Agenesis of The Corpus Callosum ACC

Neurology/anatomy Presentation
Agenesis of The Corpus Callosum ACC

1. Agenesis of The Corpus Callosum (ACC ) Dr. Ikram I. Qaysia Prepared By : Diaa Mohammad Srahin Septemper , 2015 Al-Quds University Faculty of Medicine Neuroanatomy

2. Introduction The interior of the central nervous system is organized into gray and white matter. Gray matter consists of nerve cells embedded in neuroglia; it has a gray color. White matter consists of nerve fibers embedded in neuroglia; it has a white color due to the presence of lipid material in the myelin sheaths of many of the nerve fibers .

3. Gray matter structures : ( cortex , basal nuclei ) . The white matter is composed of myelinated nerve fibers of different diameters supported by neuroglia . These fibers are classified into 3 groups : Commissural fibers . Association fibers . Projection fibers .

4. Association fibers : nerve fibers that essentially connect various cortical regions within the same hemisphere. Projection fibers : afferent and efferent nerve fibers passing to and from the brainstem to the entire cerebral cortex.

5. Commissural Fibers Commissural fibers : connect corresponding regions of the two cerebral hemispheres . - They are : Corpus Callosum . Anterior commissure . Posterior commissure . The fornix . The habenular commissure .

6.   Corpus Callosum The corpus callosum (Latin for " tough body ") The largest commissure of the brain , connects the two cerebral hemispheres . It is made of more than 200 million nerve fibers . It lies at the bottom of the longitudinal fissure . The primary function of the corpus callosum is to integrate motor, sensory, and cognitive activity between the left and right hemispheres It’s involved in several functions of the body including: Communication between b rain hemispheres . Eye movement . Maintaining the balance of arousal and attention . Tactile localization .

7. The pericallosal artery derived from the anterior cerebral artery provides blood supply of the corpus callosum . It is divided into four parts (anterior to posterior) : Rostrum : the thin part of the anterior end . Genu : the curved anterior end of the corpus callosum that bends inferiorly in front of the septum pellucidum Trunk/body : arches posteriorly and end as Splenium . Splenium : thickened posterior portion .

8. Agenesis of the Corpus Callosum Agenesis of the corpus callosum is a congenital (lifelong) brain abnormality that occurs when the corpus callosum does not develop as it should during the early prenatal period. It can occur as an isolated condition or in association with other brain abnormalities or physical or medical conditions. In a typical infant brain, the corpus callosum develops between 12 to 16 weeks after conception (near the end of the first trimester).

9. If the corpus callosum does not develop during the critical gestational stage, it will not develop later. In this case the child either has complete agenesis, meaning a complete absence of the corpus callosum ( fig 1 ), or partial agenesis meaning that part of the corpus callosum developed ( fig 2 ).

10. The types of callosal abnormality that occurs depends on the cause and timing of the disruption to prenatal brain development . Most sources estimate callosal disorders can occur in up to 4 individuals per 1,000 in the general population and occurs more frequently among persons with developmental disabilities (22-24 per 1,000 ) . Currently, there is some variation in how callosal conditions may be described in medical reports and by medical providers .

11. Below is a list of the most common terms used to describe callosal conditions : ( ACC/ AgCC ) Agenesis of the corpus callosum: All or a portion of the corpus callosum is absent . ( c-ACC ) Complete agenesis of the corpus callosum: The corpus callosum is completely absent . ( p-ACC ) Partial agenesis of the corpus callosum: A portion of the corpus callosum is absent; most often it is the posterior (back) portion that is missing. Hypoplasia of the corpus callosum: The corpus callosum is present, but is abnormally thin . Dysgenesis of the corpus callosum: The corpus callosum is present but is malformed in some way; this includes p-ACC and Hypoplasia .

