Symptoms of affection of the sciatic nerve

The sciatic nerve (n. Ischiadicus) is a long branch of the sacral plexus, contains neural fibers of the neurons located in the segments of the spinal cord LIV-SIII. Sciatic nerve is formed in the cavity of the small pelvis near the large sciatic foramen and leaves it through the podrugus aperture. In this opening the nerve is located more laterally; higher and to the inside of it go the lower gluteal artery with the veins accompanying it and the lower gluteal nerve. Medially passes the posterior cutaneous nerve of the thigh, as well as a neurovascular bundle consisting of the internal populous artery, veins and the genital nerve. The sciatic nerve can exit through the periembus or directly through the pear-shaped muscle (in 10% of individuals), and in the presence of two trunks - through both holes. Due to this anatomical arrangement between the pear-shaped muscle and the dense sacro-ovar sheaf, the sciatic nerve can often undergo compression at this level.

Upon exiting through the cleft under the pear-shaped muscle (subgrusiform opening), the sciatic nerve is located outside of all nerves and vessels passing through this opening. The nerve here is almost in the middle of the line drawn between the ischial tuberosus and the large trochter. Leaving from under the bottom edge of the gluteus maximus, the sciatic nerve lies in the region of the gluteal fold near the wide fascia of the thigh. Below, the nerve is covered by the long head of the biceps muscle and is located between it and the large adductor muscle. In the middle of the thigh, the long head of the biceps femoris is located across the sciatic nerve, and it is located between the biceps femoris and the semimembranous muscle. The division of the sciatic nerve into the tibial and common peroneal nerves often occurs at the level of the upper corner of the popliteal fossa. However, often the nerve divides higher - in the upper third of the thigh. Sometimes the nerve is divided even near the sacral plexus. In this case, both portions of the sciatic nerve pass through separate trunks, from which the tibial nerve passes through the lower part of the large sciatic foramen (podrushevidnoe aperture), and the common peroneal nerve - through the pectoral orifice, or it pierces the pear-shaped muscle. Sometimes, not from the sacral plexus, but from the sciatic nerve branches branch to the square muscle of the femur, the twin and the inner occlusive muscles. These branches extend either at the site of passage of the sciatic nerve through the podrushevidnoe aperture, or higher. In the hip area from the peroneal part of the sciatic nerve branches branch to the short head of the biceps femoris, from the tibial part to the large adductor, semitendinosus and semimembranous muscles, and also to the long head of the biceps femoris muscle. The branches to the last three muscles are separated from the main nerve trunk high in the gluteal region. Therefore, even with fairly high damage to the sciatic nerve, the flexion of the extremity in the knee joint is not impaired.

Semimembranous and semitendinous muscles flex the lower extremity in the knee joint, somewhat rotating it inwards.

The test for determining the strength of the semimembranous and semitendinous muscles: the examinee, lying in the supine position, is offered to bend the lower limb at an angle of 15 ° - 160 ° in the knee joint, rotating the shin inward; The examiner is resisting this movement and palpating the strained muscle tendon.

The biceps femoris flexes the lower limb in the knee joint, rotating the shin outward.

Tests for determining the strength of the biceps femoris muscle:

1. the subject, lying in a supine position with a lower limb bent in the knee and hip joint, is suggested to bend the limb at the knee joint at a sharper angle; the examiner is resisting this movement;
2. the subject, lying in the supine position, is offered to bend the lower limb in the knee joint, somewhat rotating it outward; the examiner is resisting this movement and palpating the contracted muscle and strained tendon.

In addition, the sciatic nerve provides the innervation of all the muscles of the shank and foot with branches that extend from the trunks of the tibial and peroneal nerves. From the sciatic nerve and its branches branch branches to the bags of all the joints of the lower extremities, including the hip. From the tibial and peroneal nerves branches branch off, providing sensitivity of the skin of the foot and most of the shin, except for its inner surface. Sometimes the posterior cutaneous nerve of the hip descends to the lower third of the shin, and then it overlaps the innervation zone of the tibial nerve on the posterior surface of this shin.

The common trunk of the sciatic nerve can be affected by injuries, trauma with a fracture of the pelvic bones, inflammatory processes in the pelvic floor and buttocks. However, most often this nerve suffers by the mechanism of tunnel syndrome with the involvement of the pear-shaped muscle in the pathological process.

The mechanisms of pear-shaped muscle syndrome are complex. The modified pear-shaped muscle can squeeze not only the sciatic nerve, but also other branches of SII-IV. It should also be borne in mind that between the pear-shaped muscle and the trunk of the sciatic nerve is the vascular plexus, which belongs to the system of the lower gluteal vessels. When it is squeezed, venous congestion and passive hyperemia of the vagina of the trunk of the sciatic nerve occur.

Pear-shaped muscle syndrome is primary, caused by pathological changes in the muscle itself, and secondary, due to its spasm or external compression. Often, this syndrome occurs after a trauma of the sacroiliac or gluteal region with the subsequent formation of adhesions between the pear-shaped muscle and sciatic nerve, as well as with ossifying myositis. Secondary pear-shaped muscle syndrome can occur with diseases of the sacroiliac joint. This muscle is reflexively spasmodic in the spondylogenic lesion of the roots of the spinal nerves. It is the reflex effects on the muscle tone that can occur when the focus of the nerve fibers irritation is distant from the muscle.

The presence of spasm of pear-shaped muscle in discogenic radiculitis is confirmed by the effect of Novocain blockades of this muscle. After injection of a 0.5% solution of novocaine (20-30 ml) the pain stops or significantly weakens for several hours. This is due to a temporary decrease in the spasticity of the pear-shaped muscle and its pressure on the sciatic nerve. Pear-shaped muscle participates in external rotation of the thigh with the lower limb unbent in the hip joint, and with its bending - in the femur.

