The lumbosacral plexus is formed by the ventral rami of lumbar and sacral spinal nerves and provides motor and sensory innervation to the pelvis, hips, thighs, legs and feet. It is comprised of the lumbar plexus, which forms in the psoas major muscle from L1-L4 nerves and the sacral plexus, which forms on the pelvic wall from L4-S4 nerves. Together they distribute nerves that innervate muscles and skin. Damage to the lumbosacral plexus results in neuropathic symptoms like pain, numbness and muscle weakness in the lower limbs.

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. Nervous system
Central nervous
system
Brain Spinal cord
Peripheral
nervous system
Cranial nerves Spinal nerves plexuses

5. 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
one nerve. Damage to nerves in the major plexuses causes problems in the
arms or legs that these nerves supply.

6. 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.

7. 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.

8. 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.

9. Nerve plexus
Spinal plexuses
Cervical plexus
Brachial plexus
Lumbar plexus
Sacral plexus
Coccygeal plexus
Autonomic plexuses
Auerbach’s plexus
Meissner’s plexus
Celiac plexus

10. 1. 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

11. 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).

12. Lumbar plexus

13. 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

14. 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

15. 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.

16. 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.

17. 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.)

18. 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.

19. 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

20. sacral plexus

21. 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

22. 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

23. 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

24. 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

26. 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.

27. 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.