Cells of the CNS😊

Cells of the CNS

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  • CNS: Contains neurons and glial cells.
  • Neurons: ~100 billion.
  • Glial cells: 2 to 10 times more than neurons.

Main CNS glial cells: 

Astrocyte:

  • Provides nutrition and growth factors to neurons.
  • Controls extracellular glutamate and potassium levels (mopping up excess).
  • Regulates blood brain barrier permeability.
    • NOTE:
        • Astrocyte foot processes: 
          • Do not form blood brain barrier.
        • BBB → Formed by endothelium of Brain capillaries
  • Mnemonic: A hero/STAR → Gives nutrition (), support growth () of that place → Give glutathione () to everyone

Microglial cell:

  • Phagocytic cells of CNS.
  • Mnemonic: Microglial → Microorganism catching

Oligodendrocyte:

  • Forms myelin sheath in CNS.
  • One oligodendrocyte: myelinates 30 to 50 neurons.
  • Mnemonic: O → Central →sO many neurons

Schwann cell:

  • Forms myelin sheath in PNS.
  • One Schwann cell: myelinates a single neuron only.
  • Single swan in periphery of lake

Imp

  • Demyelination:
    • Conduction velocity reduced
    • Distal latencies
  • Axonal:
    • Low amplitude

Multiple Sclerosis:

  • CNS demyelinating disease.
  • Away from equator, Low Vit D → ↑ incidence
  • There is plaque formation in the brain.
  • Revised McDonald criteria
    • Dissemination in time and space
  • Charcots triad (SIN)
    • SCANNING SPEECH
    • INTENTION TREMOR
    • NYSTAGMUS
      • Due to MLF → Internuclear Ophthalmoplegia
  • Lhermitte sign
    • Shock like sensation down the spinal cord
  • Uthoff sign
    • Increases with temp
  • Also called Dawson finger.
  • U/L Optic nerve is involved.
  • Presentation:
    • Female patient.
    • Mainly of Caucasian origin.
    • Northern part of Europe origin.
    • British women.
    • One sided decreased visual acuity.
    • Also has relative efferent pupillary defect.
    • Optic neuritis.
      • M/c = Central scotoma
        M/c = Central scotoma
    • Bladder/bowel involvement.
  • Autoimmune: 
    • Antibodies against 
      • Myelin basic protein 
      • Oligodendrocyte glycoprotein.
    • Oligodendrocytes attacked/killed by T-cells → Demyelination.
  • Effect: 
    • Decrement in nerve conduction velocity.
  • Mnemonic:
    • Myru nn pryunnath basic (Myelin basic protein) anu
    • Olipich olipich (Oligodendrocytes) nadakkum

MRI head

  • Gadolinium as there is damage to BBB: FLAIR Sequence
    • Plaque lesions
    • Dawson finger/Periventricular lesions
      • Finger-like projections in calloso-septal interface.
      • notion image
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Treatment:

  • Acute episode/First presentation:
    • Visual blurring, decreased colour vision:
      • Methylprednisolone
  • Mitoxantrone
    • Most effective
      • Condition
        DOC
        Acute Episode
        IV Steroids
        Primary Progressive
        Ocrelizumab
        Relapsing Remitting
        β-IFN

Prevention:

  • β-Interferon
  • Glatiramer
  • Dimethyl Fumarate
  • Monoclonal antibodies
    • In worst case scenario
    • Natalizumab
      • S/E → Progressive Multifocal Leucoencephalopathy
      • Aw JC virus
    • Mnemonic: Nattelilu lesions varathirikan
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Virus
Notes
Merkel Cell Virus
• Merkel Cell Carcinoma (neuroendocrine skin tumor)
SV40
• Mesothelioma
• Save size 40 Meesa
JC Virus
• Progressive Multifocal Leukoencephalopathy
•
Junkie Cerebrum (HIV AIDS)
BK Virus
• Post kidney transplant
• Bad Kidney
• Urine microscopy:
↳ large nuclei cells mimicking cancer = Decoy cells
  • JC () saved 40 () people from Bad Kidney Virus () → Marakkallee (Merkel cell virus)
    • Decoy cells
      Decoy cells

PPMS (Primary Progressive Multiple Sclerosis):

  • Ocrelizumab.
  • Mnemonic: To progress → First Ocred (Ocrelizumab)

SPMS (Secondary Progressive Multiple Sclerosis):

  • Siponimod.
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  • Mnemonic: Second sip

NOTE

  • NMOSD (Neuromyelitis Optica Spectrum Disorder).
    • Young female patient
    • Sudden onset bilateral optic neuritis
    • Recurrent
  • In multiple sclerosis:
    • Unilateral involvement.
    • Gradual slow process.
    • Secondary progressive multiple sclerosis.

