Surface electromyography biofeedback of pelvic floor musculature in the treatment of urinary incontinence.

Urinary Anatomy and Physiology

The lower urinary tract includes the distal portions of the ureters and their ureterovesical junction at the detrusor muscle. The detrusor is a smooth muscle that forms the bladder wall and provides the propulsive force that expels urine through the urethra. Smooth and striated urethra muscles are part of the lower urinary system. The pelvic floor muscles connect to and support the bladder neck, and the vaginal and the anal canal, and they have significant influence on bladder control.

A complex set of learned and reflexive control mechanisms govern the functions of urine storage and micturation. At maturity, micturition is coordinated at several levels of the nervous system, extending from the frontal lobe and sensorimotor cortex to the peripheral nervous system. Normal bladder function depends upon the integrative functions of the frontal lobes, the sensorimotor cortex, the thalamus, the hypothalamus, the basal ganglia, the cerebellum, specific centers in the brain stem, the spinal cord, nerve roots, and the peripheral nerves.

The process of urine storage and micturation also involves efferent and afferent activity from the sympathetic and parasympathetic branches of the autonomic nervous system. When experiencing a need to urinate, the sympathetic and somatic activities diminish and parasympathetic activity increases, causing detrusor contractions. The brain stem and cortical centers mediate these peripheral processes. With learning, the cerebral and cerebellar influences come to maintain continence. During filling, the pressure within the bladder must remain low compared to urethral pressure.

Disruption of the low intravesical pressure by bladder noncompliance can lead to urine overflow. The base of the bladder is the bladder neck, or trigone, which is flat during urine storage and forms a funnel during voiding. The integrity of the vesicourethral angle during storage provides a barrier to urine loss when pressure is transmitted to the bladder and the bladder neck through activities that increase intraabdominal pressure, such as laughing, coughing, sneezing, standing, and lifting. The proper functioning of the bladder neck depends on urethral pliancy, anatomic placement of the bladder neck, and support of the levator ani muscle.

Smooth muscle comprises the innermost layers of the bladder neck and the proximal urethra. Appropriate functioning of the urethra depends on the integrity of these smooth muscles. Striated muscles in the distal one-third of the urethra, periurethral area, and levator ani complex are critical for bladder support and urethral closure.

Collagen and elastin connective tissue within the urethral tissue are critical in maintaining the compliance of the urethral lumen for purposes of closure.  Vascular, epithelial, and hormonal factors also play an important role in the compliance of the urethra. Finally, all of these peripheral factors are interdependent with both central and peripheral nervous system factors that control their functions the predominant inhibitory control over bladder contractions.

Clinical Assessment of Urinary Incontinence

Assessment of urinary incontinence requires a physical examination, including an abdominal exam to detect masses, suprapubic tenderness or fullness, an estimation of urinary flow and postvoid residuals, perineal skin, atrophy, prolapse, pelvic mass, paravaginal muscle tone, urethral hypermobility, and bladder neck angle. A rectal exam should be conducted for perineal sensation, sphincter tone, bulbocavernosis reflex, fecal impaction, rectal mass, and prostate status in men. If indicated, a general exam should be conducted to detect edemetous conditions and neurological abnormalities.

Additional testing may include postvoid residual (PVR) estimation, provocative stress testing, urinalysis, urine cytology, testing for blood urea nitrogen (BUN), voiding record, evaluation of environmental and social factors, and observation of urination to detect hesitancy and straining. Specialized testing may include uroflow, cystometry, urodynamics, urethral pressure profilometry (UPP), endoscopy, and upper and lower urinary tract imaging. In addition, pelvic floor muscle external urethral sphincter surface electromyography (sEMG) has been demonstrated to be clinically reliable and predictively valid in identifying subtypes of urinary incontinence, and therefore should be a standard part of an initial evaluation for voiding dysfunctions.

Biofeedback

In the office practice of biofeedback, it is important that patients are fully medically evaluated prior to initiating treatment so that by history and examination all physiological, anatomical, pharmacological, and neurological factors can be identified and appropriately treated or ruled out. It has been claimed that external urethral and anal sEMG-assisted biofeedback is a noninvasive, benign intervention, and therefore cannot be contraindicated and does not require prior medical consultation. However, this author strongly believes in requiring patients to undergo appropriate medical evaluation prior to initiating biofeedback, as failure to do so may lead to a delay in the identification and appropriate treatment of medical conditions, including degenerative neurological diseases such as diabetic neruopathy or multiple sclerosis, a wide range of infectious diseases, or even the identification of potential malignancies, all of which may manifest as voiding disorders.

Biofeedback Application to Urinary Incontinence

Biofeedback is a self-regulation training technique derived from well-established principles of human learning. Biofeedback is a technique, not a stand-alone treatment, which is one component of a behavioral training program to facilitate acquisition of pelvic floor muscle control and other continence skills. With the use of biofeedback, physiological change can be achieved by means of operant conditioning, a type of learning that occurs as a result of feedback, or the experience and awareness of the consequences of actions to be brought under voluntary control.

For biofeedback to be effective, several prerequisites must be met. There must be a measurable response functionally related to the symptoms under treatment, in this case the sEMG response of the external urethral/anal sphincters. This response must have variability and a perceptible sensory cue associated with this variability, in this case the ability to sense changes in the activity level of the sphincter muscle. Also, the patient must have the ability to voluntarily change the status of the measured response; that is, to voluntarily contract and relax the external sphincters.

Finally, since biofeedback is an active process of learning, in this case sphincter neuromotomotor control, it requires an attentive and motivated patient.

State of the Art and a Call for Standardization and Research

The true efficacy and appropriate application of these procedures remain hotly contested because the validity and reliability of these studies have been severely hampered by the total lack of standardization in technology and application as well as training standards. It is all but impossible to run replicable, controlled studies to determine the comparative efficacy of sphincter SEMG biofeedback in the absence of any universal operationally defined standards of technology and protocols.

Standards must define:

1) Type and location of measurement, such as perianal surface patch sensors versus intravaginal/intraanal sensors and sensor size, location, orientation, impedence, stability, and response to environmental noise and material construction.

2) Instrumentation and signal processing characteristics, such as analog to digital conversion rates, preamplification/amplification signal to noise ratio, gain, common mode rejection, input impedance, bandwidth, and frequency domain analysis availability

3) The diagnostic and rehabilitative protocols, or a fixed sequence of reflexive and/or voluntary muscle activation and deactivation events; operationally defined measurements of those events, such as signal amplitude, latency, variability and spectral frequency; and specification of rehabilitative protocols, such as the use of home trainers for monitoring daily prescribed pelvic floor muscle exercises.

4) Training of personnel is another critical variable that, for the first time, is undergoing standardization with the recent pelvic floor muscle biofeedback certification criteria set forth by the Biofeedback Certification Institute of America (BCIA). Only through the development of these operationally defined standards will we be able to conduct the research necessary to fully understand the role of pelvic floor muscle sEMG biofeedback in the diagnosis and treatment of lower urogenital tract and gastrointestinal disorders such as incontinence. In the meantime, best clinical practice standards demand that practitioners seek ongoing education/training and supervision to make the best possible informed decisions on the appropriateness and methods of application of this procedure to their clients.

Howard I. Glazer, PhD, is clinical associate professor of psychology in psychiatry, and of obstetrics and gynecology at Cornell University Medical College/New York Presbyterian Hospital.