Detection of individual motor units of the puborectalis muscle by non-invasive EMG electrode arrays.

PURPOSE: The purpose of the study was to demonstrate that anatomical features of individual motor units of the puborectalis muscle can be detected with non-invasive electromyography (EMG) and to evaluate differences in electrophysiological properties of the puborectalis muscles in a small group of healthy and pathologic subjects. METHODS: Multichannel EMG was recorded by means of a flexible probe applied on the gloved index finger and carrying an array of eight equally spaced (1.15 mm) electrodes. A multichannel EMG amplifier provided seven outputs corresponding to the pairs of adjacent electrodes. Tests were performed in three different positions (dorsal, left and right) over the puborectalis muscle on 20 subjects (nine healthy, seven constipated and four incontinent patients). Motor unit action potentials (MUAPs) generated at the innervation zone of a MU and propagating along the muscle fibers generated repetitive characteristic patterns on the seven output channels allowing identification of anatomical features of the motor units. RESULTS: MUAPs were observed travelling in either one or both directions with the array in dorsal position, and mainly in ventral-to-dorsal direction in either lateral position. MUAP amplitude was lower in constipated and incontinent patients with respect to healthy subjects. The conduction velocity estimated on the identified MUAPs was lower for constipated patients with respect to healthy subjects suggesting different mechanical properties of the active motor units. CONCLUSIONS: This technique allows the extraction of relevant information about the anatomical features (innervation zone position and overlapping of motor unit branches) of the puborectalis muscle and its electrophysiological properties and maybe can be applied as an novel methodology for assessing the anorectal function in patients.

Responses of anal constipation to biofeedback treatment.

OBJECTIVE: Biofeedback is considered an effective treatment for anal constipation, but a substantial proportion of patients fail to improve. Our aim was to identify the key predictors of outcome using a comprehensive standardized evaluation of anorectal function. MATERIAL AND METHODS: We retrospectively analysed the clinical and physiological data of 148 patients consecutively treated for constipation due to functional outlet obstruction by biofeedback. Clinical evaluation was performed by means of a structured questionnaire. Anorectal evaluation included anal pressure, neural reflexes, defecatory dynamics, rectal compliance, rectal sensitivity and balloon expulsion test. Biofeedback treatment was performed using a manometric technique. The clinical response to biofeedback treatment was evaluated as good (improvement of constipation) or poor (no improvement or worsening). RESULTS: Of the 148 patients included, 112 (86 F, 26 M; age range 8-67 years) were followed-up for between 1 and 44 months, and 66% had a good response to treatment. The response depended on the severity of the defecatory dysfunction. Thus, lack of anal relaxation during straining and inability to evacuate a 1 ml intrarectal balloon were inversely related to physiological variables related to therapeutic success. Among the 49 patients with absent anal relaxation, 51% had a good response to treatment (versus 78% in patients with partial relaxation; p < 0.01), and among the 29 patients with failed balloon expulsion, 48% responded to treatment (versus 74% in patients able to evacuate > or = 1 ml intrarectal balloon; p < 0.05). CONCLUSIONS: Even in the presence of negative predictors, biofeedback is a valuable treatment option in a substantial proportion of constipated patients.

Predictors of response to biofeedback treatment in anal incontinence.

PURPOSE: Biofeedback is considered an effective treatment for anal incontinence, but a substantial proportion of patients fails to improve. The purpose of this study was to identify the key predictors of outcome. METHODS: We retrospectively analyzed the clinical and physiologic data of 145 patients consecutively treated in our unit for anal incontinence by biofeedback. Clinical evaluation was performed by means of a structured questionnaire that included previous history, symptoms of incontinence, and bowel habit. Anorectal evaluation measured anal pressure profiles, neural reflexes, defecatory dynamics, rectal compliance, and rectal sensitivity. Biofeedback treatment was performed by a manometric technique with reinforcement sessions scheduled every three months and daily exercising at home. Six months after the onset of biofeedback treatment the clinical response was evaluated as good (improvement of incontinence) or poor (no improvement or worsening). RESULTS: Of 126 patients (104 female; age range, 17-82 years) with at least six-month follow-up, 84 percent had a good response to treatment. By univariate analysis, several factors, such as age, history of constipation, abnormal defecatory maneuver, and rectal compliance, were significantly related to treatment response, but by multivariate logistic regression only age and defecatory maneuver were independent predictors of the response. The association of both factors provided the best sensitivity and specificity; 48 percent of patients younger than age 55 years and with abnormal defecatory maneuver had negative response to treatment, whereas 96 percent of patients age 55 years or older with normal defecatory maneuver had a positive response. CONCLUSION: In patients with anal incontinence scheduled for biofeedback treatment, potential alterations of defecation should be first searched for and corrected, particularly in younger patients.

Significance of pelvic floor muscles in anal incontinence.

BACKGROUND & AIMS: The pathophysiology of anal incontinence may be elusive using current parameters. Our aim was to establish the role of the levator ani in anal continence. METHODS: In 53 patients with anal incontinence, 30 with constipation as disease controls, and 15 healthy controls, we evaluated incontinence severity by a 0-12 scale, anorectal function by standard manometric tests, and levator ani contraction by a perineal dynamometer. RESULTS: Patients with incontinence exhibited various physiologic abnormalities (3.2 +/- 0.3 per patient), but multiple regression analysis showed that levator ani contraction was the independent variable with strongest relation to the severity of incontinence (R = -0.84; P < 0.0001), as well as a predictive factor of the response to treatment (R = 0.53; P < 0.01). Furthermore, in contrast to other physiologic parameters, clinical improvement in response to treatment (4.4 +/- 0.5 score vs. 7.9 +/- 0.5 score pre; P < 0.001) was associated with a marked and significant strengthening of levator ani contraction (448 +/- 47 g vs. 351 +/- 35 g pre; P < 0.05). CONCLUSIONS: We have shown the importance of levator ani failure in understanding the etiology of anal incontinence and in predicting response to treatment.