Effects of Cauda Equina Syndrome on the Bladder

In this article we explore the effects of cauda equina syndrome on bladder function, which are both complex and distressing for the patient concerned.

The nervous system and bladder function

There are three separate components that control bladder function:

1. Parasympathetic nerve

The parasympathetic nerve supplies control to the detrusor muscle in the bladder wall, which contracts to expel urine, and relaxes the urethral sphincter to allow the urine to pass from the bladder to the urethra.

2. Sympathetic nerve

A second component to the nerve supply to the bladder is via the sympathetic nerve supply. This comes via the hypogastric plexus, which leaves the spinal cord at segmental levels T11 to L3 – i.e. above the cauda equina nerves and conus (the terminal end of the spinal cord).

In most individuals this will be at the L1/L2 spinal vertebral level. The sympathetic nervous system promotes storage of urine by relaxing the detrusor muscle and contracting the internal urethral sphincter to hold the urine within the bladder.

3. Pudendal nerve

A third component of neural control of the bladder is via contraction of the external sphincter of the bladder. This is a muscle under voluntary control and the nerve supplying this is the pudendal nerve which arises from the second, third and fourth sacral nerve roots – i.e. the same nerve roots as the parasympathetic nerve supply.

These different nerve supplies form a complex set of reflex arcs that can control bladder function.

Cauda equina syndrome and bladder function

Cauda equina syndrome causes a lower motor neurone lesion that interrupts the nerve supply forming these nerve arcs, as well as inhibiting the imputing sensory supply coming from the parasympathetic system.

As a consequence, patients who have cauda equina syndrome generally lose both their sensation from the bladder and motor innervation to the bladder. This means they are unable to:

• Sense the increasing volume of the bladder as it distends
• Contract the detrusor muscle and relax the internal (non-voluntary) urethral sphincter to allow the emptying of the bladder

This therefore leads to urinary retention. Once the bladder is filled to its greatest extent, and indeed overfilled, then the pressure within the bladder is greater than that of the urethral sphincter and urine will leak out.

Hence in the early stages there will be urinary difficulties due to inefficient bladder emptying because of parasympathetic nerve compression causing poor detrusor muscle contraction. In the situation is allowed to progress, there will be the development of urinary retention with an enlarged bladder.

Permanent bladder dysfunction

Surgical decompression must be given before the clinical situation is allowed to progress to urinary retention. If medical practitioners fail to achieve this, there may be a case of medical negligence. Contact us to find out more.

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