Upper Limb Lecture

Question 1

Neuropraxia

Answer 1

• Least severe type of peripheral nerve injury.
• Only the myelin is damaged, axon & connective tissue remain intact.
• Resolves on its own within days to weeks.
• Minimal to no autonomic dysfunction.

Question 2

Axonotmesis

Answer 2

• Axon is damaged, but the surrounding Schwann cell sheath remains intact.
• Leads to motor, sensory, and autonomic dysfunction.
• Recovery possible with removal of compression, but may take months.
• Recovery is often incomplete, with potential lasting deficits.

Question 3

Neurotmesis

Answer 3

• Most severe type of peripheral nerve injury.
• Complete disruption of axon and surrounding nerve sheath.
• Often results in poor or no nerve regeneration.
• Leads to permanent motor, sensory, and autonomic deficits.

Question 4

What are the different mechanisms of Nerve Injury?

Answer 4

Direct Pressure
- Direct pressure disrupts nerve function.
- May damage myelin or axon.

Microtrauma
- Repeated small injuries (microtrauma) accumulate over time.
Can contribute to nerve dysfunction.

Stretching & Ischemia
- Stretching reduces blood flow (ischemia).
- Leads to a lack of oxygen and nutrients.
- Damages the nerve.

Compression & Ischemia
- Compression reduces blood flow (ischemia).
- Deprives nerve of oxygen and nutrients.
- Causes damage.

Severity of Injury
- Severity of injury determines extent of damage.
- Ranges from myelin disruption to complete axon damage.

Duration of Injury/Compression
- Longer exposure to injury or compression worsens damage.
- Increases risk of long-lasting effects.

Question 5

Factors Affecting the Severity of Nerve Injury?

Answer 5

• How severe the injury is
• How long the nerve is exposed to compression or injury

Question 6

What is a dermatome

Answer 6

Dermatome is the area of skin primarily supplied by a single spinal nerve

Question 7

What is a dermatome responsible for?

Answer 7

A dermatome is responsible for conveying sensory information (e.g., pain, touch, temperature) from a specific area of skin to the brain.

Question 8

What role do the dorsal root ganglia play in processing sensory information?

Answer 8

• The dorsal root ganglia serve as a hub where sensory information (such as pain, touch, and temperature) from the skin enters the nervous system.
• These ganglia contain the neurons that send sensory signals from a specific area of skin (a dermatome) up through the spinal cord to the brain.

Question 9

Cutaneous innervation refers to

Answer 9

The distribution of sensory nerves that provide sensation (such as touch, pain, temperature, and pressure) to the skin.

These nerves arise from different nerve roots or branches and are responsible for transmitting sensory information from specific areas of the skin to the brain.

Question 10

Muscle tone refers to

Answer 10

the resistance of muscles when a joint is moved passively (without the person using their muscles).

Question 11

Anterior horn cells in the spinal cord play a crucial role in,
What is the function in anterior horn cells

Answer 11

Motor control

Anterior horn cells are found in the front (anterior) part of the spinal cord

Function: They are responsible for sending signals to the muscles in the body. These cells contain the nerve cell bodies of motor neurons, which control voluntary movements.

Question 12

Within hypertonia, two specific conditions are often discussed:

Answer 12

Spasticity & Rigidity - Hypertonia is the umbrella term that includes both spasticity and rigidity

Ridigity - characterized by a constant increase in muscle tone that does not change with movement. It is often associated with conditions like Parkinson’s disease

In rigidity, the muscles feel stiff and do not relax, which can lead to a decreased range of motion and difficulty in initiating movement

Spasticity - condition characterized by increased muscle tone that results in stiff or tight muscles. It is often due to an imbalance in signals from the brain to the muscles, usually caused by conditions affecting the central nervous system, such as stroke, multiple sclerosis, or cerebral palsy.

Question 13

Within Hypertonia, how is Rigidity charactersied?
What are the different types of ridigity that can happen in the body?

