Anatomical features and structural variants
The pathogenesis of diastematomyelia is based on the abnormal cleavage (cleavage) of spinal cord tissue during embryogenesis. The lesion typically involves multiple spinal segments simultaneously. A specific feature is that caudal to (below) the cleft, the two halves of the spinal cord reunite into a single structure.
There are two main anatomical variants of meningeal formation in this malformation:
- Single dural sac. Found in approximately 50% of cases (most characteristic of the cervical spine). In this case, both halves of the spinal cord (hemicords) are enclosed within a single intrathecal space.
- Separate dural sacs. Each half of the spinal cord has its own dura mater. Crucially, a dense septum—a bony or cartilaginous spur (spur)—forms between these sacs. This spur originates from an abnormally developed vertebral arch and rigidly divides the spinal canal.
Clinical significance and complications
Despite the fact that diastematomyelia is often asymptomatic and becomes an incidental radiological finding, the presence of a rigid osseocartilaginous spur poses a serious threat.
Normally, the spinal cord should have a certain degree of mobility within the spinal canal. The spur passing through the split cord causes its rigid fixation. As the child grows (или during movements in adults), pathological tension of the spinal cord occurs, known as tethering syndrome (tethered cord syndrome).
Timely detection of the malformation allows for surgical removal of the fixation—spinal cord untethering (detethering), which reliably improves the clinical prognosis and prevents the development of irreversible neurological deficit.
MRI semiotics of diastematomyelia
Magnetic resonance imaging is the gold standard for visualizing spine malformations. For an accurate diagnosis of diastematomyelia, it is necessary to analyze images in multiple planes:
- Axial projection (T2-weighted images): Optimal for direct visualization of the split. These slices clearly show the division of the spinal cord into two separate halves and the presence (or absence) of an osseocartilaginous septum between them.
- Sagittal projection: Allows assessment of secondary signs and concomitant changes. An abnormally low position of the conus medullaris (conus medullaris) is often visualized, which is a direct consequence of its fixation. In addition, sagittal slices clearly determine associated spine anomalies, such as pathological fusion of vertebral bodies.
Differential diagnosis and associated developmental anomalies
Diastematomyelia belongs to the group of non-neoplastic spinal cord lesions and is frequently combined with other manifestations of dysraphism (neural tube closure defects):
- Lipomyelomeningocele: Also accompanied by a low-lying conus medullaris and spinal dysraphism (spina bifida), but characterized by the presence of a fatty mass fused with the spinal cord.
- Intraspinal neurenteric cysts: Formed due to abnormal separation of the embryonic notochord and endoderm. Like diastematomyelia, they are frequently combined with gross vertebral anomalies (butterfly vertebrae, hemivertebrae).
- Dermoid/epidermoid cysts and dorsal dermal sinus: Fistulous tracts extending from the skin into the spinal canal, found in various forms of occult dysraphism.
Briefly: answers to topical questions
How does lipomyelomeningocele manifest in differential diagnosis with diastematomyelia?
Lipomyelomeningocele manifests as a large fatty mass associated with the spinal cord and extending through the bone defect in spina bifida. Diastematomyelia is characterized by splitting of the spinal cord.
| Sign | Lipomyelomeningocele | Diastematomyelia |
|---|---|---|
| Mass | Large hyperintense fatty mass; signal suppresses on fat-suppression sequences | Splitting of the spinal cord into halves (hemicords) |
| Connection with the spinal cord | The spinal cord appears fused (fused) with the fatty mass | The halves of the spinal cord typically reunite caudally |
| Bone changes | Spinal dysraphism (spina bifida), fatty mass extends through the bone defect | Vertebral anomalies are possible, e.g., fusion of bodies; a bony or cartilaginous spur may be located between the halves |
| Conus medullaris | The spinal cord is located abnormally low, the conus medullaris is not clearly differentiated | A low-lying conus medullaris may be determined on sagittal slices |
What are intraspinal neurenteric cysts and what are their causes?
Intraspinal neurenteric cysts are usually intradural extramedullary, unilocular lesions lined with gastrointestinal or bronchial epithelium.
The causes of their occurrence include:
- Abnormal separation — disturbance of the separation of the embryonic notochord (notochord plate) and endoderm.
- Incomplete separation — incomplete separation of the foregut (foregut) from the notochord (notochord) in early embryogenesis.
Which vertebral bone anomalies are frequently combined with diastematomyelia?
Various vertebral developmental anomalies are frequently observed in diastematomyelia, in particular fusion of their bodies.
Characteristic bone changes include:
- Abnormal vertebral arch — serves as the source of formation of a bony or cartilaginous spur (spur) dividing the spinal cord.
- Fusion of vertebral bodies — visualized on sagittal magnetic resonance tomograms along with a low-lying conus medullaris.
Class and exam questions
Do patients with diastematomyelia always have symptoms?
No, the disease is quite often completely asymptomatic and is diagnosed incidentally during MRI.
What is the tethering syndrome in the context of this anomaly?
This is pathological tension and fixation of the spinal cord, often caused by the presence of an osseocartilaginous spur passing between the halves of the split cord.
Which MRI projection is most informative for confirming the diagnosis?
Axial T2-weighted slices, as they allow direct visualization of the division of the spinal cord into two parts.
What treatment strategy is used when complications develop?
In the presence of clinical signs of spinal cord tension, surgical intervention is indicated—removal of fixation (detethering), which improves the prognosis.
What else to study on this topic
- Lipomyelomeningocele and MRI signs of a low-lying conus medullaris.
- Intraspinal developmental cysts: neurenteric, dermoid, and ependymal.
- Chiari malformations types I and II: differential diagnosis and association with syringomyelia.
- MRI semiotics of non-neoplastic infectious lesions: tuberculous spondylodiscitis and epidural abscesses.
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