Polyneuromyopathy of critical illness: when to call in the cavalry!

Dr. Neal Porter is an Assistant Professor of Neurology here at the University of Maryland with a special clinical focus on neurophysiology. Over the last twenty years, Dr Porter has mastered the topic of ICU polyneuromyopathy and has used this knowledge to be one of the national experts in the field. Additionally, he consistently makes himself available here at Maryland (even WELL after hours) as the “go to” expert when it comes to evaluation and management of the weak critical ill patient. Today he is gracious enough to take us into his world and explain the simplistic and systematic way he approaches every case of weakness in the ICU. This is a talk you CANNOT miss as that next case of botulism might sneak in through your door any moment!!!

Pearls

Simple approach to weakness:

  • Time course leads to etiology
  • To localize/diagnose:
    • Focus on pattern of weakness
    • Associated features
      • Sensory abnormalities
      • Upper motor signs: spasticity, hyper-reflexia, upgoing toes
      • Lower motor signs: flaccidity, muscular atrophy, muscle fasciculations, areflexia, downgoing toes
  • Differentiate:
    • People who are weak BECAUSE they are in the ICU
    • People who are in the ICU BECAUSE they are weak

Critical Illness Polyneuropathy/Myopathy

  • Disuse syndrome, severe myopathy/axonal neuropathy due to a prolonged ICU stay
  • Physical exam:
    • Muscle wasting/weakness
    • Areflexia or hyporeflexia
    • Quadraplegia/Quadraparesis
    • Flaccidity (leading to prolonged ventilator use)
    • Normal mental status
  • Time frame: 2+ days of ICU stay
  • Prevalence: 50-70% of patients
  • Diagnosis: clinical appearance (NO need for an EMG)
    • FUN FACT: Direct muscle stimulation yields no response
  • Treatment: Supportive measures
  • Prognosis: 30% recover from myopathy in 3 months
    • Neuropathy is more difficult- grows 1mm/day (1″ per month)
  • Risk factors:
    • Steroid use (preventable)
    • Paralytics/Sedation (preventable)
    • Prolonged Stay with ventilatory support
    • Sepsis
  • Pathophysiology of myopathy: an acquired sodium channelopathy

Acute weakness PRIOR to the ICU

1) Nerve root: Guillain Barre Sydrome (GBS)

  • Acute areflexic paralysis (NOT ascending paralysis)
  • Starts with a viral prodrome  back pain (first symptom)  tingling of hands/feet  proximal>distal weakness (polyradiculopathy)
    • Difficulty getting out of chairs/climbing stairs
  • Diagnosis: demylelination nerve conduction studies (NCS)
    • LP shows cytoalbumination; low high protein and normal cell levels
      • West Nile Virus has INCREASED cells (presents similar to GBS)
  • Treatment: Plasma exchange (PLEX) or IVIG
  • Prednisone is contraindicated (small amounts leads to a worse prognosis)

2) Nerve Plexus: Parsonage-Turner Syndrome

  • AKA: Acute brachial neuritis
    • Arm pain  numbness, weakness → affects the phrenic nerve (rare cases ONLY affects the phrenic nerve)
  • Diagnosis: EMG
  • Treatment: Supportive

3) Nerves: Porphyria

  • Acute or recurrent paralysis similar to GBS
  • Presentation: abdominal pain, psychosis, weakness
    • Usually presents after a trigger: medication, infection, etc.
  • Diagnosis: NCS showing axonal loss
    • Screening: phorphobilinogen and delta-ALA
  • Treatment: supportive, avoiding offending agents

4) Neuromuscular junction: Myasthenia gravis (MG)

  • Acute or subacute diplopia, dysphagia, dysarthria
  • Exam: preserved reflexes, abnormal eye movements, ptosis, facial weakness, proximal limb weakness
  • Diagnosis: antibody testing, repetitive nerve testing
  • Treatment: PLEX > IVIG; acetylcholinesterase inhibitors (long term)

5) Neuromuscular junction: Botulism 

  • Generalized areflexia with flaccidity
  • Fasciculations with fast repetetive nerve stimualtions (also seen in Lambert Eaton Syndrome)
  • Treatment: anti-toxin

6) Muscles: Myopathies (Polymyositis, Dermatomyositis, Toxin induced)

  • Progressive proximal limb weakness with relatively preserved reflexes 
  • Diagnosis: elevated CK (40-50k); EMG shows irritable myopathy
  • Biopsy shows inflammation in myositis and necrosis in toxin induced myopathies (ex: statins)
  • Treatment: steroids and steroid sparing agents
    • Toxin induced: treat by stopping the offending agents

SUMMARY: Guide to Acute Weakness

  1. Generalized areflexia: GBS, Botulism
  2. Decent reflexes: MG, Myopathy
  3. Abnormal eye movements: GBS, MG, Botulism
  4. Sky high CK: Myopathies (inflammatory or toxin induced)

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