Neurology
Neuromuscular Junction Disorders
Neurology

Neuromuscular Junction Disorders

Myasthenia gravis vs Lambert-Eaton; diabetic neuropathy.

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◆Myasthenia gravis

  • •Fluctuating weakness worse with use, improves with rest/ice
  • •Ocular prominent (ptosis, diplopia); normal sensation/reflexes
  • •Anti-AChR (or anti-MuSK) antibodies
  • •EMG: decremental response with repetitive stimulation
  • •Treat: pyridostigmine + immunosuppression; thymectomy
  • •Myasthenic crisis → plasmapheresis or IVIG

◆Lambert-Eaton myasthenic syndrome (LEMS)

  • •Proximal weakness IMPROVES with brief exercise
  • •Autonomic dysfunction (dry mouth, ED)
  • •60% have small cell lung cancer (paraneoplastic)
  • •Anti-VGCC antibodies; EMG: incremental response
  • •Treat underlying cancer; 3,4-DAP for symptoms

◆Diabetic peripheral neuropathy

  • •Symmetric distal sensory loss (stocking-glove)
  • •Length-dependent axonal degeneration
  • •Burning, nighttime pain, ↓ vibration/pinprick, ↓ ankle reflexes
  • •From chronic hyperglycemia → polyol pathway + microvascular ischemia

◆Drug-induced neuropathy

  • •Isoniazid: pyridoxine (B6) deficiency — give B6 prophylactically
  • •Cisplatin: dose-dependent toxic neuropathy
  • •Lead: distal motor (wrist drop) + microcytic anemia + cognitive decline
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