Medical Glossary

Acrocallosal syndrome, Schinzel type
Agenesis of the corpus callosum
Aicardi syndrome
Andermann Syndrome
Anterior Commissure
Arnold Chiari Malformation
Asperger’s syndrome (AS)
Autism
Bundles of Probst
Colpocephaly
Corpus callosum
Dandy-Walker syndrome
Dysgenesis of the corpus callosum
Encephalocele
Genu
Heterotopia (singular heterotopion)
Hippocampal Commissure
Holoprosencephaly
Hydrocephalus
Hypertelorism, Ocular Hypertelorism , Orbital Hypertelorism
Hypogenesis of the corpus callosum
Hypoplasia of the corpus callosum
Lissencephaly
Macrocephaly
Meningocele
Meningoencephalocele
Menkes disease
Microcephaly
Migrational Disorder see Heterotopia
Nonverbal Learning Disorders (NLD)
Oculocerebrocutaneous Syndrome (Delleman syndrome)
Posterior Commissure
Sensory Integration Dysfunction
Septo-optic dysplasia (SOD)
Shapiro Syndrome
Splenium
Trisomy 13 syndrome
Trisomy 18 syndrome

Acrocallosal syndrome, Schinzel type:

A rare genetic disorder that is apparent at birth (congenital). Associated symptoms and findings may be variable, including among affected members of the same family. However, the disorder is typically characterized by underdevelopment (hypoplasia) or absence (agenesis) of the corpus callosum and moderate to severe mental retardation. In addition, many affected individuals have malformations of the skull and facial (craniofacial) region and/or distinctive abnormalities of the fingers and toes (digits). Characteristic craniofacial abnormalities may include an unusually large head (macrocephaly) with a prominent forehead; widely spaced eyes (ocular hypertelorism); downslanting eyelid folds (palpebral fissures); a small nose with a broad nasal bridge; and malformed (dysplastic) ears. Most affected individuals also have distinctive digital malformations, such as the presence of extra (supernumerary) fingers and toes (polydactyly) and webbing or fusion (syndactyly) of certain digits. Additional physical abnormalities may also be present, including growth retardation, resulting in short stature. Although autosomal recessive inheritance has been suggested, acrocallosal syndrome often appears to occur randomly for unknown reasons (sporadically).

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Agenesis of the corpus callosum:

A congenital abnormality in which there is a partial or complete absence of the corpus callosum.

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Aicardi syndrome:

A genetic disorder characterized by the partial or complete agenesis of the corpus callosum, infantile spasms (a characteristic form of childhood seizures), mental retardation, and an ocular (eye) abnormality called chorioretinal lacunae in which there are lacunae (holes) in the retina of the eye. Aicardi syndrome may be associated with other brain defects such as small brain (microcephaly) or cerebrospinal fluid-filled cavities or gaps in the brain (porencephalic cysts). Features associated with Aicardi syndrome include cleft lip and/or palate, fatty tumors (lipomas) of the scalp, blood vessel malformations (cavernous hemangiomas), rib and vertebral defects and scoliosis (curved spine).

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Andermann Syndrome:

Characterized by degeneration of both the central and peripheral nervous system. Two-thirds of victims are born without a corpus callosum. Symptoms include a decrease in mental ability, generalized weakness, loss of muscle bulk and scoliosis. In their early teens, patients have difficulty walking and are eventually confined to a wheelchair. In their twenties, they often develop psychosis or a hallucinatory disorder. Only people born with two abnormal copies of the Andermann Syndrome gene, whichever gene that turns out to be, acquire the disease. The disease is far more concentrated in Quebec than anywhere else in the world. The appearance of children with the disorder is very typical. They almost resemble each other, as if they were brother and sister. It became obvious that this disorder was common to the Saguenay Lac St. Jean region. Physical features include brachycephaly, large ears, widely spaced eyes (hypertelorism), high arched palate, open mouth with protruding fissured tongue, hand and foot deformities, absence of reflexes (areflexia), poor muscle tone (hypotonia), and weakness, among others.

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Anterior Commissure:

This structure in the anterior brain contain about 50,000 neurons and connects the left and right hemispheres. It is separate from the corpus callosum. It courses through the lamina terminalis in the median plane, and interconnects structures of the olfactory system, amygdaloid complexes, and middle and inferior temporal gyri. Commissural fibers are interhemispheric and connect mirror image (homotopic) regions of the two hemispheres.

