Diastematomyelia

At a glance

It is a rare form of spinal dysraphism resulting in division of the spinal cord into two parts by a fibrocartilaginous or bony posterior projection of the posterior vertebral body. It is characterized by the presence of a complete or incomplete sagittal cleft of varying extent that splits the spinal cord into two hemicords at the conus medullaris, or filum terminale. It is often associated with splaying of the posterior vertebral elements. This condition is caused by an osseous, cartilaginous, or fibrous septum. It may be isolated or associated with other segmental anomalies of the vertebral bodies. When the split does not reunite distally to the spur, the condition is referred to as a diplomyelia or true duplication of the spinal cord. The clinical features may include neurologic deficits of the lower limbs and perineum, causing gait disorders, sphincter disturbances, muscular atrophy, reflex changes, congenital scoliosis, and foot deformities.

Synonym

Split Cord Syndrome.

Incidence

The exact incidence remains unknown. Girls are affected more often than boys.

Genetic inheritance

There are a few reports of autosomal recessive cases in the literature.

Definitions

There are related radiological and clinical entities that may occasionally confuse the diagnosis of diastematomyelia. They consist of:

• Myeloschisis: Characterized by a cleft spinal cord as a result of a failure of the neural plate to close. It corresponds to: spina bifida occulta, meningocele, and myelomeningocele. The most frequent is located in the lumbar region but occasionally can be seen in the thoracic and neck regions. Signs of spina bifida occulta include hairy patch, dimple, dark spot, or swelling at the level of the spine defect. Meningocele is associated with mild physical anomalies Myelomeningocele, also known as open spina bifida, is the most severe form. It is characterized by gait problem, hydrocephalus, tethered spinal cord, and most often latex allergy.

• Diplomyelia: Characterized by a complete duplication of spinal cord where two well defined dural sacs are seen and two pairs of anterior and posterior nerve roots can be located.

Pathophysiology

Differentiation of the neural ectoderm from the epithelial ectoderm occurs between weeks 3 and 5 of gestation. Diastematomyelia is a result of a defect in neural tube fusion with persistence of the mesodermal tube from the developing neurenteric canal, which acts as a septum. Neurologic signs are thought to result from traction and trauma with extension and flexion of the cord.

Diagnosis

Neurologic presentation and confirmation by imaging of the spinal cord by either CT or MRI scanning. Approximately 50% of cases involve the first three lumbar vertebrae. The symptoms usually are not obvious until the child starts to walk. Most often, however, patients present ...