Diastematomyelia
Encyclopedia
Diastematomyelia is a congenital disorder
in which a part of the spinal cord
is split, usually at the level of the upper lumbar vertebra.
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 distally to the spur, the condition is referred to as a Diplomyelia, or true duplication of the spinal cord.
, kyphoscoliosis
, butterfly vertebra, hemivertebra and block vertebrae which are observed in most of the cases. Scoliosis
is 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 malformation
s have been described in medical literature, but they are exceptionally rare.
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 any 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 showed the bony spur typically situated at the most inferior aspect of the dural cleft. They advised that if the imaging 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 the cases. While the level of the cleft is variable, it is most commonly found in the lumbar region. The two hemicords usually reunite caudally 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 ("Diplomyelia").
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 of anterior and posterior nerve roots.
is usually made in childhood. Cutaneous lesions (or stigmata), such as a hairy patch, dimple
, Hemangioma
, subcutaneous mass, Lipoma
or Teratoma
override the affected area of the spine is found 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.
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 to 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 have a favorable prognosis. Prenate ultrasound could also detect whether the diastematomyelia is isolated, with the skin intact or association with any serious neural tube defects. Progressive neurological lesions may result 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.
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 includes decompression
of neural elements and removal of bony spur. This may be accomplished with or without resection and repair of the duplicated dural sacs. Resection and repair of the duplicated dural sacs is preferred since the dural abnormality may partly contribute to the "tethering" process responsible for the symptoms of this condition.
Observation
Asymptomatic patients do not require surgical treatment. These patients should have regular neurological examinations since it is known that the condition can deteriorate. If any progression is identified, then a resection should be performed.
Congenital disorder
A congenital disorder, or congenital disease, is a condition existing at birth and often before birth, or that develops during the first month of life , regardless of causation...
in which a part of the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
is split, usually at the level of the upper lumbar vertebra.
Diastematomyelia is a rare congenital anomaly that results in the "splitting" of the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
in a longitudinal
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
(sagittal) direction. Females are affected much more commonly than males. This condition occurs in the presence of an osseous (bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
), cartilaginous or fibrous septum in the central portion of the spinal canal
Spinal canal
The spinal canal is the space in vertebrae through which the spinal cord passes. It is a process of the dorsal human body cavity. This canal is enclosed within the vertebral foramen of the vertebrae...
which then produces a complete or incomplete sagittal division of the spinal cord into two hemicords. 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.
Pathophysiology
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 BifidaSpina bifida
Spina bifida is a developmental congenital disorder caused by the incomplete closing of the embryonic neural tube. Some vertebrae overlying the spinal cord are not fully formed and remain unfused and open. If the opening is large enough, this allows a portion of the spinal cord to protrude through...
, kyphoscoliosis
Kyphoscoliosis
Kyphoscoliosis describes an abnormal curvature of the spine in both a coronal and sagittal plane. It is a combination of kyphosis and scoliosis. Kyphoscoliosis is a musculoskeletal disorder causing chronic underventilation of the lungs and may be one of the major causes of pulmonary hypertension...
, butterfly vertebra, hemivertebra and block vertebrae which are observed in most of the cases. Scoliosis
Scoliosis
Scoliosis is a medical condition in which a person's spine is curved from side to side. Although it is a complex three-dimensional deformity, on an X-ray, viewed from the rear, the spine of an individual with scoliosis may look more like an "S" or a "C" than a straight line...
is 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
Spicule
Spicules are tiny spike-like structures of diverse origin and function found in many organisms, such as the copulatory spicules of certain nematodes or the grains on the skin of some frogs.In sponges, spicules perform a structural function....
or fibrous band, each half being surrounded by a dural sac. Other conditions, such as intramedullary tumors, tethered cord, dermoids, lipoma
Lipoma
A lipoma is a benign tumor composed of adipose tissue. It is the most common form of soft tissue tumor. Lipomas are soft to the touch, usually movable, and are generally painless. Many lipomas are small but can enlarge to sizes greater than six centimeters. Lipomas are commonly found in adults...
, syringomyelia
Syringomyelia
Syringomyelia is a generic term referring to a disorder in which a cyst or cavity forms within the spinal cord. This cyst, called a syrinx, can expand and elongate over time, destroying the spinal cord. The damage may result in pain, paralysis, weakness, and stiffness in the back, shoulders, and...
