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Amyotrophic Lateral Sclerosis (ALS) – Reading & Sharing

Definition, Etiology, and Incidence


Amyotrophic Lateral Sclerosis (ALS), also known as Lou Gehrig disease after the famous New York Yankees baseball player, is a devastating neurologic disorder that selectively affects motor function with an unknown origin, results in muscle weakness, disability, respiratory insufficiency, and eventually death. ALS has an annual incidence of 0.5-2 per 100,000 population, is primarily a disorder of middle to late adulthood, affecting people most frequently in their fifties, with men developing the disease nearly twice as often as women. The median survival duration for patient is approximately 3 years, yet approximately 20% of patients survive greater than 5 years, and 10% will survive for greater than 10 years.

As the main area of involvement is the motor neurons of the brain and spinal cord, ASL affects motor neurons in three locations as follows: the anterior horn cells (lower motor neurons – LMNs) of the spinal cord; the motor nuclei of the brain stem, particularly the hypoglossal nuclei; and the upper motor neurons (UMNs) of the cerebral cortex. The death of the LMNs leads to denervation, with subsequent shrinkage of musculature and muscle fiber atrophy. It is this fiber atrophy, called amyotrophy, which appears in the name of the disease. The loss of nerve fibers in lateral columns of the white matter of the spinal cord, along with fibrillary gliosis, imparts a firmness or sclerosis to this CNS tissue. The term lateral sclerosis designates these changes.

A remarkable feature of the disease is that the entire sensory system, the regulatory mechanisms of control and coordination of movement, and the intellect remain intact.

Physical Findings & Clinical Presentation

ALS, as a rapidly progressing degenerative neuromuscular disease with the involvement of the motor neurons of the brain and spinal cord, approximately half of those patients will have difficulty swallowing (dysphagia) as their first symptom.

The symptoms of ALS may be referable to UMNs or LMNs involvement. Manifestations of UMNs lesions include weakness, spasticity or stiffness, and impaired fine motor control. Dysphagia (difficulty swallowing), dysarthria (impaired articulation of speech) may result from brain stem LMN involvement or from dysfunction of UMNs descending to the brain stem. Manifestations of LMN destruction include fasciculations, weakness, muscle atrophy, and hyporeflexia. Muscle cramps involving the distal legs often are an early symptom. As the disease progress, weakness affects both the upper and lower neurons. Eventually, UMNs and LMNs involving multiple limbs and the head are affected. In the more advanced stages, muscles of the palate, pharynx, tongue, neck, and shoulders become involved, causing impairment of chewing, swallowing, and speech. Dysphagia with recurrent aspiration and weakness of the respiratory muscles produces the most significant acute complications of the disease. Death generally results from respiratory failure due to weakness in the diaphragm along with decreased laryngeal and lingual functionality.

Diagnosis

Diagnosis is based on clinical findings, EMG results, and exclusion of alternative causes. A referral to a neurologist experienced in neuromuscular disease is recommended to confirm the diagnosis.


Treatment

Currently, there is no cure for ALS. Management of people with ALS is challenging and requires a multidisciplinary team, involving specialized neurologists, physical therapists, occupational therapists, speech therapists, and social workers. The measures are to assist people with the disorder to manage their symptoms (e.g., weakness and muscle spasm, dysphagia, communication difficulty, excessive watery saliva, and emotional lability), nutritional status, and respiratory muscle weakness allow people with the disorder to survive longer than would otherwise have been the case and to improve the quality of life.

  1. Muscle weakness – A major symptom in ALS.
    • Physical therapy should begin in the early stages of the disease, however, to the point of exhaustion is considered counterproductive.
    • As weakness progressed, passive physiotherapy gains importance in preventing contractures and stiffness.
    • Assistive devices should be used to maintain mobility.
  2. Dysarthria –
    • A speech and language therapist is an important member of the care team and should be involved early after disease onset to continuously evaluate the patient for dysphagia and dysarthria.
    • Alternative communication devices should be introduced early and communication may be eased with computerized assistive devices.
  3. Sialorrhea – drooling, which is caused by a combination of facial muscle weakness and a reduced ability to swallow.
    • Sialorrhea has been linked to aspiration pneumonia.
    • Management options include the use of medications.
    • Suction device for sialorrhea may be considered.
  4. Pseudobulbar affect (emotional lability) -Caused by bilateral corticobulbar tract degeneration and is not considered to be an emotional disorder per se. Management options include the use of medications.
  5. Muscle spasticity – Spasticity may cause painful spasms. Management options include the use of medications.
  6. Muscle cramps – associated with severe pain and discomfort. Management options include the use of medications.
  7. Pain-
    • Secondary to muscle spasms, cramps, and contractures, as well as musculoskeletal pain causes by reduced mobility.
    • Frequent changes in position are essential to prevent the skin from breaking down.
    • Physical therapy might help to avoid joint stiffness
    • Other management options include the use of medications.
  8. Psychosocial symptoms – major depression
    • Both patient and caregivers should be offered counseling, and pharmacological treatment should be considered.
  9. Insomnia – mostly secondary to other problems associated with ALS, identification and treatment of the underlying causes is crucial to treating the insomnia.
    • anxiety
    • depression
    • dysphagia
    • dyspnea
    • the inability to change position, which can result in discomfort and pain
  10. Dysphagia – one of  the most common symptoms of ALS
    • chocking due to food intake or weight loss of 10% or more of body weight should trigger a conversation about the placement of a PEG tube. As PEG tube placement improves nutritional intake, promotes weight stabilization, and eases medication administration.
    • Swallowing and oral nourishment are of high concern for theses patients.
    • Loss of motility in the tongue and hypopharynx result in the loss of ability to manipulate food as well as creating speech and communication barriers.
  11. Dyspnea – at the onset of respiratory symptoms indicating hypoventilation, or when a patient’s forced vital capacity drops below 50%, the patient should be counseled about noninvasive mechanical ventilation as well as the terminal phase of the disease.
    • Noninvasive positive-pressure ventilation may improve quality of life and may increase tracheostomy-free survival in patients with respiratory difficulty
    • As ALS progress, the goal of patient care should focus on effective and compassionate care rather than maximizing function. Patients who are not ventilated mechanically usually transition from sleep into coma due to increasing hypercapnia.

An anti-glutamate drug, Riluzole, is the only drug approved by the FDA and Health Canada for treatment of ALS at this time. The drug is designed to decrease glutamate accumulation and slow the progression of the disease, and known to extend tracheostomy-free survival in patients with ALS. Other neuroprotective treatments such as vaccine therapy, stem cell injections, and pacing of the diaphragm are in trial stages but, again, are not focused on stopping or eradicating the disease.

References:

Ferri, F. F. (2017) 2017 Ferri’s Clinical Advisor 5 books in 1

Grossman, S. C. & Porth, C. M. (2014) Porth’s Pathophysiology: Concepts of Altered Health States (9th ed.)

Yennurajalingam, S. & Bruera, E. (2016) Oxford American Handbook of Hospice and Palliative Medicine and Supportive Care (2nd ed.)

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