Amyotrophic Lateral Sclerosis, or ALS, is a progressive neurodegenerative disease that targets nerve cells in the brain and spinal cord. These specific nerve cells, known as motor neurons, are responsible for transmitting signals from the brain to the voluntary muscles throughout the body. As the disease advances, these motor neurons deteriorate and die, severing the communication link with the muscles. This loss of connection leads to muscle weakening, wasting away, and ultimately, a loss of voluntary control over movement.
The name “amyotrophic” is Greek for “no muscle nourishment,” which refers to the muscle atrophy that occurs when muscles are no longer nourished by nerves. The term “lateral sclerosis” refers to the scarring that occurs in the lateral areas of the spinal cord where affected nerve fibers are located. While the disease progresses, it does not typically impair a person’s senses or cognitive abilities.
Initial Signs and Symptoms
The onset of ALS is often subtle, with initial signs that can be easily overlooked or attributed to other causes. The disease can manifest in two primary ways, depending on which motor neurons are affected first. The more common presentation is “limb-onset” ALS, where the first symptoms appear in the arms or legs. This might present as a newfound clumsiness, such as difficulty buttoning a shirt, a tendency to drop things, or tripping and falling.
A person might notice weakness in a specific area, like a hand or a foot, that gradually spreads. Muscle twitches, known as fasciculations, and cramping are also common early indicators. The muscles may also feel unusually tight or stiff, a condition called spasticity.
Less commonly, the disease begins with “bulbar-onset” ALS, which affects the muscles of the face, neck, and throat. The first signs in these cases are often related to speech and swallowing. An individual might develop slurred or nasal-sounding speech, making it difficult for others to understand them. Difficulty swallowing, known as dysphagia, can also be an early symptom.
The Path to an ALS Diagnosis
Diagnosing ALS is not a straightforward process and involves a period of uncertainty. No single test can confirm the disease. Instead, neurologists arrive at a diagnosis by ruling out other conditions that mimic ALS symptoms in a process known as a “diagnosis of exclusion.”
To do this, physicians use a combination of clinical examinations and diagnostic tests.
- An Electromyography (EMG) assesses the health of muscles and their controlling nerve cells by detecting electrical activity that indicates nerve damage.
- A Nerve Conduction Velocity (NCV) study is performed alongside an EMG to measure the speed and quality of the body’s electrical signals in the nerves.
- Magnetic Resonance Imaging (MRI) of the brain and spinal cord helps identify other potential causes of symptoms, such as a tumor or a herniated disk.
- Blood and urine tests are conducted to eliminate the possibility of other diseases.
Progressive Physical Changes
Following a diagnosis, the physical changes of ALS become more pronounced as the disease progresses from its initial sites. The weakness that started in one limb will gradually spread to other parts of the body. This progression impacts nearly all voluntary muscles, leading to changes in a person’s physical capabilities.
Mobility is one of the first major functions to be affected. Weakness in the leg muscles that may have initially caused stumbling will eventually lead to an inability to walk, requiring the use of a wheelchair for mobility. Simple tasks that require fine motor skills, such as writing, typing, or feeding oneself, become increasingly difficult as the muscles in the hands and arms weaken and atrophy.
For those with either limb or bulbar-onset ALS, challenges with speech and swallowing will worsen over time. Speech may progress from being slurred to being completely lost, a condition known as anarthria. The weakening of the bulbar muscles also makes swallowing more difficult and dangerous, increasing the risk of choking and aspiration. This difficulty in swallowing, or dysphagia, can lead to malnutrition and dehydration if not properly managed.
The impact of the disease is on respiratory function. The diaphragm and muscles in the chest wall, which are necessary for breathing, progressively weaken. Initially, this may cause shortness of breath during activity or when lying down. As the respiratory muscles continue to decline, breathing becomes increasingly labored, eventually necessitating the use of mechanical ventilation to support this basic life function. Most individuals with ALS die from respiratory failure.
Managing Daily Life with ALS
Adapting to life with ALS involves an approach focused on managing symptoms and maintaining quality of life. This is achieved through the coordinated efforts of a multidisciplinary care team. This team often includes a neurologist, physical therapist, occupational therapist, speech-language pathologist, respiratory therapist, and nutritionist, all working together to address the evolving needs of the individual.
To counteract the loss of mobility and fine motor skills, various pieces of adaptive equipment become necessary. Power wheelchairs provide a means of mobility and independence, while home modifications like ramps and grab bars can improve safety and accessibility. Occupational therapists can recommend devices to assist with daily tasks like eating and dressing, helping to preserve a person’s autonomy.
As speech and swallowing abilities decline, speech-language pathologists introduce augmentative and alternative communication (AAC) devices. These can range from simple letter boards to sophisticated eye-gaze systems that allow a person to communicate by controlling a computer with their eye movements. To address nutritional needs when swallowing becomes unsafe, a feeding tube can be placed to provide necessary hydration and calories directly to the stomach.
Respiratory support is another part of ALS management. Non-invasive ventilation (NIV), delivered through a mask, helps with breathing, especially at night. As the disease progresses, some individuals may opt for invasive mechanical ventilation, which requires a tracheostomy.