What is the diagnosis and treatment for myotonia with urinary incontinence?

Myotonia with Urinary Incontinence: Diagnosis and Management

Critical Diagnostic Consideration

This presentation of myotonia (sustained muscle contraction/delayed relaxation) combined with urinary incontinence strongly suggests myotonic dystrophy type 1 (DM1), a multisystem neuromuscular disorder that commonly affects both skeletal muscle and smooth muscle function, including the bladder. The urinary incontinence in this context is neurogenic in origin, requiring a fundamentally different approach than idiopathic incontinence.

Diagnostic Approach

Essential History and Physical Examination Elements

• Myotonia characteristics: Document grip myotonia (inability to quickly release hand grip), percussion myotonia (sustained muscle contraction after percussion), and facial weakness with temporal wasting 1
• Urinary symptom characterization: Determine if incontinence is stress-type (leakage with coughing/straining), urgency-type (sudden compelling urge), mixed, or overflow (from retention with neurogenic bladder) 1
• Neurologic assessment: Evaluate for cognitive impairment, motor skills related to toileting (ability to dress independently), and lower extremity function 1
• Medication review: Identify drugs that may worsen urinary symptoms or myotonia 1

Required Diagnostic Testing

• Urinalysis: Rule out urinary tract infection and hematuria as contributing factors 1
• Post-void residual volume: Essential to identify neurogenic urinary retention, which is common in myotonic dystrophy and fundamentally changes management 1, 2
• Urodynamic testing is indicated for this non-index patient with neurogenic lower urinary tract dysfunction 1

When to Refer

Immediate referral to neurology and urology is warranted given the neurogenic etiology. This is not an index patient with simple stress incontinence 1.

Treatment Algorithm for Neurogenic Urinary Incontinence

Step 1: Address Urinary Retention First (If Present)

• If elevated post-void residual is found, intermittent catheterization may be necessary before addressing incontinence, as overflow incontinence from retention requires bladder decompression 3
• Avoid antimuscarinic medications if significant retention is present, as they worsen urinary retention 1, 2

Step 2: Conservative Management (First-Line)

Behavioral interventions should be attempted initially, though efficacy may be limited in neurogenic cases:

• Bladder training: Scheduled voiding with gradually extended intervals, though this requires adequate cognitive function and motor skills for toileting 4, 5, 2
• Pelvic floor muscle training (PFMT): May have limited benefit in neurogenic incontinence due to underlying neuromuscular pathology, but can be attempted if patient has adequate motor control 4
• Fluid management: Regulate intake, particularly reducing evening consumption to minimize nighttime symptoms 5

Step 3: Pharmacologic Management (Second-Line)

Exercise extreme caution with antimuscarinic medications in myotonic dystrophy patients:

• Antimuscarinics (oxybutynin, tolterodine, solifenacin, fesoterodine) may help urgency symptoms but carry significant risks 4, 5, 2
• Major concern: These medications can worsen myotonia, cause cognitive impairment (already a risk in DM1), worsen constipation (common in DM1), and precipitate urinary retention 5, 2
• Contraindications: Avoid in patients with urinary retention, impaired gastric emptying, or narrow-angle glaucoma 2
• If used, start with lowest doses and monitor closely for adverse effects 2

Step 4: Advanced Interventions

For refractory neurogenic incontinence:

• Botulinum toxin type A (BoNTA) injections into the detrusor muscle 6
• Sacral neuromodulation (SNM) 6
• Intermittent catheterization for mixed retention and incontinence 3

Critical Pitfalls to Avoid

• Do not perform anti-incontinence surgery (midurethral slings, retropubic suspension) in neurogenic incontinence without extensive urodynamic evaluation, as outcomes are unpredictable and complications are higher 1, 4
• Do not use duloxetine or other medications for stress incontinence in neurogenic cases, as they are ineffective and represent wrong treatment for the underlying pathophysiology 4
• Do not skip post-void residual measurement, as missing urinary retention leads to inappropriate treatment that worsens the condition 1, 2
• Do not prescribe antimuscarinics without assessing retention risk, particularly in neuromuscular disorders where bladder dysfunction is multifactorial 1, 2

Monitoring and Follow-Up

• Assess treatment response after 2-4 weeks of behavioral interventions 5, 2
• Use voiding diaries to document frequency, volume, and incontinence episodes 2
• Monitor for medication side effects closely, particularly cognitive changes, constipation, and urinary retention 5, 2
• Reassess post-void residual if symptoms worsen or new voiding difficulty develops 1, 2

Quality of Life Considerations

Treatment decisions must be closely linked to symptom bother and impact on quality of life 1. In myotonic dystrophy patients with limited mobility and cognitive impairment, practical solutions (bedside commode, absorbent products, caregiver assistance) may provide better quality of life than aggressive medical management with significant side effects 5.