Fibular neuropathy is one of the mononeuropathies of the lower extremities, accompanied by the syndrome of the hanging foot — the inability of the back flexion of the foot and extension of its fingers, as well as sensory disorders of the skin of the anterolateral region of the lower leg and the back of the foot. The diagnosis is made on the basis of anamnesis, neurological examination, electromyography or electroneurography data. Additionally, an ultrasound of the nerve and a study of the osteoarticular apparatus of the lower leg and foot are performed. Conservative treatment is carried out by a combination of medication, physiotherapy and orthopedic methods. If it fails, surgery is indicated (decompression, nerve suture, tendon transposition, etc.).
General information
Fibular neuropathy, or peroneal neuropathy, occupies a special position among peripheral mononeuropathies, which also include: tibial neuropathy, femoral neuropathy, sciatic nerve neuropathy, etc. Since the peroneal nerve consists of thick nerve fibers with a larger layer of myelin sheath, it is more susceptible to damage in metabolic disorders and anoxia. Probably this moment causes a fairly wide prevalence of peroneal neuropathy. According to some data, fibular neuropathy is noted in 60% of patients in traumatology departments who have undergone surgery and are being treated with splints or plaster bandages. Only in 30% of cases, neuropathy in such patients is associated with primary nerve damage.
It should also be noted that often specialists in the field of neurology have to deal with patients who have a certain experience of peroneal neuropathy, including the postoperative period or the time of immobilization. This complicates treatment, increases its duration and worsens the result, because the earlier therapy is started, the more effective it is.
Anatomy of the peroneal nerve
The fibular nerve (n. peroneus) departs from the sciatic nerve at the level of the lower 1/3 of the thigh. It consists mainly of fibers of LIV-LV and SI-SII spinal nerves. After passing through the popliteal fossa, the fibular nerve exits to the head of the bone of the same name, where its common trunk is divided into deep and superficial branches. The deep fibular nerve passes into the anterior part of the lower leg, descends down, passes to the back of the foot and divides into internal and external branches. It innervates the muscles responsible for extension (back flexion) foot and fingers, pronation (lifting of the outer edge) of the foot.
The superficial fibular nerve runs along the anterolateral surface of the lower leg, where it gives the motor branch to the fibular muscles responsible for the pronation of the foot with its simultaneous plantar flexion. In the medial 1/3 of the tibia, the superficial branch of the n. peroneus passes under the skin and divides into 2 dorsal cutaneous nerves — intermediate and medial. The first one innervates the skin of the lower 1/3 of the lower leg, the back surface of the foot and the III-IV, IV-V interdigital spaces. The second one is responsible for the sensitivity of the medial edge of the foot, the back of the I finger and the II-III interdigital space.
Anatomically determined areas of the greatest vulnerability of the fibular nerve are: the place of its passage in the area of the head of the fibula and the place of exit of the nerve to the foot.
Causes
There are several groups of triggers that can initiate the development of peroneal neuropathy: nerve injuries; nerve compression by surrounding musculoskeletal structures; vascular disorders leading to nerve ischemia; infectious and toxic lesions. Fibular neuropathy of traumatic origin is possible with knee bruises and other knee joint injuries, a fracture of the tibia, an isolated fracture of the fibula, dislocation, damage to tendons or sprains of the ankle joint, iatrogenic nerve damage during the reposition of the shin bones, knee joint or ankle surgery.
Compression neuropathy (so—called tunnel syndrome) n. peroneus most often develops at the level of its passage at the head of the fibula -upper tunnel syndrome. It may be associated with professional activities, for example, berry pickers, parquet workers, etc. people whose work involves a long stay “squatting”. Such neuropathy is possible after sitting for a long time with one foot on the other. With compression of the fibular nerve at the place of its exit to the foot, the lower tunnel syndrome develops. It can be caused by wearing excessively tight shoes. Often, compression-type fibular neuropathy is caused by nerve compression during immobilization. In addition, compression of N. peroneus may have a secondary vertebrogenic character, i.e. develop in connection with changes in the musculoskeletal system and reflex musculotonic disorders caused by diseases and curvatures of the spine (osteochondrosis, scoliosis, spondyloarthrosis). Iatrogenic compression-ischemic neuropathy of the fibular nerve is possible after its compression due to the incorrect position of the leg during various surgical interventions.
