Symptoms of lesions of the lumbar plexus and its branches

The lumbar plexus (pl. lumbalis) is formed from the anterior branches of the three upper lumbar, as well as part of the fibers of the TVII and LIV spinal nerves. It is located in front of the transverse processes of the lumbar vertebrae, on the anterior surface of the quadratus lumborum muscle and in the thickness of the psoas major muscle. The following nerves branch off sequentially from this plexus: iliohypogastric, ilioinguinal, genitofemoral, lateral cutaneous nerve of the thigh, obturator and femoral. With the help of two or three connecting branches, the lumbar plexus anastomoses with the pelvic part of the sympathetic trunk. The motor fibers that are part of the lumbar plexus innervate the muscles of the abdominal wall and pelvic girdle. These muscles flex and tilt the spine, flex and extend the lower limb at the hip joint, abduct, adduct and rotate the lower limb, and extend it at the knee joint. The sensory fibers of this plexus innervate the skin of the lower abdomen, the anterior, medial and outer surfaces of the thigh, the scrotum and the upper outer parts of the buttock.

Due to its large extent, the lumbar plexus is completely affected relatively rarely. Sometimes this is observed in muscle injuries with a sharp object, bone fragments (in fractures of the spine and pelvic bones) or in compression by a hematoma, tumors of surrounding tissues, a pregnant uterus, in inflammatory processes in the retroperitoneal space (myositis of the lumbar muscles, phlegmon, abscess) and infiltration due to inflammatory processes in the ovaries, vermiform appendix, etc. Unilateral damage to the plexus, or part of it, is more common.

Symptoms of lumbar plexitis are characterized by pain in the innervation zone of the lower abdomen, lumbar region, pelvic bones (neuralgic form of plexitis). All types of sensitivity are reduced (hypesthesia or anesthesia of the skin of the pelvic girdle and thighs.

Pain is detected with deep palpation through the anterior abdominal wall of the lateral sections of the spine and behind in the area of the quadrangular space between the lower rib and the iliac crest, where the square muscle of the lumbar spine is located and attached. Increased pain occurs when raising the straightened lower limb upward (with the patient lying on his back) and when bending the lumbar spine to the sides. With the paralytic form of lumbar plexitis, weakness, hypotension and hypotrophy of the muscles of the pelvic girdle and thighs develop. The knee reflex is reduced or lost. Movements in the lumbar spine, hip and knee joints are impaired.

Topical differential diagnosis must be carried out with multiple lesions of the spinal nerves that form it (in the initial phase of infectious-allergic polyradiculoneuritis of the Guillain-Barré-Strohl type, with epiduritis) and with compression of the upper sections of the equine tail.

The iliohypogastric nerve (n. iliohypogastricuras) is formed by the fibers of the THII and LI spinal roots. From the lumbar plexus, it emerges from under the lateral edge of m. psoas major and is directed along the anterior surface of the quadratus lumborum muscle (behind the lower pole of the kidney) obliquely downwards and laterally. Above the iliac crest, the nerve pierces the transverse abdominal muscle and is located between it and the internal oblique abdominal muscle along and above the cristae iliacae.

Reaching the inguinal (pupart's) ligament, the iliohypogastric nerve passes through the thickness of the internal oblique muscle of the abdomen and is located under the aponeurosis of the external oblique muscle, along and above the inguinal ligament, then approaches the lateral edge of the rectus abdominis muscle and branches in the skin of the hypogastric region. Along the way, this nerve anastomoses with the ilioinguinal nerve, and then three branches depart from it: motor (directed to the lower parts of the abdominal wall muscles) and two sensory - lateral and anterior cutaneous branches. The lateral and cutaneous branch departs above the middle of the iliac crest and, piercing the oblique muscles, goes to the skin above the gluteus medius muscle and the muscle that tenses the fascia of the thigh. The anterior cutaneous branch is terminal and penetrates the anterior wall of the rectus sheath above the external ring of the inguinal canal, where it ends in the skin above and medial to the external opening of the inguinal canal.

This nerve is usually affected during surgery on the abdominal and pelvic organs or during herniotomy. In the postoperative period, constant pain appears, which intensifies when walking and bending the body forward. The pain is localized in the lower abdomen above the inguinal ligament, sometimes in the area of the greater trochanter of the femur. Increased pain and paresthesia are noted during palpation of the upper edge of the outer ring of the inguinal canal and at the level of the greater trochanter of the femur. Hypoesthesia is localized above the gluteus medius muscle and in the groin area.

