Lumbosacral (lumbar & sacral) plexus

anatomy of lumbar and sacral plexus

1. Lumbosacral (lumbar & sacral) Plexus By Ali Faris

2. The Nervous System The nervous system can be defined as the network of nerve cells and fibers that sends messages for controlling movement and feeling between the brain and the other parts of the body. This nervous system is divided into two main parts, the central nervous system (CNS ), which consists of the brain and spinal cord , and the peripheral nervous system (PNS ) , which consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves and their associated ganglia. Functionally, the nervous system can be further divided into the somatic nervous system , which controls voluntary activities, and the autonomic nervous system , which controls involuntary activities .

3. functions of the nervous system The three basic functions of the nervous system: Motor output: Respond via muscle or glandular action Sensory input: Receive sensations from inside and outside the body Integration: Process and interpret sensations and make decisions. The nervous system, together with the endocrine system, controls and integrates the activities of the different parts of the body.

4. Nerve plexus plexus /pleksəs/ noun a network of nerves, blood vessels or lymphatics. A nerve plexus is a system of connected nerve fibers that link spinal nerves with specific areas of the body. Fibers in a plexus connect the spinal cord and the body by grouping themselves into one larger nerve. The human body consists of several nerve plexuses, including the brachial plexus, the cervical plexus, the coccygeal plexus, the lumbar plexus, the sacral plexus, and the solar plexus. A plexus is like an electrical junction box, which distributes wires to different parts of a house. In a plexus, nerve fibers from different spinal nerves (which connect the spinal cord to the rest of the body) are sorted. The fibers are recombined so that all fibers going to a specific body part are put together in one nerve. Damage to nerves in the major plexuses causes problems in the arms or legs that these nerves supply.

5. NERVE PLEXUS ANATOMY     The nerve plexus is actually made up of a multitude of nerve branches. These branches come from the spinal nerves, except for the thoracic spinal nerves 2 through 12. The remaining nerves donate their anterior rami, which branch off from the spinal nerves only to adjoin with each other . A nerve plexus is composed of afferent and efferent fibers that arise from the merging of the anterior rami of spinal nerves and blood vessels.

6. NERVE PLEXUS STRUCTURE Once they connect, they break off again and develop the network of nerve fibers known as the nerve plexus. There are actually 4 of these nerve plexuses in the human body, the brachial plexus, cervical plexus, the sacral plexus and the lumbar plexus.   At the root of the limbs, the anterior rami join one another to form complicated nerve plexus. The cervical and brachial plexuses are found at the root of the upper limbs, and the lumbar and sacral plexuses are found at the root of the lower limbs. The nerves which come out of the various plexus are typically named either for the specific area which they innervate or the basic course which can be traced along the way.

7. The main function of a nerve plexus   The main function of a nerve plexus is to ensure that all areas of the body are innervated, thereby equipping each region with the ability to send and receive messages from the peripheral nervous system. The different plexuses are charged with innervating different portions of the body and help to control the functions unique to each portion. A nerve plexus is formed during development, when disparate muscles of the skeleton fuse together and result in large muscles requiring innervation . The nerves that arise from the plexuses have both sensory and motor functions. These functions include muscle contraction, the maintenance of body coordination and control, and the reaction to sensations such as heat, cold, pain and pressure.

8. Spinal plexus At each vertebral level, paired spinal nerves leave the spinal cord via the intervertebral foramina of the vertebral column. There are five spinal nerve plexuses

9. Lumbar plexus Lumbar Plexus—Serves the Back, Abdomen, Groin, Thighs, Knees, and Calves   The lumbar plexus is formed by the ventral rami of L1–L5 spinal nerves with a contribution of T12 form the lumbar plexus. This plexus lies within the psoas major muscle.   lumbar plexus one formed by the ventral branches of the second to fifth lumbar nerves in the psoas major muscle (the branches of the first lumbar nerve often are included).

