Split Cord Malformation (Diastematomyelia)

• Primary neurulation failure: Split notochord or adhesion between ectoderm and endoderm
• Pang unified theory: Both Type I and II result from similar embryologic error at days 18-25
• Associated anomalies: Hemivertebra, block vertebra, rib fusions, diastematomyelia at same or remote level

• Incidence: Rare, estimated 1 in 5000-10000 live births
• Sex ratio: Slight female predominance
• Presentation age: Infancy to adolescence; many diagnosed during scoliosis workup
• Scoliosis link: 60-80 percent of SCM patients have congenital vertebral anomalies

Low-lying conus (below L2) or thickened filum greater than 2 mm is common, and how common depends sharply on the level. In Pang's series every lumbar SCM had both a low-lying conus and at least one additional tethering lesion, whereas only 1 of 7 cervical and high thoracic lesions did. A lumbar split cord therefore obliges you to hunt for the second lesion and plan to deal with it, because releasing the septum alone leaves the cord tethered. The split itself acts as a tether point. Growth spurts or spinal lengthening during scoliosis surgery increase tension and produce acute or progressive deficit.

Correction of congenital scoliosis often requires distraction, derotation, or vertebral column resection. An unrecognized bony septum will act as a fulcrum and tear the hemicords. Even Type II fibrous bands can produce significant stretch injury once the spine is lengthened.

• Cutaneous lesion: Noted at birth or during growth
• Neurological progression: Leg weakness, numbness, or gait change
• Bladder/bowel: Incontinence, recurrent UTI, constipation
• Scoliosis history: Curve noticed by parents or school screen
• Prior surgery: Any previous spinal procedure without MRI

• Skin: Hairy patch, dermal sinus, lipoma, asymmetric cleft
• Legs: Asymmetric atrophy, cavus feet, trophic ulcers
• Neurology: Asymmetric reflexes, sensory level, Babinski
• Spine: Congenital curve, kyphosis, local tenderness
• Urodynamics: If any bladder symptom or before surgery

• Progressive tethered-cord syndrome: worsening leg weakness, sensory loss, cavus foot deformity and gait deterioration with growth
• Neurogenic bladder/bowel: detrusor-sphincter dyssynergia, recurrent UTI, incontinence - may be irreversible if late
• Syringomyelia extending into the hemicords
• CATASTROPHIC intra-operative cord injury: distraction/derotation across an unrecognised bony septum can transect the hemicords - the feared, preventable disaster of congenital-scoliosis surgery
• Curve progression while definitive correction is deferred

• New or worsened neurological deficit (motor, sensory, bladder) from manipulation of the hemicords
• CSF leak / pseudomeningocele - especially the difficult dual-tube dural closure in Type I
• Wound infection / meningitis
• Re-tethering from scar (may present with late deterioration after initial improvement)
• Incomplete release leaving a residual tether (e.g. unsectioned thick filum) with persistent symptoms

• SCM prevalence is consistent across ethnic groups; most series come from high-volume pediatric spine centers in North America, Europe, India and East Asia
• Congenital scoliosis association: 60-80 percent of patients WITH an SCM have a congenital scoliosis. There is no SCM registry, so this range comes from surgical series rather than population data - and it must not be read backwards as the yield of screening scoliosis, which is 18.3 percent overall and 52 percent at its worst pattern
• Missed diagnosis remains the leading cause of catastrophic intraoperative cord injury in congenital deformity surgery worldwide

• High-resource centers: routine whole-spine MRI with contrast for every congenital curve; intraoperative ultrasound and neuromonitoring
• Limited-resource settings: MRI access may be delayed; plain film and clinical markers still drive referral, but outcomes suffer when imaging is unavailable
• Universal principle: any child with congenital scoliosis and a cutaneous marker or neurological asymmetry must reach an MRI-capable center before surgery

Some centers advocate early release of every identified SCM even without deficit, arguing that growth or future surgery will eventually produce symptoms. Others observe selected asymptomatic patients with serial MRI and neurology. No randomized data exist; decision is individualized by age, curve magnitude, and family preference.

When both detethering and major osteotomy are required, some teams prefer two separate anesthetics to reduce operative time and blood loss. Others perform both in one sitting with two teams. Outcomes appear similar when neuromonitoring is used; choice depends on institutional resources and surgeon experience.

Ultrasound can confirm cord pulsation and free movement after release, but adds time and requires an open dural field. Its routine use is not universal; many experienced teams rely on direct visualization and neuromonitoring alone.

Rare adult presentations with new deficit after decades of compensation exist. Whether to operate on a stable adult with incidentally discovered SCM is controversial; most reserve surgery for progressive symptoms or when major spinal surgery is planned for other reasons.