The ilioinguinal nerve (n. ilioinguinalis) is formed from the anterior branch of the LI (sometimes LII) spinal root and is located below, parallel to the iliohypogastric nerve. In the intra-abdominal section, the nerve passes under the large psoas muscle, then pierces or bends around its outer part and then goes along the anterior surface of the quadratus lumborum muscle under the fascia. To the inside of the anterior superior iliac spine is the site of possible compression of the nerve, since at this level it first pierces the transverse abdominal muscle or its aponeurosis, then at an angle of about 90° pierces the internal oblique muscle of the abdomen and again changes its course almost at a right angle, heading into the gap between the internal and external oblique abdominal muscles. Motor branches extend from the ilioinguinal nerve to the lowest parts of the transverse and internal oblique abdominal muscles. The terminal sensory branch pierces the external oblique abdominal muscle or its aponeurosis immediately ventrocaudal to the anterior superior iliac spine and continues inside the inguinal canal. Its branches supply the skin above the pubis, and in men, above the root of the penis and the proximal part of the scrotum, and in women, the upper part of the labia majora. Sensory branches also supply a small area in the upper part of the anterointernal surface of the thigh, but this area may be overlapped by the genitofemoral nerve. There is also a sensory recurrent branch, which supplies a narrow strip of skin above the inguinal ligament up to the iliac crest.

Non-traumatic damage to the ilioinguinal nerve usually occurs near the anterior superior iliac spine, where the nerve passes through the transverse and internal oblique muscles of the abdomen and changes its direction in a zigzag pattern at the level of the contacting edges of these muscles. Here, the nerve can be subject to mechanical irritation by muscle or fibrous bands when their edges, compacting, press on the nerve during constant or periodic muscle tension, for example, when walking. Compression-ischemic neuropathy develops according to the tunnel syndrome type. In addition, the ilioinguinal nerve is often damaged during surgical interventions, most often after herniotomy, appendectomy, nephrectomy. Neuralgia of the ilioinguinal nerve after herniotomy is possible when the nerve is tightened with a silk suture in the area of the internal oblique muscle of the abdomen. The nerve may also be pressed on by the aponeurosis after the Bassini procedure, or the nerve may be compressed many months or even years after the procedure by scar tissue that forms between the internal and external oblique abdominal muscles.

Clinical manifestations of ilioinguinal neuropathy are divided into two groups - symptoms of damage to sensory and motor fibers. Damage to sensory fibers has the greatest diagnostic value. Patients experience pain and paresthesia in the groin area, sometimes painful sensations spread to the upper parts of the anterointernal surface of the thigh and to the lumbar region.

Characteristic is palpation pain in the typical location of nerve compression - at a point located slightly above and 1-1.5 cm medially from the superior anterior iliac spine. Digital compression at this point in case of damage to the ilioinguinal nerve, as a rule, causes or increases painful sensations. Palpation in the area of the external opening of the inguinal canal is painful. However, this symptom is not pathognomonic. Palpation pain at this point is also noted in case of damage to the femoral-genital nerve. In addition, in compression syndromes, the entire distal section of the nerve trunk, starting from the level of compression, has increased excitability to mechanical irritation.

Therefore, with digital compression or probing in the area of the nerve projection, only the upper level of pain provocation corresponds to the compression site. The zone of sensitive disorders includes the area along the inguinal ligament, half of the pubic region, the upper two-thirds of the scrotum or labia majora, and the upper section of the anteroinner surface of the thigh. Sometimes a characteristic antalgic posture occurs when walking - with a forward tilt of the trunk, slight flexion and internal rotation of the thigh on the affected side. Similar antalgic fixation of the thigh is also noted when the patient is lying on his back. Some patients adopt a forced position on their side with their lower limbs drawn to their stomach. Patients with such mononeuropathy have limited extension, internal rotation, and abduction of the hip. Increased pain along the nerve is noted when trying to sit up from a supine position with simultaneous rotation of the trunk. A decrease or increase in the tone of the lower abdominal muscles on the affected side is possible. Since the ilioinguinal nerve innervates only part of the internal oblique and transverse abdominal muscles, their weakness in this neuropathy is difficult to detect using clinical examination methods; it can be detected using electromyography. At rest, fibrillation and even fasciculation potentials are noted on the affected side. At maximum tension (pulling in the abdomen), the oscillation amplitude on the interference electromyogram is significantly reduced compared to the norm. In addition, the amplitude of potentials on the affected side is 1.5-2 times lower than on the healthy side. Sometimes the cremasteric reflex is reduced.

Damage to the ilioinguinal nerve is not easy to differentiate from pathology of the genitofemoral nerve, since they both innervate the scrotum or labia majora. In the first case, the upper level of provocation of painful sensations with digital compression is near the superior anterior iliac spine, in the second - at the internal opening of the inguinal canal. The zones of sensitive prolapses also differ. In case of damage to the genitofemoral nerve, there is no area of skin hypoesthesia along the inguinal ligament.

