Hidden spinal dysraphism

　　The causes of隐性spina bifida include damage to the spinal cord and spinal nerves, genetic factors, and environmental factors, and their specific etiology and pathogenesis are described as follows.

　　1. Etiology

　　Since the 1960s, countries around the world have陆续 begun to conduct research on the etiology of neural tube defects, mainly spina bifida and anencephaly. In the 1970s, through a series of animal experiments, clinical observations, and comprehensive epidemiological research, scholars from various countries have generally recognized that neural tube defects are the result of the combined action of genetic factors and environmental factors, among which environmental factors include adverse stimuli such as radiation, toxins, hormone drugs, hypoxia, and acidosis during the early stages of pregnancy. Research results in the 1980s suggest that a lack of vitamins in the early stages of pregnancy may be the main cause of neural tube defects. They observed that the incidence of neural tube defects in women in poor and malnourished conditions is much higher than that in women who are wealthy and well-nourished. Research results in the 1990s indicate that a lack of folic acid in the early stages of pregnancy is the main cause of neural tube defects. Genetic factors are also a cause of neural tube defects, with some statistics showing that 8% to 20% of children with the disease have parents with隐性spina bifida. Some researchers have used an acidic culture medium for fertilized eggs to obtain a frog model of spina bifida. However, the mechanism of its occurrence is still not fully understood. Families or couples with a history of neural tube defects, those with unexplained miscarriage, preterm birth, stillbirth, or fetal death, those with a history of teratogenic or radioactive substance exposure, those who are closely related by marriage, and those who have been confirmed or may be carriers of genetic disease致病genes have a higher risk of having offspring with neural tube defects.

　　2. Pathogenesis

　　The central nervous system, that is, the brain and spinal cord, begins to develop in the first month of the embryo; in the second week of the embryo, the dorsal side forms a neural plate. By the third to fourth week of the embryo, the neural tube is formed. If the closure of the neural tube is blocked at this stage, it will cause defects in the bone or skin covering the central nervous system. The front end of the neural tube closes approximately on the 24th day of the embryo, and then it is repeatedly differentiated and divided to finally form the brain. The closure of the posterior neural foramen at the end of the neural tube occurs on the 27th day of the embryo and differentiates and develops into the lumbar and sacral region of the spine. Abnormalities that occur during the closure process of the neural tube and its covering are known as neural tube defects. Neural tube defects most commonly occur at the ends of the neural tube, but they may also occur at any part between the ends of the neural tube. If it occurs at the anterior end, the skull may split open, brain tissue may be destroyed, and anencephaly may form. If it occurs at the posterior end, a cleft in the spine may appear, and the spinal cord may be completely exposed outside, or it may protrude in a cyst, known as spina bifida and meningocele.

　　There are many pathological forms of concealed spinal bifida. Simple concealed spinal bifida does not involve other spinal or nerve lesions, and the contents of the vertebral canal do not bulge outward. On the external appearance of the spine, it is mostly normal skin, with occasional local hair hyperplasia, hyperpigmented spots, plaques of capillary hemangiomas, small skin depressions, skin fistulas, and other conditions. These complex pathological changes often cause tethering and compression of the spinal cord.

　　Complex concealed spinal bifida often coexists with spinal or nerve developmental abnormalities, such as local scars, adhesions, thickening and thickening of the filum terminale, which fix the spinal cord to the vertebral bone and limit the upward migration of the spinal cord during development. There may also be chondromas, lipomas, epidermoid cysts, dermoid cysts, teratomas, arachnoid cysts,空洞症 of the spinal cord end, formation of nerve root diverticula, gliosis within the spinal cord, or expansion of the central canal. Sometimes, there may be hemivertebrae, scoliosis, developmental deformities of intervertebral foramina and ribs.

　　The symptoms of concealed spinal bifida are mainly caused by damage to the spinal cord and spinal nerves at the involved segments, which is related to whether they are compressed and the degree of nerve damage. Local skin may have increased hair growth, inward indentation of the skin, and some may present with irregular capillary hemangiomas or hyperpigmentation. Onset can be early or late, with some developing symptoms in infancy, while others may not appear until adulthood. This is consistent with a series of secondary pathological changes caused by spinal bifida and the gradual worsening of spinal cord tethering leading to ischemic changes. Clinically, there are mild, moderate, and severe conditions, but a considerable number of patients with spinal bifida do not develop symptoms throughout their lives.

　　1. Mild condition

　　The symptoms at onset include weak lower limb strength, mild muscle atrophy, numbness, enuresis, and sometimes back pain or leg pain. It usually affects one lower limb, but there are also cases where both lower limbs are affected simultaneously. Examination shows peripheral nerve damage, with low muscle tone, flaccid mild muscle weakness, and reduced superficial and deep sensation in the lower limbs and perineum.

　　2. Moderate condition

　　The above motor and sensory impairments are relatively obvious, commonly with clubfoot deformity, and sometimes with lumbar pain, sciatica, or associated with urinary incontinence.

　　3. Severe condition

　　Significant muscle weakness and even paralysis are evident in the lower limbs; sensation is also significantly reduced or absent, often accompanied by nutritional changes in the nerves, coldness and cyanosis in the distal lower limbs, and the appearance of nutritional ulcers. Some individuals may also experience nutritional ulcers at the sacral tail, with marked sensory disturbances in the sacral nerve distribution area. Over time, the lower limbs may present with disuse atrophy, with the Achilles reflex disappearing or developing into a contracture. Foot deformities may include hammertoe, clubfoot, in-toe or out-toe. Some patients may present with complete paraplegia and urinary incontinence, as well as fecal and urinary incontinence. A few may have lumbar disc herniation or spondylolisthesis, and there are also cases where upper limb symptoms are caused by spinal cord tethering.

