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

The hearing was to discuss guidelines for distributing funds from the Temporary Assistance for Needy Families program, which paid millions to Favre’s alma mater, the University of Southern Mississippi, and to Prevacus, a now-defunct pharmaceutical company he supported.

“Unfortunately, I also lost my investment in a company that I believed was developing a breakthrough concussion drug that I thought would help others,” Favre said. “I’m sure you’ll understand that while it’s too late for me – I was recently diagnosed with Parkinson’s – this is also a cause that is very close to my heart.”

Favre played in 20 NFL seasons and previously shared The Bubba Army radio show that he had suffered “thousands” of concussions during his football career. “Every time my head hit the turf, the bell would ring or stars would go off, flashing lights, but I could still play,” he said in the interview. “That’s the scary thing about concussions. It’s the seemingly mild ones that do the damage because you can keep going, and even today there are probably people who have them and say, ‘I’m not going out.'” Favre also produced the new Apple TV film Concussed: 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 is a brain disease that causes symptoms such as involuntary or uncontrollable movements, including tremors, stiffness, and problems with balance and coordination, according to the National Institute on Aging (NIA). “One of the main characteristics of the disease is slowing of movements,” Dr. Gian Pal, a neurologist and movement disorder specialist at Rutgers Health Robert Wood Johnson Medical School, tells Yahoo Life. “Stiffness, problems with balance, and tremors can also occur, but slow movements are common.”

The disease, which actor Michael J. Fox also suffers from, is progressive, meaning that symptoms worsen over time. About 500,000 Americans have been diagnosed with Parkinson’s, although the National Institute of Neurological Disorders and Stroke (NINDS) says the actual number of sufferers is likely much higher.

What causes Parkinson’s disease?

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

• OldIn most people, the disease develops with increasing age; the average age of onset is 60 years.

• Gender. Men are more susceptible to the disease than women.

• geneticsPeople whose parents or siblings have Parkinson’s disease are twice as likely to develop the disease.

• Environmental causesThese include contact with 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 injuries and the risk of developing Parkinson’s. A study published in the journal Neurology found that even a mild brain injury increased the risk of developing Parkinson’s by as much as 56%. Another study published in the journal Family Medicine and Community Health found that people who had suffered a concussion had a 57% higher risk of developing Parkinson’s.

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

But Parkinson’s is a complicated disease, and not everyone who suffers a concussion goes on to develop the disease, Pal stresses. “The connection is not clear. More research is needed,” he says.

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

Pal also points out that a JAMA study published last year found that playing soccer was linked to a higher risk of being diagnosed with parkinsonism (a group of conditions that cause symptoms similar to Parkinson’s) or Parkinson’s – and the odds were higher the longer a person played the sport. Still, this link is not clear. “Playing soccer could be a risk factor for Parkinson’s, but the evidence is not yet clear,” Pal says.

Symptoms of Parkinson’s disease

Symptoms of the disease can vary from person to person. According to the NIA, the four main symptoms of Parkinson’s are:

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

• Muscle stiffness

• Slowness of movement

• Problems with balance and coordination

According to the NIA, people with Parkinson’s may also experience depression and other mood swings, difficulty swallowing, chewing and speaking, problems urinating, constipation and skin problems.

How is Parkinson’s disease diagnosed?

There are no blood or lab tests to diagnose non-genetic Parkinson’s disease, so doctors typically make a diagnosis based on medical history and a neurological exam, according to the NIA. They may also try a short, low-dose course of Parkinson’s disease medications to see if symptoms improve, according to the Mayo Clinic. “But that’s not necessary for diagnosis,” Pal says.

Treatments for Parkinson’s disease

“One of the main problems with Parkinson’s is the lack of dopamine in the brain – this causes many of the physical symptoms of the disease,” says Pal. “We have good drugs to replace this dopamine.”

But in the early stages of the disease, Pal says, someone may not need treatment. Instead, the patient and doctor usually decide together whether the symptoms are so disabling that medication is necessary. “If it’s causing functional limitations in everyday life, then they would consider medication,” he says.

Aside from medication, physical activity can also help relieve symptoms, Pal says.

If you have symptoms of Parkinson’s disease, Pal recommends getting evaluated by a movement disorder specialist as soon as possible to determine if it could be the disease or something else entirely. “Then they can better understand what the long-term outlook is,” he says.

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

Pal stresses that there are medications and treatments that help. “In general, Parkinson’s is a slowly progressive disease,” he says. “There are many treatment options available to us.”