ALS(Amyotrophic Lateral Sclerosis)

ALS (Amyotrophic Lateral Sclerosis) is a progressive and fatal neurodegenerative disease affecting nerve cells in the brain and spinal cord that control voluntary muscles, leading to muscle weakness, paralysis, and ultimately respiratory failure.

Core Features

ALS primarily causes loss of motor neurons, which are critical for muscle movement, including walking, talking, swallowing, and breathing. The disease progresses with increasing muscle weakness, stiffness, twitching, and eventually atrophy. Over time, most people lose the ability to move, speak, eat, and breathe without mechanical assistance. While people with ALS typically retain senses such as hearing, sight, touch, smell, and taste, about half may experience minor changes in thinking and behavior, with some developing frontotemporal dementia.

Types and Onset

ALS can present in different forms:

Limb-onset: Begins with muscle weakness in the arms or legs; accounts for most cases.
Bulbar-onset: Starts with difficulty in speech or swallowing.
Respiratory-onset: Initial symptoms are breathing difficulties.

There are also subtypes such as primary lateral sclerosis (PLS), which progresses more slowly and primarily affects upper motor neurons, and progressive muscular atrophy (PMA), which primarily affects lower motor neurons.

Causes and Risk

Most ALS cases (90–95%) are sporadic without a known specific cause, though both genetic and environmental factors are involved. The remaining cases (5–10%) are hereditary, linked to gene mutations.

Symptoms

Typical ALS symptoms include:

Muscle twitching and cramps.
Muscle weakness or stiffness in arms, legs, neck, or face.
Difficulty speaking, swallowing, or breathing.
Weight loss and eventual immobility.

Ocular manifestations of ALS include a variety of eye movement abnormalities, subtle visual dysfunction, and specific retinal changes that are increasingly recognized as part of the disease process.

Eye Movement Abnormalities

Although eye movements are traditionally considered spared in ALS, research now shows several types of ocular motor dysfunction:

Square-wave jerks, saccade hypometria, and abnormal cogwheeling during smooth pursuit are observed in many ALS patients, especially those with bulbar involvement.
Impairment in gaze fixation and stability, vertical and horizontal saccadic movement disturbances, and slowed or inaccurate saccades have been reported.
Eyelid apraxia (difficulty initiating eyelid movements) and restricted upgaze may occur.

Retinal and Visual Pathway Changes

Recent studies indicate that ALS can involve the anterior visual pathway:

Intraretinal deposits and axonal degeneration in the retinal nerve fiber layer have been documented, particularly in those with specific genetic mutations such as C9orf72.
Thinning of the retina and inclusion bodies suggest neuronal degeneration may extend beyond motor neurons to the visual system.
Some patients experience reduced visual acuity and poor contrast sensitivity, although this is usually mild and often asymptomatic.

Physical Ocular Complications

Muscle weakness from ALS affects eyelid muscles, leading to incomplete blinking and impaired eye closure, increasing the risk of:

Ocular surface dryness (exposure keratopathy), irritation, and even ulceration in severe cases, which can impact vision and comfort.

Disease Progression and Research

While these ocular manifestations are not classic ALS symptoms and may be overlooked, their recognition highlights ALS as a multisystem neurodegenerative disorder. The severity and type of ocular involvement can vary based on disease progression and subtype, with bulbar-onset ALS associated with more pronounced eye movement abnormalities due to extensive brainstem pathology.

In summary, ALS can affect eye movements, retinal structure, and eyelid function, but overt vision loss or significant ophthalmic complaints are generally less common and tend to occur in advanced cases.

Progression and Prognosis

As ALS advances, people lose the ability to perform daily tasks, including eating, moving, or breathing independently. Most people die from respiratory failure within three to five years from the onset of symptoms, although around 10% survive for ten years or longer. There is currently no cure, though treatments may extend survival and improve quality of life.

https://www.metrowestdailynews.com/story/news/local/2025/10/02/framingham-ma-woman-who-died-of-als-writes-her-own-humorous-obituary/86458858007/

Author

Paddy Kalish OD, JD and B.Arch Author and Blogger

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