Overview of the peripheral nerves
Peripheral nerves are cerebral and spinal nerves other than the olfactory and optic nerves, including 10 pairs of cerebral nerves and 31 pairs of spinal nerves. Peripheral neuropathies are diseases that originate from structural or functional damage to the peripheral nervous system. Peripheral spinal neuropathies can be categorized in a number of different forms and nomenclatures. Typology based on the distribution of the involved nerves, i.e., the type of nerve distribution, is categorized as (1) mononeuropathy, (2) multiple mononeuropathies, (3) plexiform neuropathies, and (4) (distal symmetrical) polyneuropathies.
Mononeuropathy refers to damage to a single nerve that produces symptoms and signs of motor, sensory, and autonomic deficits consistent with the range of innervation of that nerve. The peripheral spinal cord neuropathies described here include brachial plexopathy and lumbosacral plexopathy among the plexopathies, and intercostal neuralgia and sciatica among the mononeuropathies.
Causes
1. Brachial plexopathy
(1) Trauma Violent pulling and impingement of the upper extremities during car accidents and mechanical strangulation are the most common causes of traumatic brachial plexus neuropathy.
(2) Thoracic outlet syndrome
(3) Physical injuries such as electric shock and radiation injury.
(4) Acute brachial plexus neuritis Also known as neuralgia myasthenia gravis. It often starts acutely or subacutely after influenza or the use of drugs such as penicillin, and may be related to autoimmunity.
(5) Genetic factors, such as familial recurrent brachial plexopathy or hereditary familial brachial plexopathy, nerve biopsy in some patients can be seen in myelin hypertrophy, saliciform changes, similar to hereditary pressure susceptibility peripheral neuropathy.
(6) Tumor The most common tumor is brachial plexus nerve sheath tumor, followed by brachial plexus neurofibroma.
(7) Perinatal brachial plexus neuropathy During labor and delivery, when it is difficult to deliver the fetal shoulder, it is easy to cause brachial plexus nerve injury by forcefully pulling the head of the fetus, which mostly occurs in huge infants weighing more than 4000g. However, brachial plexus injuries can also occur in a significant number of newborns weighing less than 4000 g without shoulder delivery difficulties, suggesting that there may be causes other than birth injury.
(8) Chronic brachial plexopathy is a group of slowly progressive idiopathic brachial plexopathies of undetermined cause.
2. Intercostal neuralgia
It is mainly related to the lesions of adjacent tissues and organs involving the intercostal nerves, and the common causes include pleurisy, pneumonia, aortic aneurysm; trauma, tumor, deformity of thoracic vertebrae and ribs; and cavities, inflammation and tumors of the thoracic medulla oblongata. Varicella or herpes zoster infection and post-infectious intercostal neuralgia are common in the elderly, HIV patients, patients with malignancy and chemotherapy.
3. Lumbosacral plexus neuropathy
(1) Diabetic proximal myasthenia is thought to be caused by bilateral lumbosacral plexus involvement, and immune mechanisms play an important role in nerve injury.
(2) Trauma and bleeding disorders Pelvic fracture caused by trauma, hematoma in the psoas major muscle or pelvis, dislocation and fracture of the hip joint can cause lumbosacral plexus injury. Hematologic diseases or patients applying anticoagulation therapy can be complicated by hematoma of lumbar major muscle or iliopsoas muscle, which directly invades the lumbosacral plexus.
(3) Medical origin Abdominal and pelvic surgeries such as hysterectomy, kidney transplantation, prostate and bladder surgeries, etc. can cause injuries due to the use of self-limiting retractors, whose sharp blades tend to compress the lumbosacral plexus nerves and cause injuries. In renal transplantation, the anastomosis of the donor renal artery with the recipient’s inferior vena cava artery is prone to arterial steal, causing ischemia of the lumbosacral plexus nerves. During hip arthroplasty, the adhesive is extruded out of the pelvis and can compress the plexus.
(4) Aortic and pelvic arterial malformations Rupture and bleeding of malformed blood vessels can form hematoma in the pelvis and compress the lumbosacral plexus.
(5) Delivery process, primigravida or large fetus, due to the long labor and prolonged truncal position, the hip joint is overly abducted, which may cause lumbosacral plexus injury.
