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Determine if patient has actual neuromuscular weakness (suggesting CNS dysfuction) or non-neuromuscular weakness.

Clincial Features


  • True motor weakness (neuromuscular weakness)? Bilateral or unilateral (distribution of weakness)?
    • Bilateral weakness:
      • Symmetric ascending paralysis? Guillain-Barre Syndrome
      • Weakness involving both CN + PNS? Inflammatory/Autoimmune or toxic/metabolic
      • Discrete sensory level and/or bladder dysfxn? Spinal Cord Lesion
      • Involvement of proximal > distal musculature? Myopathy
    • Unilateral weakness: CVA, TIA
  • If non-neuromuscular weakness then BROAD Ddx obtain:
    • ECG, CBC, Chem10, LFTs, blood cx, UA/UCx, drug levels, CXR, Consider Head CT (focal deficit, AMS, h/o CA, anticoagulation w/minor trauma)
  • Onset of weakness sudden or gradual?
    • Sudden suggests vaso-occlusive etiology CVA/TIA
    • Gradual onset likely non-vascular
  • Significant event surrounding onset of weakness?
    • SZ prior to weakness? Todd’s paralysis
    • Migraine HA? Complicated migraine
    • Sudden onset of severe HA? SAH
    • Trauma? Epidural or Subdural Hematoma
    • Severe migratory neck or chest pain? Arterial dissection syndromes
  • Temporal pattern to weakness? Fluctuating or fixed weakness?
  • Associated Sx?
    • HA: SAH, epidural/SDH, complicated migraines (young females), not usually stroke/TIA (unless high ICP)
    • Vision changes: Posterior circulation stroke, Myasthenia Gravis
    • SOB: CV etiology
    • CP or neck pain: Acute arterial dissection, AMI
    • Abdominal or back pain:
    • N/V: sign of ↑ ICP, can lead to electrolyte imbalances
    • Rash: Dermatomyositis

Physical Exam

Focus on clarifying if patient has true loss of strength and determining distribution of deficits. Check for trauma, carotid bruits, thyroid enlargement, irregular rhythm, unequal pulses, rashes or ticks.

Location Weakness Bowel/Bladder Reflexes Sensory Pain
Upper motor neuron
Brain Variable Increased Diminished No
Brainstem "crossed" findings - ipsilateral cranial nerve weakness and contralateral hemiparesis
Cord Fixed level Yes Increased Diminished +/-
Lower motor neuron
Nerve Distal > proximal and ascends No Diminished Nl/parethesias No
Motor end plate Ooccular,bulbar and descends, fatigable No Nl/diminished Nl/parethesias No
Muscle Proximal > distal No Nl/diminished Normal +/-

Differential Diagnosis




On all patients:


  • CK (mypoathies)
  • ESR
  • CXR and UA (if infectious symptoms or elderly)
  • FVC (if e/o resp compromise, i.e. Myasthenia, GBS)
  • CT head (if focal findings, AMS, h/o cancer, h/o any trauma in patient on anticoagulation)
  • LP (CNS infection, GBS)


Intubation Indications

  • Severe fatigue
  • Inability protect airway
  • Rapidly increasing PaCO2
  • Hypoxemia despite O2
  • FVC <12 mL/kg
  • Neg Insp Force <20 cm H2O


  • Depends on process
    • If normal initial workup, make sure has no respiratory compromise