Diastematomyelia, also termed split cord malformation (SCM), is a rare congenital spinal anomaly characterized by sagittal division of the spinal cord into two distinct hemicords. Commonly separated by a bony, cartilaginous, or fibrous septum, its clinical evaluation and neurosurgical management focus on tethered cord release and preserving neurological function.
Diastematomyelia, also called split cord malformation (SCM), is a rare congenital spinal condition in which the spinal cord is divided into two distinct segments. This division is usually caused by a fibrous, cartilaginous, or bony septum and is most often located in the thoracic or lumbar spine. Many cases are identified in childhood, but mild forms may go undiagnosed until adulthood. It forms a key clinical entity within pediatric dysraphic disorders, distinct from neoplastic conditions such as spinal tumors and pediatric spinal tumors.
Causes and Risk Factors
Diastematomyelia develops during early embryonic morphogenesis due to abnormal neural tube closure and persistent endodermal-ectodermal adhesions:
- Congenital Origin: Present at birth as a direct result of faulty neuro-embryological spinal cord development.
- Associated Anomalies: Frequently co-occurs with spina bifida, tethered cord syndrome, congenital scoliosis, hypertrichosis, or other neural tube closure defects.
- Genetic & Environmental Influences: Multifactorial developmental mechanisms believed to contribute to abnormal embryonic axial skeleton formation.
Diastematomyelia Types
Split cord malformations are classified into two primary anatomical subtypes based on dural arrangement and septum composition:
Type I Split Cord Malformation
Each of the two hemicords is housed within its own separate dural sac, divided by a rigid, osseous (bony) or cartilaginous median septum. This type frequently produces mechanical cord tethering and symptomatic neurological decline.
Type II Split Cord Malformation
Both hemicords reside within a single, shared dural sac, separated only by a non-rigid fibrous band or adventitial tissue. Typically presents with a milder neurological course.
Diastematomyelia Symptoms
Clinical manifestations vary depending on SCM subtype, patient age, degree of spinal cord tethering, and secondary vertebral deformities:
- Persistent, localized back or lower spinal axial pain
- Progressive lower extremity weakness, numbness, or tingling paresthesias
- Difficulty walking, gait instability, and motor coordination deficits
- Progressive spinal deformities, particularly congenital or rigid scoliosis
- Cutaneous stigmata along the dorsal midline spine (hypertrichosis/hairy patch, hemangioma, dermal dimple, or lipoma)
- Neurogenic bladder or bowel dysfunction in advanced or tethered cord cases
Diagnostic Methods
Establishing an accurate diagnosis requires multi-planar neuroimaging to evaluate soft tissue and bony spinal anatomy:
Magnetic Resonance Imaging (MRI)
The gold standard diagnostic modality. MRI clearly visualizes hemicord separation, conus medullaris level, filum terminale thickness, soft tissue septa, and associated syringomyelia.
Computed Tomography (CT)
Thin-slice 3D CT reconstruction provides precise detail regarding bony septa, vertebral body anomalies (spina bifida, hemivertebrae), and posterior element canal widening.
Plain Radiography (X-rays)
Standing spinal X-rays serve as an essential tool to screen for, quantify, and monitor associated congenital scoliosis or kyphotic spinal curvatures.
Diastematomyelia Treatment Options
Management is tailored according to SCM subtype, neurological symptoms, and associated spinal deformities:
1. Conservative Surveillance
In asymptomatic or very mild cases discovered incidentally, careful non-surgical monitoring with serial neurological examinations and physical therapy may be recommended under close pediatric neurosurgical supervision.
2. Microsurgical Resection & Cord Release
Surgical intervention is the definitive treatment for symptomatic or tethered cases:
- Excision of the Septum: Resection of the bony, cartilaginous, or fibrous spur to eliminate mechanical impingement and unite the dural sac (in Type I SCM).
- Tethered Cord Release: Transection of a thickened filum terminale or release of dural bands to free the spinal cord from mechanical traction.
- Corrective Scoliosis Surgery: Staged or combined orthopedic/neurosurgical spinal instrumentation for progressive scoliosis after cord untethering.
Conclusion
Although rare, diastematomyelia can cause progressive neurological deficits and spinal deformities if left untreated. Early diagnostic detection and timely neurosurgical intervention are crucial to prevent irreversible nerve impairment. Long-term multi-specialty follow-up, especially during pediatric growth spurts, is essential to monitor for retethering and ensure optimal spinal alignment and quality of life.
Frequently Asked Questions
What is diastematomyelia (split cord malformation)?
Diastematomyelia is a rare congenital condition where the spinal cord is split longitudinally into two separate hemicords, usually by a bony, cartilaginous, or fibrous spur.
What is the difference between Type I and Type II split cord malformation?
In Type I, the two hemicords are located in separate dural sacs divided by a rigid bony or cartilaginous septum. In Type II, both hemicords are contained within a single dural sac separated by a fibrous band.
What are the physical signs of diastematomyelia in children?
Physical signs often include midline skin marks over the back (such as a hairy patch, birthmark, or dimple), progressive leg weakness, gait difficulty, and scoliosis.
How is diastematomyelia diagnosed?
Diagnosis is confirmed using high-resolution spine MRI to visualize the split spinal cord, paired with 3D CT scans to detail the bony septum and spinal column structure.
Why is surgery performed for diastematomyelia?
Surgery is performed to remove the dividing spur and release the tethered spinal cord, preventing progressive neurological damage, pain, leg weakness, and worsening scoliosis.
Can diastematomyelia lead to tethered cord syndrome?
Yes. The central septum or associated abnormal dural attachments anchor the spinal cord, preventing normal movement during growth and causing tethered cord syndrome.