ADEM - Acute Disseminated Encephalomyelitis

  • <20yrs
  • Monophasic
  • Antecedent infection
  • ON : B/L
  • Spinal cord: Long segment

Optic Neuritis

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  • Definition: Inflammation of the optic nerve.
  • Cause: Most common cause is Multiple Sclerosis.

Clinical Features:

  • Mnemonic: 2 CUP mar
  • Central scotoma.
  • Color blindness (red & green).
  • Unilateral loss of vision.
  • Pain in eye on ocular movements.
  • Marcus Gunn pupil (RAPD).
  • Uhthoff sign:
    • Worsening of symptoms with increased body temperature (e.g., exercise).
    • Mnemonic: Uhthoff → Utto → Up → Temperature
  • Pulfrich sign:
    • Tachtokinetic dissociation.
    • Illusion of depth perception
    • Mnemonic: Pullil thotta ariyulla
  • Lhermitten’s sign
    • Passive neck flexion causing an electric shock-like sensation radiating to the spine and shoulders
    • Due to increased sensitivity of the myelin to stretch

Investigation

  • MRI
  • LP
    • NMO (Neuromyelitis optica antibodies → Anti Aquaporin 4 antibody)
      • Nemo (NMO) fish → aquatic (Anti Aquaporin 4)
    • MOG (Myelin Oligocyte Glycoprotein) antibodies

Treatment:

  • Steroids (IV →f/b oral)
  • f/b β Interferons
  • Glatiramer acetate : 30 mg s/c injection.

Mnemonic:

  • Vinnu → calls myre (myelin basic protein), pulle (pulfrich), then spits - thphuuu (uhthoff)
  • Olipich (oligodendrocytes) nadakkunavan vannu
  • she took gun (marcus gunn) → fire to his eyes
  • he got eye pain (pain on movement)
  • Kandavar scoot ayi (scotoma)

NEUROMYELITIS OPTICA / DEVIC'S DISEASE

NMOSD (Neuromyelitis Optica Spectrum Disorder)
DEVIC'S DISEASE

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  • DEVIC'S DISEASE
  • 20 -40 yrs
  • Female: Male ratio = 3:1.
  • Demyelinating disease.
  • Disease is Astrocytopathy
    • Damage to astrocyte foot processes causes cerebral edema and death.
      • Astrocyte foot processes: 
        • Do not form blood brain barrier.
      • BBB → Formed by endothelium of Brain capillaries

Cause

  • Can be secondary (2°) to Multiple Sclerosis

Death

  • Spinal cord involvement at C3, C4, C5
  • Phrenic nerve supply to diaphragm is affected.
    • Causes respiratory failure.
  • NOTE: In many neurological diseases
    • parkinsonism, Alzheimer’s, VCJD
      • death is often due to pneumonia from being bedridden and aspirating.

Antibodies:

  • NMO IgG antibodies / Anti-Aquaporin-4 antibody
    • Damages water channel,
    • Causes cerebral edema
  • Anti-MOG
    • Myelin oligodendrocyte glycoprotein antibody.

Manifestation:

  1. Optic neuritis
      • Sudden onset blindness
      • bilateral
      • Increased (↑) chance of relapse
        • More frequent than in Multiple Sclerosis alone
      • History of recurrent Optic Neuritis
        • most important to differentiate from MS
  1. Longitudinal extensive transverse myelitis:
      • >3 consecutive spinal segments.
      • Symptoms:
        • Pin, needle sensations,
        • Root pain/radicular pain below level.
        • Acid or boiling pain
  1. Spectrum disorder manifestations:
      • A: Area postrema syndrome (protracted vomiting).
      • B: Brainstem syndrome (3rd cranial nerve or any other nerve palsy).
      • C: Cerebral syndrome (seizures, encephalopathy).
      • D: Diencephalic syndrome (hypothalamus affected)
        • Hunger affected → Anorexia, Weightless
      • N: Narcolepsy (damage to Reticular activating system).

NOTE

  • Multiple sclerosis:
    • Relapsing/remitting course,
    • mostly unilateral ocular deficit.

Diagnosis criteria for NMOSD

  • At least
    • 1 clinical core feature + Anti aquaporin 4 antibody.
  • If antibody not identified:
    • 2 clinical core features + Gadolinium enhanced MRI.
  • MRI:
    • Optic neuritis.
    • MRI spine: >3 segments involved.
    • Cloud like brain lesions (parenchyma or brain stem).

Treatment:

  • β-Interferon, Glatiramer: Contraindicated.
  • Methylprednisolone.
  • No improvement: Plasmapheresis.

Prevention:

  • Immunomodulators +
    • Mycophenolate, Azathioprine
  • Steroids

Important Information

  • Therapeutic Plasmapheresis indicated in:
    • HUS.
    • TTP.
    • NMOSD.
    • GBS
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