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, hemi-vertebra and "block"
vertebrae which are identified in a high proportion of cases.
Scoliosis usually affects half of these patients.
In most of the symptomatic patients, the Spinal Cord is split
into halves by a bony spicule or fibrous band with each
half being surrounded by a dural sac. It is
exceptionally rare for any other disease states or conditions
that may the Spinal Cord to be coincident with Diastematomyelia
(such as intramedullary tumors, tethered cord, Dermoids, Lipoma,
Syringomyelia, Hydromyelia and Arnold-Chiari malformations).
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. The length
of Spinal Cord involved is variable from one patient to another.
Involvement of the Cervical levels is a very rare entity.
The two Hemicords, each covered by an intact layer of pia
arachnoid, travel through a single subarachnoid space surrounded by a
single dural sac in 60% of patients with Diastematomyelia. Each
Hemicord has its own blood supply (Anterior Spinal Artery.)
This form of Diastematomyelia is usually 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
The Conus Medullaris (the "end" of the Spinal Cord which
normally is at the T12-L2, levels) is situated below the L2
level in more than 75% of these Diastematomyelia patients.
The Filum Terminale is thickened in over half of these
patients. While the level of the Diastematomyelia is
variable (with most occurring in the Lumbar regions), the two
Hemicords usually reunite at some point distal to the
"cleft". Occasionally the cleft will extend unusually low and
each Cord will end with its own Conus Medullaris and its own Filum
Terminale (a condition referred to as "Diplomyelia").
The following definitions 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
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.
At any age, the cause of progressive neurological deficits
relates to the fixation of the Spinal Cord ("Tethered Spinal Cord
Syndrome") by the Diastematomyelia phenomenon (or any of the
associated disorders of the Spinal Cord.) which creates tissue
attachments that limit the movement of the Spinal Cord within the
Spinal Column. These attachments cause an abnormal
stretching of the Spinal Cord.
While the course of the disorder is progressive, the
neurological symptoms are nonspecific and usually
indistinguishable from other causes of Spinal Cord Tethering.
This delayed presentation of symptoms is related
to the degree of strain placed on the Spinal Cord over time.
In children, symptoms may include:
Adult presentation in Diastematomyelia is
unusual. The symptoms in adulthood often include:
- Foot and spinal deformities
- Weakness in the legs
- Low back pain
Prenatal ultrasound diagnosis of Diastematomyelia is
possible in the early mid third-trimester thus
allowing for early surgical intervention and a
more favorable prognosis depending on whether the
Diastematomyelia is an isolated phenomenon with the skin intact or is
in association with more serious neural tube defects.
- Progressive sensory and motor problems
- Bowel and bladder incontinence
- Onset of pain
- Autonomic symptoms
The signs and symptoms of Diastematomyelia may become manifest
at any time in any patient. In current times the diagnosis is
more commonly made in childhood. It is common for
skin lesions (such as a hairy patch, dimple,
Hemangioma, subcutaneous mass, Lipoma or Teratoma) to be
present at or near the level of the Diastematomyelia.
MRI and CT Scan techniques have dramatically improved
the accurate diagnosis of the various types and
forms of Spinal Dysraphism. In adults the upper three
lumbar vertebrae levels are the most common location for
Diastematomyelia whereas Lumbosacral Diastematomyelia
is very rare.
MRI scanning is probably the most effective
"screening test" for most spinal conditions which
includes "Dysraphism". MRI scanning usually provides
adequate information about the Spinal Cord and its
deformities although it has some significant limitations
in giving detailed bone anatomy. Spinal myelography and more
specifically 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.
Figure 1: Post-myelographic CT Scan (Axial View L2,3 level) Diplomyelia
This demonstrates the asymmetrical
nature of the duplicated Spinal Cords (the 2 dark "spots"
within the Spinal Canal). When there is a bony spicule
present, it is usually projects posteriorly from its site of
origin in the anterior part of the Spinal Canal
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 significant relief of symptoms or stops the
progression of symptoms. In general, more favorable results are
obtained in patients who manifest lesser severity of neurological
deficits, have had symptoms and signs for shorter lengths of time
and are younger.
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.
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This page last edited on 2/19