Congenital anomalies are the product of errors in "embryogenesis"
(malformations consequent to errors in the developmental stages of
the embryo) or the result of intrauterine events that affect embryonic
and fetal growth (deformations and disruptions). As a general rule, it
is apparent that the more complex the formation of a structure, the
more opportunities for malformation. Some of the most serious
neurological abnormalities affect the Brain (conditions that are
reviewed elsewhere on this website) develop in the first two months
of gestation and represent defects in neural tube (the embryonic
precursor of the entire central nervous system) formation. The medical
term for this is "dysraphia". Some of these affect the Spine and
the Spinal Cord as well.
Modern investigative methods, such as amniocentesis and ultrasonography
may provide an accurate in utero detection of many malformations.
Genetic counseling for parents of a child with a major neurological
abnormality is important, since the risk of a subsequent child's having
such a defect is high. These parents frequently also need psychological
help and support. Women who have had a pregnancy resulting in an
infant or fetus with a neural tube defect should be advised that
folic acid supplementation (4 mg/day) before conception and during
early pregnancy may substantially reduce the risk of neural tube
defects in subsequent pregnancies.
Diastematomyelia is a rare congenital anomaly that results in the
"splitting" of the spinal cord in a longitudinal (sagittal) direction.
Females are affected much more commonly than males. This condition
occurs in the presence of an osseous (bone), cartilaginous or fibrous
septum in the central portion of the spinal canal which then produces
a complete or incomplete sagittal division of the spinal cord into
two hemicords. When the split does not reunite distal to the spur,
the condition is referred to as a Diplomyelia (which is a "true
duplication" of the Spinal Cord.)
Diastematomyelia is a "dysraphic state" of unknown embryonic origin,
but is probably initiated by an accessory neurenteric canal (an
additional embryonic spinal canal.) This condition may be an isolated
phenomenon or may be associated with other segmental anomalies of
the vertebral bodies such as Spina Bifida, kyphoscoliosis, butterfly
vertebra, hemivertebra and block vertebrae which are observed in a
high proportion of cases. Scoliosis is usually identified in more
than half of these patients. In most of the symptomatic patients,
the spinal cord is split into halves by a bony spicule or fibrous
band, each half being surrounded by a dural sac. Other conditions,
such as intramedullary tumors, tethered cord, Dermoids, Lipoma,
Syringomyelia, Hydromyelia and Arnold-Chiari malformations have
been described in the medical literature, but are exceptionally
Diastematomyelia usually occurs between 9th Thoracic
and 1st Sacral
levels of the Spinal Column with most being at the level of the
upper lumbar vertebra. Cervical Diastematomyelia is a very rare
entity. The extent (or length of spinal cord involved) varies
from one affected individual to another. In approximately 60% of
patients with Diastematomyelia, the two hemicords, each covered by
an intact layer of pia arachnoid, travel through a single
subarachnoid space surrounded by a single dural sac. Each hemicord
has its own anterior spinal artery. This form of Diastematomyelia
is not accompanied by a bony spur or fibrous band and is rarely
symptomatic unless hydromyelia or tethering is present. The other
40% of patients have a bony spur or a fibrous band that passes
through the two hemicords. In these cases, the dura and arachnoid
are split into two separate dural and arachnoidal sacs, each
surrounding the corresponding hemicord which are not necessarily
symmetric. Each hemicord contains a central canal, one dorsal horn
(giving rise to a dorsal nerve root), and one ventral horn (giving
rise to a ventral nerve root.) One study of these entities
identified the bony spur as typically being situated at the most
inferior aspect of the dural cleft. They advise that if the imaging
study appears to show otherwise, a second spur (present in about
5% of patients with Diastematomyelia) is likely to be present.
The conus medullaris is situated below the L2 level in more than
75% of these Diastematomyelia patients. Thickening of the Filum
Terminale is seen in over half of them. While the level of the
cleft is variable, it is most commonly found in the lumbar region.
The two hemicords usually reunite caudal to the cleft. Occasionally,
however, the cleft will extend unusually low and the cord will
end with two separate coni medullarae and two fila terminale
(sometimes called "Diplomyelia").
The following definitions from may help in the understanding of
Diastematomyelia (di·a·stem·a·to·my·elia) is a congenital
anomaly, often associated with spina bifida, in which the spinal
cord is split into halves by a bony spicule or fibrous band, each
half being surrounded by a dural sac.
Myeloschisis (my·elos·chi·sis) is a developmental anomaly
characterized by a cleft spinal cord, owing to failure of the
neural plate to form a complete neural tube or to rupture of the
neural tube after closure.
