Spastic bladder

A spastic bladder, also known as a reflex bladder or automatic bladder, is a form of neurogenic bladder—a condition where bladder function is disrupted due to damage to the nervous system. Specifically, a spastic bladder is caused by a lesion or injury to the spinal cord that occurs above the sacral voiding reflex center (typically at or above the T12 vertebra).

This injury severs the communication between the brain and the bladder. While the bladder's local reflex to empty itself remains intact, it is no longer under voluntary control from the brain. The result is a bladder that contracts automatically and uncontrollably once it fills to a certain point.

Neurological Basis: Upper Motor Neuron Lesion

Normal urination is a coordinated process involving the brain, spinal cord, and bladder. The brain gives conscious permission for the bladder muscle (the detrusor) to contract while simultaneously telling the sphincter muscles to relax.

In a spastic bladder, the injury is to the upper motor neurons (UMN). This means:

1. Brain Control is Lost: The brain can no longer receive sensations of fullness from the bladder, nor can it send signals to inhibit or permit urination. This leads to a loss of bladder control and sensation.
2. The Reflex Arc is Intact: The local reflex arc located in the sacral region of the spinal cord (S2-S4) remains functional. When the bladder stretches as it fills with urine, it triggers this reflex automatically, causing the detrusor muscle to contract.
3. Detrusor-Sphincter Dyssynergia (DSD): A common and serious problem in spastic bladder is the loss of coordination between the bladder muscle and the external sphincter muscle. The detrusor muscle contracts to empty, but the sphincter also contracts at the same time, essentially closing the outlet. This creates a functional obstruction.

This uninhibited, uncoordinated reflex activity leads to the characteristic symptoms of a spastic bladder.

Symptoms and Complications

The key signs of a spastic bladder are:

• Urge Incontinence: Frequent, involuntary leakage of urine as the bladder contracts without warning.
• Urinary Frequency: The bladder contracts when only small amounts of urine are present, leading to the need to void often.
• Incomplete and Interrupted Voiding: Due to detrusor-sphincter dyssynergia, the bladder cannot empty completely, even during an involuntary contraction. Urine flow may be weak or stop and start.
• High Bladder Pressures: The bladder muscle contracting against a closed sphincter generates dangerously high pressures inside the bladder. This is the most serious complication, as it can cause urine to back up into the kidneys (vesicoureteral reflux), leading to kidney damage, infections, and even kidney failure.

Causes

Any condition that damages the spinal cord above the sacral level can cause a spastic bladder. Common causes include:

• Spinal Cord Injury (SCI): Traumatic injury is the most frequent cause.
• Multiple Sclerosis (MS): Demyelination in the spinal cord disrupts nerve pathways.
• Spinal Tumors: A growth that compresses the spinal cord.
• Stroke: Damage to the motor control centers in the brain.
• Transverse Myelitis: Inflammation of the spinal cord.

Comparison with Flaccid Bladder

It is crucial to distinguish a spastic bladder from a flaccid bladder, as their causes and management are very different.

Feature	Spastic Bladder (UMN Lesion)	Flaccid Bladder (LMN Lesion)
Cause	Injury above the sacral spinal cord.	Injury at the sacral spinal cord or the nerves leaving it.
Bladder Muscle	Hyper-reflexive; contracts involuntarily (spastic).	A-reflexive; cannot contract (flaccid, floppy).
Primary Symptom	Urge incontinence; frequent, small voids.	Overflow incontinence; bladder overfills and leaks.
Bladder Pressure	Often high and dangerous.	Low.
Bladder Capacity	Small.	Large.

Management and Treatment

The primary goals of treatment are to protect the kidneys by keeping bladder pressures low, prevent urinary tract infections (UTIs), and achieve social continence.

• Clean Intermittent Catheterization (CIC): This is the cornerstone of management. A catheter is inserted into the bladder at regular intervals (typically every 4-6 hours) to drain it completely. This prevents overfilling, keeps pressures low, and reduces the risk of incontinence and UTIs.
• Anticholinergic Medications: Drugs like oxybutynin and tolterodine are used to relax the detrusor muscle, reducing the frequency and intensity of spasms. This increases the bladder's capacity to store urine between catheterizations.
• Botulinum Toxin (Botox®) Injections: Botox can be injected directly into the detrusor muscle via a cystoscope. It is highly effective at relaxing the bladder muscle, reducing spasticity and high pressures for several months.
• Surgical Options: In severe cases that do not respond to other treatments, surgery may be considered. This can include procedures to enlarge the bladder (augmentation cystoplasty) or to create a urinary diversion (urostomy).