Symptoms of sacral plexus lesions

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 the LIV. It is often referred to as the "lumbosacral" plexus. It is located near the sacroiliac joint on the anterior surface of the piriformis and partly on the coccygeal muscles, between the coccygeal muscles and the wall of the rectum. A group of short and long branches extends from it. The short branches go to the pelvic muscles, gluteal muscles and external genitalia. The long branches of this plexus are the sciatic nerve and the posterior cutaneous nerve of the thigh. Externally, the sacral plexus has the shape of a triangle, from the apex of which the largest nerve, n. ischiadicus, emerges.

The anterior surface of the plexus is covered by a fibrous plate, which is part of the aponeurosis of the lesser pelvis and extends from the corresponding intervertebral openings to the greater sciatic opening. Medially from it is the parietal leaf of the peritoneum. Both of these leaves in men and women separate the plexus from the internal iliac artery and vein, the sympathetic trunk and the rectum, and in women - from the uterus, ovaries and tubes. The motor fibers that are part of the short branches of the sacral plexus innervate the following muscles of the pelvic girdle: piriformis, internal, obturator, superior and inferior gemellus, quadratus femoris, gluteus maximus, medius and minimus, tensor fasciae lata. These muscles abduct and rotate the lower limb outward, extend it at the hip joint, straighten the torso in a standing position and tilt it to the appropriate side. Sensory fibers supply the skin of the gluteal region, perineum, scrotum, back of the thigh, and upper leg.

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

More often, partial damage to the sacral plexus and its individual branches is observed.

Symptoms of sacral plexus lesions are characterized by intense pain in the sacrum, buttocks, perineum, back of the thighs, shins and plantar surface of the foot (neuralgic variant of sacral plexitis). With deeper lesions of the plexus, pain and paresthesia of the above localization are accompanied by sensitivity disorders (hypesthesia, anesthesia) in this area and paresis (paralysis) of the innervated muscles of the pelvic girdle, back of the thigh, shin and all muscles of the foot, Achilles and plantar reflexes, reflex from the long extensor of the big toe are reduced or fade away.

The internal obturator nerve (n. obturatorius internus) is formed by the motor fibers of the LIV spinal root and innervates the internal obturator muscle, which rotates the thigh outward.

The piriform nerve (n. piriformis) consists of motor fibers SI - SIII, spinal roots and supplies the piriformis muscle. The latter divides the sciatic opening into two parts - the supra- and infrapiriform openings, through which vessels and nerves pass. When this muscle contracts, external rotation of the thigh is achieved.

The nerve of the quadratus femoris (n. quadratus femoris) is formed by fibers of the LIV - SI spinal roots, innervates the quadratus femoris and both (upper and lower) gemellus muscles. These muscles participate in the external rotation of the thigh.

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

1. the subject, who is in a prone position with the lower limb bent at the knee joint at an angle of 90°, is asked to move the lower leg towards the other lower limb; the examiner resists this movement;
2. the subject, who is lying on his back, is asked to rotate his lower limb outward; the examiner prevents this movement - if the nerve of the quadratus femoris is damaged, paresis of the muscles mentioned above develops and resistance to outward rotation of the lower limb is weakened.

The superior gluteal nerve (n. gluteus superior) is formed by the fibers of the LIV - LV, SI- SV spinal roots, passes over the piriformis muscle together with the superior gluteal artery, goes to the gluteal region, penetrating under the gluteus maximus muscle, is located between the middle and small gluteal muscles, which it supplies. Both of these muscles abduct the straightened limb.

Test for determining the strength of the gluteus medius and minimus: the subject, lying on his back or side with his lower limbs straightened, is asked to move them to the side or upward; the examiner resists this movement and palpates the contracted muscle; a branch of this nerve also supplies the tensor muscle of the thigh, which rotates the thigh slightly inward.

The clinical picture of damage to the superior gluteal nerve is manifested by difficulty in abducting the lower limb. Rotation of the thigh inward is partially impaired due to weakness of the tensor fasciae latae. With paralysis of these muscles, moderate rotation of the lower limb outward is observed, this is especially noticeable when the patient is lying on his back and when bending the lower limb at the hip joint (the iliopsoas muscle rotates the thigh outward when bending at the hip joint). When standing and walking, the middle and small gluteal muscles participate in maintaining the vertical position of the body. With bilateral paralysis of these muscles, the patient stands unsteadily, the gait is also characteristic - waddling from side to side (the so-called duck gait).

The inferior gluteal nerve (n. gluteus inferior) is formed by fibers of the LV – SI-II spinal roots and exits the pelvic cavity through the infrapiriform opening, lateral to the inferior gluteal artery. It innervates the gluteus maximus muscle, which extends the lower limb at the hip joint, slightly rotating it outward; with a fixed hip, it tilts the pelvis backward.

Test for determining the strength of the m. glutaei maximi: the subject, lying on his stomach, is asked to raise his straightened lower limb; the examiner resists this movement and palpates the contracted muscle.

Damage to the inferior gluteal nerve leads to difficulty in extending the lower limb at the hip joint. In a standing position, it is difficult to straighten the tilted pelvis (the pelvis in such patients is tilted forward, and there is a compensatory lordosis in the lumbar spine). These patients have difficulty climbing stairs, running, jumping, and getting up from a sitting position. Hypotrophy and hypotonia of the gluteal muscles are observed.

The posterior cutaneous nerve of the thigh (n. cutaneus femoris posterior) of the plexus is formed by the sensory fibers of the SI - SIII spinal nerves, exits the pelvic cavity together with the sciatic nerve through the greater sciatic opening below the piriformis muscle. The nerve then lies under the gluteus maximus muscle and passes to the back of the thigh. From the medial side, the nerve gives off branches that go under the skin of the lower part of the buttock (nn. clunii inferiores) and to the perineum (rami perineales). Subcutaneously along the back of the thigh, this nerve goes to the popliteal fossa and branches, innervating the entire back of the thigh and a section of skin on the upper third of the back of the leg.

Most often, the nerve is affected at the level of the greater sciatic foramen, especially with spasm of the piriformis muscle. Another pathogenetic factor for this compression-ischemic neuropathy is cicatricial-adhesive processes after damage to deep tissues (penetrating wounds) of the gluteal region and the upper third of the back of the thigh.

The clinical picture is represented by pain, numbness and paresthesia in the gluteal region, perineal region and on the back of the thigh. The pain increases when walking and sitting.

The area of the pathological process is determined by palpation, by pain points. The diagnostic value and therapeutic effect is provided by the introduction of 0.5 - 1% solution of novocaine paraneurally or into the piriformis muscle, after which the pain disappears.

[ 1 ], [ 2 ], [ 3 ]