Strength Duration Test: An Old Tool with New Usefulness

Introduction: Our present inability to fully elucidate pelvic neuropathy has lead to a reconsideration of the strength-duration test (SDT) as a complimentary investigation for Pelvic-floor dysfunction (PFD). Combined with manometric, SDT could discriminate between normal and faecal incontinence patients with a sensitivity and specificity of 95% and 100% respectively.

Aim: The aim of our study was to determine the relationship of SDT with other established measures of anorectal function.

Patients and Methods: Forty-three females undergoing assessment for PFD participated in the study (mean age of 53.3±14.6 years, and mean parity of 8±3). After excluding other causes of incontinence and obstructive defecation, these patients also had SDT.

Results: Logistic regression [logitP ] for the faecal incontinence and constipation subgroups was +0.344 and -0.581 respectively. A negative score indicates normality and a positive score denotes faecal incontinence. This model has a sensitivity of 95% and a specificity of 100%. The strength duration test was repeatable and significant correlations were found between SDT at pulse durations of 0.05ms, 0.1ms, 0.2ms, 0.5ms, 1ms and 2ms with PNTMLT of the right pudendal nerve; and 0.5ms and 1ms for the left pudendal nerve. A significant correlation was also found between SDT at pulse durations of 0.05ms, 0.1ms, 0.5ms, and 1ms with sensation of urgency to stool and maximum tolerated volume. The maximum squeeze pressure showed significant correlation with pulse durations of 20ms, 30ms, 70ms and 100ms.

Conclusion: This minimally invasive and significantly more acceptable procedure provides a simplified and easy to learn technique for the neurological evaluation of PFD.