Weakness

• 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

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.

• Neuromuscular weakness
  • Upper motor neuron:
    • CVA
    • Hemorrhagic stroke
    • Multiple sclerosis
    • Amyotrophic Lateral Sclerosis (ALS) (UMN & LMN)
  • Lower motor neuron:
    • Spinal and bulbar muscular atrophy (Kennedy's syndrome)
  • Spinal cord disease:
    • Infection (Epidural abscess)
    • Infarction/ischemia
    • Trauma (Spinal Cord Syndromes)
    • Inflammation (Transverse Myelitis)
    • Degenerative (Spinal muscular atrophy)
    • Tumor
  • Peripheral nerve disease:
    • Guillain-Barre syndrome
    • Toxins (Ciguatera)
    • Tick paralysis
    • Diabetic peripheral neuropathy
  • NMJ disease:
    • Myasthenia gravis crisis
    • Botulism
    • Organophosphate toxicity
    • Lambert-Eaton myasthenic syndrome
  • Muscle disease:
    • Rhabdomyolysis
    • Dermatomyositis
    • Polymyositis
    • Alcoholic myopathy
• Non-neuromuscular weakness
  • Can't miss diagnoses:
    • ACS
    • Arrhythmia/Syncope
    • Severe infection/Sepsis
    • Hypoglycemia
    • Periodic paralysis (electrolyte disturbance, K, Mg, Ca)
      • Hypokalemic periodic paralysis
      • Thyrotoxic periodic paralysis
    • Respiratory failure
  • Emergent Diagnoses:
    • Symptomatic Anemia
    • Severe dehydration
    • Hypothyroidism
    • Polypharmacy
    • Malignancy
  • Other causes of weakness and paralysis
    • Acute intermittent porphyria (ascending weakness)

On all patients:

• CBC (anemia)
• Chem 10 (electrolyte disturbance, hypoglycemia, uremia)
• ECG (Ischemia, hypo/hyperkalemia)

Consider:

• 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)

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