Sciatic Nerve Lesion Flashcards
The Path
originate
upper leg
The sciatic nerve is the strongest and longest of the peripheral nerves
It primarily provides motor supply to the hamstrings and lower leg and foot and sensory supply to the posterior leg, most the anterior and posterior lower leg and the foot
The sciatic nerve originates from the L4-S1(L4-S3) nerve roots
It consists of two independent nerves (the tibial and peroneal division
- The nerve leaves the sacral plexus, passing through the greater sciatic foramen and usually under the piriformis muscle
It travels between the ischial tuberosity and the greater trochanter
The nerve goes deep, following adductor magnus down the leg
At the popliteal fossa it splits into two nerves
Path
lower leg posterior
The tibial nerve is the larger of the two
It travels through the popliteal fossa, between the heads of gastrocs
At the ankle, the nerve travels between the medial malleolus and the Achilles tendon and travels deep to the flexor retinaculum
The tibial nerve divides into the medial and lateral plantar nerves
There is a cutaneous branch from both the tibial nerve and the common peroneal nerve which forms the sural nerve
Path
lower leg anterior
The second branch of the sciatic nerve is the common peroneal nerve
After passing through the popliteal fossa, it travels around and below the head of the fibula
It then splits into two divisions: the superficial and deep peroneal nerves
The deep branch travels deep to extensor digitorum longus and continues down to the malleoli and on the dorsal surface of the foot
The superficial division is found between peroneus longus and extensor digitorum longus
Muscles Innervated by the Sciatic Nerve
- Hamstrings:
Semitendinosus
Semimembranosus
Long head of biceps femoris (tibial)
Short head of biceps femoris (peroneal)
- ½ of adductor magnus
Muscles Innervated by the Tibial Division
- Gastrocnemius
- Plantaris
- Popliteus
- Soleus
- Tibialis posterior
- Flexor digitorum longus
- Flexor hallucis longus
- Intrinsic foot muscles:
Flexor digitorum brevis
Flexor hallucis brevis
Abductor hallucis
Abductor digiti minimi
Adductor hallucis
Lumbricals
interossei
Muscles Innervated by the Peroneal Division
Extensor digitorum longus
Peroneus longus
Tibialis anterior
Extensor hallucis longus
Peroneus brevis
Peroneus tertius
Extensor digitorum brevis
Extensor hallucis brevis
Causes of Lesions of the Sciatic Nerve
- Fractures:
At the pelvis, femur, tibia or fibular head or ankle
- Dislocations:
Of the hip, knee or ankle
Iatrogenic reactions
From injections in the gluteal muscles, hip surgery, meniscal repair, improper positioning during surgery or traction post surgery
- Compression from internal sources:
Such as piriformis muscle causing piriformis syndrome, from the flexor retinaculum in the foot causing tarsal tunnel syndrome, from a ganglion or a Morton’s foot structure
- Compression from an external source:
Against the fibular head or prolonged squatting which compresses the nerve under the tendon of peroneus longus
- Trauma:
Such as a contusion in the gluteals
Symptom Picture:
foot drop
Presentation of a complete sciatic nerve lesion is known as a foot drop
Paralysis of dorsiflexors and evertors of the foot cause it to hang limply in plantarflexion and inversion
To walk, the person must lift the leg unusually high so it can be placed on the ground, toe first
This type of walk is called a steppage gait
Symptom Picture:
claw toe
The loss of intrinsic foot muscles with a tibial nerve lesion may result in “claw toe” deformity
This presents as a combination of hyperextension at the MCP joints (extensor digitorum brevis and extensor hallucis brevis are intact) and unopposed and flexion of the IP joints
Muscle wasting may affect the hamstrings
Injuries that can lead to infection and pressure sores may go unnoticed by the client as a result of sensory loss at the heel and foot
Symptom Picture:
The tibial portion of the sciatic nerve carries the majority of autonomic fibres. Lesions with this nerve result in severe trophic changes and edema in the sole of the foot and toes
Causalgia may occur with sciatic nerve lesions affecting the tibial division
Sensory Dysfunction as a Result of a Lesion
Tibial Division:
Altered sensation is experienced on the posterior leg, heel and sole of the foot including the toes
Sensory Dysfunction as a Result of a Lesion
Peroneal Division
Altered sensation is experienced on the lateral and anterior surface of the lower leg and foot, not including the toes, as well as on the area medial to the medial malleolus and a thin strip at the edge of the foot
Anesthesia is experienced on the dorsal surface of the foot, at the web space between the great toe and second digit
Sites of impingement:
Tibial nerve
Tibial nerve (from popliteal fossa to leg & foot)
Sites of impingement
* Less often affected due to nerve being well protected
* If affected, often due to direct trauma but possible compromise from nerve root irritation
Signs/symptoms
* Pain or loss of sensation to sole of foot, weakness of plantar flexion
Sites of impingement:
Common fibular (peroneal) nerve
Sites of impingement:
* Most often affected at the head or neck of fibula
* Common causes include anterior compartment syndrome (esp. by extensor digitorum longus), fractures & dislocations of fibula
* May also be affected due to tight cast, splint or brace of knee/leg
Signs/symptoms:
* Mild pain or loss of sensation to anterolateral leg & dorsum of foot
* Foot drop with subsequent steppage gait
* Anterior compartment syndrome (shin splints) may compromise the deep branch of common peroneal nerve resulting in isolated sensation loss to web space between 1st & 2nd toe
Related Conditions
Lumbar Spine conditions
Piriformis Syndrome
Acute Disc Herniation
Degenerative Disc Disease
Will be covered in Ortho Treatment II
