Diastematomyelia

Disorder 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.

(Figure)

(Figure)

Split Cord Syndrome.

Unknown, but girls are affected more often than boys.

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

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.

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 at preschool age. The spinal cord is (often asymmetrically) split into two hemicords (with a separate central canal and a spinal anterior artery supplying each half), which reunite caudally of the defect, or, if the lesion extends very low down the lumbar spine, extends in two separate coni medullares and fila terminales.

• Type I: Affects 55% of patients. The two spinal hemicords are surrounded by one dural-arachnoid sleeve. This form often is asymptomatic initially, unless tethering or hydromelia occurs.
• Type II: Affects 45% of patients. Each spinal hemicord has its own dural-arachnoid sleeve, separated by a bony, cartilaginous, or fibrous septum. By fixing the spinal cord to the vertebral bodies on the affected level, this sagittal septum precludes the normal cephalad shift of the spinal cord during growth, resulting in the symptoms described below.

In more than 70% of patients, a localized area of hyperpigmentation and/or hypertrichosis can be found in the skin area directly overlying the defect. The symptomatology varies from asymptomatic to significant neurologic and skeletal abnormalities. Unilateral changes may include foot abnormalities (talipes equinovarus), loss of pain and temperature sensation, and atrophy of the gastrocnemius muscle. Bilateral abnormalities present with sensory and motor changes (gait disturbances) and lead to muscle atrophy, absent ankle jerks, urinary incontinence, and back pain. Neurologic symptoms arise from flexion-extension movements of the spine, resulting in traction and potential trauma. In most of these patients, the conus medullaris is located below the L2 level, and thickening of ...