Both Parkinson’s disease and Huntington’s disease are progressive neurodegenerative disorders that affect the central nervous system (brain and spinal cord). “Progressive” means they worsen over time, and “neurodegenerative” means they lead to the dysfunction and death of nerve cells, or neurons.
Although both diseases cause involuntary movements, their motor symptoms differ, and so do their causes. Neither disease is curable, but medications and other treatment options help some people manage their symptoms.
Having Parkinson’s or Huntington’s disease can make daily living more challenging for the person diagnosed and their caregivers and other loved ones. Understanding available treatment options and what to expect can help you prepare for the future.
Parkinson’s is the second most common neurodegenerative disorder in the United States — it comes after Alzheimer’s disease.
Approximately 500,000 Americans are known to be living with it, but some researchers suspect the number may be closer to a million. It can be challenging to diagnose and may be misdiagnosed or go undiagnosed.
Actor Michael J. Fox was diagnosed with Parkinson’s in 1991, when he was 29. However, people who develop the disease are usually 60 or older — the risk of Parkinson’s increases with age. Parkinson’s is 1.5 times more common among males than females, according to NPJ Parkinson’s Disease.
Huntington’s disease is much less common than Parkinson’s disease — it affects about 15,000 people in the United States and is passed through families. According to UCSF Health, Huntington’s affects males and females at similar rates, and the age of onset is usually 30 to 55. When the condition develops in children and teenagers, it’s known as juvenile Huntington’s disease.
Huntington’s disease can shorten a person’s life span, with death generally occurring 10 to 30 years after symptoms first appear.
One main difference between Parkinson’s and Huntington’s is what causes them. Huntington’s is an inherited disease, meaning a parent passes a genetic mutation (change) to their child. Parkinson’s is an idiopathic disease, which means the cause is generally unknown.
Health experts believe Parkinson’s is caused by a combination of factors, including genetics, environmental factors, and aging. An estimated 30 percent of cases are genetic, but not everyone with the genetic mutations linked to Parkinson’s will develop the disease.
A person who inherits the genetic mutation for Huntington’s, however, will surely develop Huntington’s symptoms at some point. The gene that causes Huntington’s is the huntingtin (HTT) gene. A parent with Huntington’s has a 50 percent chance of passing the HTT gene on to their child. In rare cases, Huntington’s occurs without a proven family history. This is called sporadic Huntington’s.
Both Parkinson’s and Huntington’s diseases cause involuntary movements when neurons in the brain stop working or die. Symptoms of both may be mild at first and affect people differently. While there is some symptom overlap, like muscle rigidity and trouble balancing, some of the involuntary movements are distinguishable.
Parkinson’s causes a rhythmic shaking or tremor in the hands or fingers. It also leads to bradykinesia, a slowing down of movements and reflexes. The primary symptoms of Parkinson’s are the result of cell death or deterioration in a region of the brain that’s essential for motor control. This area, called the substantia nigra, produces dopamine.
Dopamine is a neurotransmitter that helps send messages within your brain and between your brain and the rest of your body. It plays a role in muscle movement, mood, memory, and other essential functions. Low dopamine levels result in the tremors and slow movements associated with Parkinson’s.
Huntington’s causes jerking or writhing movements called chorea, which are sometimes described as dancelike. Chorea can affect the hands, fingers, face, feet, or torso, making it more of a full-body movement in some people.
Both diseases can cause cognitive impairment, mood swings, insomnia, and other symptoms.
Diagnosing Parkinson’s or Huntington’s disease can be challenging and may require more than one appointment. There’s no specific test to diagnose either condition.
Your doctor will likely start with a physical exam and ask questions about your symptoms, medical history, and family medical history. If they suspect Parkinson’s, Huntington’s, or another nervous system disorder, they’ll probably recommend a neurological or psychiatric evaluation. Additional tests may help confirm or rule out a diagnosis.
Imaging tests like CT or MRI scans may show some brain changes or abnormalities in people with Huntington’s. However, imaging tests are more helpful for ruling out other diseases than for confirming a diagnosis for either disorder.
Blood tests also can’t diagnose Parkinson’s but can help rule out other diseases. For Huntington’s, your health care provider may request a blood sample for genetic testing, especially if you have a family history of Huntington’s. They’ll be looking for the HTT gene.
Through a combination of conversations and tests, your doctor may diagnose you with Parkinson’s or Huntington’s. It can take time, so try to be patient with the process. While having a progressive disease may be life-changing, once you know the cause of your symptoms, you and your care team can work together to treat them.
There’s currently no way to stop or slow the disease progression of Parkinson’s or Huntington’s disease. Treatment goals for both include easing symptoms and maintaining quality of life.
Neurologists with extensive training in movement disorders typically treat both conditions. These neurology experts, known as movement disorder specialists, will collaborate with your other health care providers. Your care team may include physical, occupational, and speech therapists, as well as mental health professionals, nutritionists, and others. There’s no one-size-fits-all treatment plan for either neurodegenerative disease.
Currently, the most effective drug for treating Parkinson’s is levodopa-carbidopa (Duopa, Parcopa, Rytary, Sinemet). Levodopa is a natural chemical that the brain converts to dopamine, and carbidopa keeps the body from processing the drug too early. Low dopamine levels cause tremors, difficulty walking, and other motor symptoms, so medications that increase dopamine can often ease or reduce symptoms.
Sometimes Parkinson’s is treated with medications called dopamine agonists. These medications don’t convert to dopamine but instead have a similar effect as dopamine. Other drugs keep certain enzymes in the brain from breaking down dopamine.
Deep brain stimulation is sometimes used when symptoms don’t respond to medications. This surgical treatment uses electrodes implanted in the brain to stimulate or control brain cells, chemicals, and abnormal impulses.
There are fewer treatment options for Huntington’s disease than for Parkinson’s. Examples of medications for managing the involuntary movements of Huntington’s include tetrabenazine (Xenazine) and deutetrabenazine (Austedo). Many Huntington’s treatments bring the risk of side effects that may outweigh their benefits.
Currently, researchers are evaluating deep brain stimulation as a potential treatment for Huntington’s.
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