Agenesis of the corpus callosum

The image at the left is an actual brain scan of a person with complete absence of a corpus callosum. The image to the right  is an image of a person with a normal corpus callosum .

The image in the middle is the brain of someone who is missing part of the corpus callosum. (source:http://www.umaine.edu/edhd/research/accnetwork/whatisacc.htm)

Why am I showing you these? Because I am a person who is in the "middle", I was born missing part of my corpus callosum, a medical condition known as "Agenesis of the corpus callosum. (The word "agenesis" means "a congenital absence of an organ or part, usually caused by a lack of primordial tissue and failure of development in the embryo. The word "agenesis" has a greek origin and means a + genein, not to produce).

The corpus callosum is a grouping of nerve fibers which exist between the two hemispheres of the human brain,to connect the two hemispheres and allow them to communicate with each other. The term "agenesis of the corpus callosum" refers is a rare birth defect (congenital disorder..this means a person is born with the condition) in which there is a complete or partial absence of the corpus callosum Agenesis of the corpus callosum occurs when the corpus callosum, the band of tissue connecting the two hemispheres of the brain, fails to develop normally, typically in utero, resulting in disconnected brain hemispheres. In reality those of us with this condition tend to switch from being right-brained to left brained throughout the day.

(1)Prevelence of agenesis of the corpus callosum in humans:

From researching on the internet I have discovered that only one-half of one percent of the world's population have this medical condition. However at a specific website http://emotion.caltech.edu/agcc/info.html, I found this statement: "Estimates of the frequency of AgCC (including both complete and partial agenesis of the corpus callosum, but not other corpus callosum malformations) vary greatly. Recent studies in the United States suggest that the broad category of AgCC occurs in approximately 1:4,000 live births, which is likely to be an underestimate. A study of head ultrasounds performed on apparently healthy full-term newborns in Taiwan suggests an incidence of 1:1,000, while a study in France reported 1 case per 7,000 births that resulted in elective pregnancy terminations because of the AgCC diagnosis."

(2) Consequences to the individual who is born with partial or complete agenesis of the corpus callosum:

For some reason, some people who are born with agenesis of the corpus callosum, or even with no corpus callosum at all are blessed because they seem to have no or minimal physical,cognitive and psychological problems resulting from being born with the condition. However, for other people, having agenesis of the corpus callosum is a severe problem which causes the individual to have severe medical, cognitive and psychological problems. I have accessed many websites dealing with the medical, cognitive and psychological problems which people who have agenesis of the corpus callosum have to contend with. People with this medical condition usually begin to experience the problems relating to the total absence or partial absence of the corpus callosum at age 12. What happens is the individual begins to fall behind his or her peers at this age, which makes it difficult to achieve in school and in other activities, including working.

(3) How is partial or complete agenesis of the corpus callosum diagnosed medically? What is the cause of partial or complete agenesis of the corpus callosum?
Callosal disorders can only be diagnosed through a brain scan They may be diagnosed through an MRI,CT Scan, prenatal ultrasound, or prenatal MRI.

The cause of Agenesis of the corpus callosum is now understood by the medical community. This condition is caused by disruption to development of the fetal brain between the 5th and 16th week of pregnancy.In most cases, it is not possible to know what caused an individual to have ACC or another callosal disorder. However, research suggests that some possible causes may include chromosome errors, inherited genetic factors, prenatal infections or injuries, prenatal toxic exposures, structural blockage by cysts or other brain abnormalities, and metabolic disorders. (sources:http://www.umaine.edu/edhd/research/accnetwork/whatisacc.htm and http://www.nodcc.org/what_is_a_callosal_disorder.php.)

(4)Agenesis of the corpus callosum is a cilipathic disease.

Agenesis of the corpus callosum is part of an emerging class of diseases called cilopathies. A ciliopathy is a genetic disorder of the cellular cilia or the cilia anchoring structures, the basal bodies. (source:http://en.wikipedia.org/wiki/Ciliopathy). Cilia are projections from the cell. They are made up of microtubules ( Microtubules are conveyer belts inside the cells.) They move vesicles, granules, organelles like mitochondria, and chromosomes via special attachment proteins. A vesicle is a small bubble of liquid within a cell. More technically, a vesicle is a small, intracellular, membrane-enclosed sac that stores or transports substances within a cell. In cell-biology, a granule can be any structure barely visible by light microscopy. The term is most often used to describe a secretory vesicle (a sac thats stores or moves proteins out of a living cell.) An organelle (pronunciation: /ɔː(r)gəˡnɛl/) is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid (fat) membrane.

The name organelle comes from the idea that these structures are to cells what an organ is to the body.The cilia defects adversely affect "numerous critical developmental signaling pathways" essential to cellular development and thus offer a plausible hypothesis for the often multi-symptom nature of a large set of syndromes and diseases.

