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The Neurology of Bladder Incont...

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Losing it - How we Micturate Properly



Rendean's questions about her urogynecologist's statements made me realize that we need a good explanation of the very complicated way in which we control urination. So, this is a condensed description of the process and then in a later installment, a description of my current experiences with Bladder Physical Therapy.


(Disclaimer - the actual act of urinating in a nutshell is NOT recommended. Experience shows that this results in a large cleanup and the uttering of bad words.)

The brain is the master controller of the process of micturition - known outside the medically uppity world as urination. The bladder is supposed to be submissive to the power of the brain.

The cycle of urination begins with the bladder filling up. This is passive as the bladder quietly receives the urine produced by the kidneys. The great bladder wall muscle, the Detrusor - has a low tone and allows the filling and stretching of the bladder to hold a normal amount of urine. At the same time the external sphincter keeps a high tone squeezing the urethra closed. As long as the tone in the sphincter is higher than that of the bladder wall, the detrusor, you are continent. (Other continents are Europe, Africa, North and South America, Australia, Asia and Antarctica)

When the bladder is appropriately full the stretch receptor of the detrusor muscle sends a signal to the pons. The pons is part of the brainstem and houses the Pontine Micturition Center, the PMC. The PMC is a major coordinator of all the things that need to happen to stay continent. (see above) Think of the PMC as a set of relay switches. The PMC relays the signal of bladder fullness to the brain, specifically to the Micturition Control Center in the frontal lobe of the brain. The purpose of this center is to cause you and me to be aware of the need to urinate. The brain at the same time sends screaming signals to the bladder, via the PMC, to "hold on" and wait until we find a socially acceptable time and place to relieve ourselves. This is where we recognize that a nutshell, a theater seat or the dance floor is not "the right place." This part of the cycle is completely under the control of the normal person. (Meanwhile I am headed toward the nearest bathroom at a discouraging slow, lurching place looking longing at all nutshells, purses and planters and 'woe be' if I am hurrying through a department store's cookware section!)

As infants the nervous system is immature, and the PMC does not communicate with the brain. So the cycle of filling is followed immediately and involuntarily by emptying. The brain's recongnition of the signal of fullness from the PMC shows up typically by the age of 3 to 5 years and allows successful toilet training.

Upon arriving at said socially acceptable place and removing the necessary layers of clothes, the brain then sends out the "voluntary" signal to let it all out. This signal goes to the pontine center which sends out signals for the urinary sphincter to relax and for the detrusor muscle to contract and expel the urine. This is to happen easily and full emptying to occur forthwith. A relieved *sigh* is optional. Necessary layers are then reassembled and the cycle begins again. (and again....and again....)

Neurogenic Bladder

Quote: "Neurogenic bladder is a term applied to a malfunctioning urinary bladder due to neurologic dysfuntion or insult...Symptoms of neurogenic bladder range from detrusor (bladder muscle) underactivity (low tone) or overactivity (high pressures), depending on the site of neurologic injury....

MS and the Urinary Bladder

MS is most likely to affect the smooth process of urination by damage to the brainstem or the spinal cord, but a lesion anywhere along the route from the bladder to the sacral nerves to the spinal cord to the PMC to the brain will disturb the whole cycle. With a spinal cord lesion the person will experience a spastic bladder most typically. This is called Detrusor Hyperrflexia or DH. Spastic bladders have high resting pressures. They have "urge incontinence" because the high pressure in the bladder exceeds the pressure in the sphinctor as the spasm of the bladder becomes worse. This is when the bladder empties too quickly and too frequently with the brain not being allowed to play its rightful role. We may feel an overwhelming need to urinate and begin to look favorably on our briefcase, purse or an innocent nutshell. But, in MS it is also common to have spasms in the sphincter as well. If both the bladder and the sphincter spasm at the same time we won't be able to empty the bladder effectively because the sphincter is tight also. The net result may be retention of urine - a common endpoint in persons with MS. This loss of coordination between the bladder and the sphincter is called Detrusor-Sphincter Dyssynergia, DSD. The normal synergy of bladder contraction coupled with sphincter relaxation is lost.

Some people may assume that severe urinary retention is always caused by a bladder that cannot contract, a floopy bladder, but in MS this is not usually the case.

This article states that between 50% and 90% (depending on the studies) of people with MS who have urinary problems will have Detrusor Hyperreflexia (high tone in the bladder). The typical location of MS damage is in the posterior and lateral columns of the spinal cord. There is a poor correlation between symptoms and what is actually happening. As my urogynecologist stated, "The MS bladder is a poor historian." Along with the findings of excessive pressures in the detrusor muscle, about 50% will also have the discoordination with relaxation of the sphincter. This is called Detrusor Sphincter Dyssynergia - Detrusor Hyperreflexia or DSD-DH

Now, among people with MS who have urinating troubles (beyond the errant desire to pee into nutshells) 20% to 30% will have an areflexic bladder ("a-" meaning "without"). This is called Detrusor Areflexia or floppy bladder. The sphincter my be normal, spastic or weak.

Any questions?


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