Perineal branch of S4

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The perineal branch of S4 is a mixed motor and sensory nerve from the sacral plexus and should not be confused with the perineal branch of the pudendal nerve.

Origin

The nerve originates from the anterior ramus of the 4th sacral nerve root.

Course

The nerve travels inferiorly after exiting the 4th sacral foramina and passes between the levator ani and the iliococcygeus. Following this, it passes into the ischioanal fossa.

Supply
  • puborectalis
  • pubourethralis
  • pubovaginalis
  • cutaneous innervation of the posterior aspect of the ischioanal fossa