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Arnold Chiari Malformation:

This is a benign structural problem affecting the cerebellum. Essentially there is extra cerebellum crowding the outlet of the brainstem/spinal cord from the skull on its way to the spinal canal. This crowding will commonly lead to headaches, neck pain, funny feelings in the arms and/or legs, stiffness, and less often will cause difficulties with swallowing or gagging. Often the symptoms are made worse with straining. When the diagnosis is suspected the study of choice is an MRI scan. These malformations are very difficult to see on CT scans and impossible to see on plain x-rays. Sometimes these malformations can be made worse by, or can cause hydrocephalus. In addition they can often lead to fluid filled cavities in the spinal cord known as syrinxes. In general the symptoms of the type I malformations are less severe than that of the type II malformation. Untreated, the chronic crowding of the brainstem and spinal cord can lead to very serious consequences including paralysis. In addition they can lead to the development of syrinxes which may further injure the child’s spinal cord and function. There are many ways to treat Chiari malformations, but all require surgery.

  • The most common form of is Type I, which involves extension of only the lower part of the cerebellum into the foramen magnum without involving the brainstem. It is generally asymptomatic during childhood, but often manifests with headaches and cerebellar symptoms.
  • Type II (also called Arnold-Chiari malformation) is usually accompanied by a myelomeningocele-a form of spina bifida causing the spinal cord to protrude through an opening in the back. This can cause partial or complete paralysis below the spinal opening. There is abnormal development of the cerebellar vermis (the area between the cerebellar hemispheres) and medulla, and they both descend into the foramen magnum. Hydrocephalus is nearly always present.
  • Type III causes severe neurological defects. It is associated with an encephalocele-a form of spina bifida causing cerebral spina fluid, brain tissue, and meninges to protrude through an opening in the back.
  • Type IV involves a failure of brain development.

Asperger’s syndrome (AS):

An autism spectrum disorder. It is milder than autism but shares some of its symptoms. It is more common in boys than girls. An obsessive interest in a single subject is a major symptom of AS. Some children with AS have become experts on dinosaurs, makes and models of cars, even objects as seemingly odd as vacuum cleaners. Their expertise, high level of vocabulary and formal speech patterns make them seem like little professors. Children with AS have trouble reading social cues and recognizing other people’s feelings. They may have strange movements or mannerisms. All of these make it difficult for them to make friends. Problems with motor skills are also common in children with AS. They may be late learning to ride a bike or catch a ball, for example. Treatment focuses on the three main symptoms: poor communication skills, obsessive or repetitive routines, and physical clumsiness.

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Autism:

Autism is one of a group of disorders known as autism spectrum disorders (ASDs). ASDs are developmental disabilities that cause substantial impairments in social interaction and communication and the presence of unusual behaviors and interests. Many people with ASDs also have unusual ways of learning, paying attention, and reacting to different sensations. The thinking and learning abilities of people with ASDs can vary—from gifted to severely challenged. An ASD begins before the age of 3 and lasts throughout a person’s life. ASDs include autistic disorder, pervasive developmental disorder – not otherwise specified (PDD-NOS, including atypical autism), and Asperger syndrome. These conditions all have some of the same symptoms, but they differ in terms of when the symptoms start, how severe they are, and the exact nature of the symptoms. The three conditions, along with Rett syndrome and childhood disintegrative disorder, make up the broad diagnosis category of pervasive developmental disorders.

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Bundles of Probst:

In ACC the corpus callosum fibers which were unable to cross between the hemispheres form neural tracks within each hemisphere running from front to back of the brain.

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Colpocephaly:

A brain disorder in which there is an abnormal enlargement of the occipital horns of the brain –the posterior or rear portion of the lateral ventricles of the brain. This enlargement occurs when there is an underdevelopment or lack of thickening of the white matter in the posterior cerebrum. Colpocephaly is characterized by microcephaly (abnormally small head) and mental retardation. Other features may include motor abnormalities, muscle spasms, and seizures.

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Corpus callosum:

The main transverse tract of fibers that connects the two cerebral hemispheres. It contains over 200 million nerve fibers. The primary function of the corpus callosum is to integrate motor, cognitive, and sensory functions between the cerebral hemispheres.

