Week 10

Question 1

There are three clases in the seddon classification of nerve injuries. Class I is neurapraxia, class II is axonotmesis and class III is neurotmesis. Briefly describe each

Answer 1

Neurapraxia - mildest type. A temporary physiological block. Conduction is intact in distal segment but not over area of injury. No wallerian degeneration

Axonotmesis - Loss of continuity of the axons and their myelin sheath. Wallerian degeneration occurs after 24 hours distal to the site of injury

Neurotmesis - Complete division of the nerve, wallerian degeneration occhrs ditral to the site of injury, effects are severe

Question 2

Briefly explain wallerian degeneration

Answer 2

The axon distal to the injury degenerates, myelin sheath then degenerates and macrophages infiltrate. Remaining schwann cells then redirect the new growing nerve fibres to the site of injury.

Question 3

Other than traumatic division of nerves give some other causes of neuropathy

Answer 3

Structures causing pressure like tumours or abcesses/traction during birth/medial caonditions like alcohol excess and diabetes/tumours of the nerves usch as neuromas

Question 4

What intervertebral discs are the most common sites for a slipped disc and why?

Answer 4

L4/L5 L5/S1 due to the mechanical loading at these joints.

Question 5

What nerve roots are compressed in paracentral herniation of the L3/L4 disc?

Answer 5

The traversing nerve root which is L4

Question 6

What are the nerve roots of the sciatic nerve?

Answer 6

L4-S3

Question 7

Explain the muscular innervation and sensory distribution of the sciatic nerve

Answer 7

Muscles - hamstrings, hamstring portion of adductor magnus. Common peroneal part of sciatic innervates short head of rectus femoris and the other hamstrings by the tibial component of the sciatic nerve. (important because they are both in sciatic nerve here still). Muscles of leg and foot vai the tibial and common peroneal branches

Sensory - sural nerve is made of branches of tibial and common peroneal so this is effectively sciatic, lateral leg and dorsum of foot via the superficial and deep peroneal. (saphenous is femora so medial leg is femoral). Almost all of the sole of the foot via the medial calcaneal (tibial branch), sural, lateral and medial plantar nerves (tibial)

Question 8

What is piriformis syndrome?

Give some symptoms

Answer 8

Sciatica like symtpoms that DO NOT originate from the compression of spinal nerve roots but instead are due to the compression of the sciatic nerve by the piriformis muscle

Symptoms include - dull ache in the buttock/typical sciatica in thigh , leg and foot/pain when walking up stairs/reduced range of motion at hip

Question 9

What are the roots of the superior gluteal nerve and where does it enter the pelvis?

Answer 9

L4-S1, through the greater sciatic foramen (formed by sacrospinous and sacrubtuberous ligaments)

Question 10

If the superior gluteal nerve has been injured the patient will have a positive trendelenburg sign, explain what this is

Answer 10

Patient is asked to stand on one leg, contralateral pelvis will drop due to the loos of innervation of the gluteus medius and minimus muscles.

Question 11

The lateral femoral cutaneous nerve is not a branch of the femoral nerve it is a direct branch of the lumbar plexus (L2-L3). Compression of this nerve results in meralgia paraesthetica. Patient experiences a burning sensation over the anterolateral thigh. Give a common cause

Answer 11

Obesity, wearing a tool belt, tight clothing

Question 12

What are the roots of the femoral nerve?

Answer 12

L2-L4.

Question 13

Describe the muscles that the femoral nerve innervates and its sensory distribution

Answer 13

Muscles - rectus femoris, vastus medials, lateralis and intermedius, pectineus, sartorius and iliacus.

Sensory - anteromedial thigh via the anterior femoral cutaneous nerve and the medial leg and foot via the saphenous nerve

Question 14

Describe symptoms of a femoral nerve injury

Answer 14

Weakness and wasting of the quadriceps. Active extension of the knee will be lost and anasthesia and parasthesia over the sensory distribution of the nerve

Question 15

What are the roots of the tibial nerve?

Answer 15

L4-S3, it is the larger branch

Question 16

Describe the presentation of a tibial nerve injury

Answer 16

Loss of plantarflexion due to muscle distribution, active flexion of the toes will be lost, inversion will be compromised
anasthesia/parasthesia in most of the sole of the foot apart from that supplied by the saphenous and sural nerves

Question 17

What are the nerve roots of the common peroneal nerve?

Answer 17

L4-S2

Question 18

Describe the classical appearance of a common peroneal nerve injury

Answer 18

Loss of dorsiflexion and eversion, compromised inversion, inability to extend toes. Resulting in characteristic ‘foot drop’
Lost sensation of lateral leg and dorsum of foot

Question 19

Describe superficial peroneal nerve (L4-S1) injury

Answer 19

Loss of active eversion, loss of sensation over distal anterolateral leg and dorsum of foot excluding the first interweb space

Question 20

Deep peroneal nerve injury (L4, L5), describe injury to it presentation

Answer 20

Foot drop, inability to effectively extend toes, small patch of numbness in first interweb space.

Question 21

Describe a likely injury causing
common peroneal injury
deep peroneal

sural
superficial peroneal
sciatic
femoral

Answer 21

sural - stripping of short saphenous nerve
Deep peroneal - motor neuron disease/ischaemia/diabetes
Superficial peroneal - fractures of the fibula
Common peroneal - neck of fibula where it winds around
Tibial nerve - popliteal fossa damage
Femoral - stab to the groin
sciatic - misplaced IM injection