Symptoms of peroneal nerve damage

The common peroneal nerve (n. peroneus communis) consists of fibers of the LIV-LV and SI-SIII spinal nerves and passes through the popliteal fossa towards the neck of the fibula. Here it divides into superficial, deep and recurrent branches. Above these branches, which are directly adjacent to the bone, at the point of their division, there is an arch-shaped fibrous band of the long peroneus muscle. It can press these nerve branches to the bone when the muscle is stretched during overstretching of the ligaments of the ankle joint with forced lifting of its inner edge. In this case, the nerves are also stretched. Such a mechanism is present in case of an ankle injury with inversion of the foot inward and simultaneous plantar flexion.

The external cutaneous nerve of the gastrocnemius muscle, which supplies the lateral and posterior surface of the leg, departs from the trunk of the common peroneal nerve in the popliteal fossa, above the site of its division. At the level of the lower third of the leg, this nerve anastomoses with the cutaneous medial nerve of the leg (a branch of the tibial nerve) and together they form the sural nerve (n. suralis).

The superficial peroneal nerve runs down the anterolateral surface of the leg, giving off branches to the long and short peroneal muscles. These muscles abduct and lift the outer edge of the foot (perform pronation, while simultaneously flexing it.

Test to determine the strength of the long and short peroneus muscles: the subject, lying on his back, is asked to abduct and raise the outer edge of the foot, simultaneously flexing the foot; the examiner resists this movement and palpates the contracted muscle.

At the level of the middle third of the leg, the superficial peroneal nerve, piercing the fascia of the short peroneal muscle, exits under the skin and divides into its terminal branches - the medial and intermediate dorsal cutaneous nerves.

The medial dorsal cutaneous nerve supplies the inner edge and part of the dorsum of the foot, the first toe and the facing surfaces of the second and third toes.

The intermediate dorsal cutaneous nerve gives off branches to the skin of the lower third of the leg and the dorsum of the foot, to the dorsum between the III and IV, IV and V toes.

The deep peroneal nerve, piercing the thickness of the long peroneus muscle and the anterior intermuscular septum, penetrates into the anterior region of the leg, where it can be subject to compression during ischemic muscle necrosis. In the upper parts of the leg, the nerve passes between the long extensor of the fingers and the anterior tibialis muscle, in the lower parts of the leg - between the latter and the long extensor of the big toe, giving off branches to these muscles.

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

Test to determine the strength of the anterior tibialis muscle: the patient, lying on his back, is asked to straighten the limb at the ankle joint, adduct and raise the inner edge of the foot; the examiner resists this movement and palpates the contracted muscle.

The long extensor of the fingers extends the II - V fingers and the foot at the ankle joint, abducts and pronates the foot (innervated by the LIV - SI segment).

A test to determine its strength: the subject, lying on his back, is asked to straighten the proximal phalanges of the II - V fingers; the examiner resists this movement and palpates the tense tendon of the muscle.

The long extensor of the big toe extends the first toe and the foot at the ankle joint, supinating it (innervated by the LIV - SI segment).

A test to determine its strength: the subject is asked to straighten the first toe of the foot; the examiner prevents this movement and palpates the tense tendon of the muscle.

When passing to the dorsum of the foot, the deep peroneal nerve is located first under the superior and then under the inferior extensor ligament and the tendon of the long extensor of the 1st toe. Here, compression of this nerve is possible. When exiting the foot, the deep peroneal nerve divides into two branches. The outer branch goes to the short extensors of the toes, and the inner one reaches the 1st interosseous space, where, passing under the tendon of the short extensor of the 1st toe, it divides into terminal branches that branch out in the skin of adjacent surfaces - the medial surface of the 1st and lateral surface of the 2nd toe.

The short extensor of the fingers extends the II - IV fingers with a slight abduction outward (innervated by the LIV - SI segment); the short extensor of the big toe extends the first finger of the foot and abducts it slightly to the side.

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

When the common peroneal nerve is affected, the ability to extend the foot at the ankle joint and toes, abduct the foot, and pronate its outer edge is lost. The foot hangs down sluggishly and is rotated inward. The toes are bent at the proximal phalanges. With prolonged damage to this nerve, due to the action of the antagonist muscles (gastrocnemius and interosseous muscles), a contracture may form, leading to persistent plantar flexion of the foot and the main phalanges of the toes. The foot takes the form of a "horse foot" (pes equinovarus). The characteristic gait of such patients: in order to avoid touching the floor with the dorsum of the foot, the patient raises the thigh high; when lowering it, the hanging foot first rests on the toes, and then lowers to the floor with the entire sole. This gait is similar to the step of a horse or a rooster ("horse" or "rooster" gait - steppage). The muscles of the anterior outer surface of the leg atrophy. The zone of sensitivity disorder extends to the anterior outer surface of the leg (lateral cutaneous nerve of the leg) and to the back of the foot, including the first interdigital space.

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

Vasomotor or trophic disorders are expressed much less strongly in case of damage to the peroneal nerve than to the tibial nerve, since the peroneal nerve contains few autonomic fibers.

