NFL Hall of Famer Brett Favre was recently diagnosed with Parkinson’s disease. The 54-year-old shared the news Tuesday during testimony at a congressional hearing on federal welfare reform.

The hearing was held to discuss restrictions on the distribution of Temporary Assistance for Needy Families funds, which distributed millions to Favre’s alma mater, the University of Southern Mississippi, and Prevacus, a pharmaceutical company he supported that no longer exists.

“Unfortunately, I also lost my investment in a company that I believed was developing a breakthrough drug for concussions that I thought would help others,” Favre said. “As you can imagine, it’s too late for me — I was recently diagnosed with Parkinson’s — but this is also a cause that is close to my heart.”

Favre played in 20 NFL seasons and previously shared The Bubba Army radio show that he suffered “thousands” of concussions during his football career. “Every time my head hit the grass, there was a ping or stars, flashes, but I could still play,” he said in the interview. “That’s what makes it a little scary about concussions. It’s the small ones that do the damage, because you can keep going, and there’s probably still guys out there who have them, who (say) ‘I’m not going out.'” Favre also produced the new Apple TV movie Concussion: The American Dream.

Favre’s revelation has raised many questions about Parkinson’s disease, including a possible connection to concussions. Here’s what neurologists want you to know.

What is Parkinson’s disease?

Parkinson’s disease is a brain disorder that causes symptoms such as unintentional or uncontrollable movements, including shaking, stiffness, and problems with balance and coordination, according to the National Institute on Aging (NIA). “One of the hallmarks of the disease is slowness of movement,” Dr. Gian Pal, a neurologist and movement disorders specialist at Rutgers Health Robert Wood Johnson Medical School, tells Yahoo Life. “There can also be stiffness, balance problems and tremors, but slow movement is very common.”

The disease, which actor Michael J. Fox also has, is progressive, meaning symptoms get worse over time. About 500,000 Americans are diagnosed with Parkinson’s disease, though the National Institute of Neurological Disorders and Stroke (NINDS) says the actual number of people with the disease is likely much higher.

What causes Parkinson’s disease?

The exact cause of Parkinson’s disease is unknown. However, there are a few risk factors associated with developing the disease. According to Johns Hopkins Medicine, these include:

• AgeMost people develop the condition as they get older. The average age of onset is 60.

• GenderMen are more likely to develop the condition than women.

• GeneticsPeople who have a parent or sibling with Parkinson’s disease are twice as likely to develop the condition themselves.

• Environmental causesExamples include exposure to pesticides and herbicides, working with heavy metals, cleaning agents and solvents, and exposure to Agent Orange during the Vietnam War.

Can concussions increase the risk of Parkinson’s disease?

That’s not entirely clear at this point. Research has found a link between head trauma and the risk of developing Parkinson’s disease. A study published in the journal Neurology found that even a mild brain injury increased the risk of developing Parkinson’s disease by 56 percent. Another study published in the journal Family Medicine and Community Health found that people who had suffered a concussion were 57 percent more likely to develop Parkinson’s disease.

“There is a possible connection,” says Dr. Daniel Truong, neurologist and medical director of the Truong Neuroscience Institute at MemorialCare Orange Coast Medical Center in Fountain Valley, California.

But Parkinson’s is a complex condition, and not everyone who has a concussion will develop the disease, Pal points out. “The association is not conclusive. It warrants further investigation,” he says.

“Parkinson’s disease is associated with higher levels of tau, a protein, in the brain,” Dr. Amit Sachdev, medical director of the Department of Neurology at Michigan State University, tells Yahoo Life. “It’s hard to know for sure whether concussions are associated with increased tau and, if so, whether it’s deposited in the brain in a pattern that causes the disease.”

Pal also notes that a JAMA study published last year found that playing soccer was linked to a greater likelihood of a diagnosis of parkinsonism (a group of conditions that cause similar Parkinson’s-like symptoms) or a diagnosis of Parkinson’s disease — and the odds were higher the longer someone played the sport. Still, this link isn’t definitive. “Playing soccer may be a risk factor for Parkinson’s, but the evidence is still mixed,” Pal says.

Symptoms of Parkinson’s disease

Symptoms of the disease can vary from person to person, but according to the NIA, these are the four main symptoms of Parkinson’s disease:

• Tremors in hands, arms, legs, jaw or head

• Muscle stiffness

• Inertia of motion

• Problems with balance and coordination

According to the NIA, people with Parkinson’s disease may also experience depression and other emotional changes, problems swallowing, chewing and speaking, problems with urination, constipation and skin problems.

How is Parkinson’s disease diagnosed?

There are no blood or lab tests used to diagnose nongenetic Parkinson’s disease. As a result, doctors will typically make a diagnosis based on medical history and a neurological exam, the NIA says. They may also try a short, low-dose treatment with medications used to treat Parkinson’s disease to see if symptoms improve, the Mayo Clinic says. “That’s not required for diagnosis, though,” Pal says.

Treatments for Parkinson’s Disease

“One of the major problems with Parkinson’s is that there’s very little dopamine in the brain — that’s what causes a lot of the physical symptoms of the disease,” Pal says. “We have good drugs to replace that dopamine.”

But in the early stages of the disease, Pal says, someone may not need treatment. Instead, a patient and their doctor will typically decide together whether the symptoms are disabling enough that they need medication. “If it’s causing functional limitations in their day-to-day, then they would think about medication,” he says.

In addition to medications, physical activity can also help manage symptoms, Pal says.

If you have symptoms of Parkinson’s disease, Pal recommends getting an evaluation from a movement disorder specialist as soon as possible to see if it could be the disease or something else entirely. “That way they’ll have a better understanding of what the long-term outlook is going to be,” he says.

“Parkinson’s is a progressive disorder with many features,” Sachdev adds. “Early diagnosis is important.”

Pal emphasizes that there are medications and treatments that can help. “In general, Parkinson’s is a slow, progressive disease,” he says. “We have many treatments available.”