10. Lumbar plexus

11. Branches of the Lumbar Plexus and their Distribution Iliohypogastric nerve : External oblique, internal oblique, transversus abdominis muscles of anterior abdominal wall skin over lower anterior abdominal wall and buttock. Ilioinguinal nerve : External oblique, internal oblique, transversus abdominis muscles of anterior abdominal wall ; skin of upper medial aspect of thigh; root of penis and scrotum in the male; mons pubis and labia majora in the female. Lateral cutaneous nerve of the thigh: Skin of anterior and lateral surfaces of the thigh. Genitofemoral nerve (L1, 2 ): Cremaster muscle in scrotum in male; skin over anterior surface of thigh; nervous pathway for cremasteric reflex. T A B L E 5 . 1

12. Branches of the Lumbar Plexus and their Distribution Femoral nerve (L2, 3, 4 ): Iliacus , pectineus , sartorius , quadriceps femoris muscles, and intermediate cutaneous branches to the skin of the anterior surface of the thigh and by saphenous branch to the skin of the medial side of the leg and foot; articular branches to hip and knee joints Obturator nerve (L2, 3, 4): Gracilis , adductor brevis, adductor longus , obturator externus, pectineus , adductor magnus (adductor portion), and skin on medial surface of thigh; articular branches to hip and knee joints Segmental branches : Quadratus lumborum and psoas muscles

13. Lumbar stenosis The term "stenosis" comes from the Greek word meaning "choking" and is often the result of degenerative conditions such as osteoarthritis and/or degenerative spondylolisthesis. When the spinal nerves in the lower back are choked, lumbar spinal stenosis occurs and most often leads to leg pain and other symptoms. Lumbar Spinal Stenosis Symptoms : The typical symptom is increased pain in the legs with walking ( pseudoclaudication ), which can markedly diminish one's activity level. Patients with lumbar spinal stenosis are typically comfortable at rest but cannot walk far without developing leg pain. Pain relief is achieved, sometimes almost immediately, when they sit down again . The cause of spinal stenosis in the lumbar spine is commonly associated with aging. The facet joints (small stabilizing joints located between and behind vertebrae) tend to get larger as they degenerate and can compress the spinal nerve roots in the lower back, often producing lumbar stenosis symptoms of pain, especially with activity.

14. sacral plexus Sacral Plexus—Serves the Pelvis, Buttocks, Genitals, Thighs, Calves, and Feet The sacral plexus is formed by the ventral rami of L4-S3, with parts of the L4 and S4 spinal nerves. It is located on the posterior wall of the pelvic cavity . sacral plexus a plexus arising from the ventral branches of the last two lumbar and first four sacral spinal nerves .

15. Gross Anatomy The sacral plexus is formed by the union of the lumbosacral trunk (from the anterior rami of L4 and L5) and the anterior rami of the first, second, third, and fourth sacral nerves. The anterior rami of the upper 4 sacral nerves enter the pelvis through the anterior sacral foramina; the anterior rami of the fifth sacral nerve enter between the sacrum and coccyx. [1] (See the following image.)

16. Gross Anatomy The nerves forming the sacral plexus converge toward the lower part of the greater sciatic foramen and unite to form a flattened band.The band continues primarily as the sciatic nerve, which splits in the back of the thigh into the tibial nerve and common fibular nerve. These 2 nerves sometimes arise separately from the plexus, and in all cases their independence can be shown by dissection . The anterior rami of the first and second sacral nerves are large; the third, fourth, and fifth diminish progressively in size. Each receives a gray ramus communicans from the corresponding ganglion of the sympathetic trunk. From the second, third, and fourth sacral nerves, a pelvic splanchnic nerve is given to the inferior hypogastric plexus. These are parasympathetic fibers that supply the hindgut and the pelvic viscera.

