Nerve Injuries (Session 10) Flashcards
Upper and Lower limb
Where does the radial nerve run on the humerus?
In radial(spiral) groove
Posterior surface
If someone damages their radial nerve in a mid-shaft fracture, will they still be able to extend their elbow?
Yes, extension may be mildly compromised
Nerve supply to long and medial heads of triceps given off before spiral groove
Why will the wrist and fingers be flexed when the patients wrist is pronated in a radial nerve injury due to a mid-shaft fracture of the humerus?
- Paralysis of:
- Brachioradialis
- All extensor muscles of wrist and fingers
- Gravity
Causes Wrist Drop
What is the likely sensory impairment if there is injury to the radial nerve due to a mid-shaft fracture of the humerus?
Superficial branch of radial nerve
Where does the median nerve branch off to supply the muscles of the superficial, anterior compartment of the forearm?
Medial epicondyle
What muscles does the median nerve supply in the arm?
None
What will be the effect of an injury to the median nerve above the level of the elbow?
Paralyse muscles supplied by median nerve in forearm and hand:
- Pronators
- Flexors of wrist
-
EXCEPT:
- FCU
- Ulnar half of Flexor Digitorum Profundus
-
EXCEPT:
- Flexor pollicis longus
- (But flexor pollicis brevis may have some innervation from ulnar nerve)
- Opponens pollicis
- Palmar abduction
Forearm will be:
Supinated
Adduction during flexion (due to pull of flexor carpi ulnaris
Long standing lesions will cause a wasting of the thenar eminence
What might cause injury to the median nerve above the elbow?
Supracondylar fracture of the humerus
What will happen if you ask a patient with a high median nerve injury to make a fist?
Hand of benediction
What does the following image show?
Ape hand deformity
(Due to long standing lesions on high median nerve)
Thenar wasting
Where will the patient have sensory loss in a high median nerve lesion?
What may cause injury to the median nerve at the wrist? (2)
- Penetrating injury
- Compression in carpal tunnel
How does the presentation of a low median nerve injury (at wrist) differ from the high median nerve injury (in spiral groove)?
- Flexors of forearm (arising from medial epicondyl)=spared
- Pronator teres
- FCR
- Plamaris longus
- Flexor digitorum superficialis and Flexor digitorum profundus= spared
LOAF muscles will be paralysed
What does LOAF stand for?
- Lumbricals to index and middle finger
- Opponens pollicis
- Abductor pollicis brevis
- Flexor pollicis brevis
What will be the area of pain and numbness in a low median nerve injury?
What will be the resulting deformity which is seen in a low median nerve injury?
Ape Hand Deformity
- Thenar eminence=flattened
- Thumb=adducted and externally rotated
What may cause a high ulnar nerve lesion? (injury at elbow) (2)
- Medial epicondylar fracture
- Compression in cubital tunnel
In a low ulnar nerve injury (at the wrist) why is it the muscles supplied by the ulnar nerve in forearm are intact?
Ulnar nerve gives off branch to before wrist:
- FCU
- Ulnar half of Flexor Digitorum Profundus (ring and little finger)
Will the palmar cutaneous branch of the ulnar nerve and the dorsal cutaneous branch of the ulnar be intact in a low ulnar nerve injury?
Yes (branch off before wrist)
What may cause a lower ulnar nerve injury? (2)
- Laceration
- Compression in Guyon’s canal
What muscles will be affected by an injury to the ulnar nerve in the wrist?
- Hypothenar eminence (pictured)
- Adductor pollicis
- Deep head of flexor pollicis brevis
- Interossei
- Lumbricals to ring finger and little finger
- Palmaris brevis
Where would the sensory loss be with a a low ulnar nerve injury?
Palmar aspect of ulnar 1.5 digits and dorsum over distal phalanges only
What deformity may be seen with long standing damge to the ulnar nerve at the wrist?
Claw hand
MCPJs- hyperextended- unopposed extension from extensor digitorum in posterior compartment of forearm
Proximal and distal IP joints- unopposed flexion from long flexor muscles in anterior compartment
What muscles will be affected in a high ulnar nerve lesion?
- FCU
- Ulnar side of flexor digitorum profundus
- Hypothenar eminence (pictured)
- Adductor pollicis
- Deep head of flexor pollicis brevis
- Interossei
- Lumbricals to ring finger and little finger
- Palmaris brevis
What will be the sensory loss in a high ulnar nerve lesion (at elbow)?
Throughout ulnar nerve distribution in hand
How does the deformity due to an ulnar injury at the wrist differ from an injury at the elbow?
Claw= less pronounced
FDP= parlaysed- no flexion of DIPJ at ring and little fingers
What are the actions of the interossei?
PAD: Palmar Adduction
DAB: Dorsal Abduction
Which muscles are innervated by the median nerve in the hand?
LOAF
What are the Thenar muscles?
- Opponens pollicis
- Abductor pollicis brevis
- Flexor pollicis brevis
What are the Hypothenar muscles?
- Opponens digiti minimi
- Abductor digiti minimi
- Flexor digiti minimi
What are the 3 classes of nerve injury? (Seddon)
- Neurapraxia: temporary physical block of conduction
- Axonotmesis: loss of continuity of axons and myelin sheath BUT endoneurium, perineurium and epineurium= intact- regeneration usually possible
- Neurotmesis: complete division
What is wallerian degeneration? What happens after it?
- Axon distal to injury degenerates (after degradation of myelin sheath and infiltration by macrophages
- Schwann cells eventually start to proliferate and regeneration occurs (provided severed ends=surgically opposed)
What happens if axonal regeneration is unsuccessful (ends aren’t opposed)?