, hydromyelia and Arnold-Chiari malformation
Arnold-Chiari malformation
Arnold–Chiari malformation, or often simply Chiari malformation, is a malformation of the brain. It consists of a downward displacement of the cerebellar tonsils through the foramen magnum , sometimes causing non-communicating hydrocephalus as a result of obstruction of cerebrospinal fluid outflow...
s have been described in medical literature, but they are exceptionally rare.
Diastematomyelia usually occurs between 9th thoracic and 1st sacral
Sacral
Sacral may refer to:*sacred*sacrum...
levels of the spinal column with most being at the level of the upper lumbar vertebra. Cervical
Cervical vertebrae
In vertebrates, cervical vertebrae are those vertebrae immediately inferior to the skull.Thoracic vertebrae in all mammalian species are defined as those vertebrae that also carry a pair of ribs, and lie caudal to the cervical vertebrae. Further caudally follow the lumbar vertebrae, which also...
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
Pia
Pia or Piá may refer to:*Pia, Polynesian arrowroot*Pia , a Korean rock band*Pia Carry, a lifesaving technique*Pia , a given name*Pia, France, a French commune*Pia mater, a layer of the meninges in the brain...
arachnoid
Arachnoid
Arachnoid may refer to:*Relating to arachnids*Arachnoid mater, a layer of the meninges, membranes that contain the central nervous system*Arachnoid , a geological structure found only on the planet Venus...
, travel through a single subarachnoid space
Subarachnoid space
In the central nervous system, the subarachnoid cavity is the interval between the arachnoid membrane and pia mater....
surrounded by a single dural sac. Each hemicord has its own anterior spinal artery
Anterior spinal artery
In human anatomy, the anterior spinal artery is the blood vessel that supplies the anterior portion of the spinal cord. It arises from branches of the vertebral arteries and is supplied by the anterior segmental medullary arteries, including the artery of Adamkiewicz, and courses along the anterior...
. This form of diastematomyelia is not accompanied by any 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
Dura
Dura may refer to:* Dura , a Palestinian town in the southern West Bank located eleven kilometers southwest of Hebron in the Hebron Governorate* Dura language, a critically endangered language of Nepal...
and arachnoid
Arachnoid
Arachnoid may refer to:*Relating to arachnids*Arachnoid mater, a layer of the meninges, membranes that contain the central nervous system*Arachnoid , a geological structure found only on the planet Venus...
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 showed the bony spur typically situated at the most inferior aspect of the dural cleft. They advised that if the imaging appears to show otherwise, a second spur (present in about 5% of patients with diastematomyelia) is likely to be present.
The conus medullaris
Conus medullaris
The conus medullaris is the terminal end of the spinal cord. It occurs near lumbar vertebral levels 1 and 2 . After the spinal cord tapers out, the spinal nerves continue as dangling nerve roots called cauda equina. This terminal nerve root tail is referred to as the filum terminale...
is situated below the L2 level in more than 75% of these diastematomyelia patients. Thickening of the Filum Terminale
Filum terminale
The filum terminale , is a delicate strand of fibrous tissue, about 20 cm. in length, proceeding downward from the apex of the conus medullaris. It gives longitudinal support to the spinal cord and consists of two parts:...
is seen in over half of the cases. While the level of the cleft is variable, it is most commonly found in the lumbar region. The two hemicords usually reunite caudally 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 ("Diplomyelia").
Definitions
The following definitions may help to understand some of the related entities: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
Neural plate
In human embryology, formation of neural plate is the first step of neurulation. It is created by a flat thickening opposite to the primitive streak of the ectoderm.-Development:...
to form a complete neural tube
Neural tube
In the developing vertebrate, the neural tube is the embryo's precursor to the central nervous system, which comprises the brain and spinal cord...
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 of anterior and posterior nerve roots.
Signs and symptoms
The signs and symptoms of diastematomyelia may appear at any time of life, although the diagnosisDiagnosis
Diagnosis is the identification of the nature and cause of anything. Diagnosis is used in many different disciplines with variations in the use of logics, analytics, and experience to determine the cause and effect relationships...
is usually made in childhood. Cutaneous lesions (or stigmata), such as a hairy patch, dimple
Dimple
A dimple is a small natural indentation in the flesh on a part of the human body, most notably in the cheek or on the chin.-More about dimples:...