Answer 13

Ridigity - Increased resistance occurs regardless of movement direction. It is often associated with conditions like Parkinson’s disease

• Both agonist (prime mover) and antagonist (opposing) muscles are affected equally—this is called Lead-Pipe rigidity. (Commonly associated with Parkinson’s disease.)
• When there are ratchet-like jerks during movement (like a ticking sensation), often linked to tremors, it’s known as Cogwheel rigidity.

Question 13

Rigidity is usually a sign of

Answer 13

Extrapyramidal dysfunction,

typically involving the Basal Ganglia (a part of the brain involved in movement control).

Question 14

Hypotonia refers to..

Answer 14

excessive floppiness in the muscles

• There is reduced resistance to passive movement, meaning:
  ○ The limb can be easily moved, especially the distal parts (hands and feet).
  ○ The muscle belly may appear flattened and feels less firm when palpated.

Question 15

Hypotonia is often related to…

Answer 15

Lower Motor Neuron Lesion (LMNL)

but it can also be linked to:
- Disruption of the afferent aspect of the reflex arc (problems in the pathway that carries sensory information to the spinal cord).

• Cerebellar disease (problems in the part of the brain that coordinates movement).

Question 16

Abnormal muscle tone often seen in elderly patients

Answer 16

Paratonia

Question 17

Two Types of Paratonia?

Answer 17

Involuntary Resistance: The patient seems unable to relax and involuntarily resists your attempts to move their limb.

Facilitated Movement: The patient seems unable to relax and actively assists (facilitates) your attempts to move their limb.

Question 18

Cause of Paratonia?

Answer 18

often points to frontal lobe damage or cerebral disease, such as:
○ Anterior cerebral artery occlusion (blockage of a key brain artery).
○ Arteriosclerotic parkinsonism (Parkinsonism due to hardening of the brain’s arteries).

Question 19

What are the 5 main nerves coming from the brachial plexus?

Answer 19

1. Axillary nerve
   
   2. Musculocutaneous nerve
   3. Radial nerve
   4. Median nerve
   5. Ulnar nerve

Question 20

The brachial plexus can be compressed or irritated by various factors, causing _______________
These factors can include:…

Answer 20

Thoracic Outlet Syndrome

These factors include:
○ Tight scalene muscles (anterior, middle, and posterior)
○ Enlarged transverse processes (TVP)
○ Cervical rib (an extra rib above the first rib)
○ Tight pectoralis minor muscle
○ Compression in the subclavicular space (space under the clavicle)
○ Pancoast tumor (a tumor at the top of the lung)
○ Trauma
These issues can compress the nerves or blood vessels passing through the thoracic outlet, leading to pain, numbness, and weakness in the arms and hands

Question 21

Axiliary Nerve Originates from __ __

Answer 21

C5-C6

Question 22

Axiliary branch divides into 2 branches, what muscles do they innervate? (Anterior and posterior)

Answer 22

Anterior branch: Innervates the anterior and lateral deltiod muscle (front and side of shoulder)
Posterior branch: Innervates the teres minor and posterior deltiod

Question 23

Axillary Nerve Cutaneous Innervation

Answer 23

The axillary nerve provides cutaneous innervation via the upper lateral cutaneous nerve of the arm (superior lateral brachial cutaneous nerve).

Damage to the axillary nerve (e.g., from shoulder dislocation) may result in numbness or sensory loss in this area.

Question 24

The axillary nerve passes through the ____ space

Answer 24

quadrangular space

Question 25

Increased Risk Factors for Axillary & Brachial Plexus Nerve Injuries After Shoulder Dislocation

Answer 25

The risk of axillary and brachial plexus nerve injuries increases significantly after a shoulder dislocation, especially if: There is an associated fracture of the humeral head. The dislocation lasts longer than 12 hours.

Question 26

Prevalence of Axillary Nerve Damage in Shoulder Injuries

Answer 26

9-65% of shoulder injuries involve damage to the axillary nerve.

Question 27

Musculocutaneous Nerve - Origin

Answer 27

Arises from the lateral cord of the brachial plexus. Derived from roots C5, C6, C7

Question 28

Musculocutaneous Nerve - Muscle Innervation

Answer 28

The musculocutaneous nerve innervates the muscles of the anterior compartment of the arm, specifically: BBC Biceps brachii Brachialis Coracobrachialis These muscles are responsible for flexion of the elbow and supination of the forearm.

