So What's the Difference Between ALS and Parkinson's Disease?

Clockwise from top left: Robin Williams had been diagnosed with Parkinson’s before his death; Stephen Hawking has been living with ALS for 50 years; Lou Gehrig brought ALS, now also know as Lou Gehrig’s disease, to the public’s attention; and Michael J. Fox received his Parkinson’s diagnosis in 1992. (Photos: Getty Images)

News that Robin Williams had been grappling with a diagnosis of Parkinson’s disease before ending his life has sparked increased interest in the disorder this week. And that’s coincided with a fast-rising awareness of a similar disease — amyotrophic lateral sclerosis, or ALS — due to the Ice Bucket Challenge, a fundraising campaign that’s swept social media recently, prompting everyone from Ethel Kennedy to Justin Timberlake to dump freezing water over their heads in the name of research. (And it’s worked, raising millions for the cause.) So how closely linked to Parkinson’s is ALS? Both are progressive neurodegenerative diseases, and neither has a cure. But beyond that, the differences are vast.

“Both occur because some cells in the brain degenerate, and both are diseases of the motor system, meaning they affect how someone moves,” Dr. U. Shivraj Sohur, a movement disorder specialist with the MassGeneral Institute for Neurodegenerative Disease, told Yahoo Health. “From there, the separation happens quickly, both from a neurology point of view and from a patient’s experience.”

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While ALS is currently getting perhaps its biggest publicity boost since baseball player Lou Gehrig’s suffering made it part of the public lexicon in 1939, Parkinson’s has consistently been in the sphere of public knowledge. And much of that, Sohur said, is due to “sheer numbers.” Currently, an estimated 30,000 Americans are living with ALS and about 5,600 are diagnosed each year. Meanwhile, the number of those living with Parkinson’s is closer to 1 million, which translates to about 60,000 diagnoses a year. Funding for each disease tends to reflect those numbers — according to the National Institutes of Health, ALS public funding in 2013 totaled $39 million, while public funds for Parkinson’s hit $135 million.

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“Awareness is an important thing,” Jim Beck, PhD, vice president of scientific affairs for the Parkinson’s Disease Foundation, told Yahoo Health, “as is scientific research.” He stressed that breakthroughs for either could very well inform the other, as well as myriad other neurological disorders, and added, “You never know where it could lead.” To that end, we’ve broken down the details on both diseases:

ALS (Lou Gehrig’s disease)

What it is: The progressive disease results from a degeneration of motor neurons until those neurons die off, Sohur explained. “Two groups are affected — a group of cells on top of the brain, on the cortex,” he said, “and those within the spinal cord.” Amyotrophic comes from Greek, the ALS Association explains on its website, with “A” meaning no or negative, “myo” referring to muscle, and “trophic” meaning nourishment, so “No muscle nourishment.” When a muscle has no nourishment, it atrophies, or wastes away.

Who gets it: ALS can strike anyone between the ages of 40 and 70. It’s 20 percent more common in men than in women, and, though typically not genetic, can be hereditary in about 10 percent of cases.

History: ALS was first discovered in 1869 by the French neurologist Jean-Martin Charcot, but Lou Gehrig, through his own diagnosis, first brought national and international attention to the disease (as well as an alternative name) in 1939.

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Symptoms: Early clues can include increasing muscle weakness, particularly in one’s limbs, that can also affect speech, swallowing or breathing. “It’s initially difficult to recognize,” noted Sohur. “Usually muscles will jump and there will be weakness in one muscle at a time, all while a person is in generally good health.” Because the disease progresses quickly, though, diagnosis gets easier, he said. As muscles stop functioning, they begin to atrophy, and patients in the later stages of the disease may become completely paralyzed, while affected muscle regions harden — the aspect known as “sclerosis.”

Treatments: While nothing can stop or reverse the effects of ALS, there is a single FDA-approved drug, Riluzole, that slightly slows its progression; several other drugs in clinical trials are promising, according to the ALS Foundation.

Prognosis: “An ALS diagnosis is a death sentence,” said Beck. The average life expectancy from time of diagnosis is just two to five years. However, he added, “It’s a complicated disease, meaning the way it presents itself is always different.” More than half of all patients live more than three years after diagnosis, while ten percent will live for more than 10 years and 5 percent more than 20. Physicist Stephen Hawking, who has lived with the disease for nearly 50 years now, represents an exceptionally rare case.

Parkinson’s disease

What it is: Parkinson’s is caused by the malfunction and death of neurons in an area of the brain called the basal ganglia and, within that, the “substantia nigra,” Sohur said. Some of the dying neurons produce dopamine, a chemical that sends messages to the part of the brain that controls movement and coordination.

Who gets it: The average age of onset is 60. Still, while incidence of the disease increases with age, an estimated 4 percent of people with Parkinson’s are diagnosed before the age of 50. Men are one and a half times more susceptible than women.

History: While the condition has been known about since ancient times, London doctor James Parkinson was the first to formally describe it in a detailed medical essay, in 1817.

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Symptoms: While very early signs can include sleep disorders and the loss of one’s sense of smell, the most common collection of primary symptoms is something Sohur refers to with the acronym TRAP: tremor (involuntary trembling of a limb or limbs); rigidity (muscle stiffness); akinesia (slowness or difficulty when moving); and postural instability (trouble with balance or walking). Other signs may include shrinking handwriting and a masklike expression.

Treatments: There are many medications available to treat Parkinson’s symptoms, though none reverse the disease. Some people respond to an option called deep brain stimulation surgery, which involves electrodes being inserted into the brain, while a device called an impulse generator (similar to a pacemaker) is implanted under the collarbone to provide an electrical impulse to the brain’s motor function region.

Prognosis: “People don’t die of Parkinson’s; they die of complications from Parkinson’s disease,” said Sohur. And, like ALS, its presentation and progression vary from person to person. “I always say, if you’ve met one person with Parkinson’s, you’ve met one person with Parkinson’s,” Beck said. “Their journey is often as unique as their own lives.”

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