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Dandy-Walker syndrome:

A congenital brain malformation involving the cerebellum and the fluid filled spaces around it. The key features of this syndrome are an enlargement of the fourth ventricle, a partial or complete absence of the cerebellar vermiss (the area between the two cerebellar hemispheres) and cyst formation near the internal base of the skull. An increase in the size of the fluid spaces surrounding the brain as well as an increase in pressure may also be present. The syndrome can appear dramatically or develop unnoticed. Symptoms, which often occur in early infancy, include slow motor development and progressive enlargement of the skull. In older children, symptoms of increased intracranial pressure such as irritability, vomiting and convulsions and signs of cerebellar dysfunction such as unsteadiness, lack of muscle coordination or jerky movements of the eyes may occur. Other symptoms include increased head circumference, bulging at the back of the skull, problems with the nerves that control the eyes, face and neck, and abnormal breathing patterns. Dandy-Walker syndrome is frequently associated with disorders of other areas of the central nervous system including absence of the corpus callosum, and malformations of the heart, face, limbs, fingers and toes. The Dandy Walker complex is a genetically sporadic disorder that occurs one in every 25,000 live births, mostly in females.

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Dysgenesis of the Corpus Callosum:

A malformation of the corpus callosum.

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Encephalocele:

A rare disorder in which the bones of the skull do not close completely, creating a gap through which cerebral spinal fluid, brain tissue and the membrane that covers the brain (the meninges) can protrude into a sac-like formation. An encephalocele (sometimes called a cephalocele, or meningoencephalocele) is classified as a neural tube defect.

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Genu:

The anterior portion of the corpus callosum which curves ventrally and forms the rostrum.

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Heterotopia (singular heterotopion):

A neurological disorder caused by clumps of grey matter being located in the wrong part of the brain. It is characterized as a type of cortical dysplasia. The neurons in heterotopia appear to be normal, except for their mislocation. Nuclear studies have shown glucose metabolism equal to that of normally positioned gray matter. The condition causes a variety of symptoms, but usually includes some degree of epilepsy or recurring seizures, and often affects the brain’s ability to function on higher levels. Symptoms range from nonexistent to profound.

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Hippocampal Commissure:

Connects the left and right hippocampi (memory centers of the brain), dentate gyri, and hippocampal gyri. It is located beneath the posterior portion of the corpus callosum. Commissural fibers are interhemispheric and connect mirror image (homotopic) regions of the two hemispheres.

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Holoprosencephaly:

A relatively common birth defect of the brain, which often also affects facial features, causing closely spaced eyes, small head size, and sometimes clefts of the lip and roof of the mouth. Not all individuals with holoprosencephaly (HPE) are affected to the same degree, even in families where more than one individual has this predisposition. Holoprosencephaly is characterized by the failure of the prosencephalon (the forebrain of the embryo) to develop. During normal development, the forebrain is formed and the face begins to develop in the fifth and sixth weeks of pregnancy. Holoprosencephaly is caused by a failure of the embryo’s forebrain to divide to form bilateral cerebral hemispheres (the left and right halves of the brain), causing defects in the development of the face and in brain structure and function. There are three classifications of holoprosencephaly. Alobar holoprosencephaly, the most serious form in which the brain fails to separate, is usually associated with severe facial anomalies. Semilobar holoprosencephaly, in which the brain’s hemispheres have a slight tendency to separate, is an intermediate form of the disease. Lobar holoprosencephaly, in which there is considerable evidence of separate brain hemispheres, is the least severe form. In some cases of lobar holoprosencephaly, the patient’s brain may be nearly normal. Holoprosencephaly, once called arhinencephaly, consists of a spectrum of defects or malformations of the brain and face. At the most severe end of this spectrum are cases involving serious malformations of the brain, malformations so severe that they are incompatible with life and often cause spontaneous intrauterine death. At the other end of the spectrum are individuals with facial defects – which may affect the eyes, nose, and upper lip – and normal or near-normal brain development. Seizures and mental retardation may occur.

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Hydrocephalus:

An abnormal buildup of cerebrospinal fluid (CSF) in the ventricles of the brain. The fluid is often under increased pressure and can compress and damage the brain. Hydrocephalus can arise before birth or any time afterward. It may be due to many causes including a birth defect, hemorrhage into the brain, infection, meningitis, tumor, or head injury. Most forms of hydrocephalus are the result of obstructed CSF flow in the ventricular system. With birth defects, physical obstruction of CSF flow in the ventricular system is usually the cause of the hydrocephalus. Hydrocephalus is a common companion of spina bifida (meningomyelocele).

