Symptoms of affection of the peroneal nerve

The common peroneus nerve (n. Peroneus communis) consists of fibers LIV-LV and SI-SII of the spinal nerves and passes through the popliteal fossa towards the cervix of the fibula. Here it is divided into superficial, deep and recurrent branches. Above these branches directly adjacent to the bone, the fibrous band of the long fibular muscle is located in the form of an arch in the place of their division. It can press these nerve branches to the bone when the muscle stretches with the overgrowing of the ligaments of the ankle joint with the forced lifting of its inner edge. At the same time, nerves are stretched too. Such a mechanism is available in case of an ankle injury with the turn of the foot to the inside and simultaneous plantar flexion.

The external cutaneous nerve of the gastrocnemius muscle, which supplies the lateral and posterior surface of the tibia, extends from the trunk of the common peroneal nerve in the popliteal fossa, beyond its division. At the level of the lower third of the shin, this nerve is anastomosed with the cutaneous medial nerve of the shin (branch of the tibial nerve) and together they form the gastrocnemius nerve (n. Suralis).

The superficial peroneal nerve is directed downward along the anterior surface of the tibia, giving the branches to the long and short fibular muscles. These muscles withdraw and raise the outer edge of the foot (perform pronation, while simultaneously flexing it.

The test for determining the strength of long and short peroneal muscles: in the supine position on the back, it is proposed to withdraw and raise the outer edge of the foot while simultaneously performing the flexion of the foot; The examiner is resisting this movement and palpating the contracted muscle.

At the level of the middle third of the shin the superficial peroneal nerve, perforating the fascia of the short fibular muscle, comes under the skin and divides into its terminal branches - the medial and the inferior dermal nerves of the skin.

The medial dorsal cutaneous nerve provides the inner edge and part of the rear of the foot, the first finger and the facing surfaces of the II-III toes.

The intermediate dorsal cutaneous nerve gives twigs to the skin of the lower third of the tibia and the rear of the foot, to the rear surface between the III and IV, IV and V fingers.

The deep peroneal nerve, perforating the thickness of the long fibular muscle and the anterior intermuscular septum, penetrates into the anterior region of the shin, where it can undergo compression under ischemic necrosis of the muscles. In the upper parts of the lower leg, the nerve passes between the long extensor of the fingers and the anterior tibial muscle, in the lower parts of the shin - between the last and the long extensor of the thumb, giving branches to these muscles.

The anterior tibialis muscle (innervated by segment LIV-SI) unbends the foot in the ankle joint, leads and raises its inner edge (supination).

Test to determine the strength of the anterior tibial muscle: the patient in the supine position is offered to unbend the limb in the ankle joint, lead and raise the inner edge of the foot; The examiner is resisting this movement and palpating the contracted muscle.

The long extensor extends the II - V fingers and foot in the ankle joint, retracts and perforates the foot (innervated by the LIV - SI segment).

Test to determine its strength: the patient in the supine position is offered to unbend the proximal phalanges of the II-V fingers; The examiner is resisting this movement and palpating the strained tendon of the muscle.

The long extensor extends the 1st toe and toe in the ankle, spinning it (innervated by the LIV-SI segment).

A test to determine its strength; the subject is offered to unbend the first finger of the foot; The examiner prevents this movement and palpates the strained tendon of the muscle.

When going to the rear of the foot, the deep peroneal nerve is located first under the upper and then under the lower ligament of the extensor and the tendon of the long extensor of the first finger. Here, the compression of this nerve is possible. When entering the foot, the deep peroneal nerve is divided into two branches. The outer branch is directed to the short extensors of the fingers, and the inner branch reaches the I intercostal space, where, passing under the tendon of the short extensor of the 1st finger, it divides into terminal branches branched in the skin of adjacent surfaces - the medial surface I and the lateral surface II of the finger.

The short extensor of the fingers unbends the II - IV fingers with a slight outward retraction (innervated by the LIV-SI segment); a short extensor of the big toe expands the palea of the foot and somewhat pulls it aside.

In approximately 1/4 of the individuals, the outer part of the short extensor of the fingers (to the IV-V fingers) is innervated by an additional deep peroneal nerve, a branch of the superficial peroneal nerve.

With the defeat of the common peroneal nerve, the possibility of unbending the foot in the ankle and fingers, losing the foot and pronating its outer edge, is lost. The foot sluggishly slackens and rotates to the inside. The fingers are bent in the proximal phalanges. With prolonged damage to this nerve due to the action of the muscles-antagonists (gastrocnemius and interosseous muscles), a contracture can result, leading to a firm plantar flexion of the foot and the main phalanges of the fingers. The foot takes the form of a "horse foot" (pes equinovarus). Typical gait of such patients: in order to avoid touching the floor with the back surface of the foot, the patient high-lifts the hip, when lowering it - the hanging foot first leans on the fingers and then sinks to the floor with the entire sole. This gait is similar to the step of a horse or a cock ("horse" or "cock" gait - steppe). Atrophy of the anterior anterior muscles of the tibia. The area of sensitivity disorder extends to the anteroposterior crural surface (lateral cutaneous cutaneous nerve) and to the rear of the foot, including the first interdigital space.

Achilles reflex is preserved, however the reflex from the tendon of the long extensor of the big toe disappears or decreases.

Vasomotor or trophic disorders are much less pronounced in the lesion of the peroneal nerve than the tibial nerve, since there are few vegetative fibers in the composition of the capillary nerve.