Diplomyelia (diplo.my.elia) is a true duplication of spinal
cord in which these are two dural sacs with two pairs or anterior
and posterior nerve roots.
The signs and symptoms of Diastematomyelia may appear at any time of
life, although the diagnosis, in modern times, is usually made in
childhood. Cutaneous lesions (or stigmata), such as a hairy patch,
dimple, Hemangioma, subcutaneous mass, Lipoma or Teratoma (at or
near the level of the Diastematomyelia) override the affected area
of spine in more than half of cases. Neurological symptoms are
nonspecific, indistinguishable from other causes of cord tethering.
The symptoms are caused by tissue attachments that limit the movement
of the spinal cord within the spinal column. These attachments
cause an abnormal stretching of the spinal cord. The course of the
disorder is progressive. In children, symptoms may include the
"stigmata" mentioned above and/or foot and spinal deformities;
weakness in the legs; low back pain; scoliosis; and incontinence.
In adulthood, the signs and symptoms often include progressive
sensory and motor problems and loss of bowel and bladder control.
This delayed presentation of symptoms is related to the degree of
strain placed on the spinal cord over time. Tethered spinal cord
syndrome appears to be the result of improper growth of the neural
tube during fetal development, and is closely linked to spina
bifida. Tethering may also develop after spinal cord injury and
scar tissue can block the flow of fluids around the spinal cord.
Fluid pressure may cause cysts to form in the spinal cord, a
condition called syringomyelia. This can lead to additional loss
of movement, feeling or the onset of pain or autonomic symptoms.
Adult presentation in Diastematomyelia is unusual. With modern
imaging techniques, various types of spinal dysraphism are being
diagnosed in adults with increasing frequency. The common location
is from first to third lumbar vertebrae. Lumbosacral adult
Diastematomyelia is even rarer. Bony malformations and dysplasias
are generally recognized on plain x-rays (which, in modern times
are less frequently done). MRI scanning is often the first (or
"screening test") technique of choice for dysraphism as well as
most spinal conditions. MRI will generally allow adequate analysis
of the spinal cord deformities although it has some limitations in
giving detailed bone anatomy. Combined myelographic and
post-myelographic CT scan is the most effective diagnostic tool in
demonstrating the detailed bone, intradural and extradural
pathological anatomy of the affected and adjacent spinal canal
levels and of the bony spur.
Prenatal ultrasound diagnosis of this anomaly is usually possible
in the early mid third-trimester. An extra posterior echogenic
focus between the fetal spinal laminae is seen with splaying of
the posterior elements, thus allowing for early surgical
intervention and a favorable prognosis. Depending on whether the
Diastematomyelia is isolated, with the skin intact or is in
association with more serious neural tube defects, prenatal
diagnosis of this condition is possible. The cause of progressive
neurological lesions results from the "tethering cord syndrome"
(fixation of the spinal cord) by the Diastematomyelia phenomenon
or any of the associated disorders such as myelodysplasia,
dysraphia of the spinal cord.
We believe that surgical intervention is warranted in patients who
present with new onset neurological signs and symptoms or have a
history of progressive neurological manifestations which can be
related to this abnormality. The surgical procedure required for the
effective treatment of Diastematomyelia requires the decompression of
neural elements and removal of bony spur. This may be accomplished
with or without resection and repair of the duplicated dural sacs.
Our preference is to resect and repair the duplicated dural sacs
since the dural abnormality may partly contribute to the "tethering"
process responsible for the symptoms of this condition.
Minimally Invasive Microsurgical Techniques are becoming available
to accomplish these operative tasks. This most often results in
complete relief of symptoms or stops the progression of symptoms.
Patients, who are asymptomatic and have been identified with this
anomaly while being investigated for other unrelated issues, do
not require surgical treatment. These patients should undergo
periodic neurological examinations since it is known that the
condition can be "progressive". In the event that progressive
neurological manifestations are identified, then a resection
should then be performed.
Additional information is available from the following organizations:
American Association of Neurological Surgeons
American Syringomyelia Alliance Project (ASAP)
P.O. Box 1586
Longview, TX 75606-1586
Tel: 903-236-7079 800-ASAP-282 (272-7282)
National Organization for Rare Disorders (NORD)
P.O. Box 1968
(55 Kenosia Avenue)
Danbury, CT 06813-1968
Tel: 203-744-0100 Voice Mail 800-999-NORD (6673)
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This page last edited on 2/20