Figure 3.

(a) Voluntary and involuntary contraction of a healthy subject (woman 18 years old). There is a normal voluntary contraction of the external anal sphincter and puborectal muscle. In addition, there is activation of the anal external sphincter continence reflex and the puborectal continence reflex which regulate the involuntary contractions of the external anal sphincter and the puborectal muscle, respectively 2, 3. (b) Voluntary and involuntary contraction of a patient with pudendal neuropathy (woman 52 years old). The voluntary contractions of both the external anal sphincter and the puborectal muscle are diminished, due to the pudendal nerve damage. However, there is still activation of the anal external sphincter continence reflex and the puborectal continence reflex, which results in normal involuntary contractions.