Psychophysical evidence of nociceptor sensitization in vulvar vestibulitis syndrome

Vulvar vestibulitis syndrome (VVS) is a long lasting disorder of superficial dyspareunia in young women. Quantitative sensory testing, including mechanical and temperature pain thresholds and warm/cold difference limen (WCL), was performed in the vestibular mucosa in 22 women (mean age 25.0 years) with vestibulitis and 20 control subjects (mean age 25.6 years). The tests were carried out on days 7-11 of the menstrual cycle. Patients had allodynia to mechanical testing with von Frey filaments, 14.3+/-3.1mN in the symptomatic posterior area as compared with 158+/-33.5mN in healthy subjects, P<0.0001. The pain threshold to heat was 38.6+/-0.6 degrees C in patients and 43.8+/-0.8 degrees C in controls, P<0.0001. In addition, pain threshold to cold was 21.6+/-1.2 degrees C in patients whereas cooling down to 6 degrees C was usually not painful in controls. WCL was 4.9+/-0.5 degrees C in patients and 9.6+/-1.5 degrees C in healthy subjects, P<0.01. The results are compatible with the hypothesis that patients with VVS have an increased innervation and/or sensitization of thermoreceptors and nociceptors in their vestibular mucosa.