Diastematomyelia is a partial or complete splitting of the spinal cord by a longitudinal septum into two halves, each of which contains a central canal. A congenital anomaly usually affects the lumbar-thoracic spine, is characterized by skin manifestations, neurological and orthopedic disorders, and is accompanied by other neural tube defects. Pathology is diagnosed by physical examination, confirmed by neuroimaging methods (ultrasonography, radiography, CT, MRI of the spine and spinal cord). Treatment of manifest forms is only surgical.
Diastematomyelia (from the Greek diastematos – the gap, myelos – the brain) is a rare pathology of the spinal canal. There is no exact information about the prevalence of the anomaly in the population, it is only known that it accounts for about 5% of all congenital spinal defects. According to some data, pathology is present in 73% of children with latent forms of spinal dysraphy. Most cases are diagnosed before the age of 7, less often the disease is first detected in the elderly. Women suffer 1.5-9 times more often than men. There are no significant ethnogeographic differences in statistical indicators, although a slightly higher incidence of the defect is reported among residents of the Mediterranean, India.
The exact causes of the pathology remain unknown. Many researchers recognize its polyethological nature due to a combination of genetic predisposition and environmental factors. Several family cases in the female line suggest X-linked dominant inheritance. Symptoms of spinal dysraphism are three times more common among relatives, in monozygotic twins. Exogenous factors potentially affecting the formation of diastematomyelia are considered:
- Deficiency of nutrients. The development of many fetal neural tube defects is associated with a lack of folic acid in the mother’s diet. Nutritional status disorders include hypo- or hypervitaminosis A, zinc deficiency, high nitrate content in products. The negative effect of metabolites of mold fungi (cytochalazine) ingested with food is described.
- Toxic effects. Intoxication with chemicals (petroleum products, pesticides, heavy metal salts), alcohol and drug abuse lead to damage to fetal tissues. Pathology is provoked by taking embryotoxic drugs – valproates, methotrexate, sulfonamides. Ionizing radiation has mutagenic activity.
- Diseases of the mother. Intrauterine infection of the fetus with TORCH infections is considered as an important cause of embryogenesis disorders in early pregnancy. The damaging effect is realized directly or through chromosomal aberrations. The risk of having a child with a neural tube defect increases with diabetes mellitus, severe obesity.
Among other reasons, it is necessary to note the influence of injuries, increased body temperature of a woman with feverish conditions, visiting a sauna, taking hot baths. The development of diastematomyelia is affected by the age of the pregnant woman – children born to mothers older than 30 years have a 3-4 times higher risk. Sometimes, despite a thorough examination and anamnesis study, it is not possible to establish the etiology of the process.
The defect is considered to be the result of improper development of the embryonic chord and neural tube from the 15th to the 18th days of pregnancy, when the main embryonic structures are laid at the neurulation stage. An abnormal communication between the rudiment of the spinal cord and the primitive neuro-intestinal canal or amniotic sac is formed by creating an endomesenchymal tract. The latter is formed from mesodermal elements that fill the pathological fistula canal.
The separation of the caudal brain in the longitudinal direction is accompanied by the formation of a bony, cartilaginous or fibrous median septum or spur. It originates from the body or the arch of the vertebra, can extend to the entire width of the spinal canal, attaching to the ventral part of the dura mater. The spinal cord splits over several segments into two usually unequal arms equipped with its own central channel, which is the main pathomorphological feature of diastematomyelia.
Common embryogenetic mechanisms cause frequent association of pathology with other myelodysplastic conditions. The disease can be combined with myelomeningocele, spinal lipomas and cysts, dermal sinus. The association with congenital defects of the spine is revealed – hemivertebrae, butterfly-shaped vertebrae, scoliosis. With multiple signs of dysraphia, visceral defects with lesions of the kidneys, rectum and genitals occur.
There is no single universally recognized classification of diastematomyelia. In many cases, the disease is part of a more extensive spinal dysraphism syndrome (a form of spina bifida occulta), occurs in combination with other malformations. Isolated forms are less common. Taking into account the morphological features of the defect, there are two types of diastematomyelia:
- Type I. The bone-cartilaginous septum divides the brain tissue together with the membranes, each sleeve is surrounded by its own dural sac. It is often accompanied by abnormalities of vertebral segmentation, scoliosis. This form occurs in 60-70% of cases.
- Type II. Both halves of the spinal cord, separated by a connective tissue (fibrous) layer, have common membranes. The spinal canal remains continuous.
Usually, the anomaly is of a single nature with the involvement of the lumbosacral, thoracolumbar sections, cervical localization is very rare. In 5-10% of patients, there are several clefts at different levels at the same time. Structural disorders can be local, affecting 1-2 segments, or widespread. According to the structure of the septum, the following forms are distinguished: bone, cartilage, connective tissue and mixed, containing elements of various tissues.
The clinical picture is determined by the variant, localization of the defect, the presence of associated anomalies and concomitant diseases. In a number of patients, the disease is asymptomatic, especially before the age of two. Children with isolated diastematomyelia can be completely normal at birth, as the child grows, structural and functional disorders often occur. Sometimes in the neonatal period, only hypoplasia of the foot is detected. The remaining cases are manifested by noticeable symptoms.
Skin signs are not specific, since they accompany many types of spinal dysraphism. When examining the back along the median line of the body, you can notice retractions, scars, and a dermal sinus. Pigmented spots, capillary hemangiomas, subcutaneous lipoma are detected. The most typical local hypertrichosis is an abnormal growth of thick coarse hair in a limited area of the lumbar region (the so–called faun’s tail), especially characteristic of type I diastematomyelia. In the second variant of the disease, foci of fluffy hair are more often described.
