Radial nerve neuropathy

Hand movement in the elbow joint is difficult, does it grow numb, feel weakness in the wrist? Most likely, it is radial neuropathy or neuropathy of the radial nerve - a disease of the peripheral nervous system.

According to ICD-10, this condition is defined as mononeuropathy of the upper limbs and has the code G56.3 - damage to the radial nerve.

Epidemiology

Among neurological pathologies, almost half of the cases are related to peripheral neuropathies. And with various injuries of the upper limbs, on average, more than 3.5% are nerve injuries.

The incidence of traumatic neuropathy of the radial nerve with a closed fracture of the diaphysis of the humerus is 2.5-18%. A fracture along the lower third of the humerus leads to radial neuropathy in 15-25% of patients. Acute compartment syndrome occurs in about 6% of forearm fractures. [1], [2]

The clinical statistics of compression and ischemic neuropathy of the upper extremities are unknown, but tunnel syndromes account for at least 30% of cases.

Causes radial nerve neuropathy

As in the case of other mononeuropathies of the peripheral nerves, the key causes of neuropathy of the  radial nerve  (nervus radialis), emerging from the brachial plexus (plexus brachialis) and following along the arm to the wrist and fingers, consist in its traumatic or compression-ischemic injury, which leads to certain functional disorders.

And depending on their etiology and nature, the types of radial neuropathy are determined. Thus, traumatic and post-traumatic neuropathy of the radial nerve can be the result of a  fracture of the humerus  (in particular, its diaphysis at the junction of the medial and distal thirds), as well as a fracture that affects the place where the nerve passes through the intermuscular septum. [3]

Severe dislocation and fracture of the radial head (which is part of the elbow joint), as well as a fracture of the forearm bones, often cause traumatic damage to the posterior interosseous branch of the radial nerve, which innervates the posterior muscle group from the elbow to the wrist joint.

In this case, the nerve can be damaged both by the fracture itself and as a result of transposition of bone fragments, the installation of fixation devices or traction of the limb. Also, similar consequences are possible due to iatrogenic injuries during arthroscopy, endoprosthetics or synovectomy of the elbow joint, and even with intramuscular injections into the shoulder area.

One of the most common types of  upper limb neuropathy  is compression neuropathy of the radial nerve when it is pinched and / or compressed:

• in the axillary region (in case of injury of the shoulder joint or prolonged use of crutches);
• at the level of the middle third of the shoulder, between the humerus and the heads of the triceps muscle of the shoulder - in the spiral groove (brachomuscular canal);
• in the forearm - when the deeply lying posterior interosseous branch passes under the fibrous upper edge of the instep support muscle, known as the Frose arch or arcade, as well as at the exit of the superficial branch of the radial nerve from under the brachioradialis muscle of the forearm - as a complication of a mid-forearm injury.

Ischemic neuropathy of the radial nerve associated with a lack of local blood supply and tissue hypoxia can be the result of any traumatic and compressive effect, including all of the above.

Posterior interosseous nerve syndrome (branches of the radial nerve) or forearm compartment syndrome occurs when a nerve just below the elbow is compressed due to increased tissue pressure in the space between the muscle fascia. At the same time, local blood circulation and trophism of nerve tissues deteriorate with a decrease in the functions of nerve cells. The same condition can be caused by prolonged compression of the nerve by fibrous or bone neoplasms. [4]

In essence, tunnel neuropathy of the radial nerve is also compression-ischemic, since it occurs due to compression or pinching of this nerve - its posterior and superficial branches - when passing through narrowed places (channels or tunnels). And among the tunnel neuropathies are: compression in the brachial canal - spiral canal syndrome; below the elbow joint - instep support syndrome; between the blocky shoulder joint (articulating in the elbow joint) and the distal part of the instep support muscle - radial tunnel syndrome; in the radial canal of the wrist - Wartenberg syndrome. [5]

Also read:

• Peripheral neuropathy
• Damage to the nerves of the extremities
• Ischemic neuropathy of nerves

Risk factors

The risk of developing neuropathy of the radial nerve is increased with constant (in most cases associated with the profession) overexertion of the upper limbs: actions with increased grip strength, frequent changes in power supination and pronation, adduction-abduction and vibration.

