Posterior femoral cutaneous nerve
The posterior femoral cutaneous nerve, also known as the posterior cutaneous nerve of the thigh, is a sensory branch of the sacral plexus. It arises from anterior and posterior divisions of anterior rami of S1, S2 and S3 nerves. It supplies the skin of the posterior thigh, buttock and the posterior scrotum/labia.
Interestingly, it provides the greatest surface area of supply of any cutaneous nerve .
The posterior femoral cutaneous nerve is one of six branches directly off the sacral plexus, prior to its convergence into anterior and posterior divisions. It arises from the posterior divisions of the anterior rami of S1 and S2 nerves and the anterior divisions of anterior rami of S2 and S3 nerves.
It initially emerges lateral to the anterior sacral foramina and lies upon the psoas muscle, underneath the muscle’s parietal pelvic fascia. It travels laterally into the greater sciatic foramen, where it exits the pelvis below the piriformis muscle.
Within the gluteal region, the nerve is situated underneath the gluteus maximus muscle, and overlies the sciatic nerve. It descends superficial to the long head of biceps femoris in the posterior thigh, where it is deep to fascia lata. The fascia is pierced by the nerve in the popliteal fossa, and it terminates with twigs joining the sural nerve.
Branches and supply
It has three branches:
- the cutaneous branch supplying the posterior thigh travels in a plane between the hamstrings and overlying fascia lata; it courses down the back of the thigh in the midline, with perforating branches providing cutaneous innervation; it terminates as low as mid-calf, at the lower end of the bellies of gastrocnemius; its cutaneous supply terminates at the skin of the popliteal fossa
- the gluteal branch, also known as the inferior cluneal nerve, and is derived from posterior divisions of the S1 and S2 anterior rami and it supplies the skin over the inferior half of the buttock
- the perineal branch advances medially to supply the posterior part of the scrotum or labia majora; it courses between the gracilis and overlying fascia lata toward its cutaneous distribution
Several other structures exit the greater sciatic foramen below the piriformis muscle with the posterior femoral cutaneous nerve superior to the sciatic nerve. It descends in close proximity to the inferior gluteal artery and nerve. The nerve to obturator internus, the pudendal nerve and internal pudendal artery also travel below the piriformis muscle.
The posterior femoral cutaneous nerve can also have contributions from the S4 nerve root. In one study, it was noted that in 18% of cadavers the nerve can be found as a duplicated structure .
The posterior femoral cutaneous nerve shares the same nerve segments as pelvic parasympathetic nerves (S2/3). Therefore pain from pelvic pathology can be referred to the posterior thigh, and may be confused with other pathology such as sciatica. It may be involved in pelvic pain syndrome .