Weakness

Background

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

Clinical Features

History

• 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, Polymyalgia Rheumatica
    • Involvement of distal > proximal musculature? Neuropathy
  • 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
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
End-plate/muscle
Motor end plate	Ocular, bulbar and descends, fatigable	No	Nl/diminished	Nl/parethesias	No
Muscle	Proximal > distal	No	Nl/diminished	Normal	+/-

Differential Diagnosis

Weakness

• Neuromuscular weakness
  • Upper motor neuron:
    • CVA
    • Hemorrhagic stroke
    • Multiple sclerosis
    • Amyotrophic Lateral Sclerosis (ALS) (upper and lower motor neuron)
  • 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)
      • Acute flaccid myelitis
    • Degenerative (Spinal muscular atrophy)
    • Tumor
  • Peripheral nerve disease:
    • Guillain-Barre syndrome
    • Toxins (Ciguatera)
    • Tick paralysis
    • Diabetic peripheral neuropathy
  • Neuromuscular junction 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
    • Aortic disease - occlusion, stenosis, dissection
  • Other causes of weakness and paralysis
    • Acute intermittent porphyria (ascending weakness)

Evaluation

Workup

On all patients:

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

Consider:

• CK (myopathies)
• Thyroid studies
• 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)
• MRI or CT with contrast (if a structural cord lesion is suspected)
• LP (CNS infection, GBS)

Management

Intubation Indications

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

Disposition

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