PEDIATRICS
Terms & Definitions
ACQUIRED SPINAL ABNORMALITY IN CHILDREN
Syringomyelia: A spinal fluid-filled cyst in the center of the spinal cord that can extend from just one spinal level or involve the entire spinal cord. The cyst can expand and cause compression on the spinal cord and lead to weakness or numbness. Many times syringomyelia is caused by a blockage to spinal fluid flow out of the spine caused by a Chiari malformation or a trauma. Syringomyelia needs to be treated when it causes symptoms. An MRI can detect very small amounts of fluid in the normal central canal of the spinal cord.
Treatment of Syringomyelia: The most effective treatment of syringomyelia is to remove the obstruction of spinal fluid flow by operating on the Chiari malformation or the obstruction caused by trauma. If that does not work, a very fine tube can be threaded into the spinal fluid cyst. The other end of the tube can be placed into the spinal fluid (cyst subarachnoid shunt), into the cavity of the lung (spinal cyst pleural shunt), or to the belly cavity (cyst peritoneal shunt).
Brachycephaly: Towering of the skull where the skull is abnormally elevated and short from front to back.
CONGENITAL BRAIN ABNORMALITY
Chiari malformation: The hole in the skull at the bottom that normally allows the brain to connect to the spinal cord and exit the skull is called the foramen magnum. When part of the lowest part of the brain, the cerebellum, extends through the hole more than 5 mm it is called a Chiari malformation. Chiari was a pathologist who described these malformations in the 19th Century. A Chiari I malformation involves part of the cerebellum called the tonsil extending through the foramen magnum and out into the spinal canal. Many times the tonsil can extend down as far as the second cervical vertebrae. Chiari II malformation occurs in patients with neural tube defects such as myelomeningocele. Chiari II malformation does not occur in patients without a neural tube defect. It is a far more extensive malformation and includes the vermis, another part of the cerebellum, extending down through the foramen magnum, or hole in the bottom of the skull. It also involves abnormalities to the lower brainstem (medullary kink), the upper mid brain (tectal beak), the membrane between the two halves of the brain and an enlarged connection between the two parts of the brain called the thalamus. Chiari III and Chiari IV malformations are extraordinarily rare and involve more extensive malformations of the base of the skull and upper cervical spine.
Encephalocele: A type of neural tube defect in which there is failure of the skull to close and the brain therefore protrudes out through a hole in the skull. This can be an extraordinarily small pinhole or it can be a very large hole in which a large amount of brain protrudes. In many patients, the skin is abnormal or gone, the bone is gone, the leather sac surrounding the brain (dura matter) is also not present. Encephaloceles can occur in the back of the head, in the very bottom of the skull in the back or in the front, between the eyes, or over the forehead.
Hydrocephalus: Adults make nearly a pint of spinal fluid a day. They do this by making nearly one ounce every hour of spinal fluid. The entire brain and spinal cord contains about four to six ounces of spinal fluid at any one time. The spinal fluid circulates around, comes inside the brain, around the spinal cord and then out of the skull through valves called arachnoid granulations into veins at the top of the skull and into the blood stream. When there is blockage to this flow anywhere within the brain or in the valves at the top of the skull, this leads to backing up of the spinal fluid and a condition called hydrocephalus. Hydrocephalus can be caused by the Chiari type II malformation, narrowing of the passageways of the brain inside the brain (aqueductal stenosis), or events that leave either a large amount of white blood cells (infection) or red blood cells (hemorrhage). The development of hydrocephalus can occur in the womb all the way through adulthood. Other causes of hydrocephalus can include certain types of brain tumors or cysts.
CONGENITAL SPINE DEFORMITY
Neural Tube Defects: Neural tube defects occur in the embryo at about 20 days post conception. These are deformities that involve either the brain on the spinal cord. There is an entire spectrum of severity of the abnormalities.
Craniofacial Abnormality: When a baby is born with an abnormality that causes deformity of the skull shape or the face, this is called a craniofacial abnormality.The vast majority of these abnormalities are caused by bony deformities or growth problems. They can also be caused by cysts or other abnormalities within the skull.
