Sacral Plexus

PowerPoint Presentation

Sacral Plexus Presented By:

Amitinder Singh Dhaliwal BPT IV, Roll No. 3171 Department Of Physiotherapy Punjabi University, Patiala

Spinal nerves and plexus There are 31 pairs of spinal nerves. 2. 8 cervical 3. 12 thoracic 4. 5 lumbar 5. 5 sacral 6. 1 coccygeal

Formation of a Spinal nerve and subsequent division

Ø A spinal nerve exits the spinal cord and divides into a dorsal ramus and a ventral ramus. Ø The dorsal ramus of C1 is located in the suboccipital region and is known as the suboccipital nerve. The ventral rami of T1-T11 travel between the ribs and are known as intercostal nerves. The ventral ramus of T12 travels inferiorly to the 12th rib and is known as the subcostal nerve.

Ø The dorsal rami of spinal nerves stay independent from one another and innervate structures that are located approximately at their segmental level. The ventral rami of spinal nerves in thoracic region act in same manner. However, cervical, lumbar, sacral and coccygeal ventral rami are different in that they combine with other spinal ventral rami to form plexus.

What is a Plexus? Ø A plexus means a structure in the form of a network, especially of nerves, blood vessels or the lymphatics. Ø A nerve plexus can be defined as an area where nerves branch and rejoin. Ø It is a ‘nerve net’ in which the processes of neurons join together to form a plexus.

Number of Nerve Plexus in Human Body? There are 4 primary nerve plexus in the human body, namely 2. Cervical plexus: C1-C5 3. Brachial plexus: C5-T1 4. Lumbar plexus: T12-L5 5. Sacral plexus: L4-S4

What is SACRAL PLEXUS? A nerve network originating from the nerves of the sacral spine and innervating large areas of the lower trunk and legs esp. via the sciatic nerve.

Composition of Sacral Plexus The sacral plexus is formed by: Ø The lumbosacral trunk, Ø The ventral rami of the first to third sacral nerves, Ø And some portion of the fourth sacral nerve.

Ø The lumbosacral trunk is formed by the descending branch of the ventral ramus of nerve L4 and the whole L5. Ø It appears at the medial margin of the Psoas major. ØThe trunk descends over the ala of the sacrum, crosses the pelvic brim in front of the sacroiliac joint and joins the nerve S1.

Location and associated anatomical structures Ø The sacral plexus lies on the back of the pelvis between the Piriformis and the pelvic fascia in front of it are the hypogastric vessels, the ureter and the sigmoid colon. Ø The superior gluteal vessels run between the lumbosacral trunk and the first sacral nerve. Ø The inferior gluteal vessels between the second and third sacral nerves.

Main terminal branches of the sacral plexus

The LUMBOSACRAL TRUNK, SCIATIC NERVE and PUDENDAL NERVE

The Nerves

Taking origin from the sacral plexus

1. Superior gluteal nerve- L4,L5, S1 2. Inferior gluteal nerve- L5, S1, S2 3. Nerve to Piriformis- S1, S2 4. Nerve to Obturator internus- L5, S1, S2 5. Nerve to Quadratus femoris- L4, L5, S1 6. Perforating cutaneous nerve- S2, S3 7. Posterior cutaneous nerve of thigh- S1, S2, S3

8. Sciatic nerve- L4, L5, S1, S2, S3 – Tibial portion – Common peroneal portion

9. Pudendal nerve- S1, S2, S3 - Inferior anal nerves -Perineal nerve -Dorsal nerve of penis/Dorsal nerve of clitoris

Superior gluteal nerve ØIt originates in the pelvis and supplies the gluteus medius, the gluteus minimus, and the tensor fasciae latae muscles. ØIt arises from the dorsal divisions of the fourth and fifth lumbar and first sacral nerves.

Ø It leaves the pelvis through the greater sciatic foramen above the Piriformis, accompanied by the superior gluteal artery and the superior gluteal vein. Ø It then divides into a superior and an inferior branch.

