Peripheral neuropathy

• May be caused by two types of pathology;
  • Distal axonal degeneration
  • Demyelination of nerve fibres

 

• Nerve impulses become diminished or delayed
• Most impaired in long nerves because the nerve impulse have to travel further and meets more unmyelinated segments
• Legs and feet are more likely to be affected compared with arms and hands
• Deep tendon reflexes are also
• Can affect motor or sensory neurones

 

• Common causes;
  • Alcohol  - directly toxic to nerves and may also coexist with a Vit B1 deficiency
  • Vit B12 deficiency
  • Diabetes
  • Guillian-Barre syndrome
  • Paraneoplastic from bronchial carcinoma
  • CT disease
  • RA
  • SLE
  • Polyarteritis nodosum
  • Charcot-Marie-Tooth disease (hereditary motor and sensory neuropathy)
    • Duplication for the gene for peripheral myelin protein 22
  • Idiopathic in 50% of cases

 

Guillian-Barre syndrome

 

• Rapid onset over a few days
• Affects nerve roots as well as peripheral nerves as it involves myelin
• Occurs commonly a week or two after infection and is thought to be autoimmune
• Limb weakness and sensory deficits that can progress to serious paralysis of the limbs, trunk, chest muscles and muscles supplied by the cranial nerves
• Involvement of autonomic nerves can lead to erratic rises and falls in BP and pulse and profound constipation

 

• Patients may require ventilation
• Plasma exchange or I.V. immunoglobulin may prevent deterioration
• Generally resolves after weeks-months
• Recovery is due to the ability of Schwann cells to reconstitute myelin sheaths after the initial demyelination
• The involvement of nerve roots can give rise to one of the diagnostic features of disease – protein in the CSF