Spinal cord cavity, Chiari malformation 1. What is spinal cord cavitation? It is a slowly progressive spinal cord pathology characterized by the formation of a tubular cavity in the spinal cord, which causes a series of clinical manifestations, and is affected by various pathogenic factors. 2. What are the causes? There are two types of spinal cord cavities: congenital abnormal development and secondary spinal cord cavitation. The former is mostly combined with subungual herniation malformation of the cerebellum, while the latter is often caused by trauma, tumor, inflammation, etc. The latter is rare and refers to spinal cord compression secondary to spinal cord tumors, trauma, inflammation, cervical spondylosis, spinal stenosis, etc. For those caused by congenital developmental abnormalities, there are several theories as follows. I. Congenital atresia of the spinal cord neural tube: The disease is often accompanied by other congenital anomalies such as spina bifida, cervical ribs, scoliosis, and circumoccipital malformation to support this view. Second, embryonic cell proliferation: the residual embryonic cell mass in the gray matter of the spinal cord proliferates slowly and the center is necrotic and liquefied to form a cavity. 3. Mechanical factors: The outlet of the fourth ventricle is obstructed due to congenital factors, and the flow of cerebrospinal fluid from the fourth ventricle to the subarachnoid space is obstructed, which causes the pulsating wave of cerebrospinal fluid to impact downward on the central canal of the spinal cord, resulting in the expansion of the minority of the central canal and breaking through the wall of the central canal to form a cavity. 3. How does spinal cord cavitation develop? ① Cerebrospinal fluid pulsatile transmission theory When there are lesions causing obstruction in the foramen magnum area (such as chronic subcerebellar tonsillar herniation, craniocervical malformation and arachnoiditis and adhesions at the base of the skull), the rise in intracranial pressure will cause the subcerebellar tonsillar herniation to posteriorly compress the subarachnoid space of the spinal canal, making the exit of cerebrospinal fluid from the skull obstructed, which makes the intracranial pressure rise further. When a certain level is reached, the pulsating impact of cerebrospinal fluid within the fourth ventricle enlarges the opening of the central canal of the supraspinal rami, and cerebrospinal fluid enters the originally degenerated central canal of the spinal cord. If the central canal of the spinal cord is simply made to form a row-like dilated cavity, it is called spinal hydrocele. If the ventricular canal membrane is damaged and torn, the spinal cord tissue under the ventricular canal membrane becomes edematous under pressure, and the perivascular space near the ventricular canal membrane is forced to expand, and the fluid in the central canal pulses outward to expand the central canal and form a central cavity on the one hand, while entering the perivascular space under the ruptured ventricular canal membrane and the adjacent cellular space along the ruptured ventricular canal membrane to form some small pools between the cells, and these small pools penetrate and pool to form a cavity outside the central canal, which is called cavernous hydrocele. This is called spinal cavernous effusion. ② Compression theory The posterior cranial fossa and occipital foramen are crowded and compress the lower brainstem and upper cervical medulla causing cerebrospinal fluid separation. Due to the intracranial pressure forming a kind of ball-and-flap effect, the cerebrospinal fluid flows to the cranial side while preventing its reverse flow. During sitting up or Valsalva maneuver (forceful breath-holding), the transient pressure increases, pumping the ventricular fluid into the central canal and forming a cavity, and after the cavity is formed, the peridural venous pressure changes can centrifuge the cavity fluid and produce a new cavity,. (iii) Adhesion theory Dall Dayan believes that during Valsalva action, venous pressure increases and is transmitted to the peridural venous plexus of the spinal cord, but because the obstruction at the foramen magnum does not allow cerebrospinal fluid to flow cranially, but enters the spinal cord parenchyma through the Virochow-Robin gap, the cavity may not communicate with the fourth ventricle or the central canal, and the water-soluble contrast agent Amipaque may delay The water-soluble contrast agent Amipaque can delay the entry into the cavity lumen, supporting the conclusion that the cavity is connected to the subarachnoid space. 