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Hypertelorism, Ocular Hypertelorism , Orbital Hypertelorism:

Increase in the interorbital distance, frequently due to an enlarged sphenoid bone, often associated with clavicular and cranial (cleidocranial) or craniofacial disorders of bone development (dysostosis) and sometimes with mental deficiency. Also called Greig’s Syndrome.

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Hypogenesis of the Corpus Callosum:

A partial formation of the corpus callosum

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Hypoplasia of the Corpus Callosum:

Underdevelopment of the corpus callosum.

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Lissencephaly:

A brain malformation characterized by microcephaly and the lack of normal convolutions (folds) in the brain. Lissencephaly literally means “smooth brain.” It is caused by defective neuronal migration, a defect in the process in which nerve cells move from their place of origin to their permanent location. The surface of a normal brain is formed by a complex series of folds and grooves. The folds are called gyri or convolutions, and the grooves are called sulci. In children with lissencephaly, the normal convolutions are absent or only partly formed, making the surface of the brain smooth. Children born with lissencephaly may have an unusual facial appearance, difficulty swallowing, failure to thrive, and severe psychomotor retardation. Anomalies of the hands, fingers, or toes, muscle spasms, and seizures may also occur.

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Macrocephaly:

A type of cephalic disorder, macrocephaly is a condition in which the head circumference is larger than average for the age and sex of the infant or child. It is a descriptive rather than a diagnostic term, and is a characteristic of a variety of disorders. Macrocephaly also may be inherited. Although one form of macrocephaly may be associated with mental retardation, in approximately one-half of cases mental development is normal. Macrocephaly may be caused by an enlarged brain or hydrocephalus.

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Meningocele:

A rare disorder in which the bones of the skull do not close completely, creating a gap through which cerebral spinal fluid and the membrane that covers the brain (the meninges) can protrude into a sac-like formation. It is classified as a neural tube defect.

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Meningoencephalocele:

The protrusion of the meninges and the brain through a congenital defect in the cranium, also called encephalomeningocele.

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Menkes disease:

A genetic disorder of copper metabolism that is detectable before birth (prenatally) and which follows a progressively degenerative path involving several organs of the body but especially the brain. It is characterized by seizures, mental retardation, stunted growth, failure to thrive, unstable body temperature, and very unusual color and texture of hair. It is the failure of the copper transport systems within the cell and then across the cell membrane that are responsible for the symptoms of the disorder. Because of the failure of this transport system, copper is unavailable to various cells where it is essential for the structure and function of various enzymes that control the development of hair, brain, bones, liver and arteries. Menkes disease is inherited as an X-linked recessive trait and is found disproportionately in male children.

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Microcephaly:

An abnormally small head due to failure of brain growth. In precise terms, microcephaly is a head circumference that is more than 2 standard deviations below the normal mean for age, sex, race, and gestation. (Some authorities define microcephaly as more than 3 standard deviations below the mean.)

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Migrational Disorder: see Heterotopia

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Nonverbal Learning Disorders (NLD):

A neurological syndrome consisting of specific assets and deficits. The assets include early speech and vocabulary development, remarkable rote memory skills, attention to detail, early reading skills development and excellent spelling skills. In addition, these individuals have the verbal ability to express themselves eloquently. Moreover, persons with NLD have strong auditory retention. Four major categories of deficits and dysfunction also present themselves: •motor: lack of coordination, severe balance problems, and difficulties with graphomotor skills •visual-spatial-organizational: lack of image, poor visual recall, faulty spatial perceptions, difficulties with executive functioning and problems with spatial relations. •social: lack of ability to comprehend nonverbal communication, difficulties adjusting to transitions and novel situations, and deficits in social judgment and social interaction •sensory: sensitivity in any of the sensory modes: visual, auditory, tactile, taste or olfactory

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Oculocerebrocutaneous Syndrome (Delleman syndrome):

A multiple congenital anomaly syndrome characterized by orbital cysts, cerebral malformations, and focal dermal hypoplasia. In addition to orbital cysts there might be microphthalmia, a persistent hyaloid artery and numerous skin tags involving the eyelids, especially at their lateral margins, but also on the cheeks. Aplasia (localized areas of the skin are absent or scarred at birth), hypoplasia, and punched-out areas of skin over the ears, behind the ears, on the scalp, trunk and lips occur. Mental retardation, hydrocephalus, porencephaly (central nervous system disorder involving a cyst or cavity in a cerebral hemisphere of the brain), agenesis of the corpus callosum and meningoencephaloceles (protrusion of the meninges and the brain through a congenital defect in the cranium) have been reported.