Question 29

Musculocutaneous Nerve - Cutaneous Innervation

Answer 29

The musculocutaneous nerve provides cutaneous innervation via the lateral cutaneous nerve of the forearm. This supplies sensation to the lateral aspect of the forearm, including the skin over the radial side of the forearm.

Question 30

Radial Nerve - Origin

Answer 30

Arises from the posterior cord of the brachial plexus. Derived from roots C5, C6, C7, C8, T1.

Question 31

Radial Nerve - Muscle Innervation

Answer 31

Triceps Brachii Brachioradialis Extensor Carpi Radialis Longus Part of Brachialis (mostly innervated by the musculocutaneous nerve)

Question 32

Radial Tunnel Syndrome - Location of Compression

Answer 32

The radial nerve exits between the brachioradialis and brachialis muscles. It travels under the supinator muscle, particularly at the Frohse arcade (a fibrous band at the top of the supinator). Compression can occur at this point.

Question 33

Radial Tunnel Syndrome - Affected Nerves

Answer 33

The deep branch (motor) of the radial nerve is most commonly compressed. Sometimes the superficial branch (sensory) may also be compressed.

Question 34

Radial Tunnel Syndrome - Symptoms

Answer 34

Pain: A deep, aching pain in the upper forearm (extensor side). Sensory changes: Possible abnormal sensations (dysesthesia) in the superficial radial nerve distribution. Weakness: Possible weakening of extension in the fingers, thumb, or wrist.

Question 35

What is Posterior Interosseous Syndrome?

Answer 35

A nerve compression where the posterior interosseous nerve (branch of the radial nerve) gets trapped.

Question 36

Causes of Posterior Interosseous Syndrome?

Answer 36

Compression in or around the supinator muscle. Injuries like radial head fractures or growths (ganglions, lipomas).

Question 37

Symptoms of Posterior Interosseous Syndrome

Answer 37

Pain: In the forearm near the elbow. Weakness: In finger and wrist extension. No sensory loss: Motor-only nerve

Question 38

Radial Nerve Connection?

Answer 38

The posterior interosseous nerve is a branch of the radial nerve. Compression leads to motor issues, no sensory loss.

Question 39

Muscle Sparing in Posterior Interosseous Syndrome?

Answer 39

Muscles like **extensor carpi radialis brevis, brachioradialis, and extensor carpi radialis longus** may function because their nerves are unaffected.

Question 40

Median Nerve - Origin?

Answer 40

Arises from **lateral and medial cords** of the brachial plexus. Spinal Roots: C5, C6, C7, C8, T1 (C5-T1)

Question 41

Median Nerve - Muscle Innervation?

Answer 41

Pronator Teres Flexor Carpi Radialis Flexor Digitorum Superficialis Palmaris Longus

Question 42

Ulnar Nerve - Origin?

Answer 42

Arises from the medial cord of the brachial plexus. Roots: **C8 and T1**.

Question 43

Ulnar Nerve - Muscular Innervation?

Answer 43

Flexor Carpi Ulnaris Flexor Digitorum Profundus (medial half) Palmaris Brevis All 8 Interossei Adductor Pollicis Medial Lumbricals (2) Abductor Digiti Minimi Flexor Digiti Minimi Opponens Digiti Minimi

Question 44

Ulnar Nerve - Cutaneous Innervation?

Answer 44

Front of Hand: - Supplies sensation to the medial aspect of the palm, including the little finger and half of the ring finger. Back of Hand: - Innervates the skin on the back of the hand for the little finger and half of the ring finger, extending to the distal phalanges.

Question 45

Cubital Tunnel Syndrome - Overview (definition, location of compression and demographics)

Answer 45

Definition: Second most common compressive neuropathy. Location of Compression: Most damage occurs at the elbow, particularly where the ulnar nerve passes through the cubital tunnel. Demographics: Affects men more often than women.

