By Beth Shelly, Melanie Morin & Helena Frawley
Standardization of medical terms improves accuracy and understanding across languages and professions. In addition, accurate and consistent terminology underpins the advancement of research and clinical practice. The recently published International Continence Society report on the terminology for pelvic floor muscle (PFM) assessment (Frawley et al. 2021) outlines terms to describe symptoms, signs, investigations, and diagnoses related to PFM dysfunction. Several of these terms have been a source of variability and confusion in literature to date and are highlighted below.
Pelvic Floor Muscle Tenderness
Tenderness is a sensation of discomfort, or pain. Discomfort elicited through palpation of any tissue indicates increased sensitivity to pressure or touch (Frawley et al. 2021). Higher levels of PFM tenderness have been consistently found in women and men with chronic pelvic pain (CPP) in comparison to asymptomatic controls (Hetrick et al. 2003, Tu et al. 2008, Montenegro et al. 2010, Loving et al. 2014, Hellman et al. 2015). Algometry, a test to assess the pain response to application of blunt pressure, may be useful to objectively assess tenderness, as it quantifies the amount of pressure applied to elicit a particular pain response. To assess PFM tenderness, pain threshold and pain tolerance can be measured while exerting pressure on the perineal/PFM tissue externally or intravaginally. Studies have demonstrated higher sensitivity (lower pressure-pain threshold) in women with CPP compared to asymptomatic controls (Loving et al. 2014, Hellman et al. 2015).
Magnitude of tenderness on palpation (using a numeric rating scale) has been shown to correlate with pressure-pain thresholds and aftersensation measured by algometry; therefore, digital palpation of PFM tenderness may be used by health professionals in the clinic where quantitative sensory testing is unavailable (Hellman et al. 2015). Clinicians should note the location of pressure applied and any referral patterns along with severity of pain on a numeric rating scale (0-10). A tender point is an area of localized tenderness occurring in muscle, muscle-tendon junction, bursa, or fat pad. (Frawley et al. 2021). PFM tenderness may occur with or without changes in PFM tone.
Pelvic Floor Muscle Tone
Tone is characterized as a state of the muscle, usually defined by its resting tension, clinically determined by resistance to passive movement (Bo et al. 2017, Frawley et al. 2021). Tone has an active (electrogenic) component related to neural drive and a passive component reflecting the viscoelastic properties of the pelvic structures. Increased PFM resting tone is often a finding in the assessment of patients with pelvic pain conditions. The current terminology document (Frawley et al. 2021) outlines the specific usage of the term "hypertonicity": this term should only be used in patients with a documented neurological condition, and the term "increased tone" in those patients without a neurological condition. There are several devices being used in the clinic and in research to reliably measure tone: dynamometry, myotonometry, manometry, electromyography, shear-wave elastography. However, the interpretation derived from each PFM tone assessment tool is complex regarding the exact physiological property being assessed. Different tools may assess different aspects of tone, e.g., passive resistance, stiffness, spasm, flexibility, relaxation, and each term have a different meaning (Frawley et al. 2021). Further, different tools may assess different components of PFM tone; different parts and layers of the PFM (superficial versus deep versus both); and some tools may measure a surrogate property of tone, e.g., morphometry, or intra-vaginal/anal pressure. Most tools provide a summative measure of both the active and passive components of tone. Electromyography is the only device able to specifically measure the active component of tone and therefore the term "overactivity" can be assigned when EMG is used (see below). Digital palpation also measures the combination of active and passive tone but has been criticized for its subjectivity (Davidson et al. 2020). Therefore, we suggest when using digital palpation to measure tone, the findings are limited to only ‘increased tone’, ‘normal tone’, or ‘decreased tone’. If more objective assessment of tone is required, the investigations listed above are preferred.
Pelvic Floor Muscle “Trigger Points”
The term "trigger point" has been defined by several authors to refer to a tender point in a taut band (localized increased tone) and a recognized pain referral. Despite widespread use in the pelvic pain literature, there is no clear consensus of the diagnostic criteria associated with trigger points, and the underlying pathophysiological mechanisms remain incompletely understood (Tough et al. 2007, Quintner et al. 2015, Bourgaize et al. 2019). The definition of trigger points encompasses a ‘composite’ finding of two different properties (muscle tenderness and increased muscle tone/tension), therefore
Frawley et al. (2021) recommend rating these properties separately. This clarity of reporting findings will aid re-assessment following intervention, as tenderness may change but not muscle tone, or vice versa.
Overactive PFM / Overactivity in the PFM
Overactive PFM was proposed as a diagnosis in the first PFM Assessment terminology document (Messelink et al. 2005). This term has been used broadly to refer to the finding of increased PFM tone, without distinction as to the source of the increased tone (contractile versus non contractile elements). In the recent standardization document, the term "overactive PFM" is recommended to be used only as a finding of EMG in the case of inconsistent or elevating baseline, or slow de-recruitment. It may occur concurrently with muscle tenderness in the diagnosis of PFM tension myalgia but is not a defining criterion. In other words, it is possible to have PFM tension myalgia without increase in electromyography resting activity suggesting the presence of non-contractile (viscoelastic) increased tone and muscle tenderness. Recognizing the proper usage of the term overactivity may lead to more targeted treatment choices.
This new standardization of terms document calls all health professionals to carefully assess relevant properties of PFM function to become better diagnosticians of PFM dysfunction.
References
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