Examination of the median nerve

Anatomy
thumb|450px|right|Anatomie karpálního tunelu. Nervus medianus arises from the C5−Th1 segments of the cervicobrachial plexus. It runs along the inside of the arm, near the elbow it dives deep, in the wrist area it runs just below the retinaculum flexorum to the fingertips. It has both a sensory and a motor component, so it is a mixed nerve.

Motor innervation area

 * m. flexor digitorum superficialis
 * m. flexor digitorum profundus
 * m. flexor pollicis longus et m. flexor pollicis brevis
 * m. abductor pollicis brevis
 * m. opponens pollicis
 * m. pronator teres
 * m. pronator quadratus
 * m. flexor carpi radialis
 * m. palmaris longus
 * mm. lumbricales I. et II

Sensitive innervation area
The median nerve sensitively innervates the entire II on the dorsal side of the hand. and III., the ulnar side of IV. and I. finger. On the palmar side, it innervates I.–III. finger and radial side of finger IV. and much of the thenar.

Thumb abduction test
We invite the patient to place the hand with the palm on the table and move the thumb away from the other fingers. However, he can't handle this move due the m. abductor pollicis brevis being weakened.

Thumb opposition test
We invite the patient to place the hand dorsally on the table and connect the thumb and little finger with the end of the nail. Because of the weakening of the m. opponens pollicis, the patient is unable to perform this movement.

Thumb circling test
We invite the patient to interlace his fingers and then circle his thumbs around himself. It will happen that on the paretic limb the thumb will not move and will be encircled by the thumb of the non-paretic hand.

Compass test
we invite the patient to place the back of the hand on the table and to circle the tips of the fingers with the thumb. It will happen that by IV. and the V. finger will not reach the thumb, thanks to the weakening of m. opponens pollicis.

Connected hands test
We invite the patient to join the hands with the palms together while simultaneously flexing the MP joints, DIP and PIP. It will happen that I.–III. the finger will remain extended.

Fist test
We invite the patient to hold his hand into a fist. Thanks to the weakening of m. adductor pollicis, m. flexor pollicis longus, m. flexor pollicis brevis and m. opponens pollicis and m. flexor digitorum longus et brevis the patient is unable to hold a fist, I.–III. fingers will be semiflexed or unmoved.

Bottle test
We invite the patient to hug the body of the bottle with the thumb and forefinger. What happens is that the thumb does not completely wrap around the bottle and the patient is unable to lift the bottle.

Muscle test
A muscle test for the relevant muscles is the most objective indicator of the extent of damage.

Clinical image of lesion
The lesion begins insidiously, at first with only classic tingling in the thumb and thenar area, then sensitive denervation is added. A typical symptom is the so-called monkey hand, where the thumb is dragged by m. adductor pollicis (inervace: n. ulnaris)in line with the other fingers, II. and III. the finger is in semiflexion to extension.

Causes of lesion
The most common place where the lesion occurs is the wrist, where the median nerve is located relatively superficially. Here also under the retinaculum flexorum oppression can occur due to overload, then we are talking about the so-called carpal tunnel syndrome.Furthermore, compression may occur in the axillaor in the elbow area due to impact supracondylar fractures.

Connected articles

 * Vyšetření n. radialis | Vyšetření n. tibialis | Vyšetření n. ulnaris
 * Syndrom karpálního tunelu