Sprouting of axons from severed nerve- forms traumatic neuroma
can be v painful
Muscle eventually replaced by fibrous tissue and fat
What are the myotomes for the lower limb?
L2: Hip flexion
L3: Knee extension
L4: Ankle dorsiflexion
L5: Great toe extension
S1: Ankle plantar flexion
S2: Great toe flexion
What are the most common sights for a slipped disc and why?
L4/5
L5/S1
Mechanical loading
Which nerve emerges through the L4/L5 intervertebral foramen?
L4
What are the nerve roots for the sciatic nerve?
L4-S3
Which muscles does the sciatic nerve innervate?
Hamstring muscles:
- Biceps femoris - Common fibular (peroneal) nerve division
- Semimebranosus- Tibial division
- Semitendinosus- Tibial division
- Hamstring portion of adductor magnus- Tibial division
Where do the peroneal (fibular) and tibial terminal branches arise (from the sciatic nerve)?
Superior aspect of popliteal fossa
What is the sensory innervation of the sciatic nerve (by extension of the peroneal and tibial nerves)?
Outline the path of the sciatic nerve from leaving the pelvis to the anterior thigh.
Through greater sciatic foramen
Anterior to piriformis
Crosses posterior surface of short external rotators
Passes deep to long head of biceps femoris
Between biceps femoris and adductor magnus
Does the sciatic nerve emerge inferior to the piriformis in everyone?
No
What is piriformis syndrome?
Sciatica like symptoms
Due to compression of sciatic nerve by piriformis muscle
(Not from compression of spinal nerve roots)
What are the symptoms of piriformis syndrome? (5)
- Dull ache in buttock
- Typical sciatica pain in thigh, leg and foot
- Pain when walking up inclines
- Increased pain after prolonged sitting
- Reduced range of motion in hip joint
What causes sciatic nerve entrapment by the piriformis muscle?
- Muscle spasm (overuse eg athletes)
- Direct trauma
- Anatomical variations
How is piriformis syndrome treated?
Activity modification
Using NSAIDs
Physiotherapy
Give 3 mechanisms of injury to the sciatic nerve in the buttock.
- Stab wound
- Misplaced intramuscular injection
- Posterior hip dislocation
If the sciatic nerve were completely transected in the buttock, what would be the motor and sensory loss?
- Hip would stil be able to extend due to gluteus maximus
- Knee flexion=absent
- Dorsiflexion of ankle=absent
- Plantarflexion of ankle=absent
- Inversion and eversion of midfoot=absent
- All movement of toes= paralysed
What’s the differencee between the ventrogluteal site and the dorsogluteal site for an intramuscular in the gluteal region?
- Dorsogluteal site= young children
- Ventrogluteal site= 7+ yrs
What is the dorsogluteal injection site?
What is the ventrogluteal site?
What is meralgia paraesthetica?
Injury to lateral cutaneous nerve of thigh
(Compression as it pierces inguinal ligament/fascia lata in thigh)
(aka lateral femoral cutaneous nerve
What are some causes of meralgia paresthetica?
Obesity
Pregnancy
Tight clothing
Wearing tool belt
What are the symptoms of maralgia paraesthetica?
Burning/stingin sensation in distribution of nerve
Aggravated by walking, standing
Relieved by lying down with hip flexed
Tenderness on palpation
Positive Tinels sign (sometimes) -percussing nerve at site of entrapment generates tingling or paresthesia
Which nerve roots does the femoral nerve arise from?
L2,3,4
What is the sensory innervation of the femoral nerve?
What reflex will be absent in a femoral nerve lesion?
Knee jerk reflex
What is the pathway of the tibial nerve?
Passes beneath flexor retinaculum at medial malleolus
Gives of medial calcaneal branch to heel
Then divides into medial and lateral plantar nerves supplying sole of foot
What will a patient with a tibial nerve injury not be able to do?
Plantarflex ankle - walk on tiptoe
Actively flex toes
Inversion of foot
Patient will develop calcaneovalgus posture
What are the root values for the common peroneal nerve?
L4-S2
What causes an injury to the common peroneal nerve?
- Prolonged bed rest
- Tight plaster cast
- Poorly placed stirrups in operating theatre
- Fractures of neck of fibula
What complication is caused by an injury to the common peroneal nerve?
Foot drop
Inversion of ankle
What may cause damage to the superficial peroneal nerve?
Fracture of proximal fibula
Penetrating injury to lateral leg
What will be the consequences of damage to the common peroneal nerve?
Loss of active eversion of midfoot
Which muscles are supplied by the deep peroneal nerve?
Tibialis anterior
Extensor hallucis longus
Extensor digitorum longus
Peroneus tertius
(Skin: first dorsal webspace)
(Patient will have foot drop and inability to extend toes)
What might cause deep peroneal nerve damage?
Motor neuron disease
Diabetes
Ischaemia
Vasculitis
Total knee replacement
What muscles are supplied by the saphenous nerve?
(Branches from femoral nerve in femoral triangle)
(travels in subsatorial canal)
None= purely sensory
Why is the saphenous vein vulnerable to injury?
Subcutaneous course in medial leg
Which procedures may result in an injury to the saphenous nerve?
- Saphenous vein cut down (obtain venous access in emergency)
- Orthopaedic surgery
- Saphenous vein harvest for bypass surgery
Which muscles are innervated by the sural nerve?
None= sensory nerve
Communicating branches from:
- Tibial nerve
- Common peroneal
= Unite
Where does the sural nerve run relative to the lateral malleolus?
posterior and inferior
Why is the sural nerve harvested for nerve grafting?
Relatively minor sensory deficit
