Abnormalities of Corpus Callosum


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Abnormalities of Corpus Callosum

  1. 1. Abnormalities of corpus callosum Dr.S.Lakshmy Ravi Shri Lakshmi Clinic Kaveripattinam
  2. 2. Callosal abnormality - incidence Once thought to be a rare condition experts now do not agree with this concept National organisation for disorders of the corpus callosum (NODCC) reports an incidence as high as seven in 1000 children Do we report such a high incidence on antenatal ultrasound
  3. 3. An abnormality of corpus callosum is a frequently missed malformation because imaging the entire corpus callosum per se is not a part of our routine anomaly scan Indirect markers of an evidence of abnormality of callosum is easily obtained from routine axial views but may sometimes be associated with pitfalls Midline sagittal section of the brain is generally not included in every anomaly scan
  4. 4. Two structures of importance visualised in the midsagittal view are the corpus callosum and cerebellar vermis
  5. 5. Midsagittal view is inevitable in two CNS anomalies ACC DWM
  6. 6. The three standard views quoted in the anomaly scan do not image the corpus callosum per se  Transthalamic view  Ventricular view  Transcerebellar view Axial views show only the cavum septum pellucidum and not the corpus callosum
  7. 7. CAVUM SEPTUM PELLUCIDUM The corpus callosum is in close anatomic and embryologic relationship with underlying cavum septum pellucidum.
  8. 8. DIAGNOSIS OF CC ABNORMALITY In the present scenario a suspicion of callossal abnormality arises only by looking at the CSP. Demonstration of the normal CSP is considered sufficient in a routine anomaly scan WHAT ARE THE PITFALLS IN IMAGING CSP
  9. 9. High riding third ventricle
  10. 10. High riding third ventricle
  11. 11. Fused frontal horns mimic the presence of CSP Lobar holoprosencephaly and septo-optic dysplasia are associated with agenesis of corpus callosum and CSP
  12. 12. Mimickers of CSP in callosal agenesis  High riding third ventricle  Fusion of the frontal horns  Presence of small interhemispheric cyst Ideal to image the CSP along with frontal horns
  13. 13. Corpus callosum splenium body genu rostrum
  14. 14. Etiology of ACC  Chromosomal abnormalities  Inherited genetic factors - genetic syndromes  Metabolic syndromes  Maternal phenylketonuria  Prenatal infections (rubella) and injuries  Prenatal toxic exposures (alcohol,valproate)  Structural blockage by cysts or other abnormalities.
  15. 15. Embryology Derived from the massa commisuralis which is an embryologic structure formed by the fusion of lateral margins of the groove that separates the primitive telencephalic vesicle. Agenesis is caused by disruption to development of fetal brain between 3rd and 12th week
  16. 16. Absence of the corpus callosum  prosencephalic cleavage failure (holoprosencephaly),  an abnormal commissural plate formation (agenesis of the anterior commisures),  an abnormality in the area of the commissural plate destined to form the corpus callosum (agenesis of the corpus callosum),  failure of cortical axons to reach the corpus callosum analogue (agenesis of the corpus callosum),  a destructive lesion of the corpus callosum
  17. 17. Stages leading to the formation of the corpus callosum. The light blue line represents a time-line. Numbers on top of the blue line represent days of gestation. The different stages are represented by the multicolor line above the light blue line. Pink: prosencephalic cleavage (28 to 35 days); dark blue: commisural plate formation (36 to 73 days); green: corpus callosum formation (74 to 115 days); gray: corpus callosum growth (after 115 days).
