Experimental pain sensitivity in women with vestibulodynia: a pilot study

Laura A. Frey Law, Department of Physical Therapy and Rehabilitation Science, University of Iowa, Iowa City, Iowa
Avery M. Whitis, University of Iowa Carver College of Medicine, Iowa City, Iowa
Colleen K. Stockdale, University of Iowa Hospitals and Clinics, Department of Obstetrics and Gynecology, Iowa City, Iowa


Objective: Investigate pain sensitivity in women with vestibulodynia using two experimental pain assessments outside the vulvar region: intramuscular infusion of an acidic phosphate buffer and pressure pain thresholds (PPTs) of the lower limb.

Methods: Three women with a history of vestibulodynia (all 24 years) participated after providing written informed consent. PPTs of the lower limb were assessed using a hand-held Somedic digital algometer (30 kilopascal (kPa)/sec) at baseline (pre-infusion) and during the intramuscular infusion. The acidic phosphate buffer (pH 5.2) was infused into the anterior tibialis muscle at a rate of 40 ml/hr for 15 min (10 ml total). Peak local (infusion site) and referred (ankle) pain ratings were assessed verbally, as well as vulvar pain at the time of the infusion (0 – 10 Borg Scale).

Results: Peak local pain was higher in two of the three subjects (2.5, 4.0, 9.5) than the average pain ratings in 34 healthy age-matched (21 – 27 yrs.) women from our laboratory, mean 3.0/10 (standard deviation (SD) 2.2; range 0.5 to 10). Peak referred pain was also higher in the same two subjects (0, 4.25, and 7.5) than the average of the controls (mean 1.5; SD 1.8; range 0 – 9.0). Similarly, vulvar pain patients all exhibited greater mechanical pain sensitivity (lower PPT values) than the average of the healthy controls (mean [SD] 246.3 [101.7] kPa in patients vs. 431.3 [109.33] in controls).

Conclusion: Preliminary data suggests women with vestibulodynia may exhibit greater generalized pain sensitivity to noxious stimuli than the general population of women.