4. Pathological changes in the spinal cord at the site of the cavity may be normal in appearance, or pyknotic in expansion, or atrophic in appearance. The cavity cavity is filled with fluid and usually communicates with the central canal, and the cavity wall is composed of glial cells and glial fibers. The cavity is often located in the anterior and posterior gray matter junction of the lower cervical and upper thoracic segments of the spinal cord and at the base of the posterior horn on one or both sides. The cavity may be limited to a few segments, or it may extend up to the medulla oblongata and down to the entire length of the spinal cord, and the cavity may vary in size and shape in cross-section. During the development of the cavity and its surrounding gliosis, the anterior, lateral, and posterior horns of the gray matter and the anterior gray-white matter are first damaged, and then the long tracts of the white matter are affected, causing degeneration, necrosis, and loss of the corresponding neural tissue. Most of the cervical medullary cavernous syndromes arise from the extension of the cervical medulla and are usually located in the posterior lateral portion of the medulla in the nucleus of the trigeminal spinalis and the nucleus suspensus, before later affecting the surrounding long tracts and causing secondary degeneration. 5. About Chiari malformation (subhypophyseal herniation malformation) [Definition] is a congenital developmental anomaly due to abnormal development of the midline brain structures in the posterior cranial recess during the embryonic period, where the cerebellar tonsils extend downward, or/and the lower part of the medulla oblongata or even the Ⅳ ventricle, and protrude into the cervical spinal canal through the foramen magnum. It is the most common cause of spinal cord cavitation. Type I: Herniation of the cerebellar tonsils and the cerebellar earthworm into the spinal canal, but the fourth ventricle remains over the foramen magnum. Type II: The fourth ventricle herniates into the spinal canal. Type III: Combined spina bifida and spondylolisthesis on top of type I and II. Diagnosis】The commonly accepted diagnostic criterion is that the sagittal MRI scan of one or both sides of the cerebellar subungual herniation exceeds the edge of the foramen magnum by less than 5 mm, and it is not difficult to make a diagnosis when combined with clinical manifestations (headache, pressure on posterior brain structures, spinal cord symptoms, hydrocephalus, etc.). Clinical manifestations] Some or all of the following symptoms may be present: cranial nerve and cervical nerve symptoms hoarseness, difficulty in swallowing, pain in the neck and neckline, and limitation of movement. Brainstem medulla symptoms Limb movement disorders, hemiparesis and quadriplegia, sensory disorders of limbs, and urinary and fecal disorders, etc. Cerebellar symptoms: ataxia, unstable walking and nystagmus. Intracranial pressure increase symptoms Headache, vomiting, fundus edema and vision loss. Spinal cord cavitation manifestations Dissociative sensory or bilateral upper limb muscle atrophy, etc. (see 6. What are the common symptoms of spinal cord cavitation?) . 6. What are the common symptoms of spinal cavernous disease? The onset of the disease is mostly in the age of 20 to 30 years old, about three times more men than women. The onset of the disease is insidious and the course of the disease is slow. The clinical manifestations are symptoms of nerve damage in the affected spinal cord segments, characterized by hyperalgesia and hyperalgesia with preserved deep sensation, as well as motor disorders and neurotrophic disorders with damage to the long tracts of the spinal cord. Clinical symptoms vary depending on the location and extent of the cavity. There are two types of sensory disorders: segmental dissociative sensory disorders innervated by the spinal cord at the site of the cavity and fascicular sensory disorders below the lesion. Segmental dissociative sensory disorders (i.e., pain and temperature disorders, while touch and deep sensation are intact or relatively normal) are the most prominent clinical signs of the disease. Patients are often found to have the disease only after they are unaware of the pain after being burned, cut, or stabbed in the arm, and are often accompanied by spontaneous pain, numbness, ankylosis, and other sensory abnormalities in the hand and arm. On examination, the pain and temperature sensations are significantly dulled or absent on one or both sides of the spinal cord segmental distribution, while the sense of touch is preserved or mildly impaired, usually up to the neck and down to the chest, with a shawl or short top-like distribution. If the cavity reaches the trigeminal sensory tract of the upper cervical medulla, pain and temperature sensation may also be impaired in the face. If the cavity starts in the lumbosacral region, the lower extremities and perineum will have a separate superficial sensory disturbance. If the cavity reaches the entrance of the posterior root, all superficial and deep sensations in the damaged segment may be lost. Bundle sensory deficits. When the cavity extends to damage the thalamic tracts of the spinal cord on one or both sides, it produces fascicular superficial sensory deficits in the contralateral or bilateral trunk below the damage. The posterior cord of the spinal cord is often the last to be damaged, in which case deep sensory deficits in the ipsilateral or bilateral soma below