Median neuropathy is a lesion of the N. medianus in any part of it, leading to pain and swelling of the hand, a disorder of the sensitivity of its palmar surface and the first 3.5 fingers, a violation of the flexion of these fingers and the opposition of the thumb. Diagnosis is carried out by a neurologist based on the results of neurological examination and electroneuromyography; additionally, using radiography, ultrasound and tomography, musculoskeletal structures are examined. The treatment includes painkillers, anti-inflammatory, neurometabolic, vascular pharmaceuticals, physical therapy, physiotherapy, massage. According to the indications, surgical interventions are performed.
General information
Median neuropathy is quite common. The main contingent of patients is young and middle—aged people. The most common lesions of the median nerve correspond to the zones of its greatest vulnerability — anatomical tunnels, in which compression is possible nerve trunk with the development of the so-called tunnel syndrome. The most common tunnel syndrome of N. medianus is carpal tunnel syndrome — compression of the nerve when it passes to the hand. The average incidence in the population is 2-3%.
The second most common site of damage to the median nerve is its section in the upper part of the forearm, running between the muscle bundles of the circular pronator. This neuropathy is called “round pronator syndrome”. In the lower third of the shoulder, the N. medianus may be compressed by an abnormal process of the humerus or a ligament of the Struser. His defeat in this place is called the Struser ribbon syndrome, or supracondylar shoulder process syndrome. In the literature, you can also find a synonymous name — Coulomb-Lord-Bedosier syndrome, which includes the names of co-authors who first described this syndrome in 1963.
Anatomy of the median nerve
N. medianus is formed when the bundles of the brachial plexus are connected, which, in turn, begin from the spinal roots C5–Th1. After passing the axillary zone, it goes next to the brachial artery along the medial edge of the humerus. In the lower third of the shoulder, it goes deeper than the artery and passes under the ligament of the Struser, when exiting to the forearm, it goes into the thickness of the round pronator. Then it passes between the flexor muscles of the fingers. On the shoulder, the median nerve does not give branches, sensory branches depart from it to the elbow joint. On the forearm, N. medianus innervates almost all the muscles of the anterior group.
From the forearm to the hand, N. medianus passes through the carpal (carpal canal). On the hand, it innervates the muscles opposing and withdrawing the thumb, partially the muscle flexing the thumb, worm-like muscles. Sensory branches of N. medianus innervate the wrist joint, the skin of the palmar surface of the radial half of the hand and the first 3.5 fingers.
Causes
Median neuropathy can develop as a result of nerve injury: its bruising, partial rupture of fibers with cut, torn, stabbed, gunshot wounds or damage by bone fragments with fractures of the shoulder and forearm, intra-articular fractures in the elbow or wrist joints. The cause of the lesion of N. medianus may be dislocations or inflammatory changes (arthrosis, arthritis, bursitis) specified joints. Compression of the median nerve in any part of it is possible with the development of tumors (lipomas, osteomas, hygromas, hemangiomas) or the formation of post-traumatic hematomas. Neuropathy can develop as a result of endocrine dysfunction (in diabetes mellitus, acromegaly, hypothyroidism), in diseases that entail changes in ligaments, tendons and bone tissues (gout, rheumatism).
The development of tunnel syndrome is caused by compression of the trunk of the median nerve in the anatomical tunnel and a violation of its blood supply due to concomitant compression of the vessels feeding the nerve. In this regard, tunnel syndrome is also called compression-ischemic. Most often, median nerve neuropathy of this genesis develops in connection with professional activity. For example, carpal tunnel syndrome affects painters, plasterers, carpenters, packers; the round pronator syndrome is observed in guitarists, flutists, pianists, nursing women who hold a sleeping baby on their arm for a long time in a position where his head is on the mother’s forearm. The cause of tunnel syndrome may be a change in the anatomical structures forming the tunnel, which is noted in subluxations, tendon damage, deforming osteoarthritis, rheumatic disease of the periarticular tissues. In rare cases (less than 1% in the entire population), compression is caused by the presence of an abnormal process of the humerus.
