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.
Asymmetrical splitting of the spinal cord into two hemicords (arrows) in
Localized hypertrichosis along the spine is often an indicator of an
underlying pathology in that area, as seen in this patient with
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