More rare causes of peroneal neuropathy include systemic diseases accompanied by connective tissue proliferation (deforming osteoarthritis, scleroderma, gout, rheumatoid arthritis, polymyositis), metabolic disorders (dysproteinemia, diabetes mellitus), severe infections, intoxication (including alcoholism, drug addiction), local tumor processes.
Symptoms
Clinical manifestations of fibular neuropathy are determined by the type and topic of the lesion. Acute nerve injury is accompanied by a sharp almost simultaneous appearance of symptoms of its lesion. Chronic injury, dysmetabolic and compression-ischemic disorders are characterized by a gradual increase in the clinic.
The defeat of the common trunk of the fibular nerve is manifested by a disorder of the extension of the foot and its fingers. As a result, the foot hangs down in the position of plantar flexion and is slightly rotated inwards. Because of this, when walking, carrying the leg forward, the patient is forced to bend it strongly at the knee joint so as not to catch the toe on the floor. When lowering the foot to the floor, the patient first stands on the toes, then rests on the lateral plantar edge, and then lowers the heel. Such a gait resembles a cock or a horse and bears the appropriate names.
Difficult or impossible: lifting the lateral edge of the sole, standing on the heels and walking on them. Motor disorders are combined with sensory disorders that spread to the antero-lateral surface of the lower leg and the back of the foot. There may be pain on the outer surface of the lower leg and foot, increasing during squats. Over time, atrophy of the muscles of the antero-lateral region of the lower leg occurs, which is clearly noticeable when compared with a healthy leg.
Fibular neuropathy with deep branch lesion is manifested by less pronounced foot overhang, reduced foot and finger extension force, sensory disorders on the back of the foot and in the 1st interdigital space. The long course of neuropathy is accompanied by atrophy of small muscles on the back of the foot, which is manifested by the sinking of the interosseous spaces.
Fibular neuropathy with lesions of the superficial branch is characterized by impaired sensory perception and pain on the lateral surface of the lower leg and medial region of the back of the foot. Upon examination, a weakening of the pronation of the foot is detected. The extension of the fingers and foot is preserved.
Diagnostics
The algorithm for diagnosing peroneal neuropathy is based on collecting anamnestic data that can indicate the genesis of the disease, and conducting a thorough study of the motor function and sensory sphere of the peripheral nerves of the affected limb. Special functional tests are conducted to assess the muscle strength of various muscles of the lower leg and foot. The analysis of surface sensitivity is carried out using a special needle. Additionally, electromyography and electroneurography are used to determine the level of nerve damage by the speed of action potentials. Recently, ultrasound of the nerve has been used to study the structure of the nerve trunk and the structures located next to it.
In case of traumatic neuropathy, a traumatologist’s consultation is required, according to indications — ultrasound or radiography of the knee joint, radiography of the shin bones, ultrasound or radiography of the ankle joint. In some cases, diagnostic novocaine nerve blockades may be used.
Fibular neuropathy requires differential diagnosis with LV-SI radiculopathy, hereditary recurrent neuropathy, Charcot-Marie-Toute disease, PMA syndrome (peroneal muscular atrophy), ALS, polyneuropathy, other mononeuropathies of the lower extremities, cerebral tumors and spinal tumors.
Treatment
Patients with peroneal neuropathy are supervised by a neurologist. The issue of surgical treatment is solved at the consultation of a neurosurgeon. An integral part of the treatment is the elimination or reduction of the causal factor of neuropathy. In conservative therapy, the decongestant, anti-inflammatory and analgesic effect of NSAIDs (diclofenac, lornoxicam, nimesulide, ibuprofen, etc.) is used. Drugs of this group are combined with B vitamins, antioxidants (thioctic acid), means to improve nerve circulation (pentoxifylline, nicotinic acid). The appointment of ipidacrine, neostigmine is aimed at improving neuromuscular transmission.
Pharmacotherapy is successfully combined with physiotherapy: electrophoresis, amplipulstherapy, magnetotherapy, electrical stimulation, ultraphonophoresis, etc. Regular physical therapy sessions are required to restore the muscles innervated by N. peroneus. To correct the overhanging foot, patients are shown wearing orthoses that fix the leg in the correct position.
Indications for surgical treatment are cases of complete violation of nerve conduction, the absence of the effect of conservative therapy or the occurrence of relapse after its implementation. Depending on the clinical situation, neurolysis, nerve decompression, suture or plastic surgery may be performed. With long-standing neuropathies, when the muscles innervated by the peroneal nerve lose electrical excitability, surgical interventions are performed to move the tendons.