The genitofemoral nerve (n. genitofemoralis) is formed from the fibers of the LI and LIII spinal nerves. It passes obliquely through the thickness of the large psoas muscle, pierces its inner edge and then follows the anterior surface of this muscle. At this level, the nerve is located behind the ureter and goes to the inguinal region. The genitofemoral nerve can consist of one, two or three trunks, but most often it divides on the surface of the large psoas muscle (rarely in its thickness) at the level of the projection of the body of LIII into two branches - the femoral and genital.

The femoral branch of the nerve is located outside and behind the external iliac vessels. In its course, it is located first behind the iliac fascia, then in front of it, and then passes through the vascular space under the inguinal ligament, where it is located outside and in front of the femoral artery. Then it pierces the broad fascia of the thigh in the region of the subcutaneous opening of the cribriform plate and supplies the skin of this area. Its other branches innervate the skin of the upper part of the femoral triangle. These branches can connect with the anterior cutaneous branches of the femoral nerve and with the branches of the ilioinguinal nerve.

The genital branch of the nerve is located on the anterior surface of the psoas major muscle medially from the femoral branch. At first, it is located outside the iliac vessels, then crosses the lower end of the external iliac artery and enters the inguinal canal through the deep inguinal ring. In the canal, together with the genital branch, there is the spermatic cord in men, and the round ligament of the uterus in women. Leaving the canal through the superficial ring, the genital branch in men goes further to the muscle that lifts the scrotum and to the skin of the upper part of the scrotum, the membrane of the testicle and to the skin of the inner surface of the thigh. In women, this branch supplies the round ligament of the uterus, the skin of the superficial ring of the inguinal canal and the labia majora. This nerve can be affected at various levels. In addition to compression by adhesions of the main trunk of the nerve or both of its branches at the level of the psoas major muscle, sometimes the femoral and genital branches can be damaged selectively. Compression of the femoral branch occurs when it passes through the vascular space under the inguinal ligament, and of the genital branch when it passes through the inguinal canal.

The most common symptom of neuropathy of the femoral-genital nerve is pain in the groin area. It usually radiates to the upper part of the inner thigh, and occasionally to the lower abdomen. The pain is constant, felt by patients even in a lying position, but intensifies when standing and walking. In the initial stage of damage to the femoral-genital nerve, only paresthesia may be noted, pain joins later.

When diagnosing neuropathy of the genitofemoral nerve, the localization of pain and paresthesia, tenderness during palpation of the internal inguinal ring are taken into account; pain in this case radiates to the upper part of the inner surface of the thigh. Increased or occurrence of pain during hyperextension of the limb in the hip joint is typical. Hypesthesia corresponds to the innervation zone of this nerve.

The lateral cutaneous nerve of the thigh (n. cutaneus femoris lateralis) most often forms from the spinal roots LII and LIII, but there are variants in which it forms from the roots LI and LII. It begins from the lumbar plexus, which is located under the large psoas muscle, then pierces its outer edge and continues obliquely downwards and outwards, passes through the iliac fossa to the superior anterior iliac spine. At this level, it is located behind the inguinal ligament or in the canal formed by two leaves of the outer part of this ligament. In the iliac fossa, the nerve is located retroperitoneally. Here it crosses the iliacus muscle under the fascia covering it and the iliac branch of the iliolumbar artery. Retroperitoneally, anterior to the nerve are the cecum, appendix, and ascending colon, with the sigmoid colon on the left. After passing the inguinal ligament, the nerve most often lies on the surface of the sartorius muscle, where it divides into two branches (approximately 5 cm below the anterior superior iliac spine). The anterior branch continues downward and passes in the canal of the broad fascia of the thigh. Approximately 10 cm below the anterior superior iliac spine, it pierces the fascia and again divides into an external and internal branch for the anterolateral and lateral surfaces of the thigh, respectively. The posterior branch of the lateral femoral cutaneous nerve turns posteriorly, lies subcutaneously, and divides into branches that reach and innervate the skin over the greater trochanter along the lateral surface of the upper thigh.

Damage to this nerve is relatively common. As early as 1895, two main theories were proposed to explain its damage: infectious-toxic (Bernhardt) and compression (V.K. Roth). Some anatomical features in the place where the nerve passes have been identified, which can increase the risk of damage due to compression and tension.

