Demyelinating Diseases

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Demyelinating Diseases

• By
• Dr. Amal Mokhtar, MD.

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• Demylinating disease refers to a group of CNS
  disorders in which the primary pathology is
  demyelination without axonal degeneration.

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• Multiple Sclerosis
• MS is a disease of unkown cause ,in which
  discrete areas of demylination develop at many
  sites in the brain and spinal cord.
• Lesions develop in different sites at different
  times,usually with some capacity for regeneration
  and restoration of function.This leads to
  characteristic relpsing and remitting history in
  many patients in others ,a slowly progressive
  deficit occurs.

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• Epidemiology
• It is common in UK .
• Age peaking about 30 years ,uncommon over age of
  50 years.
• Slightly more in women than men
• Aetiology
• Acute demyelination is an inflammatory
  process and the most favoured explanation,at
  present ,is that acute demylination is the result
  of an abnormal immune response to an
  antigen,perhaps of viral origin. Genetic
  factors may be important in some instance.

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• Pathology
• Acute demyelination occurs in discrete areas
  known plaques,which may be single or multiple.
• The lesions may occre any where in central white
  matter ,but common sites are optic nerve, the
  brain stem and cerebellum,the periventricular
  regions and the cervical spinal cord.Later,glial
  scarring results in the whitish apperance of the
  chronic plaque.
• Resolution of oedema in and around plaques
  reverses conduction.
• Even without symptoms or sings,slowing of
  conduction can be often demonstrated in visual
  ,auditory and somatosensory pathways by
  electrophysiological testing.

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• Clinical picture
• Since plaques may occure at any site in central
  white matter, the clinical manifestation of MS
  are extremly variable.
• However,early in the disease a number of
  presentations are characteristic.

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• 1- Optic neuritis
• Inflammation of optic nerve may be symptomtic or
  not always unilateral,and can lead to dimming of
  vision, blurring, loss of acuity and reduced
  colour vision.
• Pain in and around the eye, particularly with
  movement is common.
• Optic neuritis usually resolves within afew weeks
  ,often without residual symptoms,but repeated
  episodes of optic neuritis

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• 2- Cervical cord
• Involvement of the cervical spinal cord is common
  earlyin MS, presenting with motor,sensory,or
  bladder,and sexual disturbance.
• Symptoms may be unilateral, but pyramidal sings
  are usually bilateral. Sensory symptoms include
  tingling and numbness.
• Erectile impotence and ejaculatory failure are
  common symptomss

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• Examination reveals disturbance of dorsal column
  function impaired joint position and vibaration
  sens and less often spinothalamic sensation.
• Bladder disturbance urgency,frequency then
  incontinence.
• Constipation is the main bowel disturbance.
• Erectile impotence and ejaculatory failure are
  common symptomss

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• 3-Brain stem and cerebellum
• Diplopia and Nystagmus are common.
• Vertigo is very common early due to plaque
  formation involving the vestibular nuclear
  complex.
• Ataxia involving limbs and trunk is also frequent
  early due to cerbellar affection.
• 4-Latar features
• Depression in longstanding MS
• Widespread cerebral demylination leads to
  dementia,altered mood euphoria,or depression
• Progressive bulbar involvement producing
  dysarthria ,dysphagia.
• Facial numbness or neuralgia.

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• 4- Latar features
• Depression in longstanding MS
• Widespread cerebral demylination leads to
  dementia,altered mood euphoria,or depression
• Progressive bulbar involvement producing
  dysarthria,dysphagia.
• Facial numbness or neuralgia.

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• The end stage of MS
• Characterised by dementia ,quadreplegia
  ,incontinence ,blindness ,pressure sores and
  recurrent respiratory and urinary tract
  infections.
• Life expectancy from the onset of symptoms is 20
  -30 years.

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• Diagnosis
• 1-clinical examination
• Evidence of more than one lesion inCNS
  together with a characteristic relapsing and
  remitting history.The finding of optic atrophy in
  a Patient presenting with a brain stem or
  cervical cord lesion is particularly helpful.
• 2- MRI is the investigation of choice.
• 3- Evoked potentials either visual ,auditory ,or
  somatosensory from the limbs,are senstive
  measures of damage in these sensory pathways.
• 4- CSF protein content may be raised.

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• Treatment
• There is no specific treatment for MS.
• 1- Corticosteroids may accelerate remission in
  relapse, by reducing oedema in acute plaque.
• 2- B-interferons in seleced cases.
• 3- Physiotherapy have large role to play.
• 4- Urinary symptoms often relieved by
  anticholinergic.

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Degenerative neuronal diseasesMotor neurone
diseaseMND

• In this disease there is progressive degeneration
  of lower and upper motor neurones LMNs, UMNs in
  the spinal cord , in the somatic motor nuclei of
  the cranial nerves and within the cortex.
• The condition is sporadic and entirely of unknown
  cause.The onst is in middle life,slight male
  predominance.
• The sensory system is not involved.

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• Clinical features
• Three patterns have been noted
• 1- Progressive muscular atrophy.
• 2- Amyotrophic lateral sclerosis.
• 3- Progressive bulbar palsy.

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• Progressive muscular atrophy
• Wasting beginning often in the small muscles of
  one hand spreads throughout the arm.Although it
  may begin unilaterally , wasting soon follows on
  the opposite side.
• Fasiculation is common, it is due to affection of
  AHC. Cramps may occur but pain does not.
• The physical signs are wasting and weakness, with
  fasiculation that is often widespread. Tendon
  reflexes are lost when the reflex arc is
  interupted by AHC loss, but are preserved or
  exaggerated when there is loss of corticospinal
  motor neurones.

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• Amyotrophic lateral sclerosisALS
• Lateral sclerosis means disease of the lateral
  corticospinal tractsi.e.one cause of spastic
  paraparesis. Amyotrophy means simply atrophy of
  muscle , which would be unusual in most other
  form of spastic tetraparesis or paraparesis.
• The clinical picture is of spastic tetraparesis
  or paraparesis with added lower motor neurone
  signs and fasiculation.

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• Progressive bulbar palsy
• Here the brunt of the disease falls initially
  upon the lower cranial nerve nuclei and there
  supranuclear connections.
• Dysarthria,dysphagia, nasal regurgitation of
  fluids and choking are common symptmos.MND is
  more common in women than men.

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• The characteristic features are of a bulbar and
  pseudobulbar palsy, with mixture of UMN and LMN
  signs in the lower cranial nerves.
• The occular movement are not affected.
• In all forms of MND there are never cerbellar or
  extrapyramidal signs.
• Awareness is preserved and dementia unusual.

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• Diagnosis
• There are no specific diagnostic tests and the
  diagnosis is made on clinical grounds.,by
  exclusion of other conditions ,and compatible
  neurophysiological studies EMG and nerve
  conduction.
• Course and Management
• Remission is unkown.The disease
  progresses,spreading gradually and causes death
  ,often from broncho-pneumonia.Survival for more
  than 3 years is most unusual.
• No treatement has been
  shown to influence the outcome of MND.
  

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