ØThe superior branch accompanies the upper branch of the deep division of the superior gluteal artery and ends in the gluteus minimus. ØThe inferior branch runs with the lower branch of the deep division of the superior gluteal artery across the gluteus minimus; it gives filaments to the gluteus medius and minimus, and ends in the tensor fasciae latae. ØThe superior gluteal nerve and vessels travel above the Piriformis muscle through the greater sciatic foramen; the inferior gluteal nerve and vessels travel below the muscle.

Pathology Ø Damage to the nerve can lead to the gait disturbance known as Trendelenburg gait. Ø Patients with a lesion of superior gluteal nerve have weakness of abducting the thigh at the hip. This type of gait may also be seen in L5 radiculopathy and after poliomyelitis.

Inferior gluteal nerve Ø innervates the gluteus maximus muscle. Ø It arises from the dorsal divisions of the fifth lumbar and first and second sacral nerves

Ø It leaves the pelvis through the greater sciatic foramen, below the Piriformis, and divides into branches which enter the deep surface of the gluteus maximus.

Nerve to Piriformis Ø Innervates the Piriformis muscle. Ø It arises from the dorsal division of the second sacral nerve, or the dorsal divisions of the first and second sacral nerves, and enters the anterior surface of the Piriformis muscle; this nerve may be double.

Nerve to Quadratus Femoris Ø The nerve to quadratus femoris is a nerve that provides innervations to the quadratus femoris and gemellus inferior muscles. Ø It arises from the ventral divisions of the fourth and fifth lumbar and first sacral nerves. Ø It leaves the pelvis through the greater sciatic foramen, below the piriformis muscle, and runs down in front of the sciatic nerve, the gemelli, and the tendon of the obturator internus, and enters the anterior surfaces of the muscles; it gives an articular branch to the hipjoint.

Nerve to Obturator Internus Ø The Nerve to the Obturator Internus and Gemellus Superior Ø arises from the ventral divisions of the fifth lumbar and first and second sacral nerves. Ø It leaves the pelvis through the greater sciatic foramen below the Piriformis, and gives off the branch to the Gemellus superior, which enters the upper part of the posterior surface of the muscle. Ø It then crosses the ischial spine, re-enters the pelvis through the lesser sciatic foramen, and pierces the pelvic surface of the Obturator internus.

The nerves on the back of thigh and leg

Posterior cutaneous nerve Ø It arises partly from the dorsal divisions of the first and second, and from the ventral divisions of the second and third sacral nerves. Ø It issues from the pelvis through the greater sciatic foramen below the Piriformis. It then descends beneath the Gluteus maximus, and runs down the back of the thigh beneath the fascia lata, and over the long head of the Biceps femoris to the back of the knee; here it pierces the deep fascia and accompanies the small saphenous vein to about the middle of the back of the leg, its terminal twigs communicating with the sural nerve. Ø Its branches are all cutaneous, and are distributed to the gluteal region, the perineum, and the back of the thigh and leg.

Perforating Cutaneous Nerve Ø The perforating cutaneous nerve arises from the 2nd and 3rd sacral nerves. Ø It is an inferior clunial (buttocks) nerve; it supplies the skin covering the medial and lower parts of gluteus maximus. Ø The perforating cutaneous nerve may arise from the pudendal nerve. Ø It is absent in approximately one third of people; its place may be taken by a branch from the posterior cutaneous nerve of thigh or by a branch from the third and fourth, or fourth and fifth, sacral nerves.

Sciatic Nerve Ø The Sciatic supplies nearly the whole of the skin of the leg, the muscles of the back of the thigh, and those of the leg and foot. Ø It is the largest nerve in the body, measuring 2 cm. in breadth, and is the continuation of the flattened band of the sacral plexus. Ø It passes out of the pelvis through the greater sciatic foramen, below the Piriformis muscle. It descends between the greater trochanter of the femur and the tuberosity of the ischium, and along the back of the thigh to about its lower third, where it divides into two large branches, the tibial and common peroneal nerves.

