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Diastematomyelia (A Patient Information Service) Congenital anomalies are the product of errors in "embryogenesis" (malformations consequent to errors in the developmental stages of the embryo) or the result of intrauterine events that affect embryonic and fetal growth (deformations and disruptions). As a general rule, it is apparent that the more complex the formation of a structure, the more opportunities for malformation. Some of the most serious neurological abnormalities affect the Brain (conditions that are reviewed elsewhere on this website) develop in the first two months of gestation and represent defects in neural tube (the embryonic precursor of the entire central nervous system) formation. The medical term for this is "dysraphia". Some of these affect the Spine and the Spinal Cord as well.Modern investigative methods, such as amniocentesis and ultrasonography may provide an accurate in utero detection of many malformations. Genetic counseling for parents of a child with a major neurological abnormality is important, since the risk of a subsequent child's having such a defect is high. These parents frequently also need psychological help and support. Women who have had a pregnancy resulting in an infant or fetus with a neural tube defect should be advised that folic acid supplementation (4 mg/day) before conception and during early pregnancy may substantially reduce the risk of neural tube defects in subsequent pregnancies. Diastematomyelia Diastematomyelia is a rare congenital anomaly that results in the "splitting" of the spinal cord in a longitudinal (sagittal) direction. Females are affected much more commonly than males. This condition occurs in the presence of an osseous (bone), cartilaginous or fibrous septum in the central portion of the spinal canal which then produces a complete or incomplete sagittal division of the spinal cord into two hemicords. When the split does not reunite distal to the spur, the condition is referred to as a Diplomyelia (which is a "true duplication" of the Spinal Cord.)Diastematomyelia is a "dysraphic state" of unknown embryonic origin, but is probably initiated by an accessory neurenteric canal (an additional embryonic spinal canal.) This condition may be an isolated phenomenon or may be associated with other segmental anomalies of the vertebral bodies such as Spina Bifida, kyphoscoliosis, butterfly vertebra, hemivertebra and block vertebrae which are observed in a high proportion of cases. Scoliosis is usually identified in more than half of these patients. In most of the symptomatic patients, the spinal cord is split into halves by a bony spicule or fibrous band, each half being surrounded by a dural sac. Other conditions, such as intramedullary tumors, tethered cord, Dermoids, Lipoma, Syringomyelia, Hydromyelia and Arnold-Chiari malformations have been described in the medical literature, but are exceptionally rare. Diastematomyelia usually occurs between 9th Thoracic and 1st Sacral levels of the Spinal Column with most being at the level of the upper lumbar vertebra. Cervical Diastematomyelia is a very rare entity. The extent (or length of spinal cord involved) varies from one affected individual to another. In approximately 60% of patients with Diastematomyelia, the two hemicords, each covered by an intact layer of pia arachnoid, travel through a single subarachnoid space surrounded by a single dural sac. Each hemicord has its own anterior spinal artery. This form of Diastematomyelia is not accompanied by a bony spur or fibrous band and is rarely symptomatic unless hydromyelia or tethering is present. The other 40% of patients have a bony spur or a fibrous band that passes through the two hemicords. In these cases, the dura and arachnoid are split into two separate dural and arachnoidal sacs, each surrounding the corresponding hemicord which are not necessarily symmetric. Each hemicord contains a central canal, one dorsal horn (giving rise to a dorsal nerve root), and one ventral horn (giving rise to a ventral nerve root.) One study of these entities identified the bony spur as typically being situated at the most inferior aspect of the dural cleft. They advise that if the imaging study appears to show otherwise, a second spur (present in about 5% of patients with Diastematomyelia) is likely to be present. The conus medullaris is situated below the L2 level in more than 75% of these Diastematomyelia patients. Thickening of the Filum Terminale is seen in over half of them. While the level of the cleft is variable, it is most commonly found in the lumbar region. The two hemicords usually reunite caudal to the cleft. Occasionally, however, the cleft will extend unusually low and the cord will end with two separate coni medullarae and two fila terminale (sometimes called "Diplomyelia"). The following definitions from may help in the understanding of these entities: Diastematomyelia (di·a·stem·a·to·my·elia) is a congenital anomaly, often associated with spina bifida, in which the spinal cord is split into halves by a bony spicule or fibrous band, each half being surrounded by a dural sac. Myeloschisis (my·elos·chi·sis) is a developmental