1. The nerve, when exiting the pelvic cavity under the inguinal ligament, makes a sharp bend at an angle and pierces the iliac fascia. In this place, it can be compressed and subject to friction against the sharp edge of the fascia of the lower limb in the hip joint when the body is tilted forward.
2. Compression and friction of the nerve can occur where it passes and bends at an angle in the area between the anterior superior iliac spine and the attachment site of the inguinal ligament.
3. The outer part of the inguinal ligament often bifurcates, forming a channel for the nerve, which can become compressed at this level.
4. The nerve may run close to the uneven bony surface of the superior iliac spine region near the sartorius tendon.
5. The nerve can pass and become compressed between the fibers of the sartorius muscle where it still consists mainly of tendon tissue.
6. The nerve sometimes crosses the iliac crest just behind the anterior superior iliac spine. Here it can be compressed by the edge of the bone and subject to friction during hip movements or forward bending of the trunk.
7. The nerve can become compressed in the tunnel formed by the broad fascia of the thigh and be subject to friction against the edge of the fascia where it exits this tunnel.

Compression of the nerve at the level of the inguinal ligament is the most common cause of its damage. Less often, the nerve can be compressed at the level of the lumbar or iliac muscles with a retroperitoneal hematoma, tumor, pregnancy, inflammatory diseases and operations in the abdominal cavity, etc.

In pregnant women, the nerve compression occurs not in its abdominal segment, but at the level of the inguinal ligament. During pregnancy, the lumbar lordosis, pelvic tilt angle, and hip extension increase. This leads to tension of the inguinal ligament and compression of the nerve if it passes through a duplication in this ligament.

This nerve can be affected by diabetes, typhoid fever, malaria, shingles, and vitamin deficiency. Wearing a tight belt, corset, or tight underwear can contribute to the development of this neuropathy.

In the clinical picture of damage to the lateral cutaneous nerve of the thigh, the most common sensations are numbness, crawling and tingling paresthesia, burning, and cold along the anterolateral surface of the thigh. Less common are itching and unbearable pain, which are sometimes causalgic in nature. The disease is called paresthetic meralgia (Roth-Bernhardt disease). Cutaneous hypoesthesia or anesthesia occurs in 68% of cases.

In paresthetic meralgia, the degree of tactile sensitivity impairment is greater than that of pain and temperature. Complete loss of all types of sensitivity also occurs: the pilomotor reflex disappears, trophic disorders may develop in the form of thinning of the skin and hyperhidrosis.

The disease can occur at any age, but most often it affects middle-aged people. Men get sick three times more often than women. There are familial cases of this disease.

Typical attacks of paresthesia and pain along the anterolateral surface of the thigh, which occur when standing or walking for a long time and when forced to lie on the back with straight legs, allow us to assume this disease. The diagnosis is confirmed by the occurrence of paresthesia and pain in the lower limb with digital compression of the outer part of the inguinal ligament near the superior anterior iliac spine. With the introduction of a local anesthetic (5-10 ml of 0.5% novocaine solution) at the level of nerve compression, the painful sensations pass, which also confirms the diagnosis. Differential diagnosis is carried out with damage to the spinal roots LII - LIII, which is usually accompanied by motor loss. With coxarthrosis, pain of uncertain localization in the upper parts of the outer surface of the thigh may occur, but there are no typical pain sensations and no hypesthesia.

The obturator nerve (n.obturatorius) is a derivative mainly of the anterior branches of the LII-LIV (sometimes LI-LV) spinal nerves and is located behind or inside the lumbar major muscle. Then it comes out from under the inner edge of this muscle, pierces the iliac fascia and passes downwards at the level of the sacroiliac joint, then descends along the lateral wall of the pelvis and enters the obturator canal together with the obturator vessels. This is a bone-fibrous tunnel, the roof of which is the obturator groove of the pubic bone, the bottom is formed by the obturator muscles, separated from the nerve by the obturator membrane. The fibrous inelastic edge of the obturator membrane is the most vulnerable place along the course of the nerve. Through the obturator canal, the nerve passes from the pelvic cavity to the thigh. Above the canal, a muscular branch separates from the obturator nerve. It also passes through the canal and then branches into the obturator externus, which rotates the lower limb. At or below the obturator canal, the nerve divides into an anterior and posterior branch.

The anterior branch supplies the long and short adductor muscles, the thin and irregular pectineus. These long and short adductor muscles adduct, flex and rotate the thigh outward. The following tests are used to determine their strength:

1. the subject, who lies on his back with straightened lower limbs, is asked to move them together; the examiner tries to spread them apart;
2. The subject, who is lying on his side, is asked to lift the lower limb that is above and bring the other lower limb to it. The examiner supports the raised lower limb and resists the movement of the other lower limb that is being brought.