(6) Tumor Tumor lumbosacral plexopathy is relatively common and difficult to diagnose, CT, MRI and lumbar puncture often have no abnormal findings. Tumors of prostate, rectum, bladder and kidney can invade lumbosacral plexus and its surrounding lymph nodes through local spread. Giant fibrous tumors of the posterior wall of the uterus as well as endometriosis can directly compress the lumbosacral plexus. In addition, aneurysms formed by aortic atherosclerosis can also involve the plexus.
(7) Infection: tuberculous abscess of lumbar major muscle, lumbar osteomyelitis, appendicitis, the inflammation can violate the lumbosacral plexus through the iliac muscle fascia. Sometimes chickenpox or herpes zoster infection can also cause lumbosacral neuralgia and herpes in the corresponding dermatomes. Systemic vasculitis can involve the lumbosacral plexus causing vasculitis peripheral neuropathy.
(8) Radiation Radiation from pelvic tumors can cause radiation lumbosacral plexus neuropathy.
(9) Idiopathic and acute brachial plexus neuritis of the upper limbs corresponds to idiopathic lumbosacral plexus neuritis of the lower limbs, and the pathologic mechanisms of both may be related to autoimmune abnormalities.
4. Sciatica
(1) Radicular sciatica is common, mainly intravertebral canal and spinal lesions, lumbar disc prolapse is the most common, others such as lumbar hypertrophic spondylitis, lumbosacral sclerospondylitis, spinal tuberculosis, spinal stenosis, vascular malformations, lumbosacral intravertebral canal tumors, or arachnoiditis.
(2) Dry sciatica Mostly due to the lumbosacral plexus and nerve trunk adjacent lesions, such as sacroiliac arthritis, tuberculosis or subluxation, as well as lumbar large muscle abscess, pelvic tumors, uterine adnexitis, uterine compression during pregnancy, inappropriate injection of gluteal muscle, gluteal trauma and infection, and so on.
Symptoms
1. Brachial plexus neuropathy
Brachial plexus nerve damage caused by various reasons is collectively called brachial plexus neuropathy, which is one of the most common plexopathies. The main clinical manifestations of brachial plexopathy include muscle weakness and atrophy of the shoulder girdle muscles, upper limbs and chest and back muscles, and numbness, pain and hypesthesia in the sensory areas of the skin corresponding to the affected brachial plexus nerve branches. Depending on the site of involvement and the degree of damage, there are different combinations of clinical symptoms.
(1) Damage to the upper brachial plexus (upper trunk of brachial plexus), also known as Duchenne-Erb palsy, is characterized by involvement of the shoulder girdle muscles and proximal muscles of the upper limb, manifesting as weakness and atrophy of the subscapularis muscle, vastus lateralis, supraspinatus, infraspinatus, deltoid muscle, clavicular head of the sternocleidomastoid muscle, radial flexor carpi radialis, rotator anterior circularis, radialis brachii, and rotator ani posteriori muscles, and the shoulder joints are unable to be extended, lifted up, flexed, and the wrist joints can’t be extended or flexed. Sensory impairment is not obvious, sometimes there is sensory loss on the radial side of the upper limb and hand.
(2) Lower brachial plexus (lower trunk of brachial plexus) damage, also known as Klumpke-Dejerine palsy, is characterized by the involvement of the hand’s motor functions, ulnar wrist flexors, earthworm muscles, large and small piriformis muscles, and all the finger flexors are paralyzed, and the atrophy of the hand muscles is obvious, resulting in the formation of a claw-shaped hand. The fingers and wrist joints could not be flexed. Finger extensors and shoulder and elbow joints are unaffected.
(3) Individual damage to the middle trunk of the brachial plexus Rarely, the main symptom is weakness of the upper extremity extensor muscles. The clinical features of total brachial plexus damage are motor paralysis of shoulder, elbow, wrist and hand joints, muscle atrophy, and disappearance of all tendon reflexes of the upper limbs. In addition to the preservation of the sensation of the inner arm near the axilla innervated by the intercostal brachial nerve, the sensation of the rest of the upper limbs is completely lost.
2. Intercostal neuralgia
Intercostal neuralgia refers to the pain in the intercostal nerve innervation area, often located in one or several intercostal space, mostly persistent burning pain, breathing, coughing and sneezing can induce pain aggravation. Sometimes the corresponding intercostal area can be seen on examination of the skin nociceptive hypersensitivity.
