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Amyotrophic Lateral Sclerosis (ALS) Overview

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that affects nerve cells in the brain and spinal cord. When the muscle is not getting enough nutrition, it will atrophy, and the area in which the nerve cell part of the human spinal cord that signals and controls the muscles also degenerates, causing scarring or hardening in that area. Motor neurons travel from the brain to the spinal cord and from the spinal cord to the muscles of the entire body. Progressive degeneration and death of motor neurons in ALS patients can cause the brain's inability to initiate and control muscle movement. People may lose the ability to speak, eat, move and breathe.

ALS can be divided into two different types: sporadic and familial. Sporadic ALS is the most common, accounting for more than 90% of all cases in North America. Familial ALS (FALS) accounts for 5% to 10% of all cases, and in these families, each offspring has a 50% chance of inheriting a genetic mutation and developing the disease.

Overview of amyotrophic lateral sclerosis pathways

Main Signaling Pathways in Amyotrophic Lateral Sclerosis (ALS)

Signs and Symptoms of ALS

Due to the degeneration of upper and lower motor neurons, patients with ALS experience symptoms of general muscle weakness, atrophy, and muscle spasms, and eventually, they'll lose the ability to initiate and control all voluntary movements. Cognitive or behavioral dysfunction is present in 30-50% of ALS patients, and frontal-temporal dementia is present in 10-15%. Repeated phrases or gestures, indifference, and loss of inhibition are also behavioral features often reported by ALS. In addition, neuropathic pain, spasms, muscle spasms, and injurious pain due to decreased mobility and muscle weakness are also symptoms experienced by most people with ALS. The sensory and autonomic nervous systems are usually unaffected, which means that most patients with ALS maintain hearing, vision, touch, smell, and taste.

Causes of ALS

The exact etiology of ALS is currently unknown, but generally it can be categorized into genetic and environmental factors. The ALS threshold model proposes that cell damage accumulates over time due to genetic factors present at birth and exposure to environmental risks throughout life. More than 20 genes associated with hereditary ALS have been identified, with C9orf72, SOD1, FUS, and TARDBP mutations being the most common. These genes explain about 70% of the causes of ALS. For most cases without a family history, analysis of numerous sample data indicates that the cause of ALS may be related to chronic occupational heavy metal exposure. Neurotoxic substances accumulate, and glutamic acid accumulates between nerve cells. Over time, it may cause nerve cell damage.

Diagnosis of ALS

Because there is currently no systematic diagnostic method, clinical medical staff mostly rely on identifying signs in upper neurons (UMN) and lower neurons (LMN) in the same body region and evidence of disease progression in other regions thereafter. A definitive diagnosis usually takes a long time to complete. This is due to the subtle nature of the symptoms of ALS, and the median time to diagnosis is about 14 months. There are diseases with symptoms similar to ALS, so a comprehensive diagnostic assessment is required, often including structural imaging and neurophysiology and laboratory tests, to reduce the possibility of misdiagnosis.

Management of ALS

ALS cannot be cured, but a focus on treating symptoms and providing supportive care can help patients improve their quality of life and extend their lives. Some drugs have a good effect in this process. For example, riluzole can extend survival by about 2-3 months, and edaravone slightly slows down the function in a few patients with ALS. Noninvasive ventilation (NIV) is the main treatment for respiratory failure in ALS. For people with normal bulbar function, it can extend survival by about seven months and significantly improve the quality of life of patients.

For research use only. Not intended for any clinical use.

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