(5)Signs and symptoms of ACC:

Signs and symptoms of ACC and other callosal disorders vary greatly among individuals. However, some characteristics common in individuals with callosal disorders include vision impairments, low muscle tone (hypertonia), poor motor coordination, delays in motor milestones such as sitting and walking, low perception of pain, delayed toilet training, and chewing and swallowing difficulties. Laboratory research has demonstrated that individuals with ACC have difficulty transferring more complex information from one hemisphere to the other.

(source:http://www.travisinstitute.org/neuroscience/agenesis.htm)

Individuals with ACC also have been shown to have some cognitive disabilities (difficulty in complex problem solving) and social difficulties (missing subtle social cues), even when their Intelligence Quotient is normal. Individuals with ACC may have a normal Intelligence Quotient (IQ; as measured by the Wechsler intelligence scales). Some individuals have even tested in the above-average range. .By the time individuals with ACC reach adolescence, basic academic achievement scores (e.g. Reading, Spelling, and Math) are typically in the normal range (presuming a normal-range IQ), but math scores tend to be lowest. Individuals with ACC have reduced overall information processing speed.
Persons with ACC have deficiencies on tasks which demand complex novel mental processing and problem solving. This is believed to be the main cognitive deficit related to absence of the corpus callosum. (source:http://www.travisinstitute.org/neuroscience/agenesis.htm).

(6)Brain anomalies and syndromes associated with Agenesis of the Corpus Callosum:

The lists below identify the more common brain anomalies and syndromes associated with ACC.
Brain anomalies that sometimes occur with ACC:
(a)Hydrocephalus -Hydrocephalus is a build up of fluid inside the skull, leading to brain swelling. Hydrocephalus means "water on the brain."Hydrocephalus is due to a problem with the flow of cerebrospinal fluid (CSF), the liquid that surrounds the brain and spinal cord.

(b)Arnold- Chiari malformation Arnold-Chiari malformation is a malformation of the brain. It consists of a downward displacement of the cerebellar tonsils ( the cerebellar tonsils are a rounded mass, situated in the hemispheres of the cerebellum. (they are part number seven in this photo of the cerebellum: )http://upload.wikimedia.org/wikipedia/commons/1/15/Human_cerebellum_anterior_view_description.JPG

This displacement causes the flow of blocking the flow of cerebrospinal fluid (the fluid within which our brain "floats"). The cerebrospinal fluid has many roles including mechanical protection of the brain, distribution of neuroendocrine factors (cells that release a hormone into the circulating blood in response to a neural stimulus. These hormones may be neurotransmitters ,neuropeptides (small protein-like molecules used by neurons (nerve cells) to communicate with each other, or amino acids (molecules which our bodies must have to live and and which have a variety of roles in metabolism (the set of chemical reactions that occur in living organism in order to maintain life . These hormones are then sent to the blood vessels and when stimulated travel to target cells and stimulate, inhibit or maintain function of these cells.

These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments.As a result of this displacement the bottom part of the brain, the cerebellum, descends out of the skull and crowds the spinal cord, putting pressure on both the brain and spine and causing many symptoms (see http://www.conquerchiari.org/index.htm).

(c)Schizencephaly (deep clefts in brain tissue), (d)Holoprosencephaly (failure of the forebrain to divide into lobes), (e)Migration disorders

(7)Syndromes associated with ACC:
1.Aicardi, 2.Andermann, 3.Shapiro, 4.Acrocallosal 5.Menkes, 6.Mowat-Wilson., 7. FG(see: source:http://www.umaine.edu/edhd/research/accnetwork/whatisacc.htm)

(8) Medical treatment for callosal disorders:

According to a website from the University of Maine (http://www.umaine.edu/edhd/research/accnetwork/whatisacc.htm),

"there are currently no specific medical treatments for callosal disorders, but individuals with ACC and other callosal disorders may benefit from a range of developmental therapies, educational support."

Recent research suggests that specific social difficulties may be a result of impaired face processing (source: http://emotion.caltech.edu/agcc/). Unusual social behavior in childhood is often mistaken for or misdiagnosed as Asperger's syndrome or other autism spectrum disorders. Other characteristics sometimes associated with callosal disorders include seizures, spasticity, early feeding difficulties and/or gastric reflux, hearing impairments, abnormal head and facial features, and severe mental handicap.

What is the prognosis for children who are born with partial or complete agenesis of the corpus callosum?Prognosis varies depending on the type of callosal abnormality and associated conditions or syndromes. It is not possible for the corpus callosum to regenerate or degenerate (i.e., the corpus callosum will not regrow or diminish).Although some individuals with callosal disorders have average intelligence and lead normal lives, neuropsychological testing reveals subtle differences in higher cortical function compared to individuals of the same age and education without ACC. (source:http://en.wikipedia.org/wiki/Agenesis_of_the_corpus_callosum)

What is my biggest fear about my future and ACC? I have read that as we age our corpus callosum actually shrinks. As I have started out life and lived life missing part of my corpus callosum, I fear that as my corpus callosum shrinks due to aging, that I am going to lose more and more of my intellectual and physical capabilities <:(