Rosen & Barkin's 5-Minute Emergency Medicine Consult (50 page)

BASICS

• Progressive, incurable disease of adults
  
• Neurodegenerative disease of the motor system at all levels
  
• Some patients have associated dementia
  
• Manifestations:
  
  • Muscle weakness
    
  • Wasting
    
  • Fasciculations
    
  • Babinski sign
    
  • Hyperreflexia
    
• Variants with predominately upper or lower motor neuron manifestations also occur
  
• May begin with bulbar symptoms of dysphagia and dysarthria
  
• Also known as “Lou Gehrig Disease” after the famous baseball player who was affected
  
• Eventually leads to respiratory compromise secondary to weakness of diaphragm and other muscles of respiration
  
• 80% of cases begin between ages 40 and 70 yr
  
• Death (usually from respiratory paralysis) typically occurs within 3–5 yr of the diagnosis
  
• 50% die within 3 yr
  
• ∼10% ALS patients live 10 yr or more
  
• Males > females
  

• Etiology of amyotrophic lateral sclerosis (ALS) is unknown
  
• ∼10% of affected patients have another affected family member
  
• Cigarette smoking and heavy metal exposure may be risk factors
  
• There is a disease cluster in the western Pacific
  
• Pathologically, there is loss of both upper and lower motor neuron cells
  
• Predilection for the motor system and sparing of other neurons
  

DIAGNOSIS

• Asymmetric limb weakness is the most common presentation of ALS (80%)
  
• May begin in either the arms (cervical onset) or the legs (lumbar onset):
  
  • Later all limbs are affected
    
• Bulbar ALS:
  
  • Usually presents with dysarthria or dysphagia
    
  • 2nd most common presentation
    
• Both lower motor neuron (weakness and wasting with fasciculation) and upper motor neuron signs (Babinski sign with hyperreflexia) occur
  
• Respiratory muscles and the vocal cords are affected late
  
• Muscle fasciculation is common, but may not be apparent to the patient
  
• Extraocular muscles, sphincters, cognition, and sensation are spared
  

• Most ED patients with ALS will present with an established diagnosis
  
• History should focus on clues regarding acute medical issues and functional decline
  
• When ALS is suspected due to a complaint of “weakness” consider that this occurs with many illnesses including:
  
  • Pulmonary disease
    
  • Cardiac disease
    
  • Anemia
    
  • Endocrine disorders
    
  • Toxidromes
    
  • Diseases of muscles or joints
    
  • Spinal cord abnormalities
    
  • Depression
    
• Differentiate true weakness from: Shortness of breath, chest pain, joint pain, fatigue, poor exercise tolerance, etc.
  
• True weakness often leads to complaints of inability to perform specific tasks:
  
  • Bulbar palsy:
    
    • Facial weakness
      
    • Weakness and fasciculation of tongue
      
    • Dysarthria
      
  • Cervical onset ALS:
    
    • Difficulty with washing hair, using comb
      
    • Impaired pincer grip
      
  • Lumbar onset ALS:
    
    • Frequent trips secondary to foot drop
      
    • Difficulty walking up stairs
      

• A detailed and thorough neurological exam is the key to diagnosis but is not typically performed in the ED
  
• Upper motor neuron disease causes slow uncoordinated movements and stiffness
  
• Lower motor neuron disease causes weakness accompanied by atrophy and muscle cramps are common
  
• Common findings:
  
  • Brisk reflexes
    
  • Fasciculations
    
  • Muscle wasting
    
• Exam should focus on excluding or confirming other conditions
  

• Previously undiagnosed ALS:
  
  • Diagnosis of ALS is clinical and rarely made in the ED:
    
    • Recognition of the possibility of this disease is sufficient and mandates referral for workup
      
  • If ALS is suspected, forced vital capacity (FVC) should be performed
    
• Known ALS patient:
  
  • Patients with known disease and progressive symptoms:
    
    • Evaluate potentially treatable complications with lab and imaging studies
      
  • FVC is a sensitive indicator of respiratory muscle weakness:
    
    • FVC <50% of predicted is considered a sign of advanced disease
      
    • FVC <50% usually requires ventilatory support
      
    • Start with noninvasive positive pressure ventilation when possible
      
    • Compare with the patient’s previous baseline
      
  • CXR may reveal aspiration or pneumonia or comorbid conditions such as CHF
    
  • Pulse oximetry and blood gas analysis aid in the diagnosis of respiratory failure
    
  • Electrolytes and other blood chemistry tests may reveal a treatable cause of increasing weakness
    

• In cases of undifferentiated weakness, consider CPK measurement along with blood chemistry:
  
  • Elevated CPK is associated with myopathy
    
• Electrolyte abnormalities such as hypokalemia, hypercalcemia, etc. may cause generalized weakness but this is typically in association with other signs and symptoms
  
• CBC, UA may be indicated to look for source of infection
  

Cervical spine, other skeletal radiography, or head CT may be needed in case of falls (common in ALS) or to rule out other conditions

• Check FVC
  
• Electromyography (EMG) may help confirm the diagnosis (not usually an ED test)
  

• Cervical cord compression:
  
  • Similar symptoms but usually acute onset with pain and sensory changes
    
  • Spinal MRI or myelography for diagnosis
    
• Thyrotoxicosis may mimic ALS:
  
  • Usually marked systemic symptoms
    
• Heavy metal poisoning (lead, mercury, arsenic)
  
• Syphilis and Lyme disease
  
• Lymphoma may have an associated lower motor neuron syndrome, which mimics ALS
  
• Bulbar ALS:
  
  • Esophageal cancer
    
  • Myasthenia gravis
    

TREATMENT

• There is no specific therapy for ALS
  
• The drug riluzole, a glutamate release inhibitor, has been shown to extend survival in ALS patients for an average of a few months
  
• Treatment issues in the ED revolve around symptomatic therapy and identification and treatment of complications
  

Controversies:

• Many patients will have advanced directives:
  
  • Unless immediate intervention is essential, intubation should be avoided until directives have been ascertained
    
  • Noninvasive means of ventilatory support may be tried first
    

• Respiratory insufficiency or failure:
  
  • Ascertain any advanced directives
    
  • Noninvasive ventilatory support
    
  • Intubation as indicated
    
• Weaning off the ventilator is very difficult:
  
  • Average survival after institution of ventilation is 19 mo
    

• Sedation and pain control as indicated:
  
  • Joint pain may respond to NSAIDs
    
• Insomnia from pressure pain (owing to immobility) may respond to diphenhydramine or amitriptyline
  
  • Insomnia may also be treated with benzodiazepines
    
• Aspiration or drooling may be treated with amitriptyline, atropine, or hyoscyamine (dries secretions)
  
• Muscle cramps may respond to baclofen or tizanidine
  
• Constipation is related to immobility and diet:
  
  • Treated with laxatives, stool softeners, and dietary changes
    

• Amitriptyline: 25–100 mg PO QHS
  
• Atropine: 0.4 mg PO q4–6h
  
• Baclofen: 10–25 mg PO TID
  
• Diphenhydramine: 25–50 mg PO nightly at bedtime
  
• Tizanidine 2–4 mg PO BID
  

FOLLOW-UP