[b][font=Arial Black][left]Lesions of the Median, Ulnar and Radial Nerves
Lesions of the Median Nerve
Median nerve lesions occur at two sites,
1. In the forearm (Pronator Syndrome)
and
2. At the wrist. (Carpal Tunnel Syndrome)
Pronator Syndrome
This is an uncommon entrapment neuropathy of the median nerve
Sites
The nerve may be involved at any of these sites.
1. As it passes alongside the fibrous band connecting the biceps tendon to the forearm fascia,
2. As it passes down between the two heads of pronator teres
3. As it passes through a fibrous arch formed by flexor digitorum superficialis.
Symtoms and Signs
Motor
There is weakness of all the muscles innervated by the median nerve, including abductor pollicis brevis and the long finger flexors.
Sensory
There is also sensory impairment on the palm of the hand(spared in the carpal tunnel syndrome because the palmar cutaneous branch of the median nerve arises above the carpal tunnel and lies superficial to it.)
Anterior interosseous nerve palsy
The anterior interosseous nerve usually arises from the median nerve proximal to the site of compression in the pronator syndrome; it may be affected with the median nerve or by itself.
Causes
1. Due to external pressure(a form of Saturday night palsy),
2. Sometimes by tight grip in association with pronation without obvious cause.
3. May be a manifestation of neuralgic amyotrophy and tends to resolve spontaneously over several months.
Motor:
An anterior interosseous nerve palsy causes weakness of pinch grip due to involvement of flexor pollicis longus and flexor digitorum profundus to the index finger.
Please note that
Innervation of flexor digitorum profundus to the middle finger is rather variable,(also by Ulnar Nerve) therefore this muscle may or may not be weak.
The branches to these three muscles (FDP,FPL,PQ)may arise separately from the median nerve, so that isolated weakness of the terminal phalanx to the thumb or index finger may occur. The pronator quadratus is also involved but is not clinically si
Lesions of the Median Nerve
Median nerve lesions occur at two sites,
1. In the forearm (Pronator Syndrome)
and
2. At the wrist. (Carpal Tunnel Syndrome)
Pronator Syndrome
This is an uncommon entrapment neuropathy of the median nerve
Sites
The nerve may be involved at any of these sites.
1. As it passes alongside the fibrous band connecting the biceps tendon to the forearm fascia,
2. As it passes down between the two heads of pronator teres
3. As it passes through a fibrous arch formed by flexor digitorum superficialis.
Symtoms and Signs
Motor
There is weakness of all the muscles innervated by the median nerve, including abductor pollicis brevis and the long finger flexors.
Sensory
There is also sensory impairment on the palm of the hand(spared in the carpal tunnel syndrome because the palmar cutaneous branch of the median nerve arises above the carpal tunnel and lies superficial to it.)
Anterior interosseous nerve palsy
The anterior interosseous nerve usually arises from the median nerve proximal to the site of compression in the pronator syndrome; it may be affected with the median nerve or by itself.
Causes
1. Due to external pressure(a form of Saturday night palsy),
2. Sometimes by tight grip in association with pronation without obvious cause.
3. May be a manifestation of neuralgic amyotrophy and tends to resolve spontaneously over several months.
Motor:
An anterior interosseous nerve palsy causes weakness of pinch grip due to involvement of flexor pollicis longus and flexor digitorum profundus to the index finger.
Please note that
Innervation of flexor digitorum profundus to the middle finger is rather variable,(also by Ulnar Nerve) therefore this muscle may or may not be weak.
The branches to these three muscles (FDP,FPL,PQ)may arise separately from the median nerve, so that isolated weakness of the terminal phalanx to the thumb or index finger may occur. The pronator quadratus is also involved but is not clinically si
عدل سابقا من قبل زهرة المنتدى في الخميس يناير 14, 2010 11:15 pm عدل 1 مرات
