Siatic Nerve

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SCIATIC NERVE

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INTRODUCTION

Sciatic nerve is thethickest, largest and the

longest nerve of the body.

It is also known as

ISCHIATIC NERVE. It begins in the pelvis and

terminates at the superior

angle of the popliteal

fossa by dividing into thetibial and common

peroneal nerves.

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ORIGIN AND ROOT VALUE

Its the terminal branch or

the continuation of thesacral plexus.

Its root value isL4,L5,S1,S2,S3.

Its is made up of 2 parts,tibial and the commonperoneal parts.

TIBIAL PART-Ventraldivisions of the anteriorprimary rami of

L4,L5,S1,S2,S3. COMMON PERONEAL

PART-Dorsal divisions of theanterior primary rami ofL4,L5,S1,S2,S3.

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COURSE AND ITS DISTRIBUTION

IN PELVIS

IN GLUTEAL REGION

IN THIGH

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IN PELVIS

Arises in the pelvis. Leaves the pelvis by

passing through greater

sciatic foramen below the

piriformis to enter thegluteal region.

No branches.

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IN GLUTEAL REGION

Enters the gluteal regionthrough greater sciaticforamen.

Here its course is b/wischial tuberosity and

greater trochanter withslight lateral convexity.

Lies deep to the gluteusmaximus and superficial toobturator internus with two

gamelli and quadratusfemoris and then enter theback of the thigh.

No branches.

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BACK OF THIGH

Enters the back of thethigh at the lower borderof gluteus maximus.

Nerve is superficial toadductor magnus and

deep to long head ofbiceps femoris.

Here it gives muscularbranches to

semitendinosus,semimembranosus, bicepsfemoris and ischial headof adductor magnus.

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TERMINATION

Terminates at the superior angle of the popliteal fossa i.e.at the junction of upper 2/3rd and lower 1/3rd of the

thigh.

Terminal branches are tibial and common peroneal

nerves

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BRANCHES

ARTICULAR-Branches to thehip joint arise in gluteal

region.

MUSCULAR-Branches given

in the upper part of thigh.

1.Tibial part-supplies long

head of the biceps

femoris,semitendinosus,

semimembranosus.

2.Common peroneal part-

supplies short head of

biceps femoris.

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SEMITENDINOSUS

ORIGIN: From the inferomedial impression on the upperpart of ischial tuberosity

INSERTION: Upper part of the medial surface of the tibia

behind sartorius and gracilis

ACTION: Flexor of the knee

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SEMIMEMBRANOSUS

ORIGIN: Superolateral impression on the upper part ofthe ischial tuberosity

INSERTION: Into the groove on the posterior surface of

the medial condyle of tibia

ACTION: Flexor of the knee

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BICEPS FEMORIS

ORIGIN:1.LONG HEAD: From the inferomedial impression on the

upper part of the ischial tuberosity

2.SHORT HEAD: From the lateral lip of linea aspera b/w

add.magnus and vastus lat. INSERTION: Head of the fibula

ACTION: Flexor of the knee.

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ADDUCTOR MAGNUS

HAMSTRING PART: ORIGIN: Tuberosity of ischium.

INSERTION: Linea aspera and adductor tubercle on

medial cndyle of the femur.

ACTION: Extension of hip joint.

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SENSORY DISTRIBUTION

Innervates the skin ofpost. Aspect of thigh and

gluteal regions

Entire lower leg except forits medial aspect

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APPLIED ANATOMY

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Sciatica

Sciatica (or sciatic neuritis) is a set of symptomsincluding pain that may be caused by general compression

and/or irritation of one of five spinal nerve roots that give

rise to each sciatic nerve, or by compression or irritation of

the left or right or both sciatic nerves. The pain is felt in the

lower back, buttock, and/or various parts of the leg and foot.

In addition to pain, which is sometimes severe, there may be

numbness, muscular weakness, pins and needles or tingling

and difficulty in moving or controlling the leg. Typically, the

symptoms are only felt on one side of the body. Sciatica is a set of symptoms rather than a diagnosis for what

is irritating the root of the nerve, causing the pain.

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Region of pain by compression of following roots of

the sciatic nerve

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Sypmtoms

Sciatica causes pain, a burning sensation, numbness, ortingling radiating from the lower back and upper buttockdown the back of the thigh to the back of the leg. Theresult is leg pain.

Sometimes the pain radiates around the hip or buttock tofeel like hip pain. While sciatica is often associated with lower backpain (lumbago), it can be present without low back pain. Severe sciatica can make walking difficult if not

impossible.

Sometimes the symptoms of sciatica are aggravated bywalking or bending at the waist and relieved by lyingdown.

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Who is prone to developing symptoms of sciatica?

Sciatica can affect just about anyone, but it is extremelyuncommon in young patients. Sciatica typically affects 30

to 50 year old patients. Often there is a sudden onset that

may be attributed to over-exertion or a back injury.

