ALS vs. Parkinson's: What Are the Differences?

Amyotrophic lateral sclerosis (ALS) and Parkinson’s disease (PD) are neurodegenerative (nerve-dying) diseases that affect movement. Despite this similarity, they are separate conditions with unique symptoms that affect different parts of the nervous system . They also have distinct treatment options and outlooks.

This article reviews the key differences between ALS and Parkinson's, including their symptoms, causes, diagnosis, and treatment.

Symptoms

The symptoms of ALS and Parkinson's disease are typically mild early on before worsening over time. Symptoms, though, differ in type and how quickly they progress.

In addition to motor symptoms (those affecting movement), Parkinson's disease is closely associated with non-motor symptoms (e.g., constipation and loss of smell). Also, ALS generally progresses faster than Parkinson's disease.

ALS Symptoms

ALS affects the brain and spinal cord's motor neurons (nerve cells that control muscle movement). The primary symptom of ALS is muscle weakness, which commonly begins in an arm or leg before spreading throughout the entire body. Arm or leg weakness in ALS often impairs a person's ability to get dressed, write, climb stairs, and walk.

As the weakness spreads, difficulties with talking, chewing, swallowing, and holding your head up develop. Eventually, the disease prevents a person from breathing independently.

Other symptoms of ALS include:

• Muscle twitching, cramping, tightening, and stiffness
• Excess saliva production and drooling
• Rapid weight loss
• Anxiety and depression over the loss of physical functioning
  

Parkinson's Disease Symptoms

With Parkinson's disease, symptoms often begin on one side of the body before spreading to the other. This condition results from the death of dopamine-producing nerve cells within an area of the brain called the substantia nigra. Since dopamine regulates movement, depletion produces motor (movement-related) symptoms.

The four cardinal motor symptoms of Parkinson's disease are:

• Tremors (uncontrollable shaking)
• Bradykinesia (slowness of movement)
• Rigidity (muscle stiffness)
• Problems with balance and coordination

Dopamine loss in Parkinson's also contributes to various non-motor symptoms, like depression, sleep problems, loss of smell, constipation, and orthostatic hypotension (sudden low blood pressure when standing up).

Causes

Even though the exact process by which ALS and Parkinson's develop remains unknown, experts believe that genetic and environmental factors contribute to both conditions.

What Causes ALS?

Researchers have identified various environmental factors that may increase a person's risk for ALS, albeit likely only to a small degree. Some of these risk factors include smoking, service in the U.S. military, head trauma, strenuous physical activity, and lead exposure.

Over 50 genes have been identified as causing or being related to the development of ALS. Many of these genes are involved in RNA metabolism. However, most people with ALS do not have a family history of the disease.

What Causes Parkinson's Disease?

In Parkinson's disease, dopamine-producing nerve cells within a brain region that regulate movement (the substantia nigra) break down and die.

Experts aren't sure what exactly causes these cells to die. Like ALS, more than one factor is likely at play, including:

• Genetics: Multiple genetic mutations (changes in DNA) are linked to Parkinson's disease, although most cases of Parkinson's are not inherited.
• Environment: Exposure to specific pesticides (rotenone or paraquat), metals (e.g., copper, iron, lead), or industrial solvents may increase a person's risk of developing PD.
• Lewy body formation: Lewy bodies are abnormal clumps of protein found in the brains of people with PD. It's unclear why or how they develop, but a toxic chemical reaction called oxidative stress might be involved.
  

Diagnosis

No single test can confirm the presence of ALS or Parkinson's disease. Instead, a neurologist (a doctor specializing in nervous system disorders) considers a person's symptoms and neurological examination when evaluating for either disease.

Various diagnostic tests are also usually performed to help pinpoint the diagnosis or rule out other possible conditions.

Magnetic resonance imaging (MRI) of the brain and spinal cord is an example of a test commonly ordered when evaluating for either ALS or Parkinson's disease.

