Peripheral nerve injuries Flashcards
Acute nerve compression causes ____ within 15 minutes.
Numbness and tingling
Acute nerve compression causes ____ after 30 minutes.
Loss of pain sensibility
Acute nerve compression causes ____ after 45 minutes.
Muscle weakness
Relief of nerve compression is followed by intense ___ lasting up to 5 minutes.
Paresthesia
What are the types of peripheral nerve injuries?
1) Transient ischemia
2) Neuropraxia
3) Axonotmesis
4) Neurotmesis
What is neuropraxia?
Reversible block to nerve conduction in which there is loss of sensation and muscle power, followed by spontaneous recovery after a few days or weeks.
What is axonotmesis?
A more severe form of nerve injury in which there is interruption of the axons in a segment of nerve
When is axonotmesis typically seen?
After closed fractures and dislocations
What happens to the denervated motor endplates and sensory receptors in axonotmesis if they are not re-innervated within 2 years?
They will never recover
What is neurotmesis?
Complete disconnect of a nerve
Where could we see neurotmesis?
Open wounds
Neurotmesis will never recover without ___.
Surgical intervention
Nerve loss in low energy injuries is likely due to:
Neuropraxia
Nerve loss in high energy injuries and open wounds is likely due to:
Axonotmesis or neurotmesis
What is a classic sign of progressive nerve recovery?
Tinel’s sign
What is Tinel’s sign?
Peripheral tingling provoked by percussing the nerve at the site of injury (where regenerating axons are most sensitive).
Which tests may help to establish the level and severity of the injury, plus progress of nerve recovery?
1) Nerve conduction tests
2) Electromyography
The brachial plexus includes which nerve roots?
C5-T1
What causes brachial plexus injuries?
Stab wound or severe traction caused by a fall on the side of the neck or the shoulder
Supraclavicular lesions typically occur in:
Motorcycle accidents
Infraclavicular lesions are usually associated with:
Fractures or dislocations of the
shoulder
Do clavicular fractures cause brachial plexus injuries?
No
___(Postganglionic/Preganglionic) brachial plexus lesions cannot recover and are surgically irreparable, while ___(Postganglionic/Preganglionic) lesions can be repaired and are capable of recovery.
Preganglionic; Postganglionic
Clinical examination of brachial plexus injuries should establish:
1) Level of the lesion
2) Preganglionic or postganglionic
3) Type of damage
Upper plexus injuries (C5 and 6) present with:
1) Arm hanging close to the body and internally rotated
2) Sensation is lost along the outer aspect of the arm and forearm
Total plexus lesions present with:
Paralysis and numbness of the entire limb
Features suggesting preganglionic root avulsion are:
1) Burning pain in an anesthetic hand
2) Paralysis of scapular muscles or diaphragm
3) Horner’s syndrome
4) Severe vascular injury
5) Associated fractures of the cervical spine
6) Spinal cord dysfunction
Is the Histamine test
positive or negative in preganglionic root avulsion?
Positive
Is the Histamine test
positive or negative in postganglionic root avulsion?
Negative
Management of brachial plexus injuries?
Emergency surgery
What is obstetrical palsy?
Palsy caused by excessive traction on the brachial plexus during childbirth (Prolonged labor and/or shoulder dystocia)
Upper root injuries in babies cause which palsy?
Erb’s palsy; (C5,C6)
Upper brachial root injuries (Erb’s palsy) are typically seen in:
Overweight babies with shoulder dystocia at delivery
Management for upper brachial root injury (Erb’s palsy)?
Nothing, they recover spontaneously
Lower brachial root injuries in babies cause which palsy?
Klumpke’s palsy; (C8 and T1)
Lower brachial root injuries (Klumpke’s palsy) are typically seen in:
After breech delivery of smaller babies
How does Klumpke’s palsy present?
1) Arm supinated and the elbow flexed
2) Loss of intrinsic muscle power in the hand
Which palsy presents with long thoracic nerve injury?
Serratus anterior palsy
How does serratus anterior palsy present?
Winging of the scapula
Where does the spinal accessory nerve run?
1) In the posterior triangle of the neck to the upper trapezius
2) Then descends obliquely behind the Digastric and Stylohyoid to the upper part of the Sternocleidomastoid
3) Then courses obliquely across
the posterior triangle of the neck, to end in the deep surface of the Trapezius
What does the spinal accessory nerve innervate?
1) Trapezius
2) SCM
When should you suspect spinal accessory nerve injuries?
In stab wounds and operations in the posterior triangle of the neck
Where can the radial nerve be injured?
1) Elbow
2) Upper arm
3) Axilla
How do low radial nerve lesions (elbow) present?