Symptoms
Median neuropathy is characterized by a pronounced pain syndrome. The pain captures the medial surface of the forearm, the hand and the 1-3 th fingers. Often it has a burning causalgic character. As a rule, the pain is accompanied by intense vegetative-trophic disorders, which is manifested by swelling, heat and redness or coldness and pallor of the wrist, radial half of the palm and 1-3 fingers.
The most noticeable symptoms of motor disorders are the inability to gather the fingers into a fist, to oppose the thumb, to bend the 1st and 2nd fingers of the hand. Bending of the 3rd finger is difficult. When bending the hand, its deviation to the elbow side is observed. The pathognomonic symptom is atrophy of the tenor muscles. The thumb is not opposed, but becomes one with the rest and the hand becomes similar to a monkey’s paw.
Sensory disturbances are manifested by numbness and hypesthesia in the area of innervation of the median nerve, i.e. the skin of the radial half of the palm, the palmar surface and the rear of the terminal phalanges of the 3.5 fingers. If the nerve is affected above the carpal canal, then the sensitivity of the palm is usually preserved, since its innervation is carried out by a branch extending from the median nerve to its entrance into the canal.
Diagnostics
In the classical version, median nerve neuropathy can be diagnosed by a neurologist during a thorough neurological examination. To detect motor insufficiency, the patient is asked to perform a series of tests: squeeze all fingers into a fist (the 1st and 2nd fingers do not bend); scratch the surface of the table with the nail of the index finger; stretch a sheet of paper, taking it only with the first two fingers of each hand; rotate the thumbs; connect the tips of the thumb and little finger.
With tunnel syndromes, a Tinnel symptom is determined — pain along the nerve when tapping at the compression site. It can be used to diagnose the site of n. medianus lesion. With round pronator syndrome, Tinnel’s symptom is determined by tapping in the area of the pronator’s snuffbox (the upper third of the inner surface of the forearm), with carpal tunnel syndrome — by tapping on the radial edge of the inner surface of the wrist. With supracondylar process syndrome, pain occurs when the patient simultaneously unbends and penetrates the forearm with flexion of the fingers.
To clarify the topic of the lesion and differentiate neuropathy N. medianus from brachial plexitis, vertebrogenic syndromes (sciatica, disc herniation, spondyloarthrosis, osteochondrosis, cervical spondylosis), polyneuropathy helps electroneuromyography. In order to assess the condition of bone structures and joints, bone x-ray, MRI, ultrasound or CT of the joints are performed. With supracondylar process syndrome, a “spur” or bone process is detected during radiography of the humerus. Depending on the etiology of neuropathy, a traumatologist, an orthopedist, an endocrinologist take part in the diagnosis. According to the indications, blood tests for RF and C-reactive protein, blood sugar analysis, hormonal studies are carried out.
Treatment
Depending on the genesis of median nerve neuropathy, its treatment, along with specialists in the field of neurology, is carried out by doctors of related medical fields: traumatology-orthopedics, endocrinology, surgery. The first priority is to eliminate the etiological factor: drainage of a hematoma, removal of a tumor, reduction of dislocation, treatment of arthritis, correction of endocrine disorders, creation of rest in the affected area of the nerve.
In parallel, anti-inflammatory and analgesic therapy is carried out with NSAIDs (orthophen, nimesulide, naklofen, diclofenac), and in more severe cases with glucocorticoids (diprospan, prednisolone). With intense pain syndrome, therapeutic blockade of the carpal canal is carried out — a combination of lidocaine + hydrocortisone is injected into the area of nerve damage. An effective analgesic is phonophoresis with dimexide, electrophoresis. A mandatory component of complex therapy are pharmaceuticals that improve nerve nutrition: neurometabolites (vitamins B1 and B6, neostigmine, ipidacrine) and vascular agents (xanthinol nicotinate, nicotinic acid). In the recovery period, exercise therapy, massage of the affected hand, electromyostimulation, mud treatment, ozokerite are used.
In the absence of the effect of conservative therapy, especially with traumatic nerve damage, median nerve neuropathy is an indication for surgical intervention. Depending on the situation, nerve suture, neurolysis with temporary implantation of an electrostimulator, nerve plasty are used.