Search This Blog

Saturday, May 12, 2018

Neurogenic Bladder: UMN vs LMN: Physiology made easy.

Basic Physiology of Micturition

Micturition is a spinal reflex modulated by CNS.
Neural control of micturition.
Source: http://physiologyplus.com/micturition-reflex-steps/

The pre-frontal cortex is responsible for the cognitive control of the micturition which analyses the signals from bladder and conveys signals according to void or not to void depending on the social setting.

The higher control of micturition is mediated by pontine micturition centre (PMC) from where nerve fibre arise and travel along the lateral columns bilaterally. It is the mechanical control of micturition. It coordinates the function of baldder and sphincter.

The Sympathetic fibres are thoracolumbar (T10-L2) outflow of nerve fibres and terminate in the hypogastric ganglion.

The Parasympathetic fibres are sacral (S2-S4) outflow.

The voluntary control over the external urtheral spincter is mediated by somatic fibres of Pudendal nerve. 
Intact Spinal cord is essential for normal micturition as it serves as a intermediate relay between the brain and the sacral center of micturition. Sacral reflex center is the primitive voiding center which is responsible for infants diaper need, since there is a continuous cycle of bladder filling and voiding. The higher mental function gradually enhances in kids as they are growing and accordingly they are trained to use toilet with their enhanced higher mental function.


Sympathetic
ParaSympathetic
Bladder (Detrusor Muscle)
Relaxation
Contraction
Bladder Neck
Contarction
Relaxation

The bladder wall is relaxed and the neck constricted with sympathetic stimulation which allows for retention of urine. The parasympathetic stimulation causes bladder wall to contract and sphincter to relax easing the voiding of urine.

Analogy of Skeletal Muscle contraction and Bladder
Character  UMN Type  LMN Type   Spastic Bladder Flaccid Bladder Tone  Hypertonic (Increased) Hypotonic (Decreased) Volume  Normal or small Large Detrussor contraction  Involuntary intermittent contractions (Overactiity) Absent  (Underactivity)  Pressure  High  Low Incontinence type Urge  Overflow  Symptom Urgency and Frequency  nocturia  Leaking of urine  Dribbling of urine  Erectile edysfunction in men  Retention  Incomplete bladder voiding  (Detrussor-Sphincter Dyssynergia) Uncoordinated bladder contraction and sphincter relaxation Detrusor Aflexia  Conditions  Spinal Cord damage above T12 Cerebrovascular accidents   Spinal cord damage at S2-S4 Peripheral Nerve injury  Acute Stage of spinal cord injury  Cauda Equina, Conus medullaris
LMN vs UMN Lesion : Effect on Bladder

There is a lot of analogy between skeletal muscle contraction and bladder.

In the absence of higher control, overdistension of bladder causes reflex detrusor contraction. Similar to     the muscle stretch reflex mediated by spindle fibre in skeletal muscle.

The upper motor neuron lesion of the brain and the spinal cord causes features similar to that of the UMN lesion of in the muscle characterized by Spastic bladder/ Hypertonic baldder.This is due to the reflex detrusor contraction. There is increased tone of the detrusor muscle. However, the bladder contracts with overdistension, the sphincter does not relax causing bladder sphincter dyssyenrgia. This causes urgency and urge incontinence. The volume of residual urine in the bladder is increased which causes high risk for UTI and chronic renal failure due to obstructive uropathy. The site of the lesion is generally the Spinal cord or pons or higher. There is no gross dilatation of the bladder due to the reflex contraction which results in low volume high pressure inside the bladder.




The lower motor neuron lesion to the fibre supplying bladder causes overflow incontinence. This occurs because bladder is overdistended however the reflex detrusor contraction doesnot comes into play. So what happens is the bladder leaks over time when it is beyond its holding capacity without the detrusor muscle contracting. The bladder is grossly dilated resulting in high vomule and low ressure inside the bladder.This can be described as flaccid or atonic bladder similar to flaccid paralysis of muscles in LMN lesion.The patient cannot initiate the micturition. The site of injury is generally the sacral fibres or peripheral nerve fibres

The last type of neurogenic bladder ocuurs due to injury in the prefrontal cortex which is responsible for social control of micturition. It allows us to find us to micturate in appropriate place. The patient doesnot have the sense of bladder fullness. They have trouble initiating micturition and they micturitate at inappropriate places.

Character
UMN Type
LMN Type

Spastic Bladder
Flaccid Bladder
Tone
Hypertonic (Increased)
Hypotonic (Decreased)
Volume
Normal or small
Large
Detrussor contraction
Involuntary intermittent contractions
(Overactiity)
Absent
(Underactivity)
Pressure
High
Low
Incontinence type
Urge
Overflow
Symptom
Urgency and Frequency
nocturia
Leaking of urine
Dribbling of urine
Erectile edysfunction in men
Retention
Incomplete bladder voiding
(Detrussor-Sphincter Dyssynergia)
Uncoordinated bladder contraction and sphincter relaxation
Detrusor Aflexia
Conditions
 Spinal Cord damage above T12
Cerebrovascular accidents

Spinal cord damage at S2-S4
Peripheral Nerve injury
Acute Stage of spinal cord injury
Cauda Equina, Conus medullaris
  
Source: Davidson, Merck’s Manual, Medscape

10 comments:

  1. Piles can be very much frustrating, but the traditional treatments are even more frustrating. Consider Laser proctology for piles treatment. Piles Doctor in HSR Layout, Koramangala, Bangalore

    ReplyDelete
  2. This comment has been removed by the author.

    ReplyDelete
  3. excellent explanation and the diagram makes it very easy to capture the concept. If i may ask, can you please tell me name of the book from where the diagram is taken.

    ReplyDelete
  4. Thanks for sharing such an amazing post .I am huge fan of your writing skills. If you are looking for design of aluminium doors and windows, you must visit - Eternia Windows.

    ReplyDelete
  5. thanks for sharing amazing info explore real-estate projects at https://home4us.in/

    ReplyDelete