Complications of Spinal Muscular Atrophy: Urinary Incontinence

Reviewed by: HU Medical Review Board | Last reviewed: August 2021

Children with spinal muscular atrophy (SMA) have progressive muscle weakness due to defective motor neurons in the spine. This can lead to potentially life-threatening complications that impair mobility. One complication of SMA that is less severe is urinary incontinence. This is the involuntary leakage of urine, either during the day or at night.1,2

Urinary incontinence may occur in children with SMA because of the disease itself. It may also be caused by other behaviors. If parents seek treatment, children will see a specialist who can diagnose the cause and suggest treatment options. We do not yet know enough about treating urinary incontinence specifically in children with SMA. Doctors may suggest treatments used by the general population, as well as other ways to reduce the burden of urinary incontinence.1,2

What is urinary incontinence?

Urinary incontinence is involuntary urination caused by a loss of bladder control. When it only happens during sleep, incontinence is called “enuresis.” A related term is “nocturia.” This is waking up at night to urinate, but it does not always mean that there is loss of bladder control.1,2

Urinary incontinence is often caused by medical conditions. These may include urinary tract infections or constipation. It can also be caused by everyday behaviors. For example, certain foods and medicines may cause temporary urinary incontinence. These “diuretics” increase the volume of urine and include:3

  • Alcohol and caffeine
  • Carbonated drinks
  • Chocolate
  • Foods high in spice, sugar, or acid

Other causes of urinary incontinence include:3

  • Stress placed on the bladder by coughing, sneezing, laughing, or exercising
  • Inability of the bladder to empty completely
  • Physical or mental impairment that makes it difficult to reach the toilet in time

Why does SMA cause urinary incontinence?

Loss of bladder control is a common problem for all children. About 10 percent of 7-year-old children experience bedwetting. However, children with SMA have a higher risk of urinary incontinence. About 30 percent of children who are severely incapacitated with SMA involuntarily urinate during the day or night. Incontinence is worse in types 1 and 2 SMA.4

We do not yet know if children with SMA experience incontinence more often because of the disease itself or because of other behaviors. One theory is that urinary incontinence in SMA is caused by weak muscles in the urethra and pelvis. However, involuntary wetting decreases with age in SMA even though muscle weakness gets worse. It is likely that involuntary wetting has behavioral causes in SMA, as it does for children without SMA.4

Involuntary bedwetting can lead to feelings of embarrassment and guilt for children with SMA. It can also lead to other complications, including:3

  • Skin problems, such as rashes and skin infections on wet skin
  • Urinary tract infections
  • Other impacts on personal and social life

How is this treated?

Parents often do not mention their children’s urination problems to doctors or actively seek treatment. It is important for doctors to ask parents about urinary incontinence in all children with SMA. Parents can then receive information to decide if they want to start treatment. This decision usually depends on how burdensome symptoms are to children and the family.4

If parents decide to seek treatment, doctors will offer a referral to a pediatric urologist. This is a doctor who specializes in diagnosing and treating urinary tract conditions in children. They will first determine the cause of incontinence using a questionnaire. The Pediatric Incontinence Questionnaire (PinQ) is often used. They may also perform urine tests for infections.4-6

If the cause is not related to muscle weakness, children with SMA should receive standard treatments for urinary incontinence. Doctors will suggest less invasive techniques first before moving on to other options. Treatment options include:3-7

  • Bladder training to delay urinating when an urge starts
  • Scheduling toilet trips instead of waiting for the urge
  • Managing fluids and diet to avoid foods that irritate the bladder
  • Pelvic floor exercises
  • Electrical stimulation to strengthen the pelvic floor muscles
  • Medicines such as anticholinergics, mirabegron, and alpha blockers
  • Medical devices or surgery

Even if treatment is not desired or possible, there are ways to reduce the burden of urinary incontinence. Talk to your doctor or a social worker about how to minimize the physical and emotional burden of urinary incontinence on your child and the family.

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