the plane of damage occur. Since the shape and distribution of the cavities are often irregular, and segmental and fascicular sensory deficits are often mixed, careful examination is required to determine their extent and nature. ②Motor disorders of lower motor neuron paresis. When the cervical and thoracic cavities of the spinal cord reach the anterior horn, weakness, atrophy and tremor of the muscles of the forearm and interosseous muscles of the hand appear. If the hand muscles are severely atrophied, the hand may appear as an “eagle’s claw” hand. With the development of the lesion, it may gradually spread to the upper arm, shoulder girdle and some intercostal muscles, causing paralysis. The lumbosacral cavity shows muscle atrophy in the lower extremities and feet. Upper motor neuron paresis. When the lesion compresses the pyramidal fasciculus, signs of upper motor neuron paresis may appear on one or both sides below the plane of damage. (iii) Vegetative nerve dysfunction is often more pronounced, due to lesions affecting the lateral horn. It is common to see dystrophy of the upper extremities, skin thickening, burn scars or intractable ulcers, cyanosis and chills, and excessive or little sweating. Horner’s sign can be seen in the lateral horn damage of the lower cervical medulla. Bone and joint damage in about 20% of patients, often multiple, is common in the upper extremities, with swollen joints, atrophy, decalcification, and destruction by wear and tear of the bones in the joint area, but without pain; this neurogenic arthropathy is called Charcot arthropathy. ④Other symptoms are often combined with scoliosis, retroflexion, spina bifida, bowed feet, flattened skull base, hydrocephalus and congenital submedullary herniation and other deformities. ⑤ The cavity of the medulla oblongata often extends from the spinal cord and can also be the first site of the disease. The cavity often affects the nucleus suspensus of the medulla oblongata, the nucleus of the hypoglossal nerve and the nucleus of the trigeminal spinal tract, resulting in dysphagia, dysphonia, atrophy of the tongue muscles and tremor, and even inability to extend the tongue. If the cavity affects the vestibulocerebellar pathway, it may cause nystagmus, vertigo, and unstable gait. Peripheral facial palsy can occur when the facial nucleus of the pontocerebellum is damaged. 7. Diagnosis of spinal cord cavity This disease mostly develops in young and middle-aged people, and the course of the disease is slow. Segmental dissociative superficial sensory impairment, muscle atrophy and weakness, skin and joint dystrophy, often accompanied by spinal deformity, bowed feet, etc. The pressure and composition of the cerebrospinal fluid are mostly normal, but when the cavity is large, it can also cause obstruction of the spinal canal, and the protein content of the cerebrospinal fluid is increased. x-ray radiographs can confirm the accompanying skeletal deformities, and magnetic resonance imaging (MRI) is the best diagnostic method for spinal cord cavitation, which not only shows the location, shape and extent of the cavity, but also clarifies the diagnosis of related lesions (deformity, tumor, spinal stenosis, etc.). 8, spinal cavitation should be drug treatment or surgery in clinical work, we often divide the treatment of the disease into surgical treatment and conservative drug treatment. For some diseases (such as gastric ulcer), we advocate drug treatment first, and then consider surgery if it is ineffective; for other diseases (such as various deformities), we advocate surgery first, and then use appropriate drugs after surgery. Spinal cord cavitation (combined with submicrocephalic tonsillar herniation malformation) belongs to the latter category. In view of the pathological basis of the disease (combined submicrocephalic herniation malformation) and its slowly progressive nature, drug therapy is unable to correct the malformation and its efficacy is not very reliable. Surgical decompression of the deformity is the basis of all treatment, otherwise the neurological damage will continue to increase slowly or rapidly. For those who do not need surgery for the time being, have contraindications to surgery, or do not want to undergo surgery, appropriate medication is beneficial. 9.When do spinal cord cavitation and subungual herniation require surgical treatment? (1) subungual herniation with obstructive hydrocephalus and increased intracranial pressure; (2) subungual herniation with obvious symptoms of compression of the medulla oblongata, spinal cord and occipital cervical nerve roots; (3) subungual herniation with intractable pain and vertigo can be treated by surgical decompression; (4) subungual herniation combined with spinal cord cavitation, especially if the cavity is increasing in size or the symptoms are developing; (5) subungual herniation with spinal cord cavitation (5) spinal cord cavitation combined with other occipital and cervical deformities that need surgical solution; (6) simple spinal cord cavitation with obvious spinal cord compression, progressive