Amyotrophic Lateral Sclerosis



  • 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
  • Predilection for the motor system and sparing of other neurons
  • 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


Signs and Symptoms

  • 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
    • Second 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 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

Physical Exam
  • A detailed and thorough neurologic 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

Essential Workup

  • 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

Diagnostic Tests and Interpretation

  • 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

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

Differential Diagnosis

  • 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


  • The drug riluzole, a glutamate release inhibitor, has been shown to extend survival in ALS patients for an average of a few months
  • Edaravone is a free radical scavenger which may slow functional deterioration:
    • Placebo-controlled study of 137 patients within 2 yr of ALS diagnosis
    • Functional decline at 24 wk was smaller in the edaravone group
    • Difference was clinically meaningful
  • Treatment issues in the ED revolve around symptomatic therapy and identification and treatment of complications

Pre Hospital

  • 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

Initial Stabilization/Therapy

  • 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

Ed Treatment/Procedures

  • 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

Ongoing Care


Admission Criteria
  • Need for respiratory support
  • Dehydration
  • Unable to be cared for at home owing to progression of illness
  • Complications (e.g., infection) or other diagnosis that requires admission

Discharge Criteria
  • Suspected ALS: Refer for outpatient evaluation if general condition permits and other serious conditions requiring admission are ruled out
  • Complication of known ALS: Discharge if outpatient treatment available and stable respiratory status

Follow-Up Recommendations

If considering diagnosis of ALS, prompt follow-up with a neurologist should be arranged

Pearls and Pitfalls

  • ALS is a progressive neurodegenerative disease affecting all components of the motor system
  • Many patients with ALS have advanced directives—inquire prior to any aggressive intervention
  • FVC <50% usually requires ventilatory support

Additional Reading

  • EFNS Task Force on Diagnosis and Management of Amyotrophic Lateral Sclerosis, Andersen PM, Abrahams S, et al. EFNS guidelines on the clinical management of amyotrophic lateral sclerosis (MALS)–revised report of an EFNS task force. Eur J Neurol. 2012;19:360–375.
  • Gregory SA. Evaluation and management of respiratory muscle dysfunction in ALS. NeuroRehabilitation. 2007;22:435–443.
  • McGeer E, McGeer P. Pharmacologic approaches to the treatment of amyotrophic lateral sclerosis. Biodrugs. 2005;19:31–37.
  • Miller RG, Mitchell JD, Moore DH. Riluzole for amyotrophic lateral sclerosis (ALS)/motor neuron disease (MND). Cochrane Database Syst Rev. 2012;(3):CD001447.
  • Mitchell JD, Borasio GD. Amyotrophic lateral sclerosis. Lancet. 2007;369:2031–2041.
  • Servera E, Sancho J. Appropriate management of respiratory problems is of utmost importance in the treatment of patients with amyotrophic lateral sclerosis. Chest. 2005;127:1879–1882.
  • Writing Group; Edaravone (MCI-186) ALS 19 Study Group. Safety and efficacy of edaravone in well defined patients with amyotrophic lateral sclerosis: a randomised, double-blind, placebo-controlled trial. Lancet Neurol. 2017:505–512.


Richard S. Krause

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