Median nerve neuropathy
The median nerve (n. Medianus) is a nerve that is mixed in functions (it is also responsible for movement and sensitivity). The median nerve is made up of fibers of the spinal nerves C5, C6, C7, C8, and T1, which are mainly composed of the middle and lower trunks of the brachial plexus. Further, the fibers of the median nerve pass in the external and internal bundles. The upper leg of the median nerve departing from the outer bundle of the brachial plexus and the inner bundle of its lower leg merge, forming a loop of the median nerve.
Diagnostics of the neuropathy of the median nerve
With the defeat of the C7-spinal nerve or the middle trunk of the brachial plexus, the function of the median nerve is partially affected, as a result of which there is a weakening of the flexion of the hand, its rotation inward in combination with damage to the radial nerve. Almost the same loss of the function of the median nerve occurs when the external bundle of the brachial plexus is damaged, into which the fibers of the upper leg of the nerve pass from the middle trunk, but already in combination with damage to the musculocutaneous nerve.
With the defeat of the spinal nerves C8-Th1, the lower trunk, and the internal bundle of the brachial plexus (Dejerine-Klumpke paralysis), those fibers of the median nerve that make up its lower leg (weakening of the flexors of the fingers and thenar muscles) suffer in combination with the defeat of the ulnar nerve.
The motor function of the median nerve mainly consists in the rotation of the hand inward, in the palmar flexion of the hand due to the contraction of the corresponding muscles, flexion of the fingers, mainly I, II, and III, an extension of the middle and terminal phalanges of the II and III fingers.
The sensory fibers of the median nerve innervate the skin of the palmar surface of I, II, III and the radial half of the IV fingers, the corresponding part of the palm, as well as the skin of the rear of the terminal phalanges of the named fingers.
In case of damage to the median nerve, rotation of the hand inward suffers, palmar flexion of the hand is weakened, flexion of fingers I, II, and III and extension of the middle phalanges of II and III fingers is impaired.
Superficial sensitivity in neuritis of the median nerve is impaired on the hand in the zone free of innervation of the ulnar and radial nerves. Articular-muscular feeling with neuritis of the median nerve is always disturbed in the terminal phalanx of the index, and often in the second fingers.
Muscle atrophy with damage to the median nerve is most pronounced in the thenar area. The resulting flattening of the palm and bringing the thumb close and in one plane to the index one create a peculiar position of the hand, which is called "monkey". Pain with damage to the median nerve, especially partial, is quite intense and often takes on a causalgic character. In the latter case, the position of the hand can take on a bizarre character.
Also common and characteristic for lesions of the median nerve and vasomotor-secretory-trophic disorders: the skin, especially I, II, and III fingers, becomes bluish or pale; become "dull", brittle and streaked nails; there is skin atrophy, thinning of the fingers (especially II and III), sweating disorders, hyperkeratosis, hypertrichosis, ulceration, etc. These disorders, like pain, are more pronounced with partial rather than complete damage to the median nerve.
The median nerve, like the ulnar nerve, gives its first branches only to the forearm, therefore the clinical picture with a high lesion along the entire length from the axillary fossa to the upper parts of the forearm is the same. With damage to the median nerve in the middle third of the forearm, the functions of inward rotation of the hand, palmar flexion of the hand, and flexion of the middle phalanges do not suffer.
With lower lesions of the nerve, the function of flexion of the terminal phalanges of the I, II, and III fingers may also be preserved, and then all the symptoms of the lesion are limited to the defeat of the thenar muscles and vermiform muscles and impaired sensitivity in the typical zone.
The main tests for determining movement disorders that occur with damage to the median nerve are as follows:
- When clenching the hand into a fist I, II, and partly III, the fingers do not bend
- Flexion of the end phalanges of the thumb and forefinger is impossible, as well as scratching with the index finger on the table with the hand tightly attached to it.
- With a thumb test, the patient cannot hold a strip of paper with a bent thumb and will hold it by bringing the adductor muscles with a straightened thumb from the preserved ulnar nerve
Median nerve neuropathy treatment
Treatment for neuritis of the median nerve is selected individually in each case. It includes a set of conservative procedures:
- nerve and muscle stimulation
- vitamins of group "B", "C" and "E"
- homeopathic remedies
- surgical treatment (neurolysis, stitching of the nerve trunk, etc.)