anomaly characterized by a cleft spinal cord, owing to failure of the neural plate to form a complete neural tube or to rupture of the neural tube after closure. Diplomyelia (diplo.my.elia) is a true duplication of spinal cord in which these are two dural sacs with two pairs or anterior and posterior nerve roots. DIAGNOSIS The signs and symptoms of Diastematomyelia may appear at any time of life, although the diagnosis, in modern times, is usually made in childhood. Cutaneous lesions (or stigmata), such as a hairy patch, dimple, Hemangioma, subcutaneous mass, Lipoma or Teratoma (at or near the level of the Diastematomyelia) override the affected area of spine in more than half of cases. Neurological symptoms are nonspecific, indistinguishable from other causes of cord tethering. The symptoms are caused by tissue attachments that limit the movement of the spinal cord within the spinal column. These attachments cause an abnormal stretching of the spinal cord. The course of the disorder is progressive. In children, symptoms may include the "stigmata" mentioned above and/or foot and spinal deformities; weakness in the legs; low back pain; scoliosis; and incontinence. In adulthood, the signs and symptoms often include progressive sensory and motor problems and loss of bowel and bladder control. This delayed presentation of symptoms is related to the degree of strain placed on the spinal cord over time. Tethered spinal cord syndrome appears to be the result of improper growth of the neural tube during fetal development, and is closely linked to spina bifida. Tethering may also develop after spinal cord injury and scar tissue can block the flow of fluids around the spinal cord. Fluid pressure may cause cysts to form in the spinal cord, a condition called syringomyelia. This can lead to additional loss of movement, feeling or the onset of pain or autonomic symptoms.Adult presentation in Diastematomyelia is unusual. With modern imaging techniques, various types of spinal dysraphism are being diagnosed in adults with increasing frequency. The common location is from first to third lumbar vertebrae. Lumbosacral adult Diastematomyelia is even rarer. Bony malformations and dysplasias are generally recognized on plain x-rays (which, in modern times are less frequently done). MRI scanning is often the first (or "screening test") technique of choice for dysraphism as well as most spinal conditions. MRI will generally allow adequate analysis of the spinal cord deformities although it has some limitations in giving detailed bone anatomy. Combined myelographic and post-myelographic CT scan is the most effective diagnostic tool in demonstrating the detailed bone, intradural and extradural pathological anatomy of the affected and adjacent spinal canal levels and of the bony spur. Prenatal ultrasound diagnosis of this anomaly is usually possible in the early mid third-trimester. An extra posterior echogenic focus between the fetal spinal laminae is seen with splaying of the posterior elements, thus allowing for early surgical intervention and a favorable prognosis. Depending on whether the Diastematomyelia is isolated, with the skin intact or is in association with more serious neural tube defects, prenatal diagnosis of this condition is possible. The cause of progressive neurological lesions results from the "tethering cord syndrome" (fixation of the spinal cord) by the Diastematomyelia phenomenon or any of the associated disorders such as myelodysplasia, dysraphia of the spinal cord. TREATMENT Surgery We believe that surgical intervention is warranted in patients who present with new onset neurological signs and symptoms or have a history of progressive neurological manifestations which can be related to this abnormality. The surgical procedure required for the effective treatment of Diastematomyelia requires the decompression of neural elements and removal of bony spur. This may be accomplished with or without resection and repair of the duplicated dural sacs. Our preference is to resect and repair the duplicated dural sacs since the dural abnormality may partly contribute to the "tethering" process responsible for the symptoms of this condition.Minimally Invasive Microsurgical Techniques are becoming available to accomplish these operative tasks. This most often results in complete relief of symptoms or stops the progression of symptoms. Observation Patients, who are asymptomatic and have been identified with this anomaly while being investigated for other unrelated issues, do not require surgical treatment. These patients should undergo periodic neurological examinations since it is known that the condition can be "progressive". In the event that progressive neurological manifestations are identified, then a resection should then be performed.Organizations Additional information is available from the following organizations:
American Association of Neurological Surgeons
American Syringomyelia Alliance Project (ASAP)
National Organization for Rare Disorders (NORD)
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All content ©2024 by Neurosurgical Consultants, P.A. Author, Martin L. Lazar, MD, FACS All Rights Reserved. See Usage Notices. |