How to Manage Constipation Caused by Lambert-Eaton Myasthenic Syndrome (LEMS)

When you’re living with Lambert-Eaton myasthenic syndrome (LEMS), constipation can go from a bothersome, quality-of-life symptom to a serious medical issue. It can be especially difficult to manage, because some of the usual remedies for constipation don’t work or can make you even more uncomfortable when you have LEMS.

Constipation is a feature of LEMS — it’s not happening because you’re doing something wrong with your diet — which is exactly why you should talk to your doctor about it early, says Georgette Dib, MD, a neurologist at Cleveland Clinic in Ohio.

Here’s why constipation can happen with LEMS and what may help.

LEMS affects the release of acetylcholine, a chemical messenger that helps nerves send “move” signals to muscles.

When colon movement slows down, it may not squeeze and move stool forward as well as it should, says Dr. Dib. Stool can sit longer in the colon, become harder, and become more difficult to pass.

Because constipation in LEMS is typically caused by a mix of factors, your doctor will weigh contributors and remove reversible ones, she says.

Possible reasons for constipation in LEMS, according to Dib, include:

• The LEMS itself, especially if constipation comes with dry mouth, dizziness when standing, bladder symptoms, erectile dysfunction, or sweating changes.
• Less movement because of muscle weakness or fatigue.
• Dehydration, which can make stool harder to pass.
• Constipating medicines, such as opioids, iron, ondansetron (Zofran), or some antidepressants. Immunosuppressants used for LEMS generally do not cause constipation, Dib says.
• Other health issues, including an underactive thyroid, diabetes, low potassium, or high calcium.
• Cancer-related issues, especially if constipation is new or unusually severe in someone whose LEMS is linked to small cell lung cancer.

Fiber can help with constipation, but with LEMS, piling on more fiber isn’t always the fix.

That’s because LEMS-related constipation is often a slow-transit problem — stool is moving too slowly through the colon.

Some fiber works by adding bulk to stool, which can be helpful for when the colon is moving normally, but if the colon is moving slowly, extra bulk can sit there and cause more bloating, pressure, and discomfort, says Dib.

In more severe constipation in people with LEMS, too much bulk can also raise the risk that stool gets stuck or the colon becomes dangerously backed up, she says. That’s one reason to ask your doctor before adding a fiber supplement, especially if constipation is new, severe, or getting worse.

• Start with fiber-rich foods, such as oats, beans, lentils, chickpeas, apples, berries, whole-wheat bread, or whole-grain pasta.
• Add fiber gradually, along with steady water intake during the day.
• If you need a supplement, ask about psyllium, the type of soluble fiber found in Metamucil.
• Be cautious with coarse wheat bran and added fibers such as inulin, fructooligosaccharides, or chicory root, which can cause more gas and bloating.

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If fiber makes bloating and discomfort worse, don’t keep adding more on your own. Dib says severe constipation in LEMS may need a gastroenterologist’s help.

When possible, “prevent rather than rescue,” is the best way to combat constipation, says Dib. A standing daily routine can help by lowering the risk of impaction and the need for crisis management of constipation, Dib says.

She recommends the following strategies:

Try after-meal toileting. Sit on the toilet 15 to 30 minutes after a meal, especially breakfast. Eating naturally signals the colon to move.

Use a footstool when using the toilet. Raising your knees into a more squat-like position may make it easier to pass stool.

Go when you feel the urge. Don’t wait to use the bathroom. Holding it in can make stool drier and harder to pass.

Be as physically active as you safely can. Walking, assisted standing, physical therapy, or other safe movement can help keep the bowels moving. Deconditioning slows bowel transit, so staying active or seeing a physical therapist can help.

Try gentle abdominal massage. Clockwise massage follows the general path of the colon and may be a reasonable add-on. Ask a clinician, physical therapist, or occupational therapist to show you how to do it safely.

“Treating LEMS itself may help constipation,” says Dib. Taking amifampridine (Firdapse) or pyridostigmine (Mestinon) as prescribed matters, because both medicines work in ways that increase acetylcholine, a chemical messenger that helps nerves communicate with muscles, including those in the gastrointestinal tract.

• Amifampridine helps nerves release more acetylcholine. Its digestive side effects may include nausea, diarrhea, or cramping, though constipation has rarely been reported, Dib says.
• Pyridostigmine helps acetylcholine stay active longer. Because cholinesterase inhibitors such as pyridostigmine can increase colon movement, it may help bowel motility in some people with autonomic constipation, Dib says.

Navigating Laxatives Safely

If diet, fluids, changes in daily routine, and LEMS treatment are not enough, Dib recommends a stepwise plan for trying laxatives:

Osmotic Laxatives Polyethylene glycol, such as Miralax, pulls water into the colon so stool is softer and easier to pass. Dib considers osmotic laxatives a first medication step when lifestyle changes are not enough.

Stool Softeners Docusate sodium can help soften stool and reduce straining, but it may not be enough if the main problem is that the colon is moving too slowly. Ask your doctor whether it should be paired with another option, such as a mild stimulant.

Stimulant Laxatives Senna and bisacodyl make the colon contract and can be effective, but Dib recommends using them as short-term or rescue options under medical guidance.

Stimulant laxatives should not be used if stool may be stuck or the bowel may be blocked, Dib says. In that situation, forcing the colon to contract can be harmful.

Dib recommends discussing constipation with your doctor early so they can look for medication side effects, dehydration, reduced mobility, or another health issue that may be making constipation worse.

Dib recommends calling your doctor within a day or two for any of the following:

• Constipation that is not improving despite your usual measures
• Leakage of liquid stool, which can be a sign of impaction (hard stool stuck in the colon)
• Rectal bleeding
• Unexplained weight loss
• A blood test showing iron-deficiency anemia
• A major new change in bowel habits, especially in an older adult
• Worsening constipation with frequent urination, nausea, or confusion, especially if your LEMS is associated with small cell lung cancer

Seek urgent care or emergency care for:

• No stool and no gas, plus abdominal swelling, severe pain, or vomiting
• Severe pain that does not let up
• An abdomen that feels rigid, hard, or very swollen
• Fever with severe abdominal symptoms
• Vomiting that looks or smells like stool

These symptoms can point to a blockage, impaction, or acute colonic pseudo-obstruction, a serious complication that can happen when the colon becomes severely sluggish from autonomic dysmotility, Dib says.