What is the pathophysiology of reflex urinary incontinence?

Updated: Mar 19, 2019
  • Author: Sandip P Vasavada, MD; Chief Editor: Edward David Kim, MD, FACS  more...
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Answer

Reflex incontinence is due to neurologic impairment of the central nervous system. Common neurologic disorders associated with reflex incontinence include stroke, Parkinson disease, and brain tumors. Reflex incontinence also occurs in patients with spinal cord injuries and multiple sclerosis. When patients with suprapontine or suprasacral spinal cord lesions present with symptoms of urge incontinence, this is known as detrusor hyperreflexia.

Spinal cord injuries interrupt the sacral reflex arc from the suprasacral spinal cord, cerebral cortex, and higher centers. These pathways are crucial for voluntary and involuntary inhibition. In the initial phase of spinal cord injury, the bladder is areflexic and overflow incontinence results. Later, detrusor hyperreflexia usually is found upon urodynamic evaluation.

In multiple sclerosis (MS), demyelinating plaques in the frontal lobe or lateral columns can produce lower urinary tract disorders. Incontinence may be the presenting symptom of MS in about 5% of cases. Approximately 90% of individuals with MS experience urinary tract dysfunction during the course of the disease.

A summary of the published series of urodynamic findings in MS demonstrated that in patients with lower urinary tract dysfunction, the most common urodynamic diagnosis is detrusor hyperreflexia (62%). Detrusor-sphincter dyssynergia (25%) and detrusor hyporeflexia (20%) also are common. Obstructive findings are much more common in males. Of note, the urodynamic diagnosis may change over time as the disease progresses. [23]

Hemorrhage, infarction, or vascular compromise to certain areas of the brain can result in lower urinary tract dysfunction. The frontal lobe, internal capsule, brainstem, and cerebellum commonly are involved sites. Initially, urinary retention due to detrusor areflexia is observed. This may be followed by detrusor hyperreflexia.

Approximately 40-70% of patients with Parkinson disease have lower urinary tract dysfunction. Controversy exists as to whether specific neurologic problems in patients with Parkinson disease lead to bladder dysfunction or if bladder symptoms simply are related to aging. The extrapyramidal system is believed to have an inhibitory effect on the micturition center; theoretically, loss of dopaminergic activity in this area could result in loss of detrusor inhibition.

In patients with dementia, incontinence and urinary tract dysfunction may be due to specific involvement of the areas of the cerebral cortex involved in bladder control. Alternatively, incontinence may be related to global deterioration of memory, intellectual capacity, and behavior. Urodynamically, both detrusor hyperreflexia and areflexia have been found.

CNS neoplasms may result in incontinence. Tumors of the superior medial frontal lobe, spinal cord tumors above the conus medullaris, and cervical spondylosis can cause detrusor hyperreflexia.


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