Sclerosis, amyotrophic lateral

• Lou Gehrig’s disease
• ALS
• Motor neuron disease

• 728.2 Muscular wasting and disuse atrophy, not elsewhere classified

• M62.50 Muscle wasting and atrophy, not elsewhere classified, unspecified site

• 5E: Impaired motor function and sensory integrity associated with progressive disorders of the central nervous system1

Description

• Quickly progressive, degenerative motor disorder caused by the loss of nerve cells in the anterior horn of the spinal cord and motor nuclei of the brain stem2
• Loss of muscle strength and coordination

Essentials of Diagnosis

• Rapid, progressive loss of motor function not attributable to internal or external injury
• Diagnosis made by evidence of motor loss in multiple parts of the body, speed of degeneration, and ruling out other progressive neurologic disorders

General Considerations

• Onset may be either in the extremities or in the bulbar region initially; eventually, all patients experience degeneration in both areas
• Diagnosis requires evidence of denervation in at least three motor regions
• Usually does not affect the senses

Demographics

• Male-to-female ratio: 2:13
• Most patients aged > 45 years, but can be much younger3
• 10% familial (tend to have onset at younger age)3

Signs and Symptoms

• Both upper motor neuron and lower motor neuron signs and symptoms
• Limb onset ALS
  • One side will be involved initially and spread to both sides within months
  • Patients usually report unexplained tripping while walking, or difficulty with buttons and small objects
  • Muscle fasciculation evident
  • Spasticity remains mild
• Bulbar onset ALS
  • Difficulty with speech production; voice changes, hoarseness
  • Difficulty with swallowing; gagging, choking easily
  • Difficulty with saliva management, drooling
• Sensation is spared, may experience transient paresthesias due to position or nerve compression
• Bowel and bladder control usually maintained
• Respiratory compromise evident with both bulbar and limb onset

Functional Implications

• Loss of independence in mobility, self-care, eating, breathing
• Dependence on others

Possible Contributing Causes

• Primarily idiopathic
• Family member who has a hereditary form

Differential Diagnosis

• Progressive spinal muscular atrophy
• Progressive bulbar palsy
• Primary lateral sclerosis
• Parkinson’s disease
• Muscular dystrophy
• Multiple sclerosis
• Cervical spondylosis
• Inflammatory myopathy
• Myasthenia gravis
• Inclusion body myositis

Laboratory Tests

• Serum creatine kinase may be moderate elevated
• Muscle biopsy
• Genetic test for family history of ALS
• Blood tests to rule out other conditions

Imaging

• MRI may show slight atrophy of the motor cortices and wallerian degeneration of the motor tracts

Diagnostic Procedures

• Electromyography (EMG): widespread fasciculation and fibrillation
• Motor nerve conduction velocity test (NCV); if positive, demonstrates slight slowing with focal motor conduction block
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