12. Causes of ACC The causes of ACC is usually not known, but it can be inherited as either an autosomal recessive trait or an X-linked dominant trait . Possible causes include : Chromosomal (genetic) abnormalities ( e.g , trisomy 8 and 18, Andermann syndrome ) . Prenatal infections or viruses ( e.g , rubella ) . Exposure to certain medications ( e.g , valproate, an epilepsy medication ) . Toxic metabolic conditions ( e.g , Fetal Alcohol Syndrome ) . Blockage of the growth of the corpus callosum ( e.g , cysts ) . Metabolic disorders . Other unknown factors .

13. Although a callosal abnormality can occur as an isolated condition, it may also occur in association with other brain abnormalities or physical or medical conditions. It can occur as part of a or in association with a chromosome abnormality . AGENESIS OF THE CORPUS CALLOSUM in AICARDI SYNDROME

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15. Common characteristics associated with ACC   Researches suggest that persons with callosal disorders share some common physical, communication, social, behavioral and cognitive features. However, individual differences exist among persons with callosal conditions, ranging from subtle developmental and cognitive challenges to more severe disability . The following lists identify characteristics commonly associated with ACC. Individual differences are common and not all persons with ACC will experience these characteristics.

16. Common characteristics associated with ACC Health-related/Physical: Vision impairments (near/farsightedness, nystagmus , strabismus, problems with depth perception ) . Low muscle tone ( hypotonia ) . Early feeding difficulties/gastric reflux/chewing and swallowing difficulties . Abnormal head and facial features . High tolerance to pain . Sleep difficulties (e.g. getting to sleep, nighttime waking, bed-wetting ) . Seizures or spasticity . Hearing impairments . Elimination problems including chronic constipation . Less common: Genito -urinary defects, cardiac abnormalities, skeletal defects, metabolic disorders, genetic conditions

17. Common characteristics associated with ACC Developmental Delays in attaining motor milestones such as sitting, walking, riding a bike . Early speech and language delays (particularly in expressive communication ) . Clumsiness/poor motor coordination . Delayed toilet training .

18. Common characteristics associated with ACC Social/behavioral Generally happy disposition, enjoys being with others . Socially immature . Lack of self awareness . Inability to take the perspective of others . Difficulties understanding and acting on the social cues of others. Difficulty maintaining attention . Restlessness or hyperactivity . Fearfulness . Obsessive/compulsive behaviors . Challenges with peer interactions and relationships that seem to increase with age and the complexity of the social situations .

19. Diagnosis of callosal conditions ACC is frequently diagnosed during the first two years of life. An epileptic seizure can be the first symptom indicating that a child should be tested for a brain dysfunction. The disorder can also be without apparent symptoms in the mildest cases for many years. A brain scan is necessary to diagnose callosal conditions. Brain scans include : Prenatal ultrasound . Prenatal magnetic resonance imaging (MRI) . Computerized tomography (CT scan) . MRI (provides the most detailed information) .

20. Management and Treatment There are no specific treatments for ACC, However, the symptoms can be treated successfully. Depending on the severity of other brain malformations, patients can lead long healthy lives. Treatment options may include : Medications   : to control seizures . Speech therapy :  to help with speech and language development . Physical therapy :  to improve muscle strength and coordination . Occupational therapy :  to help build self-care and mobility skills such as eating, getting dressed, and walking . Special education   :as necessary for cognitive and learning problems

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22. References Clinical Neuroanatomy by Richard S. Snel . http://hubel.med.harvard.edu/book/b34.htm . http://www.emotion.caltech.edu/agcc/info.html . http://biology.about.com/od/anatomy/p/corpus-callosum.htm . http://www.ninds.nih.gov/disorders/agenesis/agenesis.htm . http://www.nodcc.org/dcc-faqs . http://umaine.edu/edhd/research/acc/what-is-agenesis-of-the-corpus-callosum-acc/ . http://www.emotion.caltech.edu/agcc/info.html . http://www.webmd.com/children/agenesis-of-corpus-callosum . http://www.healthline.com/symptom/agenesis-of-the-corpus-callosum . http://patient.info/doctor/agenesis-of-the-corpus-callosum .

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