Damage to the deep peroneal nerve leads to paresis of extension and elevation of the inner edge of the foot (paresis of the anterior tibial muscle). The foot hangs down and is slightly abducted outward, the outer edge of the foot is not lowered due to the preservation of the functions of the long and short peroneal muscles (pes equinus). The main phalanges of the toes are bent (antagonistic action of the interosseous and lumbrical muscles with paralysis of the common extensor of the fingers and the long extensor of the big toe). Sensitivity disorders are limited to the area of the first interdigital space.

Damage to the superficial peroneal nerve leads to weakening of the abduction and elevation of the outer edge of the foot (long and short peroneal muscles). The foot is slightly abducted inward, its outer edge is lowered (pes varus), but extension of the foot and toes is possible. Sensitivity is impaired in the area of the dorsum of the foot, with the exception of the first interdigital space and the outer edge of the foot.

Most often, the peroneal nerve is damaged by trauma through the mechanism of tunnel (compression-ischemic) syndrome. There are two main variants of localization of such damage - upper and lower compression-ischemic neuropathy of the peroneal nerve.

Superior tunnel syndrome of the peroneal nerve develops when it is damaged at the level of the neck of the fibula. The clinical picture is characterized by paralysis of extension of the foot, deep paresis of the extensors of the toes, abduction of the foot outward with lifting of its outer edge; pain and paresthesia in the anterolateral parts of the shin, on the base of the foot and toes, anesthesia in this area. Often, such a syndrome develops with a long stay in a monotonous "squatting" position, sitting with one leg thrown over the other, or in people of certain professions (agricultural workers, pipe and asphalt layers, fashion models, seamstresses, etc.) and is referred to in the literature as "professional paralysis of the peroneal nerve" or Guillain-de Seza-Blondin-Walter syndrome. In the squatting position, the nerve is compressed due to the tension of the biceps femoris and its proximity to the head of the fibula, and in the leg-over-leg position, the nerve is compressed between the femur and the head of the fibula. It should be noted that the peroneal nerve is highly sensitive to numerous factors (trauma, ischemia, infection, intoxication) compared to other nerves of the lower limb. This nerve contains many thick myelinated fibers and few non-myelinated fibers. It is known that thick myelinated fibers are damaged first when exposed to ischemia.

Inferior peroneal tunnel syndrome develops with damage to the deep peroneal nerve on the back of the ankle joint under the lower extensor ligament, as well as on the back of the foot in the area of the base of the first metatarsal bone. Compression-ischemic damage to the deep peroneal nerve under the lower extensor ligament is called anterior tarsal tunnel syndrome, and the same damage to the posterior tibial nerve is called medial tarsal tunnel syndrome.

The clinical picture depends on whether both branches of the deep peroneal nerve are damaged or the external and internal ones separately. With isolated damage to the external branch, the fibers that carry deep sensitivity are irritated and poorly localized pain occurs on the dorsum of the foot. Paresis and atrophy of the small muscles of the foot may develop. There are no disturbances of skin sensitivity.

If only the internal branch is compressed, signs of damage to the fibers conducting the superficial sensitivity dominate. Pain and paresthesia can be felt only in the first and second toes, 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 adjacent surfaces of the first and second toes, there are no motor loss.

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

The upper level of pain provocation on the back of the ankle joint in combination with paresis of the short extensor of the fingers and hypoesthesia in the skin area indicates damage to both branches of the nerve under the extensor ligament. If only the outer branch is compressed in this place, the following technique will help to identify paresis of the short extensor of the fingers. The patient is asked to straighten the fingers with maximum force against the direction of the resistance force and simultaneously forcefully perform dorsiflexion of the foot.

The study of the distal motor period of the deep peroneal nerve has diagnostic value: the value of the latent period fluctuates from 7 to 16.1 ms [the average value in healthy individuals is 4.02 (± 0.7) ms, with fluctuations from 2.8 to 5.4 ms]. The speed of excitation conduction along the motor fibers of the nerve in the area from the level of the head of the fibula to the lower flexor ligament remains normal. Pathological spontaneous activity in the form of fibrillation potentials and high-frequency waves appears on the electromyogram of the short extensor of the fingers. Signs of chronic denervation of the muscle appear after 2-4 weeks.

To determine the location of the nerve lesion, local administration of novocaine is used. First, 3-5 ml of 0.5-1% novocaine solution is administered subfascially in the area of the proximal part of the first intermetatarsal space. If the internal branch of the nerve is affected at this level, pain stops after anesthesia. If the pain does not go away, the same amount of solution is administered on the back of the ankle joint under the posterior talofibular extensor ligament. The disappearance of pain confirms the diagnosis of anterior tarsal tunnel syndrome. Naturally, at a higher level of damage (trunk of the deep or common peroneal nerve, sciatic nerve or LV - SI roots), a blockade in the area of the extensor ligament will not remove centripetal pain afferentation and will not stop the pain.

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