Download MEDIAN NERVE 2015년 2쿼터 PBL 12조 201478009 고진철

MEDIAN NERVE
2015년 2쿼터 PBL 12조
201478009 고진철

Median Nerve
- The median nerve is the principal nerve of the anterior compartment of the forearm. It supplies muscular
branches directly to the muscles of the superficial and intermediate layers of forearm flexors (except the FCU),
and deep muscles (except for the medial half [ulnar] of the FDP)

Median Nerve 의 주행

Median Nerve Injury
- When the median nerve is severed in the elbow region, flexion of the
proximal interphalangeal joints of the 1st- 3rd digits is lost and flexion
of the
4th
and
5th
digits is weakened.
Flexion of the
distal
interphalangeal joints of the 2nd and 3rd digits is also lost. Flexion of
the distal interphalangeal joints of the 4th and 5th digits is not affected
because the medial part of the FDP, which produces these movements, is
supplied by the ulnar nerve. The ability to flex the metecarpophalangeal
joints of the 2nd and 3rd digits is affected because the digital branches of the median nerve supply the 1 st and 2nd
lumbricals. Thus, when the person attempts to make a fist, the 2nd and
3rd fingers remain partially extended (“hand of benediction”). Thenar
muscle function (function of the muscles at the base of the thumb) is also
lost, as in carpal tunnel syndrome. When the anterior interosseous nerve is
injured, the thenar muscles are unaffected, but paresis (partial paralysis) of
the flexor digitorum profundus and flexor pollicis longus occurs. When the
person attempts to make the “okay” sign, opposing the tip of the
thumb and index finger in a circle, a “pinch” posture of the hand results instead owing to the absence of
flexion of the interphalangeal joint of the thumb and distal interphalangeal joint of the index finger (anterior
interosseous syndrome).

Nerves of hand (median nerve part)
- The median nerve enters the hand through the carpal tunnel, deep to the flexor retinaculum, along with
the nine tendons of the FDS, FDP, and FPL. The carpal tunnel syndrome is the passageway deep to the flexor
retinaculum between the tubercles of the scaphoid and trapezoid bones on the lateral side and the pisiform
and hook of the hamate on the medial side. Distal to the carpal tunnel, the median nerve supplies two and a
half thenar muscles and the 1st and 2nd lumbricals. It also sends sensory fibers to the skin on the entire palmar
surface, the sides of the first three digits, the lateral half of the 4 th digit, and the dorsum of the distal halves of
these digits. Note, however, that the palmar cutaneous branch of the median nerve, which supplies the central
palm, arises proximal to the flexor retinaculum and passes superficial to it. (It does not pass through the carpal
tunnel)

Muscles of anterior compartment of forearm

Carpal tunnel syndrome
- Carpal tunnel syndrome results from any lesion that significantly reduces the size of the carpal tunnel or,
more commonly, increases the size of some of the nine structures or their covering that pass through it (e.g.
inflammation of synovial sheaths). Fluid retention, infection, and excessive exercise of the fingers may cause
swelling of the tendons or their synovial sheaths. The median nerve is the most sensitive structure in the
tunnel. The median nerve has two terminal sensory branches that supply the skin of the hand; hence paresthesia
(tingling), hypoesthesia (diminished sensation), or anesthesia (absence of sensation) may occur in the lateral three
and a half digits. The palmar cutaneous branch of the median nerve arises proximal to, and does not pass
through, the carpal tunnel; thus sensation in the central palm remains unaffected. The nerve also has one terminal
motor branch, the recurrent branch, which serves the tree thenar muscles.
- Progressive loss of coordination and strength of the thumb (owing to weakness of the APB and opponens
pollicis) may occur if the cause of compression is not alleviated. Individuals with carpal tunnel syndrome are
unable to oppose their thumb and have difficulty buttoning a shirt or blouse as well as gripping things such as a
comb. As the condition progresses, sensory changes radiate into the forearm and axilla. Symptoms of
compression can be reproduced by compression of the median nerve with your finger at the wrist for
approximately 30 seconds. To relieve both the compression and the resulting symptoms, partial or complete
surgical division of the flexor retinaculum, a procedure called carpal tunnel release, may be necessary. The
incision for carpal tunnel release is made toward the medial side of the wrist and flexor retinaculum to avoid
possible injury to the recurrent branch of the median nerve.
+) Carpal tunnel syndrome (CTS) is caused by compression of the median nerve as it passes under the carpal
tunnel. Nerve conduction velocity tests through the hand are used to diagnosis CTS. Physical diagnostic tests
include the Phalen maneuver or Phalen test and Tinel's sign. To relieve symptoms, patients may describe a
motion similar to "shaking a thermometer", another indication of CTS.
출처) Clinically Oriented Anatomy, sixth edition, Moore, Chapter 6 Upper Limb.