　　Hidden spinal defect is the result of the combined effects of genetic factors and environmental factors, and it is necessary to prevent environmental factors, such as adverse stimulation during the early stage of pregnancy (such as radiation, toxins, hormone drugs, hypoxia acidosis, etc.). Taking vitamins in the early stage of pregnancy is helpful for the prevention of hidden spinal defect.

　　The examination of hidden spinal defect includes spinal X-ray film and CT and MRI scans, and the specific examination methods are described as follows.

　　1. Spinal X-ray film:Obtain anterior and lateral images of the lumbar sacral spine, showing widened pedicles, vertebral plate defects, and absent spinous processes. Sometimes multiple spinal defects are present, or there may be concurrent vertebral malformation, scoliosis, and other conditions.

　　2. CT and MRI scans:Especially MRI provides a more definite diagnosis for spinal defects with spinal cord tethering, often showing the lower end of the spinal cord descending to the lumbar sacral junction or within the sacral canal, and local adhesions and other signs. Nowadays, myelography has been replaced by MRI.

　　Patients with hidden spinal defect should have a balanced diet, eat more fruits and vegetables, which are high in fiber; eat more high-protein foods such as eggs and soybeans; pay attention to a light diet; and engage in moderate exercise. Avoid smoking, drinking, spicy food, coffee, and other刺激性食物.

　　The main treatment for patients with hidden spinal defect is surgery, and the specific treatment methods and prognosis are described as follows.

　　1. Treatment

　　For patients with spinal cord tethering syndrome caused by spinal defects, surgery is suitable and it is advocated to treat them as early as possible. Only by surgically releasing the factors of spinal cord tethering can the opportunity for cure and improvement be obtained. In the past, many people regarded spinal defects with urinary incontinence or fecal incontinence, or those with lower limb paralysis, as contraindications to surgery, that is, considering such severe cases as incurable. However, over the past 20 years, a large number of clinical treatment experiences have been accumulated, advocating a positive surgical attitude, even for those with incontinence or lower limb paralysis, surgery should be pursued. Therefore, it is not advisable to easily give up treatment for some severe cases.

　　1. Surgical treatment: Children mostly use general anesthesia combined with local anesthesia, while some use tracheal intubation general anesthesia; adults use strengthened anesthesia combined with local anesthesia, or use epidural anesthesia. All surgeries are performed in the prone position. Regardless of the lesion being in the cervical, thoracic, or lumbosacral segment, an supraspinous straight incision is used to facilitate the expansion of the vertebral plate incision above and below the segmental lesion of the spinal defect.

　　Taking the hidden spinal defect at the lumbosacral region with spinal cord tethering as an example, the supraspinous straight incision extends from the fourth lumbar vertebra to the middle of the sacrum. According to the usual method of vertebral plate incision surgery, the paravertebral muscles are separated, and the defective vertebral plate is exposed. Then, treatment is given according to the specific pathological condition.

　　2. Surgical operation steps: It is possible to start with a median incision at a normal location, then proceed to the deformed area. The surgical operation generally follows the following steps.

　　(1) Expand the spinal plate decompression, remove 1-2 more spinal plates upwards, and expose the terminal filament downwards. Remove all abnormal bony, cartilaginous, and soft tissues that cause traction or compression of the dural sac, spinal cord, and cauda equina. Cut the thickened yellow ligament, cut the distal end of the spinal cord, but be sure to identify the sacral nerves on both sides of the terminal filament, do not damage these nerves. If the cause of the spinal cord tethering is due to extradural, dural sac, and spinal cord compressive factors has been resolved, the surgery can be terminated without the need to incise the dural sac for exploration.

　　(2) If scar tissue, lipoma, or a cystic herniation within the spinal canal is observed connected to the perimesenteric cyst, it is necessary to continue to incise the dural sac for deep exploration, and remove the scar, separate adhesions, and remove the cyst to relieve the spinal cord and nerve roots. In cases where a lipoma surrounds the spinal cord and nerves, especially when the fat and nerve tissues are difficult to distinguish, even under a microscope, it is only possible to perform a subtotal resection of the lipoma to avoid damaging the blood circulation of the spinal cord or directly injuring the spinal cord and nerves. If congenital dermoid cysts or tumors are found, they should be removed as much as possible.

　　(3) There is no need to graft bone or perform spinal fusion surgery for缝合 hard spinal membrane and spinal plate defect area. The external can be covered with absorbable gelatin sponge (gelatin sponge), and the wound is sutured after careful hemostasis. A drainage tube can be left in the extradural space, which can be removed after 24-48 hours. Generally, about half of the patients with moderate and severe illness can achieve significant effects after surgical treatment.

　　After surgery, lie in prone or lateral position for one week. In cases with significant urinary incontinence, catheterization should be performed to maintain the cleanliness and hygiene of the surgical site; strict prevention of urinary and fecal contamination in children, and appropriate use of antibiotics to prevent infection. After the wound is sutured, rehabilitation treatment programs can be increased, such as physical therapy, acupuncture, massage, and limb function exercises, and the use of neurotrophic drugs to promote the early recovery of nerve function.

　　II. Prognosis

　　The factors for decompressing the spinal cord can be cured or improved. In cases with urinary incontinence or fecal incontinence and those with lower limb paralysis, some of the cases may recover or improve after surgery. The widespread application of modern microsurgical methods has further increased the efficacy of surgery.