Diastematomyelia (Split Cord Malformation)

What happens in diastematomyelia

During the first weeks of pregnancy, the neural tube folds to form the spinal cord. In split cord malformation, an abnormal connection during this stage leads to the cord forming as two "hemicords" over a segment, each with its own set of nerve roots.

The split is most common in the lower thoracic and lumbar spine. It is more frequent in girls. It often occurs with other spinal abnormalities: vertebral defects, spina bifida, thickened filum terminale, syringomyelia and congenital scoliosis.

Symptoms and signs

Skin markers (present in most cases)

• a tuft of hair over the spine (the classic sign)
• a dimple above the buttock crease
• a birthmark, hemangioma or skin tag
• a fatty lump

Neurological and orthopedic signs

The spur or band anchors the cord. As the spine grows faster than the cord, the cord is stretched (tethered), causing:

• weakness or wasting of one leg, often with one smaller calf or foot
• foot deformities, such as a high arch or clubfoot
• numbness or altered sensation in the legs
• back and leg pain, often worse with bending or activity
• scoliosis
• bladder problems: incontinence, urgency, recurrent infections, poor emptying
• constipation or bowel incontinence

Symptoms may appear in childhood during growth spurts, or not until adulthood, sometimes after an injury, heavy lifting or pregnancy. See tethered cord syndrome.

Diagnosis

• Prenatal ultrasound sometimes shows the bony spur.
• Spinal ultrasound in young infants with skin markers.
• MRI of the whole spine: the key test; shows the split, the level of the cord, tethering, syrinx and other abnormalities.
• CT scan: shows the bony spur in detail for surgical planning.
• Urodynamic studies: assess bladder function.
• Neurological and orthopedic exams to document baseline function.

Treatment

Surgery

Surgery is recommended for Type I malformations with symptoms, and often for Type I without symptoms in children because of the risk of progressive damage during growth. The neurosurgeon:

1. removes the bony or cartilaginous spur and the dural sleeve around it
2. reunites the dura into a single sac
3. releases other tethering structures, such as a thickened filum terminale

Type II malformations are operated on if they cause symptoms or tethering.

Results

Surgery is most effective at stopping progression. Pain often improves. Existing weakness, numbness and bladder dysfunction may improve partly, but long-standing deficits often persist, which is why early recognition matters.

Other care

• orthopedic management of scoliosis and foot deformities
• physical therapy
• bladder management, including timed voiding or intermittent catheterization
• long-term follow-up with MRI and clinical exams, as re-tethering can occur

Outlook

Many people do well, especially when diagnosed and treated before significant nerve damage. Without treatment, symptoms often worsen gradually with growth or physical stress.

Frequently asked questions

What is diastematomyelia?

Diastematomyelia, or split cord malformation, is a rare birth defect in which a section of the spinal cord is divided into two halves, often by a spike of bone or a fibrous band. It usually affects the lower back and can tether the spinal cord.

What are the symptoms of split cord malformation?

Common signs are a hairy patch or dimple over the spine, leg weakness or numbness, one smaller leg or foot, foot deformities, back pain, scoliosis and bladder or bowel problems. Some people have no symptoms until adulthood.

How is diastematomyelia diagnosed?

MRI of the whole spine is the main test, showing the split cord and any tethering. CT helps visualize a bony spur. Babies with skin markers on the lower back may first have a spinal ultrasound.

Does diastematomyelia always need surgery?

No. Type I malformations, which have a bony spur, usually need surgery, especially in growing children. Type II malformations without symptoms may be monitored. Surgery is recommended when symptoms or progressive tethering develop.

Can adults have diastematomyelia?

Yes. Some people are diagnosed in adulthood when symptoms such as back pain, leg weakness or bladder problems appear, sometimes after an injury, heavy lifting or pregnancy. Surgery can help stop further decline.