Ø In the upper part of its course the nerve rests upon the posterior surface of the ischium, the nerve to the Quadratus femoris, the Obturator internus and Gemelli, and the Quadratus femoris; it is accompanied by the posterior femoral cutaneous nerve and the inferior gluteal artery, and is covered by the Gluteus maximus. ØLower down, it lies upon the Adductor magnus, and is crossed obliquely by the long head of the Biceps femoris.

ØThe nerve gives off articular and muscular branches. Ø The articular branches arise from the upper part of the nerve and supply the hip-joint, perforating the posterior part of its capsule; they are sometimes derived from the sacral plexus. Ø The muscular branches are distributed to the Biceps femoris, Semitendinosus, Semimembranosus, and Adductor Magnus. ØThe nerve to the short head of the Biceps femoris comes from the common peroneal part of the sciatic, while the other muscular branches arise from the tibial portion.

Division of the sciatic nerve

Pathology Ø Sacral nerve is occasionally injured by wounds, fractures or intramuscular injection of drugs. Ø The component nerves may be involved by fracture, tumour or aneurysm.

ØThe Tibial Nerve the larger of the two terminal branches of the sciatic. Øarises from the anterior branches of the fourth and fifth lumbar and first, second, and third sacral nerves. ØIt descends along the back of the thigh and through the middle of the popliteal fossa, to the lower part of the Popliteus muscle, where it passes with the popliteal artery beneath the arch of the Soleus. ØIt then runs along the back of the leg to the interval between the medial malleolus and the heel, where it divides beneath the laciniate ligament into the medial and lateral plantar nerves.

The Plantar Nerves

The nerves on the front of leg

ØThe common peroneal nerve (common fibular nerve; external popliteal nerve; peroneal nerve), about one-half the size of the tibial nerve, is derived from the dorsal branches of the fourth and fifth lumbar and the first and second sacral nerves. ØIt descends obliquely along the lateral side of the popliteal fossa to the head of the fibula, close to the medial margin of the Biceps femoris muscle.

ØIt gives off articular and lateral sural cutaneous nerves. ØThe articular branches are three in number: •Two of these accompany the superior and inferior lateral genicular arteries to the knee. •The third articular nerve ascends with the anterior recurrent tibial artery through the Tibialis anterior to the front of the knee. ØThe lateral sural cutaneous nerve supplies the skin on the posterior and lateral surfaces of the leg.

The Nerves of the dorsum of foot

Trauma to the nerve can result in a condition called foot drop, where dorsiflexion of the foot is compromised and the foot drags during walking, and sensory loss to the dorsal surface of the foot and portions of the anterior, lower-lateral leg.

Pudendal Nerve ØIt originates from the ventral rami of the 2nd, 3rd and 4th sacral nerves. ØThe pudendal nerve innervates the penis and clitoris, bulbospongiosus and ischiocavernosus muscles, and areas around the scrotum, perineum, and anus.

Pudendal Nerve and its branches

Pathology ØDifficult childbirth or bicycling can compress or stretch the pudendal nerve, causing temporary loss of function, but permanent injury is rare. ØEntrapment of the nerve is very rare but can happen. ØA pelvic tumour (most notably a large sacrococcygeal teratoma), or surgery to remove the tumour, can damage this nerve permanently.

SENSORY SUPPLY

Sensory Supply by the respective nerve roots Ø L4- medial aspect of the leg Ø L5- dorsum of the foot and lateral aspect of the leg. Ø S1- sole and the posterior half of the lower part of the leg. Ø S2- posterior part of the thigh and the upper part of the leg. *Reference: Forester

THE FOLLOWING DIAGRAMS SHOW CUTANEOUS NERVE SUPPLY BY THE NERVES OF THE SACRAL PLEXUS

Anterior view

Posterior view

The plantar aspect of foot

Thank You All!

Amitinder Singh Dhaliwal, BPT-IV, Punjabi University Patiala