17. Gross Anatomy The sacral plexus lies in the back of the pelvis between the piriformis muscle and the pelvis fascia. In front of it are the internal iliac artery, internal iliac vein, the ureter, and the rectum. The superior gluteal artery and vein usually run between the lumbosacral trunk and the first sacral nerve, and the inferior gluteal artery and vein often runs between the second and third sacral nerves.All the nerve roots entering the plexus split into anterior and posterior divisions, and the nerves arising from these are as follows (see the image below):Nerve to quadratus femoris and gemellus inferior: L4-S1Nerve to obturator internus and gemellus superior: L5-S2Nerve to piriformis: S1, S2Superior gluteal nerve: L4-S1Inferior gluteal nerve: L5-S2Posterior femoral cutaneous nerve: S1-S3Tibial nerve: L4-S3Common fibular (peroneal): L4-S2

18. sacral plexus

19. Natural Variants Range of variation The sacral plexus is liable to vary in its attachments, its nerves of origin having a tendency to arise higher or lower. [2] Slight degrees of variation can be shown by a difference in the size of the contributing roots, so that a given trunk derives a larger share of its fibers from an upper spinal nerve and a smaller share from a lower spinal nerve, or vice versa. In the more marked degrees, the origin may be shifted upward or downward to the extent of one spinal nerve. Thus, 2 forms of sacral plexus variations exist, called high (prefixed) and low ( postfixed ). In some instances, the extreme forms are associated with irregularities of the vertebral column. The lumbosacral plexus is frequently asymmetric from one side to the other

20. Usual form of plexus See the list below : Nerve to quadratus femoris : L4, L5, S1 Nerve to obturator internus: L5, S1, S2 Tibial : L4, L5, S1, S2, S3 Superior gluteal: L4, L5, S1 Inferior gluteal: L5, S1, S2 Nerve to piriformis: S1, S2 Common fibular (peroneal): L4, L5, S1, S2 Posterior femoral cutaneous: S1, S2, S3 Pudendal : S2, S3, S4

21. High form of plexus See the list below : Nerve to quadratus femoris : L4, L5 Nerve to obturator internus: L4, L5, S1, S2 Tibial : L3, L4, L5, S1, S2 Superior gluteal: L4, L5, S1 Inferior gluteal : L4, L5, S1 Nerve to piriformis: L5, S1, S2 Common fibular (peroneal): L3, L4, L5, S1 Posterior femoral cutaneous: L5, S1, S2 Pudendal : S1, S2, S3

22. Low form of plexus See the list below : Nerve to quadratus femoris : L5, S1 Nerve to obturator internus: S1, S2, S3 Tibial : L5, S1, S2, S3, S4 Superior gluteal: L5, S1, S2 Inferior gluteal: L5, S1, S2 Nerve to piriformis: S1, S2, S3 Common fibular (peroneal): L5, S1, S2, S3 Posterior femoral cutaneous: S2, S3, S4 Pudendal : S2, S3, S4

23. Lumbosacral plexus Because the lumbar and sacral plexuses are interconnected, they are sometimes referred to as the lumbosacral plexus. The spinal nerves in the chest do not join a plexus. They are the intercostal nerves, which are located between the ribs.

24. lumbosacral plexopathy A lumbosacral plexopathy is a disorder affecting either the lumbar or sacral plexus of nerves. They are rare syndromes, caused by damage to the nerve bundles. A plexopathy is suspected if the symptoms cannot be localised to a single nerve. Patients may complain of neuropathic pains, numbness or weakness and wasting of muscles. One of the main causes of lumbosacral plexopathy is diabetic amyotrophy, also known as lumbosacral radioplexus neurophagy. In this condition, the high blood sugar levels damage the nerves. Idiopathic plexopathy is another cause, being the lumbosacral equivalent of Parsonage-Turner syndrome (which affects the brachial plexus). Tumours and other local invasions can cause the plexopathy due to the compression of the plexus. Treatment depends on what is causing the symptoms. For tumours and space-occupying lesions, they should be removed if possible. For diabetic and idiopathic causes, treatment with high-dose corticosteroids can be useful.