- Discussion:
- arises from
median nerve, 5 cm above medial epicondyle;
- runs on volar surface of FDP and along interosseous membrane between ulna & radius;
- supplies
FPL, lateral half of
FDP, &
pronator quadratus;
- may supply sensory branches to distal ru and carpal joints;
-
variations:
-
martin gruber anastomosis occurs in 10-15% of all forearms and in half of these cases, the nerve communication arises from the AIN branch;
- hence palsy of the AIN could lead to palsy of the hand intrinsics normally supplied to the ulnar nerve;
- diff dx: FDP avulsion
- Anatomy:
- AIN is principally a motor nerve;
- it arises from
median nerve at a variable point as it passes between two heads of the
pronator teres, descends vertically in front of
interosseous membrane between
FDP &
FPL, supply these 2 muscles, & finally terminates in
pronator quadratus near wrist joint;
- it divides from the
median nerve 4 to 6 cm below the elbow;
-
points of compression:
- as it passes between 2 heads of
pronator teres;
- deep head of
pronator teres;
- as it descends vertically in front of interosseous membrane between
FDP &
FPL;
- orgin palmaris profundis
- gantzer's muscle (accessory head to
FPL)
- origin
FDS
- origin of
FCR;
- thrombosis of ulnar collateral vessels;
-
median artery
- Exam:
- principal weakness: difficulty moving index & middle fingers;
- weakness in flexors of ip joint of thumb (
FPL) & dip joints of index and middle fingers -
FDP;
- this can be observed by observing pitch attitude of the hand;
- normally when individual pinches something between index finger & thumb, MP & IP joints of thumb and index finger are flexed;
- w/ nerve deficit, terminal phalanges of thumb and index finger are extended or hyperextended;
- note:
- unusual innervation patterns of hand will confuse picture;
-
median nerve hand (
martin gruber) anastomosis:
- entire hand is innervated by the
median nerve 
- cross over ulnar innervations of
FDP
- superficial innervations by anterior interosseous nerve;
- EMG: needle examination is difficult because of the deep location;
- C
auses of anterior interosseous nerve compression:
- tendinous origin of deep head of
pronator teres (most common);
- enlarged bicipital tendon bursa may impinge
AIN;
- aberrant or thrombosed
radial artery in midforearm;
- thrombosed
ulnar artery;
- fascial band at the origin of
FDS;
- compression w/in deep palmar compartment from aberrant accessory muscles such as
FPL (gantzer's) muscle, palmaris profundus mass, or enlarged ? FCR brevis;
- Diff Dx:
-
lateral cord lesion;
-
FDP avulsion or avulsion of index profundus tendons;
- tendon ruptures are noted by placing digits in different positions and applying tension to the flexor tendons;
- electrical stimulation may indicates whether muscle belly is partially denervated;
- succinylcholine test: which may demonstrate more fasciculations of
FPL if there is partial or complete denervation;
- in pts w/ low
ulnar nerve injury, some interosseous muscle
intrinsic function may be maintained due to
martin gruber
anastomosis between AIN nerve and unlnar nerve;
-
C-8 radiculopathy:
- rare finding;
- the correct diagnosis is made by determining the function of the muscles innervated by the C-8 portion of the ulnar nerve;
-
Parsonage-Turner Syndrome
A simple clinical test to differentiate rupture of flexor pollicis longus and incomplete anterior interosseous paralysis.
The anterior interosseous nerve syndrome.
An anomaly of the median artery associated with the anterior interosseous nerve syndrome.
Wrist Denervation and the Anterior Interosseous Nerve: Anatomic Considerations.
Neurolysis is not required for young patients with a spontaneous palsy of the anterior interosseous nerve.
Brachial neuritis presenting as anterior interosseous nerve compression--implications for diagnosis and treatment: a case report
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