sensory loss to pain Temp.

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Clinical Features

• Motor Symptoms
• Monoparesis
• Paraparesis

• Signs
• Increased tone
• Hyperactive tendon reflexes
• Absent abdominal reflexes
• Pyramidal distribution weakness

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Clinical Features Optic Neuritis

• Inflammatory demyelination of one or both optic
  nerves

• Pain around one eye
• Blurred vision
• Loss of color vision
• Swollen optic disc( Papillitis)
• Visual field defect
• Diplopia Vertigo

Uhthoff phenomenon
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Clinical Course
1- Acute MS

• Explosive onset
• Death may occur in months
• Dramatic recovery and prolonged remission may
  occur

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2- Slowly Progressive MS

• Common in older age group
• No relapse/remission
• Takes the form of a Progressive myelopathy

Disability
Time
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3- Relapsing MS

• Accumulating disability

Disability
Time
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4- Benign form

• Abrupt onset
• Good remission
• Long latent period

Disability
Time
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Investigation
No diagnostic test. Only support the clinical
suspicion.
Neuropsychological measurement of conduction
within the CNS to detect second a symptomatic
lesion.

• Visual evoked potential(VEP) in optic nerve the
  latency of the large positive wave is delayed .
  the amplitude may also be reduced.

• Somatosensory evoked response (SSEP) may detect
  central sensory pathway lesion.

• Brain stem auditory evoked potential (BAEP) may
  detect brain stem lesion.

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normal
CSF examination by lumbar puncture

• Mild pleocytosis mainly lymphocytes.

• Total protein maybe elevated

• ?gammaglobuline in 50

• Electrophoresis of CSF using agar shows discrete
  bands which are not present in serum.

Oligoclonal band
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MRI
MRI is more sensitive showing white matter
disease.
On T-2 weighted images, patchy area of abnormal
white matter are found most commonly in cerebral
hemisphere in paraventicular areas often lesions
can be present in the cerebellum , brain stem,
cervical and or thoracic spinal cord
Area of demyelination in cerebral hemisphere
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Demyelination in the Cervical Spinal Cord
MRI finding are not necessarily diagnostic
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Management
Anti-inflammatory immunpsuppressive therapy

• ACTH my shortnes the duration of relapses but
  wont influence the outcome.

• Immunosuppressive- cyclophosphamide,
  azothiaprine- no evidence of value potential
  dangerous marrow toxicity, etc. occasionally
  used in acute MS.

Enhancement of cell mediated immunity

• Interferon has been suggested but not evaluated.

Physical treatment

• Body cooling has been applied in acute situation.

Dietary measures

• Low glutein or polyunsaturated fat supplemented
  diets.

In summary

• No available specific therapy proven value.