When walking, this muscle tenses at every step. The sciatic nerve, whose mobility is limited, gets frequent tremors during walking while contracting the pear-shaped muscle. At each such jerk, nerve fibers are irritated, their excitability increases. Such patients are often in a forced position with lower limbs bent in the hip joint. In this case, compensatory lumbar lordosis arises and the nerve is pulled over the sciatic notch. To compensate for the lack of stabilization of the lumbar spine, the ileo-lumbar and pear-shaped muscles are transferred to a state of increased tonic tension. This can also be the basis for the appearance of pear-shaped muscle syndrome. The sciatic nerve at the point of exit from the small pelvis through a relatively narrow sub-tubular aperture is subjected to rather strong mechanical influences.

The clinical picture of the syndrome of the pear-shaped muscle consists of the symptoms of the defeat of the pear-shaped muscle and sciatic nerve. The first group of symptoms include:

1. tenderness in palpation of the upper internal part of the large trochanter of the thigh (the place of attachment of the muscle);
2. palipation tenderness in the lower part of the sacroiliac joint (projection of the attachment of the pear-shaped muscle to the capsule of this joint);
3. passive hip reduction with its rotation inside, causing pain in the gluteal region, less often - in the zone of innervation of the sciatic nerve on the leg (Bonnet symptom);
4. soreness in the palpation of the buttocks at the point of exit of the sciatic nerve from under the pear-shaped muscle. The last symptom is more due to palpation of the altered pear-shaped muscle than the sciatic nerve.

The second group includes symptoms of compression of the sciatic nerve and vessels. The painful sensations when compressing the sciatic nerve pear-shaped muscle have their own characteristics. Patients complain of a feeling of heaviness in the lower limb or a dull, aching pain. At the same time, compression of the spinal roots is characterized by a stabbing, shooting character of the pains with the spread of them in the zone of a certain dermatome. Pain is worse when coughing, sneezing.

Distinguish the lesion of the lumbosacral spinal roots of the sciatic nerve helps to identify the nature of loss of sensitivity. With sciatic neuropathy, sensitivity decreases on the skin of the lower leg and foot. When a herniated intervertebral disc involving the roots of LV - SI - II, there is lamp - shaped hypesesthesia. True LV - SI dermatomes extend to the entire lower limb and gluteal region. With sciatic neuropathy, the zone of reduced sensitivity does not rise above the knee joint. Motion disorders can also be informative. Compression radiculopathy often causes atrophy of the gluteus musculature, which is not usually the case with sciatic nerve damage.

When a combination of discogenic lumbosacral radiculitis and pear-shaped muscle syndrome, vegetative disturbances are also observed. In most cases, on the side of the lesion, the skin temperature and the oscillographic index decrease, which increase after injection of novocaine (0.5% solution of 20 ml) into the pear-shaped muscle region. However, these angiospastic phenomena are difficult to explain solely by sciatic neuropathy. Constrictor effects on the vessels of the extremities can proceed not only from the compressed and ischemic trunk of the sciatic nerve, but also from the nerve root undergoing similar stimulation. With the introduction of novocaine into the nerve region, its blockade interrupts the vasoconstrictive impulses coming from the higher parts of the nervous system.

When the sciatic nerve is injured at the femur level (below the exit from the pelvis and to the level of division into the small and tibial nerves), the flexion of the lower limb in the knee joint is broken due to the paresis of the semitendinous, semimembranous and biceps femoris muscles. The lower extremity is bent at the knee joint due to the antagonistic action of the quadriceps femoris muscle. Acquires a special characteristic of the gait of such patients - the straightened lower limb is carried forward like a stilt. Active movements in the foot and fingers are absent. The feet and fingers moderately hang. At rough anatomical lesion of a nerve in 2-3 weeks the atrophy of paralyzed muscles joins.

A constant sign of affection of the sciatic nerve is a violation of sensitivity along the posterior surface of the shin, the rear of the foot, fingers and soles. Muscular-articular feeling is lost in the ankle and interphalangeal joints of the fingers. Vibratory feeling is absent on the external ankle. The pain of palpation along the sciatic nerve (at the points of Ballet) is typical - on the buttock in the middle between the ischial tuberosus and the large trochanter, in the popliteal fossa, etc. Lasega's symptom is painful in the first phase of his examination. The Achilles and the plantar reflexes disappear.

With incomplete injury of the sciatic nerve, the pain is of a causal nature, there are sharp vasomotor and trophic disorders. Pain has a burning character and intensifies when the lower limb is lowered. A slight tactile irritation (touching the blanket to the lower leg and the foot) can cause an attack of aggravating pain. The foot becomes cyanotic, cold to the touch (at the beginning of the disease it is possible to raise the temperature of the skin on the shin and foot, but in the subsequent skin temperature in comparison with the temperature on the healthy side drops sharply). This is well revealed when examining the lower extremities. Often on the plantar surface, hyperkeratosis, anhidrosis (or hyperhidrosis), hypotrichosis, changes in the shape, color and growth of the nails. Sometimes trophic ulcers may appear on the heel, the outer edge of the foot, the back surface of the fingers. The roentgenograms reveal osteoporosis and decalcation of the foot bones. The muscles of the foot atrophy.

Such patients have difficulty in trying to stand on their toes and heels, beat off the foot in time with the music, raise the heel, resting their foot on the toe, and so on.

Significantly more often in clinical practice, not the trunk of the sciatic nerve itself is affected, but its distal branches - the peroneal and tibial nerves.

The sciatic nerve divides slightly above the popliteal fossa on the tibial and peroneal nerves.

[1], [2], [3], [4], [5], [6], [7]