Short notes on the pathophysiology, types and causes of urinary incontinence from a neurological point of view

1. URINARY
INCONTINENCE
Yasser Alzainy
Neurology Resident
AL-AZHAR UNIVERSITY
Faculty of Medicine
Neurology Department

2. INTRODUCTION
• Storage phase = 99%
• Voiding phase = 1%
Bladder Phase

3. NEURAL CONTROL OF THE LOWER URINARY TRACT AND ITS
DYSFUNCTION
• Parasympathetic, sympathetic and somatic
interplay.
• Detrusor muscle - sphincter synergy.
• Brain stem and cortical centers: regulate the
bladder lower urinary tract function
 switch between storage and voiding phase
 percieved bladder fullness & social appropriateness
• The site of the neurologic lesion influences the
pattern of lower urinary tract dysfunction.
Voiding
Learned
behavior
Voluntary
control
Phasic
pattern

4. INCONTINENCE
• Involuntary loss of urine
 Stress incontinence: associated with increased abdominal pressure from (laughing, sneezing,
coughing, climbing stairs)
 Urge incontinence: accompanied by or immediately preceded by urgency.
 Mixed incontinence: stress + urge incontinence.
 Overflow incontinence: retention of urine resulting in involuntary leakage. Impaired detrusor
contractility or bladder outlet obstruction.
 Functional incontinence: inability to hold urine due to reasons other than neuro-urologic and
lower urinary tract dysfunction.

6. VOIDING REFLEX
• A sense of bladder fullness reaches the sensory cortex, and micturition is initiated by descending
pathways from medial frontal micturition centers that activate the voiding, or detrusor reflex. The
detrusor reflex is mediated by intrinsic spinal cord circuits and regulated by the pontine micturition
center and possibly also by cerebellar and basal ganglia pathways.
• The reflex is normally initiated by voluntary relaxation of the external urethral sphincter, which
triggers the inhibition of sympathetics to the bladder neck, causing it to relax, and the activation of
parasympathetics, caushig detrusor muscle contraction. The sensation of urine flow through the
urethra activates continued sphincter relaxation and detrusor contraction. When flow stops, the
urethral sphincters contract, thereby triggering detrusor relaxation through the urethral reflex.
• Flow can also be interrupted at any time by voluntary closure of the urethral sphincter, which similarly
triggers detrusor relaxation.

7. BILATERAL MEDIAL FRONTAL MICTURITION CENTERS
• reflex activation of pontine and
spinal micturition centers when the
bladder is full.
• urine flow and bladder emptying are
normal.
• no voluntary control
• aware or not aware
• Causes:
 hydrocephalus
 parasagittal meningioma
 bifrontal glioblastoma
 traumatic brain injury
 neurodegenerative disorders.

8. BELOW THE PONTINE MICTURITION CENTER AND ABOVE THE
CONUS MEDULLARIS
Acontractile (atonic) bladder
• initially
• bladder is atonic (relaxed / flaccid)
• reflex contractions of the urethral sphincters
• urinary retention and (overflow incontinence)
• increased postvoid residual volume (normal
volume is less than 100 cc).
Hyperreflexic (spastic) bladder
• within weeks / months
• bladder is hyperreflexic
• detrusor-sphincter dyssynergia
• sense of urinary urgency (urge incontinence).
• increased postvoid residual volume (incomplete
emptying, but less than that of acontractile
bladder.

10. PERIPHERAL NERVES, OR OF THE SPINAL CORD AT S2 TO S4
• resembles an acontractile bladder
• Disruption of the voiding reflex arc:
 loss of parasympathetic outflow to the detrusor
 and/or loss of afferent sensory information from the bladder and urethra.
• Overflow incontinence / stress incontinence .

13. REFERENCES
• Continuum, Vol 23.2_Selected Topics in Outpatient Neurology.2017, Urogenital Symptoms in
Neurologic Patients
• Craggs MD, Balasubramaniam AV, Chung EA, Emmanuel AV 2006. Aberrant reflexes and function of the
pelvic organs following spinal cord injury in man. Auton Neurosci 126-127: 355-370.
• Fowler C, DasGupta R. 2007. Neurological causes of bladder, bowel, and sexual dysfunction. In
Neurology in Clinical Practice: Principles of Diagnosis and Management, WG Bradley RB Daroff, GM
Fenichel and CD Marsden (eds.), 5th Ed., Chapter 31. Butterworth-Heinemann, Boston.
• Sung VW. 2009. Urinary incontinence. Med Health R 192 (1): 16-19.
• Sandip P Vasavada, Edward David Kim, Urinary Incontinence. Medscape, Sep. 2019.

14. Thank you