The thin muscle (m. gracilis) adducts the thigh and flexes the leg at the knee joint, rotating it inward.

Test for determining the action of the Spitz: the subject, lying on his back, is asked to bend the lower limb at the knee joint, turning it inward and adducting the thigh; the examiner palpates the contracted muscle.

After the muscular branches depart, the anterior branch in the upper third of the thigh becomes only sensitive and supplies the skin of the inner thigh.

The posterior branch innervates the adductor magnus muscle of the thigh, the joint capsule of the hip joint and the periosteum of the posterior surface of the femur.

The adductor magnus muscle adducts the thigh.

Test for determining the strength of the large adductor muscle: the subject lies on his back, the straightened lower limb is abducted to the side; he is asked to adduct the abducted lower limb; the examiner resists this movement and palpates the contracted muscle. It should be noted that the zone of sensitive innervation of the skin of the inner thigh from the upper third of the thigh to the middle of the inner surface of the shin is individual variability. This is due to the fact that the sensitive fibers from the obturator nerve are combined with the same fibers of the femoral nerve, sometimes forming a new independent trunk - the accessory obturator nerve.

Obturator nerve lesions are possible at several levels: at the beginning of its origin - under the lumbar muscle or inside it (with retroperitoneal hematoma), at the level of the sacroiliac joint (with sacroiliitis), in the lateral wall of the pelvis (compression by the uterus during pregnancy, with a tumor of the cervix, ovaries, sigmoid colon, with appendicular infiltrate in the case of a pelvic location of the appendix, etc.), at the level of the obturator canal (with a hernia of the obturator foramen, pubic ostitis with edema of the tissues forming the walls of the canal), at the level of the superomedial surface of the thigh (with compression by scar tissue, with prolonged sharp flexion of the hip under anesthesia during surgical interventions, etc.).

The clinical picture is characterized by sensory and motor disorders. The pain extends from the groin area to the inner thigh and is especially intense when the nerve is compressed in the obturator canal. Paresthesia and a feeling of numbness in the thigh are also noted. In cases of nerve compression by a hernia of the obturator foramen, the pain increases with increased pressure in the abdominal cavity, for example, when coughing, as well as with extension, abduction and internal rotation of the hip.

Sensory loss is most often localized in the middle and lower thirds of the inner thigh, sometimes hypoesthesia can also be detected on the inner surface of the shin, up to its middle. Due to the overlap of the cutaneous innervation zone of the obturator nerve by neighboring nerves, sensory disturbances rarely reach the level of anesthesia.

When the obturator nerve is damaged, the muscles of the inner thigh become hypotrophic. It is quite pronounced, despite the fact that the adductor magnus is partially innervated by the sciatic nerve. Of the muscles supplied by the obturator nerve, the external obturator muscle rotates the thigh outward, the adductor muscles participate in the rotation and flexion of the thigh at the hip joint, and the gracilis muscle participates in the flexion of the lower leg at the knee joint. When the function of all these muscles is lost, only adduction of the thigh is noticeably impaired. Flexion and external rotation of the thigh, as well as movements in the knee joint, are performed to a sufficient extent by muscles innervated by other nerves. When the obturator nerve is switched off, pronounced weakness of adduction of the thigh develops, but this movement is not completely lost. Irritation of the nerve can cause noticeable secondary spasm of the adductor muscles, as well as reflex flexion contracture in the knee and hip joints. Since some hip movements can increase pain when the obturator nerve is irritated, patients develop a gentle gait, and hip joint movements are limited. Due to the loss of function of the adductor muscles of the thigh, stability is impaired when standing and walking. The anteroposterior direction of movement of the lower limbs when walking is replaced by an outwardly directed abduction of the limb. In this case, the foot in contact with the support and the entire lower limb are in an unstable position, and circumduction is observed when walking. On the affected side, loss or reduction of the reflex of the adductor muscles of the thigh is also noted. Difficulties arise when placing the affected leg on the healthy one (in the supine position, sitting).

Vegetative disorders in case of damage to the obturator nerve manifest themselves as anhidrosis in the zone of hypesthesia on the inner surface of the thigh.

The diagnosis of obturator nerve damage is determined by the presence of characteristic pain, sensory and motor disorders. To identify paresis of the adductor muscles of the thigh, the above methods are used.

The reflex from the adductor muscles of the thigh is evoked by a sharp blow of a percussion hammer on the doctor's first finger, placed on the skin above the adductor muscles at a right angle to their long axis, approximately 5 cm above the internal epicondyle of the thigh. In this case, contraction of the adductor muscles is felt and an asymmetry of the reflex is revealed on the healthy and affected sides.

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