3. Lumbosacral plexopathy
When the lumbosacral nerve roots are damaged, there may be radiating pain, and the pain may be aggravated by bending, sneezing, coughing and cervical flexion. Straight leg raising test is positive, lumbar spine activity is limited, spine anterior protrusion becomes straight, localized percussion pain, erector spinae muscle spasm. Simple nerve root damage usually does not affect autonomic function.
In plexus damage, the straight leg raising test is mostly negative, and the increased pressure in the spinal cord often does not cause pain aggravation. In damage to the upper lumbar plexus, there is weakness in hip flexion and abduction and knee extension, and the sensory impairment is distributed in the anterior thigh and calf. Damage to the lower plexus causes weakness of the posterior femoral, calf, and foot muscles, and sensory loss in sacral 1 and 2 spinal nerve segments. Damage to the entire lumbosacral plexus is rare and is characterized by paralysis, weakness, and atrophy of the muscles of the entire lower extremity, loss of tendon reflexes, and decreased or absent sensation from the tips of the toes to the perianal area. Autonomic nerve involvement manifests as dry, warm skin of the lower extremities, often with calf edema. Damage to the nerve trunk is mainly characterized by the involvement of motor and sensory functions related to the nerve.
(1) Damage to the femoral nerve The motor nerve fibers innervating the iliopsoas, suture muscles and quadriceps muscles are weak, manifested as weakness of knee extension and hip flexion, and thigh abduction is not involved (innervated by the obturator nerve). There is sensory impairment in the sensory distribution area of the femoral nerve in the anterior medial aspect of the thigh and calf.
(2) Damage to the obturator nerve manifests as difficulty in external rotation and flexion of the thigh, and incomplete paralysis of the adductor muscle group due to co-innervation with the sciatic nerve.
(3) Lateral femoral cutaneous nerve damage is mainly seen in middle-aged men. Clinical manifestations include numbness and tingling of the skin in the lower two thirds of the lateral thighs after prolonged standing and walking, and localized hypoaesthesia and sensory hypersensitivity.
(4) Sciatic nerve damage The main manifestation is sciatica, which is a pain syndrome along the sciatic nerve pathway and its distribution area. Acute lumbar disc herniation usually leads to pain in the distribution area of the nerve roots (lumbar 5 or sacral 1) in the back and legs, often accompanied by numbness and sensory abnormalities; motor function deficits depend on the affected nerve roots, with lumbar 5 spinal nerve roots leading to weakness in dorsiflexion of the feet and toes, and sacral 1 spinal nerve roots producing weakness in plantarflexion of the foot and weakened ankle reflexes. There may be limitation of spinal motion, limited dorsal tenderness, palpable paraspinal muscle spasm and Lasegue’s sign. Centralized lumbar disc herniation results in bilateral symptoms, signs and sphincter involvement.
4. Sciatica
According to the lesion site, it is divided into radicular and dry sciatica.
(1) Radicular sciatica is common, mainly intravertebral canal and spinal lesions, lumbar disc prolapse is the most common, and others such as lumbar hypertrophic spondylitis, lumbosacral sclerospondylitis, spinal tuberculosis, spinal stenosis, vascular malformations, lumbosacral intravertebral canal tumors, or arachnoiditis.
(2) Dry sciatica Mostly due to the lumbosacral plexus and nerve trunk adjacent lesions, such as sacroiliac arthritis, tuberculosis or subluxation, as well as lumbar large muscle abscess, pelvic tumors, uterine adnexitis, uterine compression during pregnancy, inappropriate injection of gluteal muscle, gluteal trauma and infection, and so on.
Sciatica is common in young adults, characterized by radiating pain along the sciatic nerve pathway, mostly unilateral, radiating from the lower back or buttocks to the posterior femur, posterior-lateral calf, and lateral foot, presenting a constant dull or burning pain, which can be intensified in paroxysms, and is often aggravated at night. Walking, activity or pulling can trigger or aggravate the pain, the patient to take the pain reducing posture, the affected limb slightly flexed and to the healthy side of the lying position, supine rise when the diseased side of the knee joint bending, sitting on the healthy side of the buttocks first, standing when the spine to the affected side of the convex and so on.