  18. 18. 26% 5% 5% 4% 13% 26% 4% 13% 4% corpus callossal abnormality isolated IUGR - TORCH schizencephaly interhemispheric cyst lissencephaly Other CNS malformation Midfacial hypoplasia ventriculomegaly - partial Acc acrocallosal syndrome Collection of 23 cases detected at our centre over a period of four years
  19. 19. Agenesis of corpus callosum  Axons form but are unable to cross the midline because of the absence of massa commissuralis.They form aberrant longitudinal fibre bundles that run along the medial hemispheric walls.(Probst bundles)  Axons and their parent cell bodies fail to form in the cerebral cortex.Probst bundles are not seen . This type is associated with lissencephaly and has a poor prognosis. Sonographic appearance of ACC is often a diverse spectrum and are not strictly confined
  20. 20. Presence and absence of Probst bundles
  21. 21. Absence of corpus callosum Failure of axonal cross over Longtitutidinal callossal bundles Probst bundles indenting lateral ventricle Absence of cingulate gyrus Sulci extend dorsally into 3rd ventricle Radial arrangement of sulci Roof of 3rd ventricle widens Extends into interhemispher ic fissure Interhemispher ic cyst Bodies of lateral ventricles stay parallel Dilation of posterior and occipital horns Tear drop shaped ventricles colpocephaly Architectual distortion in brain
  22. 22. Sonographic markers of ACC
  23. 23. Absence of the hypoechoic band of tissue in the midsagital plane is the only diagnostic sign for definitive diagnosis for ACC Abnormal appearance of CSP in axial plane should only prompt us to look into the midsagittal and coronal planes
  24. 24. Normal course of pericallossal artery
  26. 26. Could be an isolated malformation or may be a part of spectrum of anomalies Abnormalities of corpus callosum
  27. 27. Suspicion of ACC and DWV
  28. 28. Suspicion confirmed in the midsag plane normal
  29. 29. Compare and contrast
  30. 30. 20 wk fetus - probable diagnosis from midsag view
  31. 31. Arnold - Chiari malformation
  32. 32. Ventriculomegaly Agenesis of corpus callosum is associated with 3% of cases with ventriculomegaly Imaging the corpus callosum in the midsagital plane should never be missed in evaluating cases with ventriculomegaly
  33. 33. Ventriculomegaly- partial ACC
  34. 34. ACC with interhemispheric cyst  Type I - cyst is a diverticulum of ventricular system and thus communicates with the ventricles  Type II - multiple cysts are present that do not communicate with the ventricles often associated with subcortical heterotopia
  35. 35. Twin gestation for routine anomaly scan
  37. 37. ACC with multiple small interhemispheric cyst
  38. 38. Postnatal followup
  39. 39. Routine anomaly scan reported normal presenting with a cystic lesion in 3rd trimester
  40. 40. ACC with large interhemispheric cyst
  41. 41. ACC in schizencephaly
  42. 42. 2nd gravida - 15 week scan reported normal presenting at 28 weeks
  43. 43. Impression 28 week live gestation with 5 weeks growth lag Symmetric IUGR Minimal unilateral ventriculomegaly Inadequate imaging of CSP ? Intracerebral midline cyst Single umbilical artery Normal umbilical and MCA flow doppler
  44. 44. Midsagittal view showing absent corpus callosum and dilated 3rd ventricle
  45. 45. ACC - sequelae of intrauterine infection • Normal karyotype Infection screening - High titres of CMV and Rubella Evaluation of fetus - symmetric IUGR For chromosomal abnormality & intrauterine infection
  46. 46. Postnatal images
  47. 47. Primi,consanguinous marriage for routine evaluation at 22 weeks
  48. 48. Impression 22 week live gestation with HC falling below 5th percentile Bilateral ventriculomegaly Focal dilation of lateral ventricle ? communication with interhemispheric cyst Abnormal sulcation of fetal brain - underdeveloped brain
  50. 50. Lissencephaly Increased subarachnoid space in parasagital view
  51. 51. Acrocallosal syndrome Involvement of acra - extremity Callosal abnormality
  52. 52. Acrocallosal syndrome  Rare congenital disorder involving absence or partial formation of corpus callosum and polydactyly  Described by Schinzel - Schinzel acrocallosal syndrome  Acra - fingers and toes poly/syndactyly  Autosomal recessive pattern of inheritance  Each baby has a 25% risk of being affected
  53. 53. Primi, consanguinous marriage
  54. 54. Primi,consanguinous marriage,for routine evaluation
  55. 55. Importance of midsag view in diagnosis of ACC
  56. 56. Spectrum of callossal anomalies in midsag view
  57. 57. In a nutshell  Always image the CSP along with the frontal horns in every anomaly scan  Abnormal appearance of CSP in axial plan should prompt us to look into the midsagittal and coronal planes for a definitive diagnosis  In any suspected intracranial abnormality please do image the corpus callosum in midsagital plane
  58. 58. Ultrasound and MRI