Older people with osteoporosis are more likely to have shoulder and forearm fractures and injuries to the joints of the hands, so they are also at increased risk of peripheral neuropathies.

Diseases of the joints and periarticular structures of the upper extremities, cysts, osteomas and tumor formations of soft tissues in the shoulder, forearm and wrist are considered to be predisposing factors.

In addition, specialists consider individual anatomical abnormalities (osteophytes, accessory tendons and intermuscular septa), as well as some systemic metabolic diseases and chronic intoxication, to the risks of radial compression-ischemic neuropathy. [6]

Pathogenesis

The main mechanism of radial neuropathy in both traumatic and compression-ischemic lesions is blocking the transmission of nerve impulses along the radial nerve, that is, dysfunction of the ion channels of axonal membranes, leading to a decrease in the excitability of neurons in the peripheral nervous system. In addition, damage to the nerve can negatively affect the state of its myelin sheath with focal loss of myelin.

Features of the pathogenesis of radiation neuropathy directly depend on the degree of nerve damage and can take one of three forms. In the form of neuropraxia, compression occurs without damage to the fibers and sheath of the nerve - with a temporary interruption in the transmission of nerve signals and loss of function. But with prolonged compression (as with tunnel neuropathies) additional factors appear: ischemic changes with deterioration of blood microcirculation and edema of the endoneuria of the nerve trunk.

More severe damage in the form of axonotmesis - with intra-stem destruction of axons and their myelin sheath by the type of post-traumatic degeneration, with the transformation of blood monocytes into macrophages, with the activation of macrophages and increased production of a number of pro-inflammatory cytokines that cause an inflammatory response and the appearance of neuropathic pain.

The most severe form of damage is neurotmesis, in which there is a complete destruction of a segment of the nerve (its axons, myelin, endoneuria of the nerve trunk and connective tissue structures).

Symptoms radial nerve neuropathy

Specific clinical manifestations of radial nerve neuropathy are determined by the degree of its alteration and localization.

Injury to the radial nerve usually causes symptoms of numbness and tingling (paresthesia) on the back of the hand, near the first three fingers (thumb, index, and middle), as well as straightening problems and  neuralgia  (burning pain). [7],  [8], [9]

If compression neuropathy is caused by compression of a nerve in the upper part of the shoulder or in the armpit, then the first signs include a decrease in the skin sensitivity of the dorsal surface of the entire upper limb, as well as difficulties in its movement in the sagittal plane - flexion-extension in the elbow and wrist joints with this condition, like a  drooping hand , that is, weakness of the wrist.

With radial tunnel syndrome, the back of the hand and fingers also becomes numb, there is a burning sensation and pain in the back of the thumb, pain on the side of the elbow and the back of the forearm. Pronation of the forearm and flexion of the wrist can make symptoms worse. [10]

More details about the manifestation of this mononeuropathy in the publication -  Symptoms of damage to the radial nerve and its branches

Complications and consequences

Peripheral paresis (weakness and numbness) or paralysis of the hand can be a consequence of traumatic radial neuropathy  , since the deep branch of the radial nerve provides motor innervation to the muscles responsible for extending the elbow, wrist, and first three fingers.

Denervation and loss of motor function can be complicated by gradual  muscle atrophy  and myogenic contracture.

In addition, there is a high probability of developing focal inflammation of the trunk of the radial nerve - neuritis.

Complete destruction of the damaged area of the nerve causes fibrosis of its trunk, which prevents the regeneration of axons and leads to disability.