ALS Diagnosis

Other diagnostic tests used in the evaluation for ALS include:

• Electromyography (EMG) and nerve conduction studies: These tests are usually performed at the same visit and can help distinguish nerve from muscle disorders. They measure electrical activity in your muscles and nerve cells while they're active and at rest.
  
• Blood or urine tests or cerebrospinal fluid (obtained via a spinal tap) tests: These tests can help support an ALS diagnosis or help rule out mimicking conditions, such as myasthenia gravis, Lyme disease, or human immunodeficiency virus (HIV).

Parkinson's Disease Diagnosis

Diagnostic tests used in the evaluation of Parkinson's disease include:

• A DaTscan: A single-photon emission computed tomography (SPECT) scan involving a special injected dye that binds to dopamine-producing nerve cells in the brain. It helps distinguish PD from essential tremor (a common movement disorder that also causes tremors).
• Response to medication: A healthcare provider gives you a dose of the Parkinson's disease medication levodopa. If you have Parkinson's, symptoms should improve significantly.
  

Treatment

The goals of treatment for ALS and Parkinson's disease are to manage symptoms and maintain quality of life. Medications for ALS are also intended to prolong survival and slow disease progression.

ALS Treatment

There are several types of therapies for managing ALS, including:

• Medication: Three drugs are approved by the Food and Drug Administration (FDA) to treat ALS. Rilutek (riluzole) is taken by mouth. Radicava (edaravone) or Radica ORS is given by IV (intravenously, within a vein) or taken by mouth, respectively. Relyvrio (sodium phenylbutyrate-taurursodiol) is a powder taken as a suspension dissolved in water. 
• Rehabilitation: Gentle exercises with a physical therapist may be performed to help strengthen unaffected muscles. Likewise, a speech therapist can help people communicate, and an occupational therapist can help them perform daily activities.
• Nutrition: A feeding tube may be used to supplement or replace eating foods.
• Breathing support: Oxygen delivered through a tight-fitting mask can help with breathing.

Parkinson's Disease Treatment

Like ALS, there are various therapies for Parkinson's. Treatment plans are tailored to the individual's symptoms, age, and level of functioning.

Therapies include:

• Medication: Levodopa is a dopamine-replacement medication that is the most effective drug for reducing symptoms and improving the quality of life in people with Parkinson's. Several other types of drugs are used to treat the symptoms of PD.
• Exercise: Parkinson's disease–specific exercise programs can help people feel well and possibly, slow down their disease.
• Surgery: Deep brain stimulation is a surgical procedure that may improve symptoms if medication is not working well enough.
  

Prevention

There is no absolute way yet to prevent ALS or Parkinson's disease. However, adopting certain lifestyle habits might help lower your risk.

For example, some research suggests that consuming certain foods, like whole-grain bread, citrus fruits, and raw vegetables, may have a preventive effect on ALS.

Likewise, adopting a "brain-nourishing" diet, like the Mediterranean diet, seems to lower PD risk.

Caffeine intake and regular physical activity also have a protective role in developing Parkinson's disease, perhaps by reducing inflammation or oxidative stress within the brain.

Interestingly, the link between caffeine intake and ALS risk remains controversial. Some studies suggest a protective role, whereas others have found no effect. The role of exercise in preventing ALS also remains unknown.

Summary

ALS and Parkinson's disease are distinct diseases that affect motor nerve cells and dopamine-producing nerve cells, respectively.

ALS primarily causes muscle weakness, whereas Parkinson's disease is associated with motor symptoms (tremor, slow movements, muscle stiffness, and impaired balance) and non-motor symptoms (e.g., constipation, loss of smell, depression). Treatments for each condition are unique but aim to ease symptoms and maintain quality of life.

A Word From Verywell

Whether you or a loved one has been diagnosed with a common neurodegenerative condition like Parkinson's disease or a rare one like ALS, it's normal to feel upset and overwhelmed. As you process your diagnosis, lean on loved ones for comfort and emotional support.

Be sure to seek care and guidance from a healthcare provider specializing in your condition. As you navigate your treatment options, don't hesitate to ask questions and be open about your worries or concerns.