, Hemangioma
Hemangioma
A hemangioma of infancy is a benign self-involuting tumor of endothelial cells, the cells that line blood vessels. It usually appears during the first weeks of life and sometimes resolves by age 10. In more severe case hemangioma may have permanency, if not treated by a physician...
, subcutaneous mass, Lipoma
Lipoma
A lipoma is a benign tumor composed of adipose tissue. It is the most common form of soft tissue tumor. Lipomas are soft to the touch, usually movable, and are generally painless. Many lipomas are small but can enlarge to sizes greater than six centimeters. Lipomas are commonly found in adults...
or Teratoma
Teratoma
A teratoma is an encapsulated tumor with tissue or organ components resembling normal derivatives of all three germ layers. There are rare occasions when not all three germ layers are identifiable...
override the affected area of the spine is found 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
Stigmata
Stigmata are bodily marks, sores, or sensations of pain in locations corresponding to the crucifixion wounds of Jesus, such as the hands and feet...
" mentioned above and/or foot and spinal deformities; weakness in the legs; low back pain
Low back pain
Low back pain or lumbago is a common musculoskeletal disorder affecting 80% of people at some point in their lives. In the United States it is the most common cause of job-related disability, a leading contributor to missed work, and the second most common neurological ailment — only headache is...
; scoliosis
Scoliosis
Scoliosis is a medical condition in which a person's spine is curved from side to side. Although it is a complex three-dimensional deformity, on an X-ray, viewed from the rear, the spine of an individual with scoliosis may look more like an "S" or a "C" than a straight line...
; and incontinence
Incontinence
Incontinence or Incontinent may refer to:*Fecal incontinence, the inability to control one's bowels*Incontinence *Incontinent , a 1981 album by Fad Gadget*Urinary incontinence, the involuntary excretion of urine...
. 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
Tethered spinal cord syndrome
Tethered spinal cord syndrome or occult spinal dysraphism sequence refers to a group of neurological disorders related to malformations of the spinal cord. The various forms include: tight filum terminale, lipomeningomyelocele, split cord malformations, dermal sinus tracts, dermoids, and cystoceles...
appears to be the result of improper growth of the neural tube during fetal development, and is closely linked to spina bifida
Spina bifida
Spina bifida is a developmental congenital disorder caused by the incomplete closing of the embryonic neural tube. Some vertebrae overlying the spinal cord are not fully formed and remain unfused and open. If the opening is large enough, this allows a portion of the spinal cord to protrude through...
.
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
Syringomyelia
Syringomyelia is a generic term referring to a disorder in which a cyst or cavity forms within the spinal cord. This cyst, called a syrinx, can expand and elongate over time, destroying the spinal cord. The damage may result in pain, paralysis, weakness, and stiffness in the back, shoulders, and...
. This can lead to additional loss of movement, feeling or the onset of pain or autonomic
Autonomic nervous system
The autonomic nervous system is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils,...
symptoms.
Diagnosis
Adult presentation in diastematomyelia is unusual. With modern imaging techniques, various types of spinal dysraphism are being diagnosed in adults with increasing frequency. The commonest location of the lesion is at first to third lumbar vertebrae. Lumbosacral adult diastematomyelia is even rarer. Bony malformations and dysplasias are generally recognized on plain x-rays. MRI scanning is often the first choice of screening and diagnosis. MRI generally give adequate analysis of the spinal cord deformities although it has some limitations in giving detailed bone anatomy. Combined myelographic and post-myelographic CTComputed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
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 to 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 have a favorable prognosis. Prenate ultrasound could also detect whether the diastematomyelia is isolated, with the skin intact or association with any serious neural tube defects. Progressive neurological lesions may result 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.
Treatment
SurgerySurgical 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 includes decompression
Decompression
Decompression has several meanings:* Decompression , the release of pressure and the opposition of physical compression* Decompression sickness, a condition arising from the precipitation of dissolved gases into bubbles inside the body on depressurization* Decompression , a procedure used to treat...
of neural elements and removal of bony spur. This may be accomplished with or without resection and repair of the duplicated dural sacs. Resection and repair of the duplicated dural sacs is preferred since the dural abnormality may partly contribute to the "tethering" process responsible for the symptoms of this condition.
Observation
Asymptomatic patients do not require surgical treatment. These patients should have regular neurological examinations since it is known that the condition can deteriorate. If any progression is identified, then a resection should be performed.