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Posterior Commissure:

(Also known as the Epithalamic Commisure) It is a rounded band of white fibers crossing the midline on the dorsal aspect of the upper end of the cerebral aqueduct between the diencephalon (thalamus, hypothalamus, epithalamus, subthalamus, and pretectum) and the midbrain. It is important in the bilateral pupillary light reflex. Commissural fibers (interhemispheric fibers) connect mirror image (homotopic) regions of the two hemispheres.

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Sensory Integration Dysfunction:

Sensory Integration Dysfunction is a neurological disorder causing difficulties with processing information from the five classic senses (vision, auditory, touch, smell, and taste), the sense of movement (vestibular system), and/or the positional sense (proprioception). Sensory information is sensed normally, but perceived abnormally. This is not the same as blindness or deafness because sensory information is sensed but tends to be analyzed by the brain in an unusual way that may cause pain or confusion. Sensory integration is the ability to take in information through the senses of touch, movement, smell, taste, vision, and hearing, and to combine the resulting perceptions with prior information, memories, and knowledge already stored in the brain, in order to derive coherent meaning from processing the stimuli. The mid-brain and brainstem regions of the central nervous system are early centers in the processing pathway for sensory integration. These brain regions are involved in processes including coordination, attention, arousal, and autonomic function. After sensory information passes through these centers, it is then routed to brain regions responsible for emotions, memory, and higher level cognitive functions. Sensory integration dysfunction can be a disorder on its own, but it can also be a characteristic of other neurological conditions, including autism spectrum disorders, dyslexia, dyspraxia, pervasive developmental disorder, Tourette’s Syndrome, multiple sclerosis, and speech delays, among many other. Unlike many other neurological problems that require validation by a licensed psychiatrist or physician, this condition can only be properly diagnosed by an occupational therapist. There is no known cure; however, there are many treatments available.

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Septo-optic dysplasia (SOD):

A rare congenital disorder that includes underdevelopment of the nerves at the back of the eye(s), absence of a part of the brain called the septum pellucidum (thin membrane of nervous tissue that forms the medial wall of each lateral ventricle) and/or absence of the corpus callosum, and dysfunction of the pituitary gland. SOD is also known as DeMorsier’s syndrome and is commonly recognized as the association of three features: underdevelopment of the optic nerves (optic nerve hypoplasia), absence of midline structures of the brain (most often the septum pellucidum), and problems with the functioning of the pituitary gland. These three features of SOD most often cause partial or complete blindness and mild to severe visual problems, difficulty with coordination of mental and muscular activities, such as walking, and short stature. Individuals with SOD may have normal intelligence, or learning problems that can range from mild to severe.

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Shapiro Syndrome:

The Shapiro syndrome is a rare disorder consisting of paroxysmal hyperthermia (due to hypothalamic dysfunction of thermoregulation), epilepsy, and agenesis of the corpus callosum. There may also be associated bradycardia, hypotension, and other symptoms of hypothermia.

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Splenium:

The posterior portion of the corpus callosum.

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Trisomy 13 syndrome:

Condition with three rather than the normal two chromosomes #13. Children born with this syndrome have multiple malformations and mental retardation due to the extra chromosome #13. The congenital malformations commonly include scalp defects, hemangiomas (blood vessel malformations) of the face and nape of the neck, cleft lip and palate, malformations of the heart and abdominal organs, and flexed fingers with extra digits. The mental retardation is profound. The IQ is untestably low. The majority of trisomy 13 babies die soon after birth or in infancy. The condition is also called Patau syndrome after the late geneticist Klaus Patau (at the University of Wisconsin) who discovered the extra chromosome in 1960.

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Trisomy 18 syndrome:

There are three instead of the normal two chromosomes #18. Children with this condition have multiple malformations and mental retardation due to the extra chromosome #18. The children characteristically have low birth weight, small head (microcephaly), small jaw (micrognathia), malformations of the heart and kidneys, clenched fists with abnormal finger positioning, and malformed feet. The mental retardation is profound with the IQ too low to even test. Nineteen out of 20 (95%) of these children die before their first birthday. The condition is also called Edwards syndrome in honor of the British physician and geneticist John Edwards who discovered the extra chromosome in 1960.

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