MEDIAN NERVE COMPRESSION NEUROPATHIES

Question 1

5 potential sites of compression of median nerve

Answer 1

4 around elbow and 1 at wrist

1. Supracondylar process/ spur and ligament of Struthers
2. Lacertus fibrosus/ bicipital aponeurosis
3. Heads of PT
4. Fibrous arch of FDS
5. Carpal tunnel

Question 2

Formation of median nerve in axilla

Answer 2

• Medial and lateral roots from the medial and lateral cords of the brachial plexus
• Medial root = C8-T1 fibres and primarily motor
• Lateral root = C5-7 fibres and primarily sensory

Question 3

3 structures median nerve crosses in cubital fossa

Answer 3

1. Over the ulnar artery
2. Between heads of PT
3. Under fibrous arch of FDS

Question 4

Origin of AIN

Answer 4

• Arises from radial aspect of median nerve just distal to fibrous arch of FDS
• Approx 5cm distal to medial epicondyle

Question 5

Origin of palmar cutaneous branch of median nerve

Answer 5

• Arises from radial aspect of median nerve 5cm proximal to wrist
• Lies between PL and FCR tendons

Question 6

Anatomy of median nerve at distal margin of carpal tunnel

Answer 6

• Thickens and flattens to form recurrent motor branch
• Then divides into radial and ulnar divisions
• Radial division = common digital nerve to thumb and proper digital nerve to IF
• Ulnar division = common digital nerves to MF and radial aspect of RF

Question 7

Anatomy of cubital fossa

Answer 7

• Triangular space over anterior aspect of elbow
• Boundaries:
  1. Proximal = transepicondylar line (imaginary horizontal line between epicondyles)
  2. Inferomedial = PT
  3. Inferolateral = BR
• 4 contents from medial to lateral:
  1. Median nerve
  2. Brachial artery
  3. Biceps tendon
  4. Radial nerve

Question 8

Anatomy of supracondylar process and ligament of Struthers

Answer 8

• Supracondylar process is an embryological remnant seen in 1% of population
• Bony exostosis from medial aspect of distal humerus
• Approx 5cm proximal to medial epicondyle
• Ligament of Struthers is a fibrous band passing from supracondylar process to medial epicondyle
• Results in a fibroosseous tunnel through which brachial artery and median nerve pass = potential site for compression

Question 9

Differentiating pronator syndrome vs. CTS

Answer 9

Both cause pain, sensory deficits and motor deficits

1. Pronator syndrome
   - pain over volar forearm worse after activity
   - abnormal sensation over thenar eminence
   - weakness in all median nerve innervated muscles
2. CTS
   - nocturnal symptoms
   - normal sensation over thenar eminence
   - weakness only in thenar muscles esp. APB

Question 10

3 factors to consider with management of all compression neuropathies

Answer 10

1. Underlying cause = reversible vs. irreversible
2. Duration of symptoms
3. Severity of symptoms

Question 11

3 main surgical indications for all compression neuropathies

Answer 11

1. Failure of nonoperative measures over 3-6mo
2. Significant weakness/ wasting at presentation
3. Clear irreversible underlying cause = SOL

Question 12

Anatomy of arcade of Struthers

Answer 12

• Present in 80% of population
• Tunnel formed by fascial band passing from medial head of triceps to medial IM septum
• Lies 8cm proximal to medial epicondyle
• Ulnar nerve passes through it

Question 13

Differentiating supracondylar spur vs. osteochondroma

Answer 13

• Supracondylar spur points toward physis

- Osteochondroma points away from physis