The radial nerve provides motor innervation to the posterior arm and forearm muscles and sensory innervation to the back of the hand. It is susceptible to injury at various points along its course from the axilla to the forearm. High radial nerve palsies occur near the radial groove of the humerus and cause loss of wrist and finger extension while sparing elbow extension. Low radial nerve palsies affect function below the elbow. Physical exam assesses affected muscle groups and sensory areas. Treatment involves splinting and may include injections or surgery to repair the nerve or transfer tendons.

1. RADIAL NERVE PALSY

2. ANATOMY OF RADIAL NERVE
 CONTINUATION OF POSTERIOR CORD
OF BRACHIAL PLEXUS – C5,C6,C7,C8 AND
T1
 MIXED NERVE
 LARGEST BRANCH OF BRACHIAL PLEXUS
 IN THE AXILLA:
GIVES OFF A BRANCH TO LONG HEAD
OF TRICEPS AND ENTERS THE ARM
LEAVES THE AXILLA THROUGH THE
TRIANGULAR SPACE

3. IN THE ARM,
 HAVING PASSED THROUGH THIS INTER MUSCULAR GAP, THE RADIAL
NERVE CONTINUES POSTERIORLY IN A MEDIAL TO LATERAL FASHION
ON THE ARM WHILE IN CONJUNCTION WITH THE DEEP ARTERY OF
ARM.
 THE NERVE WILL FIRST GIVE OFF BRANCHES TO THE MEDIAL HEAD OF
THE TRICEPS BRACHII AND THEN ENTER A GROOVE ON THE HUMERUS,
THE RADIAL SULCUS ,WHERE IT INNERVATES THE LATERAL HEAD OF
THE TRICEPS.
 THEN THE RADIAL NERVE EMERGES FROM THE RADIAL GROOVE ON
THE LATERAL ASPECT OF THE HUMERUS.
 AT THIS POINT, IT PIERCES THE LATERAL INTERMUSCULAR SEPTUM
AND ENTERS THE ANTERIOR COMPARTMENT OF THE ARM.

4.  IT THEN COURSES INFERIORLY BETWEEN THE BRACHIALIS AND
BRACHIORADIALIS MUSCLES.
 WHEN THE RADIAL NERVE REACHES THE DISTAL PART OF THE
HUMERUS, IT PASSES ANTERIORLY TO THE LATERAL EPICONDYLE AND
CONTINUES IN THE FOREARM

6. IN THE ARM,
 IN THE FOREARM, IT BRANCHES INTO A SUPERFICIAL BRANCH
(PRIMARILY SENSORY) AND A DEEP BRANCH (PRIMARILY MOTOR).
 THE SUPERFICIAL BRANCH OF THE RADIAL NERVE DESCENDS IN
THE FOREARM UNDER THE BRACHIORADIALIS.
 IT EMERGES B/W BR AND ECRL, 8CM PROXIMAL TO RADIAL STYLOID
TO BECOME S/C.
 IT CROSSES ANATOMICAL SNUFF BOX B/W EPB AND EPL
 IT GIVES NERVE SUPPLY TO DORSAL ASPECT OF THUMB, INDEX
FINGER,MIDDLE FINGER AND RADIAL SIDE OF RING FINGER EXCEPT
THE NAIL BEDS, WHICH ARE SUPPLIED BY PROPER DIGITAL
BRANCHES OF MEDIAN NERVE.

7.  THE DEEP BRANCH OF THE RADIAL NERVE PIERCES THE
SUPINATOR MUSCLE, WINDS AROUND THE RADIUS UNDER THE
COVER OF SUPINATOR TO REACH POSTERIOR OF FOREARM
WHERE IT AGAIN PIERCES SUPINATOR AND AFTER WHICH IT IS
KNOWN AS THE POSTERIOR INTEROSSEOUS NERVE OF
FOREARM.
 IT PIERCES THE POSTERIOR EXTENSOR MUSCLES AND COMES TO
LIE ON POSTERIOR INTEROSSEOUS MEMBRANE JUST BELOW
EXTENSOR POLLICIS BREVIS.
 IT CONTINUES TO MOVE ALONG WITH POSTERIOR
INTEROSSEOUS ARTERY(A DEEP BRANCH OF COMMON
INTEROSSEOUS ARTERY WHICH IS A BRANCH OF ULNAR
ARTERY), AND ENDS AS A PSEUDOGANGLION BELOW EXTENSOR
RETINACULUM

