Amyotrophic Lateral Sclerosis (ALS) and cerebral palsy (CP) are both movement disorders that affect the nervous system, impacting the ability to control the muscles. While they share some common symptoms, they are quite different in their causes, prognosis, and how they affect the body.
The fundamental difference between them is that ALS is a neurodegenerative disease, while CP is primarily a congenital disorder. A neurodegenerative disease is a condition that gradually damages and destroys the function of the nervous system. They are progressive conditions, meaning that they usually begin with relatively mild symptoms that worsen over time. Examples of other neurodegenerative diseases include Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease.
A congenital disorder like cerebral palsy, on the other hand, is a condition that manifests before, during, or shortly after birth. People with CP experience the symptoms of the disease their entire lives, while almost all cases of ALS manifest in adulthood (although there are some rare forms of pediatric ALS). Also, unlike ALS and other neurodegenerative diseases, CP is not a progressive disease – the symptoms usually remain relatively stable throughout a person’s life.
What is Cerebral Palsy?
Cerebral palsy refers to a group of disorders that affect movement, muscle tone, and posture. It is caused by abnormal development or damage to the parts of the brain that control movement, usually occurring before or shortly after birth. CP is the most common motor disability in childhood, and its symptoms can range from mild, such as a slight limp, to more severe, such as significant difficulty walking or controlling the limbs.
CP is divided into four main types:
- Spastic cerebral palsy: Causes stiff muscles and awkward, difficult movements. This is the most common type of CP, representing 80% of all cases. Spastic CP is further divided into three categories, depending on the area of the body affected:
- Spastic diplegia/diparesis: Muscle stiffness primarily in the legs. This can cause the legs to turn inward and cross at the knees, leading to difficulty walking. This condition is also known as a “scissor gait.”
- Spastic hemiplegia/hemiparesis: Stiffness on one side of the body, affecting both the arm and the leg.
- Spastic quadriplegia/quadriparesis: The most severe form of CP, affecting all four limbs. Most people with this form of the disease cannot walk, and it is usually accompanied by other issues including intellectual disability.
- Dyskinetic cerebral palsy: Causes shaking and/or sudden, involuntary movements of the hands, arms, limbs, and feet. These movements can be both fast or slow and can make both walking and sitting still difficult.
- Ataxic cerebral palsy: Causes problems with balance and coordination. This can range from unsteadiness while walking to difficulty with fine motor functions like writing or buttoning a shirt.
- Mixed cerebral palsy: Any case of cerebral palsy that involves symptoms from more than one of the other three categories.
While it is not a direct symptom of the disease, about 30-50% of CP cases are accompanied by some sort of intellectual disability. Other commonly occurring conditions can include delayed growth and development of the affected limbs, seizure disorders, speech and language difficulties (dysarthria), learning difficulties, and spinal deformities like scoliosis.
ALS vs. Cerebral Palsy: Causes
Both ALS and CP can be caused by a variety of factors, both known and unknown. Both diseases, in some cases, can have genetic factors. In the case of ALS, about 15% of cases are linked to genetic factors – the causes of the other 85%, known as sporadic ALS, are unknown.
The influence of genetics in CP is even less clear – there are no genetic mutations known to cause the condition directly. However, some inheritable mutations may be a risk factor for the disease, which has led to a small number of cases (less than 2%) that are associated with a family history of the disease.
The symptoms of CP are typically present from birth or early infancy and remain stable throughout a person's life.
ALS vs. Cerebral Palsy: Prognosis
While both ALS and CP can cause relatively similar symptoms, they do so in very different ways. ALS is a progressive neurodegenerative disease, meaning that it causes motor neurons, cells that carry signals from the brain to muscles, to gradually die off. These motor neurons are responsible for controlling voluntary muscle movements like walking, speaking, and swallowing. As ALS progresses, the loss of motor neurons leads to increasing paralysis, eventually affecting a person’s ability to breathe and eat without assistance. The average life expectancy after an ALS diagnosis is 3-5 years.
In contrast, CP is not a progressive condition. The brain damage that causes CP does not worsen over time, meaning that while symptoms may change as a child grows, the underlying disorder does not advance. The prognosis of the disease varies widely depending on symptom severity. People with relatively mild CP may not need any assistance later in life and, on average, tend to live a lifespan in line with the general population. Those with the most severe forms may require lifelong care and special adaptive equipment. While it is possible that, with proper care, they may also be able to live a relatively normal lifespan, many people with severe CP do not live past adolescence or early adulthood.
What do ALS and Cerebral Palsy Have in Common?
Both ALS and CP have no cure, and while they each require different treatment approaches, managing symptoms is a primary focus for both conditions. Physical therapy plays a key role in both ALS and CP care. For people with ALS, it can help maintain muscle function for as long as possible, while for those with CP, it helps improve mobility and manage muscle tightness. Adaptive devices like wheelchairs and communication aids can also support individuals with both conditions in maintaining their independence and quality of life.
In addition, both conditions remain the subject of ongoing research. Scientists are working to better understand the genetic and environmental factors that contribute to each and to develop new therapies that could improve outcomes. The ALS Therapy Development Institute (ALS TDI) is dedicated to doing the preclinical research needed to invent and advance many potential ALS drugs to human clinical trials – and we will not stop until there are treatments for everyone with ALS.
To learn more about ALS TDI and our research to end ALS, click here.
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