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Causes

Spinal disc herniation

Spinal stenosis

Trigger points

Piriformis syndrome

Pregnancy

Habits

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Spinal disc herniation

Herniation of a disc occurs when the liquid center of the disc

bulges outwards, tearing the external ring of fibers, extrudes intothe spinal canal, and compresses a nerve root against the lamina orpedicle of a vertebra, thus causing sciatica. This extruded liquidfrom the nucleus pulposus may cause inflammation and swelling ofsurrounding tissue which may cause further compression of the

nerve root in the confined space in the spinal canal. Sciatica caused by pressure from a disc herniation and swelling of

surrounding tissue can spontaneously subside if the tear in the discheals and pulposis extrusion and inflammation cease

Sciatica can be caused by tumours impinging on the spinal cord or

the nerve roots. Severe back pain extending to the hips and feet, lossof bladder or bowel control, or muscle weakness, may result fromspinal tumours. Trauma to the spine, such as from a car accident,may also lead to sciatica.

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Sciatica due to herniated spinal disc

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Spinal stenosis

Spinal stenosis, a condition in which the spinal canal (thespaces through which the spinal cord runs) narrows and

compresses the sciatic nerve roots.

This narrowing can be caused by bone spurs,

spondylolisthesis, inflammation, or herniated disc whichdecreases available space for the spinal cord, thus

pinching and irritating nerves from the spinal cord that

travel to the sciatic nerves.

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Spinal stenosis Pain shooting down the sciatic

nerve

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Piriformis syndrome

In 15% of the population, the sciatic nerve runs throughthe piriformis muscle rather than beneath it.

When the muscle shortens or spasms due to trauma oroveruse, it can compress or strangle the sciatic nerve beneaththe muscle. Conditions of this type are generally referred to as

entrapment neuropathies; in the particular case of sciaticaand the piriformis muscle, this condition is knownas piriformis syndrome.

It has colloquially been referred to as "wallet sciatica" sincea wallet carried in a rear hip pocket will compress the

muscles of the buttocks and sciatic nerve when the bearer sitsdown.

Piriformis syndrome may be a cause of sciatica when thenerve root is normal.

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http://en.wikipedia.org/wiki/Piriformis_musclehttp://en.wikipedia.org/wiki/Neuropathyhttp://en.wikipedia.org/wiki/Piriformis_syndromehttp://en.wikipedia.org/wiki/Walletshttp://en.wikipedia.org/wiki/Walletshttp://en.wikipedia.org/wiki/Piriformis_syndromehttp://en.wikipedia.org/wiki/Piriformis_syndromehttp://en.wikipedia.org/wiki/Piriformis_syndromehttp://en.wikipedia.org/wiki/Neuropathyhttp://en.wikipedia.org/wiki/Piriformis_musclehttp://en.wikipedia.org/wiki/Piriformis_musclehttp://en.wikipedia.org/wiki/Piriformis_muscle


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Trigger points

Another source of sciatic symptoms is active triggerpoints of the lower back and the gluteus muscles. In thiscase, the referred pain is not consequent to compressionof the sciatic nerve, though the pain distribution downthe buttocks and leg is similar.

Trigger points occur when musclesbecome ischemic (having low blood flow) due to injuryor chronic muscular contraction.

The most commonly associated muscles with trigger

points triggering sciatic symptoms are: the quadratuslumborum, thegluteus medius, thegluteus minimus, andthe deep hip rotators.

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http://en.wikipedia.org/wiki/Ischemiahttp://en.wikipedia.org/wiki/Quadratus_lumborumhttp://en.wikipedia.org/wiki/Quadratus_lumborumhttp://en.wikipedia.org/wiki/Gluteus_mediushttp://en.wikipedia.org/wiki/Gluteus_minimushttp://en.wikipedia.org/wiki/Gluteus_minimushttp://en.wikipedia.org/wiki/Gluteus_minimushttp://en.wikipedia.org/wiki/Gluteus_mediushttp://en.wikipedia.org/wiki/Gluteus_mediushttp://en.wikipedia.org/wiki/Quadratus_lumborumhttp://en.wikipedia.org/wiki/Quadratus_lumborumhttp://en.wikipedia.org/wiki/Quadratus_lumborumhttp://en.wikipedia.org/wiki/Ischemia


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Pregnancy

Results from

the uterus pressing on

the sciatic nerve, and,

secondarily, from the

muscular tension and/or

vertebral compression

consequent to carrying

the extra weight of

the fetus, and the postural

changes inherent to

pregnancy

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Habits

Sitting on a wallet or

standing for prolongedperiods of time every daywhich can cause self-inflicted sciatica. Symptomsof numbness and/or pain

behind the knee cap areassociated with this form ofsciatica.

Work-related sciatica maybe caused by the use of toolbelts which hang around thehips and cause significantmisalignment of the sacralvertebrae over long timeperiods.

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There is a condition where the

nerve becomes compressed as itpasses under a muscle in the hipthat results in the nerve sendingpain messages to the brain thatin many cases are phantompains. Phantom pains from

sciatica will give the impressionthat the only place where pain isoccurring is in the heels of thefeet and there is no pain in theknee or lower leg area. Sciaticais associated with a feeling of

numbness in the heel and maybe associated with a burningpain at night. Getting treatmentfor the Sciatica in many cases isthe cure for the heel pain.

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Reference

www.google.com

www.wikipedia.com

B.D Chaurasia

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THANK YOU

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Siatic Nerve

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