Diagnostics radial nerve neuropathy

Radial nerve injuries and peripheral neuropathy are usually diagnosed by physical examination of the patient using special tests that determine the strength of the innervated muscles, the presence of motor reflexes, the nature of movement disorders, and the level of sensitivity of the upper extremities. [11]

Instrumental diagnostics are used:  electroneuromyography  (electrophysiological study of nerve conduction), radiography,  ultrasound of nerves , MRI. [12], [13]

Differential diagnosis

Differential diagnosis is carried out with neuropathy of other nerves originating in the brachial plexus (musculocutaneous, median, ulnar and medial cutaneous); with radicular syndromes and sensory neuropathies in various neurological disorders of the central nervous system; with diseases of the joints and periarticular structures of the upper limb (including professional tendovaginitis and de Quervain's syndrome); with early manifestations of syringomyelia and neurological symptoms of multiple sclerosis.

Treatment radial nerve neuropathy

With neuropathy of peripheral nerves, including radial, treatment can be conservative and operative.

Immobilization of the limb with a functional splint or orthosis is recommended to reduce pain. For the same purpose, medications are taken:

• - non-steroidal anti-inflammatory drugs -  Ibuprofen ,  Celecoxib  , etc.;
• - anticonvulsants (anticonvulsants), for example,  Gabapentin  (Gabantin, Gabalept).

Locally, it is possible to use gels and ointments with sodium diclofenac, Remisid gel   (with nimesulide); ointments that activate local blood circulation with an analgesic effect (Apizartron, Menovazin, Gevkamon, Denebol, etc.).

In extreme cases, they resort to anesthesia by  novocaine blockade .

More information from the materials:

• Treating neuropathic pain

Injections of  glucocorticoids  (Hydrocortisone, Methylprednisolone, Triamcinolone) into the area near the affected nerve are aimed at relieving inflammation.

With ischemic neuropathy, angioprotectors that activate microcirculation are prescribed -  Agapurin Retard  (Pentoxifylline) and others, as well as vitamins B1, B6 and B12.

To improve the transmission of nerve impulses parenterally, cholinesterase inhibitors Ipidacrine (Amiridin) or Galantamine (Nivalin) are used.

In addition, physiotherapy is prescribed, in particular, muscle electrical stimulation and other apparatus procedures; more details in the article -  Physiotherapy for neuritis and neuralgia of peripheral nerves . [14]

When the pain is relieved, a dosed physical load on the muscles of the upper extremities is necessary - exercise therapy for neuropathy of the radial nerve, which helps to improve tissue trophism and neuromuscular conduction. Stretching exercises for the muscles of the shoulder, forearm and hands are selected individually, taking into account the general condition and specific diagnosis. [15]

Many patients are helped by therapeutic massage for neuropathy of the radial nerve.

With neuropathic pain, herbal therapy is possible - herbal medicine. Some of the most common plants that are used to relieve pain symptoms include: Ginkgo biloba leaves, which improve blood circulation in the capillaries during ischemic tissue damage; calamus and turmeric roots; rich in zinc (necessary for tissue regeneration) tarragon; pain-reducing saffron seed; extract of sage leaves and madder roots.

If there is no clinical improvement after long-term conservative treatment, depending on the location and degree of damage to the radial nerve - in severe and progressive cases - surgical treatment is performed.

The damaged nerve can be restored by microsurgical transplantation, but most often these are operations aimed at decompression of the radial nerve, for example, when the superficial branch is compressed by the tendon, its stretching incision or movement is performed. The effectiveness of such an intervention is quite high - up to 50-80%, and the recovery time for nerve conduction ranges from three to four months.

Prevention

The main preventive measures are to prevent injuries and excessive loads of the upper limbs.

Forecast

The restoration of nerve function and the prospects for recovery depend on many factors. For example, neuropathy of the radial nerve due to a closed fracture of the humerus is cured in 92-95% of cases, although the treatment can last from several months to three to five years.

However, partial motor dysfunction and loss of sensation from damage to the axons of the nerve fiber may remain forever. [16]

But with acute compression neuropathy, the symptoms of which appear within three to four months, the prognosis is almost always favorable.