Pediatric extramedullary epidural abscess

　　First, Etiology

　　1. Routes of infection

　　(1) Hematogenous: This is the most common route of infection for abscesses (accounting for 26% to 50%), and it is often seen in suppurative infections of the peripheral skin, such as skin boils (accounting for 15%), intravenous or intramuscular injections, bacterial endocarditis, respiratory system infections, and local abscesses in the oropharynx.

　　(2) Direct extension: Decubitus ulcers in the lumbosacral region, abscesses of the psoas muscle caused by vertebral tuberculosis, open injuries to the abdomen and neck, inflammation of the oropharynx, mediastinitis, and perinephric abscess can all lead to direct extension of infection to the corresponding spinal segmental epidural space, forming abscesses.

　　(3) Iatrogenic: Unstandardized medical operations such as spinal surgery, epidural catheter anesthesia, and lumbar puncture may introduce pathogenic bacteria into the epidural space, causing abscess formation.

　　(4) Traumatic: Open injuries to the lumbar and sacral regions and penetrating injuries to the spine are also common causes of epidural abscess formation, accounting for about 30%.

　　(5) Cryptogenic: About 50% of patients may not be able to find an exact source of infection, but most cryptogenic infections are also hematogenous infections, just because of strong body resistance or the application of a large amount of antibiotics, making the primary focus of the disease not obvious.

　　2. Pathogenic microbiology The culture of pus is helpful to clarify the type of pathogenic bacteria. When a large amount of antibiotic treatment has been previously applied to the patient, the culture may also be negative. The percentage of patients with no bacteria found in bacterial culture ranges from 29% to 50%. The most common pathogenic bacteria are Staphylococcus aureus (accounting for 50%); followed by Streptococcus; Pseudomonas aeruginosa, Enterobacter, and Salmonella are also relatively common pathogenic bacteria. For chronic epidural abscess, it often secondary to vertebral tuberculosis, so Mycobacterium tuberculosis is the most common pathogenic bacteria, accounting for about 25% of the total number of patients. Organisms such as Cryptococcus tissue, Aspergillus, Bacteroides, and anaerobic bacteria are occasionally reported in chronic abscesses. Mixed infections of multiple pathogens account for about 10% of the total positive bacterial cultures, and anaerobic infections account for about 8%.

　　Second, Pathogenesis

　　1. Acute epidural abscess It is characterized by congestion, exudation, and a large number of leukocytes infiltrating the epidural space, followed by necrosis and liquefaction of adipose tissue, resulting in the accumulation of pus.

　　2. Subacute epidural abscess The epidural space has coexisting pus and inflammatory granulation tissue, and some cases may have incomplete capsules.

　　3. Chronic epidural abscess The epidural space is mainly characterized by granulation tissue and connective tissue proliferation, with pus encapsulated to form abscesses. Subacute or chronic cases often have thickening of the local dura mater, which exerts compressive effects on the spinal nerves. Previous theories believed that spinal cord dysfunction was attributed to the compressive effects of the abscess. Recent studies show that abnormal venous return plays a major role in neurological dysfunction. Pathological evidence shows no significant involvement of the spinal nerve ganglia by arteries, but venous compression and thrombosis, edema of the spinal nerve ganglia, infarction of the epidural venous plexus, and the formation of thrombotic phlebitis are relatively common. The spinal nerve ganglia themselves can also exhibit inflammatory reactions due to direct spread of infection.

　　Children with epidural abscess of the spinal dura mater may develop symptoms of infection and intoxication or sepsis, with transverse myelitis manifested as numbness in both lower limbs, complete soft paralysis, retention of urine and feces, and so on.

　　Typical manifestations can be divided into 3 stages:

　　25. 1. Spinal and nerve root pain stage:It usually appears 1-3 days after the onset of fever, chills, general malaise, and other symptoms of infection and intoxication, with corresponding root stimulation symptoms of the spinal segment, manifested as intolerable pain. When the spine is tapped, pain in the involved segment can be produced. When the child cannot describe the symptoms, it is often manifested as crying and restlessness, the spine is bent to an强迫 position to relieve pain. In cases of abscess in the thoracolumbar segment, there may be severe abdominal pain or lower limb pain, which is easily misdiagnosed as 'children's acute appendicitis'. At this stage, the systemic symptoms of infection are severe, and peripheral blood pictures show a significant increase in white blood cells.

　　22. 2. Spinal cord dysfunction stage:Spinal cord transverse damage symptoms often occur within a few hours or days of the root pain stage, manifested as numbness in both lower limbs, muscle weakness, and rapid progression of sphincter dysfunction.