Examination
1. Blood test
Including blood glucose, liver function, kidney function, blood sedimentation, routine serologic examination of hepatitis B and C; serum thyroxine and growth hormone levels; serum vitamin B1, B6, B12 and vitamin E concentration; rheumatism series, ANCA (anti-neutrophil cytoplasmic antibody), immunoglobulin electrophoresis, cryoglobulins, M proteins, anti-GM-1 antibody, anti-GD1a antibody, and anti-MAG antibody, Tumor-related antibodies (anti-Hu, Yo, Ri antibodies) and other autoimmune-related serological tests; chickenpox-herpes zoster virus, cytomegalovirus, HIV-1 and Borrelia Burgdorferi spirochete serum antibody test; serum heavy metal (lead, mercury, arsenic, thallium, etc.) concentration test.
2. Urine examination
Including urine routine, this – week protein, urine porphyrin and urinary excretion of heavy metals.
3. Cerebrospinal fluid
In addition to cerebrospinal fluid routine, anti-GM-1 and GD1b antibodies should also be detected.
4. X-ray and bone marrow cytology.
Chest and bone X-ray and bone marrow cytology should be performed when paraneoplastic peripheral neuropathy, paraprotein peripheral neuropathy or POEMS syndrome is suspected.
5. Genetic defect analysis
For example, TIR mutation detection is used for the diagnosis of amyloid peripheral neuropathy, PMP22 gene deletion is used for the diagnosis of hereditary stress-susceptible peripheral neuropathy, and PMP22 duplication, Po mutation, and ligandin-32 gene analysis are used for the diagnosis of CMT1A, 1B, and X-linked hereditary type of CMT, respectively.
6. Muscle and nerve electrophysiologic examination
It is of great significance in identifying neurogenic and myogenic damage, the site of peripheral nerve damage, and distinguishing axonal degeneration and demyelination damage.
7. Peripheral nerve biopsy
It is an important laboratory test for differential diagnosis of peripheral neuropathy.
Diagnosis
Diagnosis can be made by combining clinical manifestations and relevant examinations.
Treatment
1. Acute brachial plexus neuritis
Patients can take oral prednisone and supplemented with physical therapy. For severe pain, carbamazepine, tramadol and antidepressant amitriptyline or nortriptyline can be used. Brachial plexus tumors should in principle be surgically removed, preferably with nerve grafting. Perinatal brachial plexus nerve injury can be self-healing, but if the biceps muscle strength does not start to recover within 3 months, surgical release should be considered, and nerve grafting and functional reconstruction should be performed at the same time.
2. Intercostal neuralgia
The cause should be eliminated first, and painkillers such as non-hormonal antipyretic and analgesic drugs and morphine can be given to patients with severe pain, and nerve block therapy can also be used. Herpes zoster infection can be applied to the local skin with lidocaine or capsaicin, and the early application of the antiviral drug acyclovir can reduce the destruction of the virus on the nerve, accelerate the healing of the skin damage and alleviate the post-rash neuralgia. Oral acyclovir is not recommended for herpes zoster complicated by immune deficiency.
3. Lumbosacral plexopathy
Different treatments are available depending on the etiology. Carbamazepine or other analgesics, such as acetaminophen (paracetamol) plus codeine, and other nonsteroidal analgesics, such as ibuprofenac (ibuprofenac), naproxen, etc., can be used for severe pain. Muscle spasms can be treated with diazepam (Valium); or cyclobenzaprine.
(1) Sciatica In severe cases, dexamethasone can be injected intravenously; oral prednisone can be taken in general. Can also use procaine or plus prednisolone paravertebral closure.
(2) Lumbar intervertebral disc prolapse in the acute stage, lying in a hard bed rest for 1 to 2 weeks can often stabilize the symptoms. Lateral femoral dermatitis can be applied to local closure. The method is to inject lidocaine or hydrocortisone locally at 10cm below the anterior superior iliac spine. It can also be combined with acupuncture and physical therapy, and can be relieved by conservative treatment. When the treatment is not effective, pelvic traction or prednisolone epidural injection can be used. Surgery can be considered in individual ineffective or chronic recurrence cases. At the same time, neurotrophic therapy and functional rehabilitation training should be strengthened.