Median Nerve Palsy
MEDIAN NERVE PALSY
- Injuries to the arm, forearm or wrist area can lead to various nerve disorders. One such disorder is median nerve palsy.
CLINICAL FEATURES:
- Clinical features depend on the site of lesion:-
1) High median nerve palsy:
- Injury in arm or at elbow causes high median nerve palsy.
- All muscles supplied by median nerve are paralysed.
- There is sensory loss in the thumb, index, middle & radial half of the ring fingers & lateral 2/3 of the palm.
- Following features are seen:
Flexion of distal IP joint of thumb is not possible (due to paralysis of FPL).
- Pointing index or oschner’s clasp test: When patient is asked to clasp his hand, index finger fails to flex.
- Benediction test: Patient is unable to flex the index & middle finger on lifting the hand due to paralysis of long flexors of these two fingers(Benedict’s hand).
- Pen test: Patient is unable to touch the pen, held above the thumb (due to APB paralysis).
- Ape thumb (Simian thumb) deformity: The thumb is adducted & laterally rotated so that the thumb lies in the same plane as the other fingers. It is due to over action of adductor pollicis (supplied by ulnar nerve).
- Loss of opposition due to paralysis of opponens pollicis
- Atrophy of thenar eminence
2) Low median nerve palsy:
- Injury at wrist or in carpal tunnel produces low median nerve palsy.
- Long flexors of fingers are spared & there is paralysis of thenar muscles only.
- Following features are seen:
- Pen test for abductor pollicis brevis paralysis.
- Loss of opposition & abduction of thumb.
- Ape thumb deformity
- Loss of sensation of lateral 3 1/2 fingers & lateral 2/3 of palm.
- In contrast to high median nerve palsy, pointing index & Benediction test are not seen as long flexors are spared in low median nerve palsy.
Exam Question
- Injury or compression of median nerve at wrist (eg carpel tunnel syndrome) can be tested by
- Pen test for loss of action of Abductor pollicis brevis
- Ape thumb deformity (adducted posture of thumb)
- Loss of opposition & abduction of thumb (d/ t wasting of thenar muscles)
- Sensory loss – lateral 31/2 of digits & 2/3 palm (autonomous zone is tip of index & tniddle finger)
- Median nerve injury at wrist, is commonly tested by Contraction of abductor pollicis brevis
- Carpal tunnel syndrome is caused by the compression of the median nerve at wrist and is most common type of nerve entrapment syndrome.
- In High median nerve palsy sensory loss in the thumb, index, middle & radial half of the ring fingers & lateral 2/3 of the palm.
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