　　21. 3. Complete paralysis stage:From the second stage, it quickly enters complete soft paralysis of the limbs, all reflexes disappear, and urination and defecation are retained.

　　1. Prevent skin and mucosal infections Good skin and mucosal care for children should be done to prevent purulent infections of the skin and mucosa.

　　2. Prevent and treat respiratory infections and other infections actively prevent and treat respiratory infectious diseases and other infectious diseases.

　　3. Do a good job of various preventive vaccination work.

　　4. Prevent iatrogenic infection All treatments and operations should strictly follow sterile regulations.

　　5. Prevent various kinds of injuries to prevent open injuries to the lumbar and renal regions caused by various kinds of injuries.

　　10. Peripheral blood picture:White blood cell count and neutrophil count increase, and nuclear left shift and toxic granules may occur.

　　8. Lumbar puncture examination:Pus can be aspirated from the lumbar puncture as direct evidence of diagnosis, but there is a risk of subarachnoid infection from lumbar puncture. The needle should be inserted carefully and gradually, and after passing the yellow ligament, it should be aspirated to see if there is pus. If pus is aspirated, the needle can be withdrawn immediately; if the lumbar puncture needle does not aspirate pus and enters the subarachnoid space, clear cerebrospinal fluid can be seen flowing out, and laboratory examination shows an increase in white blood cell count and protein content, and dynamic testing shows obstruction.

　　6. Spinal X-ray film:Abnormal findings are only present when there is concurrent vertebral bone marrow inflammation, mainly manifested as bone resorption and destruction of the vertebral body.

　　4. Typical MRI manifestations are:T1 shows low or equal signal, and T2 shows high signal of the epidural space-occupying lesion. In cases of vertebral bone marrow inflammation, cancellous bone can be seen, and the signal of the affected intervertebral disc and paravertebral soft tissue decreases. During contrast-enhanced scanning, a ring-like thin-walled enhancement of the abscess wall can be seen, and irregular mass-like enhancement appears when a large amount of granulation tissue is formed.

　　Children with pediatric epidural abscess should eat more nutritious foods in their daily life, pay attention to supplementing certain vitamins and nutritional substances, and pay attention to eating more fresh fruits and vegetables, and eating less high-salt, high-sugar, and high-fat diets.

　　1. Diagnosis and active surgical treatment should be made before the onset of complete paraplegia in the early stage. Once there is a delay and complete paraplegia occurs, it is difficult to recover the spinal cord function after surgery. Therefore, once the diagnosis is clear, emergency surgery should be performed. The purpose of the surgery is: to identify the type of pathogen; to remove pus and granulation tissue; to relieve the mechanical compression of the spinal cord; to ensure adequate drainage. The operation should remove the vertebral plate at the site of the abscess, and the range should reach the normal dura mater both above and below, and be wide on the sides, but not damage the articular surface. If the abscess involves too many segments, it can be performed in the form of intermittent resection of the vertebral plate to avoid affecting the stability of the spine. During the operation, the pus and granulation tissue should be thoroughly removed, and the wound should be flushed repeatedly with antibiotic saline. The dura mater should not be incised to prevent the spread of infection to the subdural space. During the operation, attention should be paid to bone wax and gel sponge, which should not be left in the wound to prevent foreign body reaction leading to non-healing of the wound. An external drain or rubber tube should be placed in the epidural space to facilitate the continuous outflow of postoperative inflammatory exudates. If necessary, sensitive antibiotic solutions can be used to repeatedly flush the residual cavity. Generally, the drainage can be removed 2 to 4 days after surgery. For children with epidural abscesses located in the anterior part of the spinal cord and complicated with vertebral osteomyelitis, it is often necessary to clear the abscess extracorporeally through the posterior lateral approach of the vertebral body to avoid entering the abdominal or thoracic cavity, which may lead to the spread of infection to the thoracic and abdominal cavities. During the operation, necrotic vertebral bone fragments should be removed, and the pus should be routinely cultured for bacteria and drug sensitivity tests. After surgery, intravenous administration of high-dose antibiotics should be used to control infection. In the case where the pathogen causing the infection has not been determined, antibiotics targeting Staphylococcus aureus are often used, and third-generation cephalosporins can be selected, and then adjusted accordingly based on the results of the bacterial culture.

　　2. For simple epidural abscesses, it is usually treated with intravenous antibiotics for 3 to 4 weeks, followed by oral antibiotics for 4 weeks. For children with vertebral osteomyelitis, the course of antibiotic intravenous treatment needs to be extended to 6 to 8 weeks.