Gastrointestinal (GI) difficulties can be among the most bothersome of the non-motor symptoms caused by Parkinson’s disease (PD). Constipation, which involves the slowing down of the large intestine or lower gut is the most common of the GI symptoms, affecting 80-90% of people with PD. However, slowing down of the stomach or upper gut, also known as gastroparesis, is a less well-known problem in PD, but is also extremely common and can significantly affect nutrition, medication effectiveness, and overall quality of life. Despite its prevalence, gastroparesis is frequently undiagnosed and therefore untreated.
What is Gastroparesis
Gastroparesis is a disorder in which the stomach empties its contents into the small intestine more slowly than normal, even though there is no physical obstruction. In healthy digestion, coordinated muscular contractions move food through the stomach at a predictable pace. In people with PD, this coordination can become disrupted. Food may remain in the stomach for prolonged periods, leading to discomfort and sometimes debilitating symptoms. While gastroparesis is often associated with nerve damage of diabetes, PD is increasingly recognized as another major neurological cause.
Why PD Disrupts the Gut
In many patients, PD affects more than just the brain. It also involves widespread dysfunction of the autonomic nervous system, which regulates involuntary processes such as heart rate, blood pressure, and digestion. The GI tract has its own extensive nerve network, known as the enteric nervous system, which is deeply interconnected with the brain.
In PD, abnormal accumulations of the protein alpha-synuclein are found not only in the brain but also in the nerves of the gut and the vagus nerve, which connects the brain to the digestive system. This disrupts the signaling required for normal stomach contractions. Reduced dopamine activity further contributes to slowed motility, as dopamine plays a role in regulating gastrointestinal movement.
Digestive dysfunction can appear long before classic motor symptoms of PD emerge. Chronic constipation and slowed gastric emptying may precede a PD diagnosis by many years, suggesting that the disease process may begin in the gut for some individuals.
Recognizing the Symptoms of Gastroparesis
The symptoms of delayed gastric emptying in PD can vary greatly in severity and are often mistaken for medication side effects that are thought to be unrelated to actual digestion issues. Common symptoms of gastroparesis include:
- Early satiety (fullness) after starting a meal
- Bloating or abdominal distension
- Nausea and vomiting
- Abdominal pain
- Loss of appetite
- Unintentional weight loss
- Acid reflux or worsening heartburn
Because these symptoms overlap with medication side effects and other digestive conditions, they are sometimes overlooked or misunderstood.
How Gastroparesis May Affect PD Medication Response
One of the most important consequences of delayed gastric emptying in PD is erratic medication absorption. Levodopa is the most commonly used treatment in PD to manage motor symptoms of the disease and it is absorbed primarily in the small intestine. If the stomach empties unpredictably or too slowly, levodopa may not reach the intestine in a timely or consistent manner for the planned therapy.
This can lead to a variety of issues such as delayed onset of symptom relief, reduced medication effectiveness, and increased motor fluctuations throughout the day. Patients may experience “off” periods despite taking medication on schedule. In some cases, this leads to higher doses being prescribed, which may increase side effects without addressing the underlying problem.
As a result, gastrointestinal motility plays a critical but often underappreciated role in PD symptom control. In this manner, it is important to understand if gastroparesis is occurring in PD patients and how to properly implement treatment plans accordingly.
Diagnosing Gastroparesis in Parkinson’s
Diagnosing gastroparesis can be tricky in PD and requires careful evaluation. Clinicians typically begin with a detailed symptom history of the patient to understand any changes that may be occurring with meal timing such as fullness, nausea, and medication response. Objective testing however, may be necessary to confirm a diagnosis of delayed gastric emptying.
A mechanical obstruction must be ruled out first through an imaging test or endoscopy before a diagnosis of gastroparesis is made. Once it is established that there is no structural problem that is causing a delay in gastric emptying, a gastric emptying study may be used to measure how quickly a meal leaves the stomach. One example of this testing is gastric emptying scintigraphy which involves ingesting a standard meal with a small amount of a radiocative tracer, followed by imaging at 0, 1, 2, and 4 hours to measure the percentage of food remaining in the stomach. Breath tests and other noninvasive methods may also be used in some settings to determine gastric emptying rate. Even small delays in gastric emptying can have meaningful effects in PD, especially when oral treatment plans are in place.
Managing Symptoms Through Diet and Lifestyle
Once a diagnosis of gastroparesis is made, focus can turn to treatment. One of the easiest and most effective ways of managing delayed gastric emptying is through dietary changes. Helpful strategies include:
- Eating smaller meals more frequently
- Reducing high-fat and high-fiber foods that could slow digestion
- Eating more soft foods (liquids, soups, smoothies, etc.)
- Chewing food thoroughly
- Staying upright for at least 1-2 hours after eating
Incorporating these adjustments can have a significant effect on daily functioning and symptom control in PD.
Medical and Pharmacologic Approaches to Ease Gastroparesis
When lifestyle measures are insufficient, a medication may be considered. Unfortunately, some of the treatments used for gastroparesis more generally, such as when it occurs in someone with diabetes, cannot be used for people with PD because these drugs can worsen motor symptoms of PD.
Domperidone is a drug available outside of the US that can be effective for gastroparesis. It is not FDA approved due to its association with serious cardiac events such as cardiac arrythmias and is therefore not available in the US. Prucalopride is a gastrointestinal motility agent that is approved for chronic constipation. It has been used off label for gastroparesis.
Quality of Life and Emotional Impact
Gastroparesis can lead to fear of eating because of the pain associated with food as well as frustration with unpredictable medication response. Since these symptoms are not visible to others, they can easily be underestimated or dismissed. Open communication with healthcare providers is essential to ensure that these symptoms are recognized as a treatable part of PD, so be sure to speak up if you are experiencing GI concern or discomfort
Tips and Takeaways
- Gastroparesis is common in PD
- This condition results from nervous system dysfunction rather than a physical blockage in the gut
- Symptoms include early fullness, bloating, nausea, and weight loss
- Digestive symptoms may appear years before motor symptoms and can significantly affect quality of life
- Delayed gastric emptying can interfere with PD medication absorption
- Dietary and lifestyle changes are often highly effective
- Medication options exist but must be used carefully in PD
- Open communication with healthcare providers is critical
This blog was written by Clark Jones, PhD, and was reviewed, edited, and approved by Dr. Rebecca Gilbert.