AP: Neuromuscular Disorders

Question 1

What are the different disorders of peripheral nerves?

Answer 1

• Lower motor neuron
• Motor vs sensory
• Level of pathology (where)
  
  • Anterior horn cell (motor)
  • Peripheral nerve
    
    • myelin
    • axon
    • associated structures (e.g. blood vessels)
• Neuromuscular junction

Question 2

Compare the clinical presentation of UMN vs LMN syndromes

Answer 2

Type of paralysis:

• UMN: Spastic paresis (hypertonia)
• LMN: Flaccid paralysis

Atrophy:

• UMN: No disuse atrophy
• LMN: Severe atrophy

Deep tendon reflex:

• UMN: Increase
• LMN: Absent

Pathological reflex:

• UMN: Positive Babinski sign
• LMN: Absent

Superficial reflex:

• UMN: Absent
• LMN: Present

Fasciculation and fibrillation:

• UMN: Absent
• LMN: Could be present

Question 3

What is the surgical sieve for disorders of peripheral nerve?

Answer 3

• Autoimmune/inflammatory
  
  • Guillain-Barre Syndrome
• Vascular
  
  • Vasculitis, amyloidosis
• Infective
  
  • Herpes zoster, leprosy, HIV, Lyme disease
• Traumatic
• Toxic
  
  • alcohol, Pb
• Metabolic
  
  • diabetes mellitus, uraemia
• Nutritional
  
  • Vit deficiencies: B1, B6, B12
• Neoplastic
  
  • Paraneoplastic (Lambert-Eaton)
• Congenital/inherited
  
  • Charcot-Marie-Tooth neuropathy, others
• Drugs
  
  • colchicine, isoniazid, vinblastine

Question 4

How can we classify peripheral nerve disorders by anatomical patterns?

Answer 4

• Polyneuropathy
  
  • symmetrical, distal, “glove and stocking
  • Think: alcohol and diabetes
• Mononeuropathy
  
  • single nerve distribution
  • Think: shingles/zoster (1 nerve); osteoarthritis of vertical column
• Mononeuritis multiplex
  
  • random distributionof nerve involvement
  • Think: vasculitis, amyloid

Question 5

What is Guillain-Barre syndrome?

Answer 5

Rapidly progressive, acute, demyelinating motor axons - immune mediated

Deyelinating polyneuropathy - infectious trigger of EBV, CMV, HIV, Zika, Campylobacter jejuni

Question 6

What is diabetic peripheral neuropathy?

Answer 6

Diabetes mellitus - most common cause of peripheral neuropathy

Most common form is distal symmetrical sensorimotor polyneuropathy

Pathology - thickening of blood vessels and basement membrane around the nerves

Question 7

What is myasthenia gravis?

Answer 7

• Autoiummune fluctuating muscle weakness
• ABs blocking AChR
• Bimodal distribution
• Weakness of extraocular muscles
• Facial muscle weakness/swalloing weakness
• Treatment = cholinesterase inhibitors

Question 8

What are the disorders with neurogenic or myopathic injury patterns?

Answer 8

Neurogenic

• Motor neurone disease (amyotrophic lateral sclerosis)
• Spinal muscular atrophy
• Polyneuropathy

Myopathic

• Muscular dystrophies
• Mitochondrial disorders
• Myositis
• metabolic myopathies (lipid myopathies, glycogen storage disorders)

Question 9

What are the inherited disorders of skeletal muscle? (That must be excluded as they affect the family)

Answer 9

1. Muscular dystrophies
   
   • Normal muscle function at birth, progressive muscle injury
2. Congenital muscular dystrophies
   
   • progressive, early onset disease
   • e.g. Duchenne MD
3. Congenital myopathies
   
   • present in infancy, static muscle defects

Question 10

Name an ionchannel myopathy (inherited defect of ion channels in muscle fibres)

Answer 10

Malignant hyperthermia - increased susceptibility to heart stroke, can’t be given anaesthetic or will have excessive heat production

Question 11

What is an inflammatory myopathy I should know about?

Answer 11

Dermatomyositis

Children or adults - in adults consider an occult malignancy

Clinical signs:

• cutaneous:
  
  • Gottron’s papules, heliotrpe rash
• myopathic:
  
  • pain, weakness, raised CK