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

Clinical Features


  • True motor weakness (neuromuscular weakness)? Bilateral or unilateral (distribution of weakness)?
    • Bilateral weakness:
      • Symmetric ascending paralysis? Guillain-Barre Syndrome
      • Weakness involving both central and peripheral nervous system? Inflammatory/Autoimmune or toxic/metabolic
      • Discrete sensory level and/or bladder dysfunction? Spinal Cord Lesion
      • Involvement of proximal > distal musculature? Myopathy
    • Unilateral weakness: CVA, TIA
  • If non-neuromuscular weakness then BROAD differential, obtain:
    • ECG, CBC, Chem10, LFTs, blood cultures, UA/urine culture, drug levels, CXR, Consider Head CT (focal deficit, altered, history of cancer, anticoagulation with 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?
    • Seizure prior to weakness? Todd’s paralysis
    • Migraine headache? Complicated migraine
    • Sudden onset of severe headache? SAH
    • Trauma? Epidural or Subdural Hematoma
    • Severe migratory neck or chest pain? Arterial dissection syndromes
  • Temporal pattern to weakness? Fluctuating or fixed weakness?
    • Weakness with repetitive motions? Neuromuscular junction pathology like Myasthenia Gravis
  • Associated symptoms?
    • Headache: SAH, epidural/SDH, complicated migraines (young females), not usually stroke/TIA (unless high intracranial pressure)
    • Vision changes: Posterior circulation stroke, Myasthenia Gravis
    • Shortness of breath: cardiovascular etiology
    • Chest pain or neck pain: Acute carotid/vertebral/aortic dissection, AMI
    • Abdominal or back pain:
      • with alteration of bowel habits? Botulism, organophosphate poisoning, toxins, Guillain-Barre Syndrome, Electrolyte Imbalance.
      • with lower extremity weakness? AAA with spinal cord infarction
      • Back pain with unilateral weakness? Herniated disk with nerve impingement
      • Bilateral weakness with sensory level s/p trauma? SCI, Cauda Equina Syndrome
    • Nausea/vomiting: 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
Brainstem"crossed" findings - ipsilateral cranial nerve weakness and contralateral hemiparesis
CordFixed levelYesIncreasedDiminished+/-
Lower motor neuron
NerveDistal > proximal and ascendsNoDiminishedNl/parethesiasNo
Motor end plateOcular, bulbar and descends, fatigableNoNl/diminishedNl/parethesiasNo
MuscleProximal > distalNoNl/diminishedNormal+/-

Differential Diagnosis




On all patients:


  • CK (mypoathies)
  • ESR
  • CXR and UA (if infectious symptoms or elderly)
  • FVC (if evidence of respiratory compromise, i.e. Myasthenia, GBS)
  • CT head (if focal findings, altered mental status, history of cancer, history of 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


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