May 30, 2024

Nerve injuries are important short cases for clinical examinations and OSCE for medical students

Anatomy of nerve
Anatomy of nerve

Radial Nerve

Branches from Posterior Cord of Brachial plexus( Infront of subscapularis)

Anterior to lattismus dorsi

Through triangular space with profundus brachii artery

Enters upper arm between long head of triceps and medial head of triceps

Spiral groove

Courses laterally and pierces the lateral intermuscular septum

(122mm above lateral epicondyle)

Passes into the anterior compartment

At the level of the lateral epicondyle, it gives 2 branches

  • Deep Posterior Interosseous Nerve (Purely Motor) which enters extensor compartment between 2 heads of supinator (Arcade of fortse) and supplied radial side and dorsal side of the forearm which supplies to
    • Superficial group: ECU, ED, EDM
    • Deep group: A(bd)PL, EPL, EPB, EI
  • The superficial branch of the radial nerve goes deep to the brachioradialis and emerges 5 cm above the wrist between the brachioradialis and ECR which goes towards the anatomical snuffbox to supply the dorsum of the hand

Median Nerve(C6-T1)

The medial and lateral cord of the brachial plexus

The medial side of the arm between biceps brachii and brachialis

The close relation to the brachial artery

NO BRANCHES IN THE UPPER ARM

Cubital fossa (B-A-N)

(Bicep tendon- Artery- Nerve) Lateral to medial

Passes between 2 heads of pronator teres

Gives Anterior Interosseous Nerve (AIN)

In forearm continues (FDS and FDP)

Emerges just proximal to wrist between FCR and PL

Passes through the Carpal tunnel

Divide in hand as recurrent motor branches and sensory branches

  • Palmer cutaneous nerve
  • Thenar Group
    • APB
    • FPB
    • OP
    • 1st and 2nd lumbricals

Ulnar nerve (C8 – T1)

The median cord of the brachial plexus

Inferior medial to the axillary artery to continue behind the brachial artery over tricep muscle

Passes straight to the posterior aspect of medial epicondyle in ”ulnar groove” between medial epicondyle and olecranon

NO BRANCHES IN THE UPPER ARM AND AXILLA

Passes to the 2 heads of FCU

Remains deep to FCU overlying FDP muscle accompanied with the ulnar artery

Passes superficial; emerging beneath FCU and reaches Guyon’s canal at the wrist

  • Deep branches:
    • Three hypothenar
    • Medial 2 lumbricals
    • 7 Interossei
    • Adductor pollices
    • Deep head of FPB
  • Superficial branches:
    • Palmer cutaneous branches of the ulnar nerve ( sensation over palm of hand, medial dorsal aspect of hand, and one and a half finger)
    • Palmaris brevis muscle

Approach to the short case

While approaching a nerve injury patient certain questions should be answered which is expected from examiner,

Which?

Dominant or Non-dominant

When?

Time elapsed since injury

How?

Mechanism of injury

  • Tractional
  • Contusion
  • Compression
  • Laceration

What?

Treatment that patient got

At End the student should answer:

  • Nerve Involved
  • High/ Low
  • Complete/ Incomplete
  • Neuropraxia/ Axonotemesis/ Neurotomesis
  • Recovering/ Non- recovering
  • Management

Eg:

High radial nerve palsy, complete, neurotomesis as per Seddon, no sign of recovery of the non-dominant hand

Look

Site of scar

Ulcers

Smooth/ dryness

Circulatory changes

Temperature

Characteristics of posture in nerve injury

  1. Radial Nerve- Wrist drop
  2. Ulnar Nerve- Claw Hand
  3. Median Nerve – Ape thump
  4. Combined Median and Ulnar Nerve- Simian thump

Alteration of contour

Loss of muscle bulk

The prominence of bones normally masked by muscle

Muscle and its supply in the forearm and wrist

Median Nerve

Look for PT: Flex the elbow to 30 degrees and ask to pronate the forearm

Look for PQ: Completely flex the elbow and ask to pronate the forearm

APB: Pen test

FCR: Resistance against flexion of the wrist against resistance

Look for FDS, FDP

Bennet ‘O’ Sign: Not able to make O due to paralysis of FPL and FDP

Oschner’s Pointing Index

Ulnar nerve

Card Test: To test Interossei (Palmer ADduction, Dorsal ABduction)

Resistance flexion of the wrist against ulnar deviation: FCU

By abduction of individual muscles: 1st dorsal interossei

Unable to cross the index and middle finger

Pitres-stut test: Abduct the middle finger on either side

Pitres-stut sign 2: Try to make a cone with extended fingers (Not able to do it)

Unable to abduct little finger: ADM

Wartenberg sign: Due to paralyzed ADM there will be the unopposed pull of extensors==> little finger goes into abduction and extension

Jeanes Sign: Paralysis of FPB and A(dd)P-> Loss of key pinch

Smith Sign: Loss of lateral movement in extension due to paralysis of interossei

Forment book Test: Paralysis of A(dd)P= compensated by flexion of the thumb

Duchenne’s Sign: Loss of MCP flexion, Clawing

Bouvier’s maneuver: MCP stabilized in slight flexion: PIP joint extended by extensor tendons