The defeat of the deep peroneal nerve leads to paresis of extension and lifting of the inner edge of the foot (paresis of the anterior tibial muscle). The foot hangs and is slightly outward, the outer edge of the foot is not pubescent due to the safety of long and short fibular muscles (pes equinus). The main phalanges of the toes are bent (the antagonistic action of the interosseous and vermiform muscles with the paralysis of the common extensor of the fingers and the long extensor of the thumb). Sensitivity disorders are limited to the area of the first interdigital space.

The defeat of the superficial peroneal nerve leads to a weakening of the abduction and lifting of the outer edge of the foot (long and short fibular muscles). The foot is somewhat detached to the inside, the outer edge of it is lowered (pes varus), but the extension of the foot and fingers is possible. The sensitivity is disturbed in the area of the rear of the foot, except for the first interdigital space and the outer edge of the foot.

Most often, the peroneal nerve is affected by trauma by the mechanism of tunneling (compression-ischemic) syndrome. It is possible to distinguish the main two variants of localization of such a lesion - upper and lower compression-ischemic neuropathy of the peroneal nerve.

The upper tunnel syndrome of the peroneal nerve develops when it is afflicted at the level of the cervix of the fibula. The clinical picture in this case is characterized by paralysis of extension of the foot, deep paresis of the extensors of the toes, retraction of the foot outside with lifting of its outer edge; pain and paresthesias in the anterior part of the lower leg, on the fringe of the foot and fingers, anesthesia in this zone. Often, such a syndrome develops with a prolonged stay in a monotonous pose "squatting," sitting with one leg thrown over one another or in some occupations (agricultural workers, pipe and asphalt stackers, mannequins, seamstresses, etc.) and is referred to in the literature as "professional paralysis of the peroneal nerve, or Guillain-de-Céza-Blondin-Walter syndrome. In the "squatting" position, the nerve is squeezed due to the tension of the biceps femoris and its rapprochement with the fibula, and in the "leg-to-foot" position, the nerve is squeezed between the femur and the fibula. It should be noted the high sensitivity of the peroneal nerve, in comparison with other nerves of the lower limb, to the influence of numerous factors (trauma, ischemia, infection, intoxication). In the composition of this nerve is a lot of thick myelin and little non-fibrillated fibers. It is known that when exposed to ischemia, thick, myelinated fibers are primarily damaged.

The lower tunnel syndrome of the peroneal nerve develops in the lesion of the deep peroneal nerve on the ankle of the ankle under the lower ligament of the extensor, and also on the rear of the foot in the base of the I bone of the metatarsal. The compression-ischemic lesion of the deep peroneal nerve under the lower ligament of the extensor is referred to as the anterior tarsal tunnel syndrome, and the same lesion of the posterior tibial nerve as the medial tarsal tunnel syndrome.

The clinical picture depends on whether both branches of the deep peroneal nerve are broken or whether the inner and outer nerve are broken. With isolated damage to the outer branch, the fibers, the conductors of deep sensitivity, become irritated and poorly localized pain occurs on the rear of the foot. Paresis and atrophy of the small muscles of the foot can develop. There are no skin sensitivity disorders.

If only the inner branch is squeezed, signs of damage to the fibers of the surface sensory fibers dominate. Pain and paresthesia can be felt only in the first and second toes of the foot, if there is no retrograde spread of painful sensations. Sensitivity disorders correspond to the innervation zone of the skin of the first interdigital space and the adjacent surfaces of the first and second fingers, and there are no motor abscesses.

Under the lower ligament of the extensor, the common trunk of the deep peroneal nerve or both its branches is often compressed. In this case, the clinical picture will manifest itself as the sum of the symptoms of damage to the external and internal branches. Sharp irritation of sensitive fibers of the nerve due to trauma to the rear of the foot can cause local osteoporosis.

The upper level of provocation of painful sensations on the back of the ankle joint in combination with the short extensor of the fingers and hyposis in the skin zone indicates the defeat of both branches of the nerve under the bunch of extensors. If in this place only the external branch will be squeezed, the following method will help to reveal the paresis of the short extensor of the fingers. The patient is asked to unbend his fingers with maximum force against the direction of the action of the resistance force and at the same time forcibly perform the back folding of the foot.

Diagnostic value is the study of the distal motor period of the deep peroneal nerve: the latent period varies from 7 to 16.1 ms [average value in healthy individuals is 4.02 (± 0.7) ms, with oscillations from 2.8 to 5.4 ms ]. The rate of excitation of motor nerve fibers in the area from the level of the fibular head to the lower ligament of the flexors remains normal. On the electromyogram of the short extensor of the fingers appears pathological spontaneous activity in the form of potentials of fibrillation and high-frequency waves. After 2-4 weeks, there are signs of chronic denervation of the muscle.

A local injection of novocaine is used to establish the site of nerve damage. Initially, 3-5 ml of 0.5-1% solution of novocaine is administered subfascally in the region of the proximal part I of the intergluteal gap. If the internal branch of the nerve is damaged at this level, pain ceases after anestezin. If the pain does not pass, the same amount of solution is injected on the back of the ankle under the rear talon-fibular bunch of extensors. The disappearance of pain confirms the diagnosis of anterior tarsal tunnel syndrome. Naturally, with a higher lesion level (the trunk of the deep or common peroneal nerve, sciatic nerve or LV-SI rootlets), the blockade in the area of the extensor ligament will not remove the centripetal pain afferentation and will not stop the pain.

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