Question 46

Causes of Cubital Tunnel Syndrome

Answer 46

* Constricting fascial bands: Tight bands of tissue can compress the nerve. * Compromise under anesthesia: Nerve may be affected during surgery. * Subluxation of the ulnar nerve: Nerve slips out of place over the medial epicondyle. * Bony spurs: Bone growths that may press on the nerve. * Joint deformity: Conditions like osteoarthritis or rheumatoid arthritis narrow the ulnar groove, constricting the nerve. * Medial epicondylitis: Also known as golfer's elbow, associated with nerve compression. * Tumors or ganglia: Growths that can put pressure on the nerve. * Direct compression: Leaning on elbows habitually can compress the nerve. * Repetitive movements: Frequent elbow flexion/extension, heavy manual work, or playing instruments like guitar/drums can strain the area.

Question 47

Ulnar Nerve - Pathway at the Wrist?

Answer 47

After passing through the Tunnel of Guyon, the ulnar nerve branches into: Deep Motor Branch: Purely motor functions. Superficial Cutaneous Branch: Sensory functions.

Question 48

Ulnar Nerve at Wrist- Deep Motor Branch Innervation?

Answer 48

Innervates the following muscles: All 8 Interossei Muscles: Palmar Interossei: Adduct fingers (bring them together). Dorsal Interossei: Abduct fingers (spread them apart). Medial 2 Lumbricals: Flex the MCP joints. Extend the interphalangeal joints. Adductor Pollicis: Adducts the thumb. Abductor Digiti Minimi: Abducts the little finger. Flexor Digiti Minimi: Flexes the little finger. Opponens Digiti Minimi: Allows the little finger to oppose the thumb.

Question 49

Ulnar Nerve at Wrist - Superficial Cutaneous Branch Innervation

Answer 49

Provides sensory innervation to: Medial palm. 5th finger (little finger) and half of the 4th finger (ring finger). Palmaris Brevis: A small muscle on the palm.

Question 50

Ulnar Nerve at Wrist - Pathway at the Wrist

Answer 50

Passes through the Tunnel of Guyon and branches into: Deep Motor Branch: Purely motor functions. Superficial Cutaneous Branch: Sensory functions.

Question 51

Ulnar Nerve at Wrist - Deep Motor Branch Innervation

Answer 51

Innervates the following muscles: Interossei Muscles (8 total): Palmar Interossei: Adducts fingers. Dorsal Interossei: Abducts fingers. Medial 2 Lumbricals: Flexes MCP joints. Extends interphalangeal joints. Adductor Pollicis: Adducts the thumb. Abductor Digiti Minimi: Abducts the little finger. Flexor Digiti Minimi: Flexes the little finger. Opponens Digiti Minimi: Opposes the little finger to the thumb.

Question 52

Ulnar Nerve at Wrist - Superficial Cutaneous Branch Innervation

Answer 52

Provides sensory innervation to: Medial palm. 5th finger (little finger) and half of the 4th finger (ring finger). Palmaris Brevis: Small muscle on the palm.

Question 53

Pronator Teres Syndrome - Definition?

Answer 53

Condition caused by compression of the median nerve between the heads of the pronator teres muscle, leading to motor and sensory symptoms.

Question 54

Pronator Teres Syndrome - Symptoms?

Answer 54

* Paresthesia: ○ Tingling or abnormal sensations in the radial fingers (thumb, index, and middle fingers). * Tenderness: Tenderness to pressure over the pronator teres muscle.

Question 55

Pronator Teres Syndrome - Symptoms: Motor Difficulties?

Answer 55

Difficulty flexing index and middle fingers (affected: flexor digitorum profundus, lateral two lumbricals). Difficulty flexing or opposing the thumb (affected: flexor pollicis longus, flexor pollicis brevis, opponens pollicis).

Question 56

Pronator Teres Syndrome - Symptoms: Sensory Changes?

Answer 56

Front Surface: Sensation to the palmar surface of the index finger, middle finger, and half of the ring finger. Back Surface: Sensation to the dorsal surface of the distal phalanxes of the index finger, middle finger, and half of the ring finger.