10. FUNCTIONS
 CUTANEOUS INNERVATION BY THE RADIAL NERVE IS PROVIDED BY
THE FOLLOWING NERVE BRANCHES:
•POSTERIOR CUTANEOUS NERVE OF ARM (ORIGINATES IN AXILLA)
•INFERIOR LATERAL CUTANEOUS NERVE OF ARM (ORIGINATES IN ARM)
•POSTERIOR CUTANEOUS NERVE OF FOREARM (ORIGINATES IN ARM)
 THE SUPERFICIAL BRANCH OF THE RADIAL NERVE PROVIDES SENSORY
INNERVATION TO MUCH OF THE BACK OF THE HAND, INCLUDING THE
WEB OF SKIN BETWEEN THE THUMB AND INDEX FINGER

11. MUSCULAR BRANCHES OF THE RADIAL NERVE:
•TRICEPS BRACHII (LATERAL AND MEDIAL HEADS)
•ANCONEUS
•BRACHIORADIALIS
•EXTENSOR CARPI RADIALIS LONGUS
 DEEP BRANCH OF THE RADIAL NERVE:
•EXTENSOR CARPI RADIALIS BREVIS
•SUPINATOR

12. POSTERIOR INTEROSSEOUS NERVE (A CONTINUATION OF THE DEEP BRANCH
AFTER THE SUPINATOR):
•EXTENSOR DIGITORUM
•EXTENSOR DIGITI MINIMI
•EXTENSOR CARPI ULNARIS
•ABDUCTOR POLLICIS LONGUS
•EXTENSOR POLLICIS BREVIS
•EXTENSOR POLLICIS LONGUSS
•EXTENSOR INDICIS
THE RADIAL NERVE (AND ITS DEEP BRANCH) PROVIDES MOTOR INNERVATION
TO THE MUSCLES IN THE POSTERIOR COMPARTMENT OF THE ARM AND
FOREARM, WHICH ARE MOSTLY EXTENSORS.

13. AETIOLOGY AND CLINICAL FEATURES
 VERY HIGH RADIAL NERVE PALSY
IN THE AXILLA
CAUSES- CRUTCH PALSY, ANEURYSM OF AXILLARY VESSELS
SATURDAY NIGHT PALSY
CF- TOTAL PALSY
WRIST DROP

14.  HIGH RADIAL NERVE PALSY
COMMONLY IN THE RADIAL GROOVE
CAUSES- # SHAFT OF HUMERUS(COMMON),
PROLONGED APPLICATION OF TOURNIQUET,
INJECTIONS,
FORMATION OF EXCESSIVE CALLUS OF OLD FRACTURE
IMPINGING ON NERVE
CF- ELBOW EXTENSION IS SPARED
ALL MUSCLES ARE PARALYSED EXCEPT TRICEPS
LOSS OF WRIST, THUMB AND FINGER EXTENSION
SENSORY LOSS

15.  LOW RADIAL NERVE PALSY
CAUSES- DISLOCATION OF ELBOW, # NECK OF RADIUS, RHEUMATOID
SYNOVITIS OF ELBOW, CUBITUS VALGUS DEFORMITY, #LATERAL
EPICONDYLE
CF- WRIST EXTENSION IS SPARED (AS ECRL,BR,ECRB ARE SPARED)
LOSS OF THUMB AND FINGER EXTENSION
SENSORY LOSS ON DORSUM OF 1ST WEB SPACE

16. EXAMINATION
 MUSCLE EXAMINATION
TRICEPS- EXTEND HIS ELBOW AGAINST RESISTANCE
BR - FLEX HIS ELBOW FROM 90* ONWARDS KEEPING FOREARM
MIDPRONE AGINST RESISTANCE
WRIST EXTENSORS – TO R/O WRIST DROP
EXTENSOR DIGITORUM - EXTENSION OF METACARPOPHALANGEAL
JOINTS
EXTENSOR POLLICIS LONGUS - EXTENSION AT INTERPHALANGEAL
JOINT OF THUMB WITH STABILISING THE MCP JOINT

17. DIAGNOSIS
 HISTORY TAKING
 PHYSICAL EXAMINATION
 NERVE CONDUCTION STUDIES
 EMG

19. TREATMENT
• COCK UP SPLINTING – PREVENT WRIST FLEXION
• CORTICOSTEROID/ANESTHETIC INJECTION – GIVE TEMPORARY
RELIEF
• SURGICAL
NERVE REPAIR
TENDON TRANSFERS

20. WEARING A LIGHTWEIGHT WRIST SPLINT ESPECIALLY
AT NIGHT, AND TAKING MILD ANALGESICS