Symptoms of the defeat of the sacral plexus

The sacral plexus (pl., Sacralis) is the anterior branches of the LV and SI - SIV spinal nerves and the lower part of the anterior branch of LIV. Often it is referred to as a "lumbosacral" plexus. It is located near the sacroiliac articulation on the anterior surface of the pear-shaped and partly on the coccygeal muscles, between the coccygeal muscles and the rectum wall. A group of short and long branches departs from it. Short branches go to the muscles of the pelvis, gluteal muscles and the external genital organs. The long branches of this plexus are the sciatic nerve and the posterior cutaneous nerve of the thigh. Outwardly the sacral plexus has the form of a triangle, from the apex of which the largest nerve - n. Ischiadicus.

The anterior surface of the plexus is covered with a fibrous plate, which forms part of the pelvic aponeurosis and runs from the corresponding intervertebral openings to the large sciatic foramen. Inside of it is a parietal peritoneal leaflet. Both these leaflets in men and women separate the plexus from the internal iliac artery and vein, the sympathetic trunk and rectum, in addition, in women - from the uterus, ovaries and tubes. The motor fibers that form part of the short branches of the sacral plexus innervate the following muscles of the pelvic girdle: pear-shaped, internal, blocking, upper and lower twins, square thigh muscles, large, middle and small gluteus muscles, broad fascia tensor. These muscles withdraw and rotate the lower extremity to the outside, unbend it in the hip joint, in the standing position straighten the trunk and tilt it in the appropriate direction. Sensitive fibers provide the skin with the gluteal region, perineum, scrotum, hamstrings, upper legs of the lower leg.

The sacral plexus is completely affected relatively rarely. This happens with a trauma with a fracture of the pelvic bones, with tumors of the pelvic organs, with extensive inflammatory processes.

The partial defeat of the sacral plexus and its separate branches is observed more often.

Symptoms of the defeat of the sacral plexus are characterized by intense pains in the region of the sacrum, buttocks, perineum, the posterior surface of the thighs, the lower legs and the plantar surface of the foot (neuralgic variant of sacral plexitis). With deeper damage to the plexus to the pains and paresthesias of the above localization, sensitivity disorders (hypesthesia, anesthesia) in this zone and paresis of the innervated muscles of the pelvic girdle, posterior thigh, shin and all the foot muscles are reduced, or the Achilles and plantar reflexes decrease or die out , a reflex with a long extensor of the big toe.

The internal obturator nerve (n. Obturatorius internus) is formed by the motor fibers of the LIV spinal root and innervates the internal occlusive muscle that rotates the hip outward.

The pear-shaped nerve (n. Piriformis) consists of motor fibers SI-SIII, spinal roots and supplies the pear-shaped muscle. The latter divides the sciatic foramen into two parts - the over- and sub-vesicular apertures, through which the vessels and nerves pass. When this muscle is contracted, the external rotation of the thigh is performed.

The nerve of the square femur muscle (n. Quadratus femoris) is formed by fibers of the LIV-SI spinal roots, innervates the square muscle of the femur and both the upper and lower twin muscles. These muscles are involved in the rotation of the thigh to the outside.

Tests to determine the strength mm. Piriformis, obturatorii interni, gemellium, quadrati femoris:

1. the subject who is lying in the abdominal position, the lower limb is bent at the knee joint at an angle of 90 °, proposing to bring the shin toward the other lower limb; the examiner is resisting this movement;
2. The subject, who is in a supine position, is offered to rotate the lower extremity to the outside; the examiner prevents this movement - when the nerve of the square muscle of the thigh is affected, the paresis of the muscles indicated above develops and the resistance decreases when the lower extremity is rotated outwards.

The upper gluteus nerve (n. Gluteus superior) is formed by the fibers of LIV-LV, SI-SV of the spinal roots, passes over the pear-shaped muscle together with the upper gluteal artery, is directed into the gluteal region, penetrating under the gluteus maximus, located between the middle and minor gluteal muscles, which he supplies. Both these muscles divert the straightened limb.

The test for determining the strength of the middle and minor gluteal muscles: the examinee, who lies on his back or on his side with straightened lower limbs, is suggested to take them aside or up; the examiner is resisting this movement and palpating the contracted muscle; The branch of this nerve also supplies the thigh muscle, which rotates the thigh somewhat inwards.

The clinical picture when the upper gluteal nerve is affected is manifested in the difficulty of withdrawing the lower limb. Partially disrupted the rotation of the hip to the inside due to the weakness of the tensor of the broad fascia. When these muscles are paralyzed, a moderate rotation of the lower extremity outside is observed, especially in the patient's position lying on his back and when flexing the lower limb in the hip joint (the lumbosacral muscle rotates in the hip joint when flexing in the hip joint). When standing and walking, the middle and small gluteal muscles participate in maintaining the vertical position of the trunk. With the bilateral paralysis of these muscles, the patient is unstable, the gait is also characteristic - swaying from side to side (the so-called duck walk).

The lower gluteus nerve (n. Gluteus inferior) is formed by the LV-SI-II fibers of the spinal roots and exits from the pelvic cavity through the sub-pear-shaped orifice, laterally from the lower gluteal artery. It innervates the gluteus maximus, which unbends the lower limb in the hip joint, somewhat rotating it outward; with a fixed thigh - tilts the pelvis back.

Strength test m. Glutaei maximi: the subject who is in the supine position is offered to raise the straightened lower limb; The examiner is resisting this movement and palpating the contracted muscle.

The defeat of the lower gluteal nerve leads to difficulty in unbending the lower limb in the hip joint. In the standing position, the rectification of the inclined pelvis is difficult (the pelvis in these patients is tilted forward, with compensatory lordosis in the lumbar spine). These patients are difficult to climb the stairs, running, jumping, getting up from the sitting position. There is hypotrophy and hypotonia of gluteal muscles.

The posterior cutaneous nerve of the thigh (n. Cutaneus femoris posterior) of the plexus is formed by the sensitive fibers of the SI-SIII spinal nerves, exits the pelvic cavity along with the sciatic nerve through a large sciatic hole below the pear-shaped muscle. Then the nerve is located under the large gluteus muscle and passes to the back surface of the thigh. From the medial side, the nerve gives branches under the skin of the lower part of the buttock (nn. Clunii inferiores) and to the perineum (rami perineales). Subcutaneously along the posterior surface of the thigh, this nerve runs up to the popliteal fossa and branches, innervating the entire back of the thigh and the skin area on the upper third of the posterior surface of the shin.

Most often, the nerve is affected at the level of the large sciatic foramen, especially with the spasm of the pear-shaped muscle. Other pathogenetic factors for this compression-ischemic neuropathy are cicatricial-adhesive processes after damage to the deep tissues (penetrating wounds) of the gluteal region and upper third of the hamstrings.

The clinical picture is represented by pain, numbness and paresthesia in the gluteal region, perineal region and the posterior surface of the thigh. Pain increases with walking and sitting.

The zone of the pathological process is determined palpatory, by painful points. Diagnostic value and therapeutic effect is the introduction of 0.5-1% solution of novocaine in a paraneurally or pear-shaped muscle, after which the pain disappears.

[1], [2], [3]