increase of cavity or progressive aggravation of symptoms; (7) other conditions leading to spinal cord cavitation that need surgical solution, such as intraspinal tumor, spinal cord embolism, etc. 10. How to treat surgically? In the past, the surgical procedure was complicated, but recently the mainstream procedure has been recognized. The basic principles of surgery are: (1) decompression of the craniocervical junction area. The basic principles of surgery are: (1) decompression of the craniocervical junction area and treatment of possible deformities and other pathological factors in the area to eliminate the cause and prevent the development and deterioration of the lesion. (2) Reconstruct the structures that meet the physiological needs and improve the cerebrospinal fluid circulation. (3) Perform cavity aspiration or shunt to reduce the size of the cavity and relieve intrinsic compression to relieve symptoms. Through scientific and reasonable design and careful and precise surgery, satisfactory clinical results are obtained. (1) Posterior cranial fossa and craniocervical junction area incision and decompression surgery: according to the usual posterior cranial fossa decompression surgery force style. The focus is on releasing the cerebellar subungual herniation and arachnoid adhesions in the occipital foramen area, so that the cerebrospinal fluid flow out of the middle foramen of the four ventricles is unobstructed. If pathological factors such as tumors and cysts are found. -If tumors, cysts, etc. are found, they should be treated together. If decompression is not adequate. The lamina of C2 can be removed. 2) Expanded dural repair: to reconstruct a smooth cerebrospinal fluid circulation channel 3) Spinal cord cavity aspiration, incision or shunt: in the same way as spinal cord tumor surgery. Make cervical and thoracic laminectomy. The dura mater is incised. The spinal cord at the site of the cavity is explored. -In all cases, a bulge in the spinal cord can be found. The most bulging part of the spinal cord is found in the dorsal midline. Along the posterior median fissure. Select an area free of blood vessels. The spinal cord is incised longitudinally to reach the cavity. A silicone tube is left in the cavity. A spinal subarachnoid shunt is performed, or the catheter is sent to the cerebellar medullary pool or pontine pool for shunting. (4) Filling of the superior spinal cord cavity; open the posterior cranial fossa according to the posterior cranial fossa decompression procedure. Probe below the four ventricles to identify if there is central canal enlargement. If present. A small piece of muscle is taken to fill the opening with cold. The above procedures can be performed simultaneously. After surgery. In most cases, the cavity shrinks or disappears. The change of the cavity and the condition of the spinal cord can be observed by MRI scans with regular checks for comparison. However, the surgery is not radical. The recent efficacy is obvious. In advanced cases, those with large spinal cord cavities and significant neurological tissue atrophy and degeneration, the efficacy of surgery is not significant. The literature reports that the efficacy of surgery is 80%. (1) Keep the arachnoid membrane intact and do not routinely evacuate the median foramen of the four ventricles to avoid damage to the central nervous system, blood entering the subarachnoid space and artificial adhesions. (2) Not to remove the subhypophyseal tonsil because it is in a deformed state, but it is still part of the nervous system and has its own function; the so-called “subperitoneal resection” is actually difficult to do, and the process of resection will inevitably open the subarachnoid space and cause trauma to the brain tissue. (3) The dura should be cut and enlarged to fully release the bony, dural and fascial compressions and to ensure the isolation of the nervous system from the outside world. (4) The minimally invasive concept is advocated to minimize the destruction of soft tissues and bone structures; to minimize interference with the central nervous system. This is essential to maintain the stability of the cervical spine and to reduce postoperative subarachnoid adhesions. (5) Correction of congenital deformities merely keeps the lesion from continuing to worsen, but damage to the nervous system is usually irreparable. Olfactory bulb neural stem cell transplantation may be beneficial for repair of spinal cord injury. 12. What are the risks of surgical treatment of spinal cord cavitation? In general, surgical treatment of spinal cord cavernosum is a relatively safe procedure, and is safer for procedures that do not open the subarachnoid space, do not explore the median foramen of the four ventricles, and do not perform cerebellar tonsillectomy. Possible complications: incisional effusion, infection, bloody cerebrospinal fluid. Due to our advanced treatment concept mentioned above and Prof. Xiu Bo’s rich experience in spinal cord surgery, the procedure is effective, safer, minimally invasive and has a low complication rate.