A common sign of spinal abnormality is orthopedic disorders. A change in gait often becomes the first symptom that attracts the attention of parents. Deformities of the vertebral column are very significant, which in young children can be assessed as posture disorders. Severe progressive scoliosis is typical, less often – kyphosis, disproportionate development of the spine with shortening of one of the departments. In patients, deformities of the chest with hypoplasia of some ribs, persistent distortions of the pelvis, different lengths of the lower extremities are detected.
Neurological disorders are considered a sign of severe diastematomyelia and are determined by the level of lesion. They can be primary, associated with underdevelopment of the spinal cord, or secondary, due to its fixation and compression by the septum. They reveal sluggish paresis of the lower extremities, accompanied by an asymmetry of reflexes, muscle weakness, sensory deficiency. There is pain in the back and legs, muscular atrophy, peripheral pelvic organ dysfunction with urinary incontinence, feces.
The pathology picture has a wide variability – patients may have both a complete and a limited set of disraphic signs. Taking into account the prevailing symptoms, some researchers propose to distinguish several clinical groups of diastematomyelia syndrome: neuroortopedic, dermatological, associated with open spinal dysraphy. The most common is a mixed variant of the disease, but the determination of the leading symptoms is of great importance for further correction.
Many patients with diastematomyelia have a fixed spinal cord syndrome, which causes a progressive persistent neurological deficit. More than half of the cases are accompanied by a spinal cleft below the septum, reveal a connection with hydromyelia of one or both arms, myelodysplasia. An increase in the size of lipomas and dermoid cysts (intramedullary, dural) is characterized by compression of the nervous tissue. All this leads to an aggravation of functional disorders.
Severe scoliosis disrupts the work of internal organs – the digestive tract, lungs, heart. Neurogenic dysfunction of the bladder increases the risk of developing infections of the upper parts of the urological tract. Deep emotional and psychological stress arising from changes in appearance and reduced functionality becomes a source of problems in training, professional, social, and personal spheres. Some complications may persist after the correction.
Most often, diastematomyelia is diagnosed in early childhood. Due to the polymorphism of symptoms, patients can be observed by doctors of various specialties – neurologist, orthopedist, etc. Even an asymptomatic course requires an active diagnostic search aimed at identifying hidden anomalies. Therefore, neuroimaging methods are of particular importance:
- Ultrasonography. Ultrasound screening is used for antenatal (in the third trimester of pregnancy) and postnatal diagnostics. A reliable ultrasound sign of diastematomyelia is the presence of an additional echogenic focus along the median line between the posterior elements of the spine of the fetus and newborn.
- Radiography. It is the basic method of radiation diagnosis of bone dysplasia. A characteristic radiological feature is the expansion of the spinal canal across at the level of the diastema, occupying several segments. Images taken in a direct projection show well a bone or bone-cartilaginous thorn, segmental anomalies. The results of spine x-ray need further confirmation by tomographic methods.
- CT scan. Multispiral CT provides accurate visualization of the bone septum, identification of concomitant spinal canal disorders, and three-dimensional reconstruction of the affected area for preoperative planning. The nature of the splitting of nerve structures by connective tissue cords, especially in severe scoliosis, makes it possible to evaluate CT myelography.
- MRI of the spinal cord. It is recognized as the gold standard for the final diagnosis of diastematomyelia. MRI gives the most complete assessment of the anomaly, providing high-contrast images of soft tissues in any plane. The study helps to determine the nature and length of the septum, is optimally suited for detecting spinal defects, analyzing the compression of nerve structures.
Negative results of neuroimaging studies are not grounds for the final exclusion of diastematomyelia. In difficult cases, in the presence of clinical signs of dysraphism, intraoperative diagnostics allows to clarify the nature of the pathology. Neurophysiological methods (electroneuromyography, somatosensory evoked potentials) reveal a decrease in the conduction of a nerve impulse in the cone, epiconus, and ponytail. Differential diagnosis is carried out with spinal tumors, Friedreich’s ataxia, syringomyelia.
Treatment tactics for asymptomatic anomalies are not clearly defined, especially in adults. Some authors prefer a conservative approach – dynamic monitoring and counseling aimed at early detection of signs of disease progression. Such tactics are most in demand in old age against the background of polymorbidity and contraindications to surgical correction, with extensive bone septa with a high risk of postoperative deterioration of neurological function, type II diastematomyelia, cervical and upper thoracic localization of the process.
The absolute majority of researchers consider preventive surgery useful in children of the first two years of life with an asymptomatic course of the anomaly. With the development and progression of neurological disorders, the increase in spinal deformities, the importance of surgical treatment of diastematomyelia is beyond doubt – it should be performed as early as possible. Removal of the diastema can also be performed as the first stage before the planned correction of scoliosis.
It is extremely important to eliminate fixation and compression of the spinal cord. The operation involves laminectomy, resection of the bone septum with excision of adhesions, removal or restoration of the duplicate dural sac. In parallel, the correction of concomitant anomalies that worsen neurological function is carried out – a short terminal thread, cysts, lipomas. Depending on the complexity of the intervention, simultaneous or multi-stage treatment is possible.
Prognosis and prevention
Isolated diastematomyelia has a more favorable prognosis than combined with other signs of dysraphia. Asymptomatic forms do not disrupt habitual activity, but may progress over time. Severe neurological deficit is accompanied by disability, a decrease in the quality of life. Early surgical correction can prevent the progression of neurological disorders, improve the functional capabilities of patients. Antenatal prevention includes screening, elimination of significant risk factors, taking folic acid medications.