Craniosynostosis or Craniostenosis: Premature closure or fusion of two adjacent bones across a suture. This can lead to characteristic skull deformities in infants. The cause of the closure is usually uterine constraint caused by either twin birth or the baby dropping into the birth canal earlier than usual. It can be part of a congenital syndrome as well. The deformity from premature suture closure has a number of characteristic shapes. Plagiocephaly is flattening of one corner of the skull. Plagiocephaly can be frontal when one of the frontal bones is flattened or occipital when one of the bones in the back of the head is flattened. Dolichocephaly or scaphocephaly is caused when the middle suture of the skull is closed. This leads to a very elongated, narrow head often with bulging of the forehead and a rounded knob-like characteristic in the back of the head.
Surgery for craniosynostosis falls into three major types: 1) Lateral canthal advancement- surgical reconstruction of an abnormal eye socket caused by premature closure of either the coronal or metopic sutures. It can be done on one side (unilateral) or both sides (bilateral); 2) Calvarial reconstruction- the major reconstruction of all of the skull to reposition the bones due to premature closure of the sutures. It can be done for a number of causes; 3) Suturectomy- the fused or closed suture can be cut out for treatment of craniosynostosis. This is a much less invasive procedure. The outcome is much less satisfactory unless followed by several months of molding helmet therapy to reshape the bones.
Molding Helmet: A custom designed helmet that is used on an infant to reshape skull deformities. It can be used in positional head deformities or following suturectomy for craniosynostosis.
Positional Deformity: When a newborn baby lies in the same position on the head when it sleeps for the first several months the weight of the brain can deform the skull. This deformity is characteristic and comes in two forms: 1) flattening of the back of the head more on one side than the other which is called positional plagiocephaly; 2) if the flattening is in the middle of the back and equal on both sides it is called positional brachycephaly.
SPINAL ABNORMALITIES
Arachnoid Cyst: The arachnoid is a very thin membrane (just a few cells thick), which is waterproof and holds the spinal fluid inside of it. If the arachnoid is torn it can form a cyst. This cyst can contain spinal fluid and can grow. An arachnoid cyst is a spinal fluid containing cyst with an arachnoid in the wall. They can occur in the brain or in the spine.
Lipomeningocele or Lipomyelomeningocele: A neural tube defect where there is normal skin covering, but underneath there is a fatty growth or tumor. This fatty growth connects to the tip of the spinal cord. Often babies have normal strength and sensation at birth but can deteriorate due to pressure or pulling of the spinal by the lipomyelomeningocele.
Myelomeningocele or Spina Bifida Cystica: An open, exposed spinal cord. The skin, bones and coverings of the spinal cord as well as the spinal cord fail to curl up and close. This leaves the spinal cord exposed to amniotic fluid. This causes permanent damage to the spinal cord. The neurologic problems that result are related to how much of the spinal cord is exposed and at what level of the spine it is exposed.
Neurenteric Cyst: A very rare abnormality. This involves cells that normally would make stomach or lung tissue but get caught inside the spinal canal. They will form a sac which will secrete protein material like it does in the gut or stomach or lungs. This material then forms a cyst which can grow and cause compression of the spine.
Phylum Terminale: In all babies there is a band of tissue that extends from the tip of the spinal cord down to the tip of the spine. This is called phylum terminale. It is usually not much thicker than two or three hairs in diameter. If it becomes more thickened it can pull the spinal cord down and cause tethered cord syndrome.
Tethered Spinal Cord: During the first and early second trimester of pregnancy, the spinal cord with the nerves is as long as the bony spine that surrounds it. In the middle of the second trimester, the bones grow faster than the spinal cord and at birth most babies have a spinal cord that only extends down to the second lumbar spinal vertebrae, a lot of those are just nerves (cauda equina). When the spinal cord does not rise up it is because it is tied down to the bony structures. This tying down is called tethering. The tethering can be caused by a thickened phylum terminale, lipomyelomeningocele or scar tissue following a correction of a myelomeningocele or lipomyelomeningocele.
Suture: The baby's skull is composed of five arch bones and a number of small bones. The joints between the bones are very leather-like and are called sutures. The purpose of the sutures are twofold: 1) to allow the skull to mold so that the baby can get out of the birth chamber; 2) to allow the baby's brain to grow very rapidly in the first several months after birth. The rapid growth of the brain stretches these leather-like sutures, pushes the bones apart and then the bones will grow toward each other, closing the gap. If one of the sutures becomes fused too early it can lead to a deformity of the skull called craniosynostosis or craniostenosis.
