Neurology/anatomy Presentation Agenesis of The Corpus Callosum ACC

1. 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 :
1. Commissural fibers .
2. Association fibers .
3. 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 :
1. Corpus Callosum .
2. Anterior commissure .
3. Posterior commissure .
4. The fornix .
5. The habenular commissure .

7. 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 brain hemispheres .
◦ Eye movement .
◦ Maintaining the balance of arousal and attention .
◦ Tactile localization .

8.  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 .

10. 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).

11.  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 ).

12.  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.

13.  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 .

14. 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:
1. Chromosomal (genetic) abnormalities (e.g, trisomy 8 and 18,
Andermann syndrome ) .
2. Prenatal infections or viruses (e.g, rubella) .
3. Exposure to certain medications ( e.g, valproate, an epilepsy
medication ) .
4. Toxic metabolic conditions (e.g, Fetal Alcohol Syndrome) .
5. Blockage of the growth of the corpus callosum (e.g , cysts) .
6. Metabolic disorders .
7. Other unknown factors .

15.  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

16.  video

17. 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.

18. 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

19. 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 .

20. 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 .

21. 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:
1. Prenatal ultrasound .
2. Prenatal magnetic resonance imaging (MRI) .
3. Computerized tomography (CT scan) .
MRI (provides the most detailed information) .

22. 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

23.  Cartoon Clip

24. 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 .