DIASTOMATOMYELIA - Pathophysiology, Clinical Manifestations, Diagnostic Evaluations and Management
DIASTEMATOMYELIA - Pathophysiology, Clinical Manifestations, Diagnostic Evaluations and Management
Diastematomyelia is a congenital disorder in which a part of the spinal cord is split, usually at the level of the upper lumbar vertebra. It is one of many forms of spinal dysraphism or neural tube defects, which arise due to abnormal development of the lower end of the nervous system. This particular malformation is a complete or partial separation of the spinal cord into 2 separate “hemicords.” The separation generally occurs in the middle of the spinal cord and the hemicords reunite below it.
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 distally 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 most of the 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.
The signs and symptoms of diastematomyelia may appear at any time of life, although the diagnosis is usually made in childhood nowadays.
Adult presentation in diastematomyelia is unusual. With modern imaging techniques, spinal dysraphism are being diagnosed in adults with increasing frequency. The commonest location of the lesion is at first to third lumbar vertebrae. Lumbosacral adult diastematomyelia is even rarer. Bony malformations and dysplasias are generally recognized on plain x-rays. MRI scanning is often the first choice of screening and diagnosis. MRI generally gives 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 to mid third-trimester. An extra posterior echogenic focus between the fetal spinal laminae are seen with splaying of the posterior elements, thus allowing for allowing for early surgical intervention and have a favorable prognosis. Prenatal ultrasound could also detect whether the diastomatomyelia is isolated, with the skin intact or association with any serious neural tube defects.
Treatment does not aim to “reattach” the halves of the split spinal cord. However, treatment varies depending on the symptoms and severity of the malformation. Asymptomatic patients or patients who have stable symptoms which do not progress may only require conservative treatment and follow-up. However, for those patients with progressive neurological symptoms, surgical treatment may be indicated to attempt to preserve function and prevent further injury of the spinal cord.
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 includes decompression of neural elements and removal of bony spur. This may be accomplished with or without resection and repairment of the duplicated dural sacs. Resection and repairmen the duplicated dural sac is preferred since the dural abnormality may partly contribute to the “tethering” process responsible for the symptoms of this condition. Asymptomatic patients do not require surgical treatment.
These patients should have regular neurological examinations since it is known that the condition can deteriorate. If any progression is identified, then a resection should be performed.