A disease of unknown cause that results in the loss of motor neurons in the anterior horns of the spinal cord and the motor nuclei of the lower brainstem. Degeneration may occur in both the lower and upper motor neuron systems. A leading theory is that glutamate overstimulates neurons, resulting in degeneration.
- Onset: most commonly from 40 to 60 years of age, with familial ALS appearing 10 years earlier than average.
- Most cases of ALS arise sporadically, with 5% to 10% of cases being familial. Slightly more common in men, but affects all ages, sexes, and races.
- Risk Factors: Age, Autoimmune Disease, Environmental Exposure to Toxins, Family History, Smoking, Viral Infections
Clinical Manifestations
Manifestations depend on the location of the affected motor neurons. The chief symptoms are fatigue, progressive muscle weakness, cramps, fasciculation (twitching), and lack of coordination.
- Loss of motor neurons in the anterior horns of the spinal cord results in progressive weakness and atrophy of the muscles of the arms, trunks, or legs. Spasticity and hyperreflexia are often present.
- Upper motor neuron involvement results in minimal wasting, hyperreflexia, spasticity, and primitive reflexes (Babinski sign)
- Lower motor neuron involvement results in wasting, a-/hyporeflexia, flaccidity, and fasciculations (low threshold for irritation of the motor neuron)
- Bladder and anal sphincter innervation often remain intact.
- Respiratory insufficiency often occurs.
- In 25% of patients, muscles controlled by the cranial nerves are impacted first:
- Difficulty in talking, swallowing, and ultimately breathing.
- Soft palate and upper esophageal weakness results in regurgitation of water through the nose.
- Posterior tongue and palate impairs the ability to laugh, cough, or even blow the nose.
- Bulbar impairment produces difficulty in speech and swallowing, and aspiration becomes a risk.
- Speech becomes nasal and articulation is disrupted. Speech becomes unintelligible.
- Emotional lability and cognitive impairment may be present.
- Death often results from infection, respiratory insufficiency, or aspiration.
Diagnostic Examination
Diagnosis is based on characteristic symptoms. No test is specific for ALS.
- Electromyography and muscle biopsy indicate reduction in the number of functioning motor units.
- MRI may show high signal intensity in the corticospinal tracts, differentiating ALS from a multifocal motor neuropathy.
- Neuropsychological testing may aid in diagnosis.
Management
There is no cure for ALS. The main focus is the maintain or improve functioning, well-being, and quality of life.
- Riluzole and Edaravone, glutamate antagonists, are considered disease-modifying treatments for ALS, but with unknown processes.
- Spasticity: Baclofen (Lioresal), dantrolene sodium, or Diazepam (Valium).
- Fatigue: Modafinil
- Cramps: Quinine
- Monitor for complications e.g. dehydration, malnutrition, pneumonia, and respiratory failure. End-of-life issues include pain, dyspnea, and delirium.
- Alveolar Hypoventilation necessitates the use of a (negative pressure) mechanical ventilator, or a positive-pressure non-invasive ventilation.
- Aspiration and Swallowing Difficulties: Enteral Feeding via PEG/Gastrostomy tube, inserted before forced vital capacity drops below 50% of the predicted value.
- Life-support measures should be decided upon by patients and family, completing advance directives.
Nursing Interventions
- Provide nursing measures for muscle weakness and dysphagia
- Promote adequate ventilatory function
- Prevent complications of immobility
- Encourage diversional activities; spend time with the client
- Provide or refer to physical therapist as indicated
- Promote independence for as long as possible