Can’t extend the metacarpophalangeal joints
How do high radial nerve lesions present?
Wrist drop due to weakness of the wrist extensors and a small patch of sensory loss on the
back of the hand at the base of the thumb
What causes high radial nerve lesions?
1) Fractures of the humerus
2) After prolonged tourniquet pressure
3) Patients who fall asleep with the arm dangling
High radial nerve lesions cause which palsy?
Saturday night palsy
Very high radial nerve lesions cause which palsy?
Crutch palsy
How do very high radial nerve lesions present?
Triceps muscle is wasted and
paralyzed
What type of nerve injury is a radial nerve injury caused by pressure?
Axonotmesis
Do radial nerve injuries caused by pressure heal?
Yes, spontaneously
Where is the ulnar nerve usually injured?
1) Wrist
2) Elbow
How do low ulnar lesions (wrist) usually present?
1) Hypothenar wasting
2) Claw hand
3) Weak finger abduction
4) Loss of thumb adduction (Froment’s positive)
5) Sensation is lost over the pinky and half ring
What causes claw hand in ulnar nerve lesions?
Paralysis of the intrinsic muscles
How do high ulnar lesions (elbow) usually present?
Same as low with only mild claw hand
Why is claw hand not as pronounced in high ulnar lesions?
Because the ulnar half of flexor digitorum profundus is paralyzed
What is the ulnar paradox?
Claw hand gets worse at first after recovery because of reinnervation of the FDP
Where is the median nerve usually injured?
1) Wrist
2) High up in the forearm/elbow
How do low median lesions (wrist) usually present?
1) Thenar eminence is wasted
2) Weak thumb abduction and opposition
3) Sensation is lost over the palmar thumb, index, middle, and half ring
How do high median lesions (forearm/elbow) usually present?
Long flexors to the thumb, index, and middle fingers are paralyzed
How does a femoral nerve injury present?
1) Weakness of knee extension (quadriceps)
2) Numbness of the anterior
thigh and medial aspect of the leg
3) Depressed knee jerk
Where is the femoral nerve usually injured?
Thigh
What sciatic nerve injuries are common?
1) Traction
2) Compression
How does a sciatic nerve injury present?
1) Foot-drop
2) Numbness and paresthesia in the leg and foot
Which nerve palsy is one of the recognized complications of hip replacement?
Sciatic nerve palsy
Sciatic nerve injury may be mistaken for:
Peroneal nerve injury
What can cause common peroneal nerve injuries?
1) Lateral ligament injuries (when the knee is forced into varus)
2) Pressure from a splint or a plaster cast
3) Lying with the leg externally rotated
How does a common peroneal nerve injury present?
1) Foot-drop in which both dorsiflexion and eversion are weak = tendency to trip and fall while walking
2) Sensation is lost over the front and outer half of the leg and the dorsum of the foot.
How does a superficial peroneal nerve injury present?
1) Peroneal muscles are paralyzed
2) Eversion is lost
3) Loss of sensation over the outer side of the leg and foot
How does a deep peroneal nerve injury present?
1) Anterior compartment syndrome
2) Sensory loss around the first web space on the dorsum of the foot
The first step for approaching foot-drop is:
Determining if it is unilateral or bilateral
The most common sites of nerve entrapments?
1) Carpal tunnel at the wrist (median nerve)
2) Cubital tunnel at the elbow (ulnar nerve)
How can you confirm nerve entrapment?
By measuring nerve conduction velocity
What is thoracic outlet syndrome?
Compression of the lower trunk of the brachial plexus (C8 and T1) and subclavian vessels between the clavicle and the first rib.
What vessels and nerves are found in the thoracic outlet?
1) Subclavian vessels
2) Trunks of the brachial plexus
What is the most common compressive neuropathy?
Carpal tunnel syndrome
What is carpal tunnel syndrome?
Compression of the median nerve beneath transverse carpal ligament
Where are the sites of ulnar nerve compression?
1) Elbow -> Behind the medial epicondyle
2) Wrist -> Radial to the pisiform
Carpal tunnel occurs more commonly in __(men/women)
Women
Ulnar nerve compression occurs more commonly in __(men/women)
Men
Ulnar nerve compression at the elbow most commonly happens:
Spontaneously
Ulnar nerve compression at the wrist most commonly happens:
By a ganglion from the underlying joint
X-rays of the neck in thoracic outlet syndrome occasionally show:
A cervical rib or an abnormally long C7 transverse process
What should you exclude in thoracic outlet syndrome?
1) Apical tumor in lungs
2) Shoulder lesions
Differential diagnoses of thoracic outlet syndrome?
1) Tumors of the lower cervical cord or cervical vertebrae
2) Cervical spondylosis
3) Pancoast’s syndrome
