Bladder Neck Dyssynergia
Bladder neck dyssynergia is an active, involuntary contraction or failure of relaxation of the smooth muscle at the bladder neck during detrusor contraction, resulting in functional bladder outlet obstruction. 1, 2
Pathophysiology
The condition involves alpha-adrenergic mediated smooth muscle activity at the bladder neck that creates higher pressures at the bladder neck than in the bladder itself during voiding attempts. 2
This dyssynergia is dependent on alpha-1 postsynaptic and alpha-2 presynaptic adrenoreceptors, distinguishing it from the striated muscle dysfunction seen in detrusor-external sphincter dyssynergia. 2
The mechanism represents accentuated sympathetic nervous function rather than organic fibrosis, particularly in patients with increased alpha-receptor density or sympathetic hyperactivity. 1
Clinical Context and Associations
Bladder neck dyssynergia occurs predominantly in neurogenic bladder patients, particularly those with spinal cord injury at or above the mid-thoracic level. 3, 4, 2
Among spinal cord injury patients, 25 of 34 (74%) demonstrated active bladder neck dyssynergia with concomitant detrusor-external sphincter dyssynergia. 2
The condition is especially common in patients with complete spinal cord lesions at any level and those with high incomplete lesions above T-9. 3
In non-neurogenic bladder patients, bladder neck dyssynergia is rare and primarily occurs in cases with trapped benign prostatic hyperplasia or incomplete neurological lesions, not in isolated bladder neck contracture. 1
Diagnostic Characteristics
Video urodynamic studies (VUDS) with microtip transducer catheters positioned at the bladder neck demonstrate pressures higher at the bladder neck than in the bladder during detrusor contraction. 5, 1, 2
The dyssynergia is most prominent at the beginning and ending of micturition, but typically not at maximum flow. 1
Fluoroscopy during urodynamics permits direct visualization of bladder neck abnormalities and helps distinguish the specific site of obstruction. 5
Electromyography (EMG) combined with cystometry helps differentiate bladder neck dyssynergia (smooth muscle) from detrusor-external sphincter dyssynergia (striated muscle). 5
Pharmacologic Confirmation
Alpha-blocker administration (such as terazosin or phentolamine) abolishes or significantly reduces bladder neck dyssynergia, confirming its alpha-adrenergic mediated mechanism. 1, 2
Pudendal nerve blocks eliminate detrusor-external sphincter dyssynergia but do not affect bladder neck dyssynergia, demonstrating the distinct smooth muscle etiology. 2
The response to alpha-blockade is particularly pronounced in patients with associated autonomic hyperreflexia. 2
Clinical Consequences
Bladder neck dyssynergia causes voiding dysfunction with elevated detrusor pressures, incomplete bladder emptying, increased post-void residuals, and risk of upper urinary tract damage. 6, 4
Patients may present with autonomic dysreflexia episodes, which resolve after successful treatment of the bladder neck obstruction. 4
The condition contributes to urinary retention, recurrent urinary tract infections, and deterioration of bladder compliance over time. 5, 6
Treatment Implications
Transurethral incision of the bladder neck (TUI-BN) effectively treats bladder neck dyssynergia in high-level spinal cord injury patients, with 86% achieving spontaneous voiding and 88% resolution of autonomic dysreflexia. 4
In patients with complete spinal cord lesions or high incomplete lesions (above T-9), combined external sphincterotomy and bladder neck resection provides optimal outcomes. 3
For patients with low incomplete lesions (T-9 and below), bladder neck resection alone is typically sufficient. 3
Alpha-blocker therapy represents a pharmacologic alternative for managing bladder neck dyssynergia, particularly in non-surgical candidates. 5, 1
Important Clinical Pitfalls
Do not confuse bladder neck dyssynergia with detrusor-external sphincter dyssynergia—they involve different muscle types (smooth versus striated) and require different diagnostic and treatment approaches. 5, 2
Bladder neck dyssynergia is not a major factor in non-neurogenic bladder neck contracture; organic fibrosis predominates in those cases. 1
After treating external sphincter dyssynergia alone, secondary bladder neck obstruction frequently develops and requires additional intervention. 7, 3
Risk stratification is essential before any bladder outlet procedure, as increasing outlet resistance in patients with poor bladder compliance can elevate storage pressures and damage the upper urinary tracts. 5