WEEK 12 - DEMYELINATION OF THE PNS AND CNS

Question 1

Spasticity vs rigidity

Answer 1

• both refer to the resistance of movement

rigidity

• agonist vs antagonist muscles work against each other (biceps v triceps)

spasticity

• an exaggerated stretch reflex
• velocity dependent - more resistance with greater velocity
• caused by corticospinal tract damage

Question 1

Multiple Sclerosis

Answer 1

MS is an autoimmune disorder that results in aggregation of proteins, creation of plaques and demyelination of axons in the CNS (occasionally in the PNS but mainly in the spinal cord and brain).

Description

• demyelinating disease of the CNS
• autoimmune, immune system destroys its own myelin resulting in communication breakdown between neurons
• T cells pass the BBB and are stimulated by myelin. This allows for more T cells to pass through the BBB into the brain
  
  • release cytokines that dilate the BV and allows more immune cells to come in.
  • oligodendrocytes are destroyed in the immune process
    
    • early on remyelinate, over time process stops

4 types

• relapsing-remitting MS - bouts if immune attacks occuring months/years apart
• Secondary progressive MS - begins similiar to RRMS, over time, immune attack becomes constant (constant degeneration)
• Primary progressive MS - steady progression throughout life span
• Progressive relapsing MS - constant progression + bouts of immune attacks

Causes/risk factors

• genetic predisposition
  
  • females
• environmental factors
  
  • infection
  • vitamin D deficiency

symptoms

• depend on location of the plaques
• charcots neuroligic triad
  
  • dysarthria
    
    • difficult or unclear speech, swallowing
  • nystagmus
    
    • involuntary rapid eye movement
      
      • loss of vision
  • intentional tremor
    
    • plaques damaging motor pathway, resulting in
      
      • muscle weakness, spasms, tremors and ataxia
• plaques in sensory pathway
  
  • numbness, pins and needles, paresthesia
  • urinary incontinence
• higher order activities
  
  • depression and anxiety
  • poor concentration and critical thinking

diagnosis

• MRI
• CSF

treatment

• medication
  
  • corticosteroids
  • IV immuniglobin
• immunosuppressants

Question 2

Guilliane Barre Syndrome

Answer 2

description

• an acute paralytic (ascending weakness) polyneuropathy
• molecular mimicry - b cells of the immune system create antibodies against antigens on the pathogen
• these antibodies may match proteins located in nerve myelin or axon, damaging neurons

causes/risk factors

• triggered by an infection
  
  • within 4 weeks of initial infection

symptoms

• symmetric ascending weakness
  
  • feet upwards
• reduced reflexes (peripheral neuropathy)
• loss of sensation
• neuropathic pain
• facial weakness (when progressed)
• respiratory failure (rare)
• symptoms peak at 2-4 weeks
  
  • full recovery can take months/years

80% fully recover

15% have a neurological disability

5% die

treatment

• IV immunoglobins
• plasma exchange
• supportive care
• VTE prophylaxis
  
  • prevent blood clot
    
    • PE is leading cause of death with people with GBS

Question 3

Trigeminal Neuralgia

Answer 3

• Neurological condition involving recurrent episodes of facial pain
• higher prevalance in people 50+
• higher likelihood with people who have MS
  
  • precursor for MS?

pathology

• idiopathic
• compression of trigeminal nerve (80-90%)
  
  • compressed by nearby arteries and/or veins
    
    • superior cerebellar artery
• tumour induced compression
• leads to demyelination of the trigeminal nerve

symptoms

• facial pain
  
  • sudden onset
  • intense and excruciating
  • unilateral
  • aching and burning prior to
  • ‘shooting’ ‘electric’ pain
• recurrent episodes
  
  • increases in frequency over time
• duration of pain is variable
  
  • seconds —> hours —> days

caused by triggers

• movement of the muscles in the face
  
  • eating, talking, touch

treatment

• medication

Question 4

Classification of nerve injury

Answer 4

1. Neuropraxia (demyelination)
   
   1. reversible conduction block
      
      1. radial nerve compression
2. Axonotmesis (Demyelination + axon loss)
   
   1. Can grow back
   2. distal end will undergo wallerian degeneration
   3. commonly seen in crash injuries and displaced bone
3. Neurotenesis (demyelination + axon loss + involvement of,
   
   1. endoneurium - fair growth
   2. perineurium (sheet surrounding vessicle) (poor growth)
   3. epineurium (sheet around nerve) (no growth)

Question 5

Forms of neuropathy

Answer 5

Diabetic Neuropathy

• Nerve damage caused by diabetes
• occurs in 50% of patients
• chronic high BP levels causes progressive injury to nerve neurons

Peripheral neuropathy

• loss of symmetrical sensory function beginning in the feet, then legs, then hands
  
  • numbness, tingling or burning sensation
  • loss of pain sensation
    
    • increase risk of serious infection

Autonomic neuropathy

• in cardiac autonomic neuropathy, nerves that regulate HR and BP are damaged
  
  • light headedness
  • rapid HR
• Neuropathy in digestive system
  
  • naseau, vomiting, difficulty swallowing, bowel problems
• urogenital autonomic neuropathy
  
  • urinary retention
  • urinary hesistancy
  • urinary incontinence
  • sexual dysfunction
• nerve damage in the eyes
  
  • slower adjustment to changes in light and darkness
• nerve damage in sweat glands
  
  • absence of sweat OR heavy sweating (especially at night)
• hypoglycemia unawareness

Mononeuropathy

• dysfunction of a single nerve, typically due to entrapment
• most common is carpal tunnel syndrome
  
  • median nerve is compressed

Proximal neuropathy

• rare but severe
• effects thighs, hip, buttock, abdomen, chest unilaterally
  
  • severe pain and weakness