Bất sản thể chai - Agenesis of the corpus callosum - Võ Tá Sơn

1. Agenesis of the Corpus Callosum
Bs. Võ Tá Sơn
Bệnh viện Phụ sản – Nhi Đà Nẵng
HCM, 14.01.2017

2. • Mỏ: rostrum
• Gối: genu
• Thân: body
• Lồi: splenium

3. Anatomy

4. Prevalence
• From 0.3%–0.7% in the general population to
2%–3% in the developmentally disabled
population.

5. Pathophysiology
• The formation of the CC starts with the
development of the genu; the body and splenium
develop at a later stage.
• If the normal developmental process is disturbed,
the CC may be completely or partially absent
(hypogenetic). Because the developmental
process starts from the anterior part and
progresses front to rear, when the CC is
hypogenetic, usually the posterior portion is
affected (the posterior body and the splenium).

6. Pathophysiology: Rostrum?
• More recent studies based on diffusion tensor
MRI showed that the rostrum, the genu, and
the anterior part of the body were already
present at around 15 weeks’ gestation.
• Diagnosis of ACC is usually impossible before
18 to 20 weeks’ gestation because the
formation of the corpus callosum is
incomplete.

7. Pathophysiology
• 2 mechanisms:
• (1) a developmental injury (hypogenesis) from an
acquired one (destruction).
• (2) association with hypoxic-ischemic injury and
infectious causes.
• 2 types of ACC
• (1) the axons are present but are unable to cross
the midline; they form large aberrant fiber
bundles (Probst bundles) along the medial
hemispheric walls.
• (2) apparently less frequent, the axons fail to
form; no Probst bundles are found.

8. Etiology
• Chromosomal, monogenic, and teratogenic.
• Chromosomal abnormalities are present in
20% of cases, especially trisomies 18 and 13.
• More than 100 syndromes involving ACC have
been reported.
• Some environmental and metabolic factors
also have been implicated in ACC, such as in
utero cytomegalovirus and rubella infection
and fetal alcohol exposure.

9. Characteristics of ACC
• Lateral separation of the frontal horns and bodies
of the lateral ventricles
• Angled lateral peaks of the frontal horns and
bodies of the lateral ventricles
• Elevation and variable dilatation of the third
ventricle
• Dilatation of the occipital horns
• Concave medial wall of the lateral ventricles
related to the bundles of Probst
• Abnormal radial orientation of medial cerebral gyri
extending from the roof of the third ventricle

10. Ultrasound diagnosis
• In fetuses in cephalic presentation, the
transvaginal approach is preferred; in fetuses
in breech presentation, a transfundal
approach is suggested.

11. Ultrasound diagnosis

12. Axial planes (Indirect signs)
• (1) On the axial transventricular view at 2nd trim:
hypoplastic or absent CSP complete ACC
because of common anatomic and
embryogenetic formation.
• (2) Colpocephaly (= tear drop sign) (dilatation of
the atria and occipital horns, “which is
determined by the absence of the splenium and
by a defect of the intrinsic association bundles of
the occipital lobe);
• (3) Increased separation of the hemispheres with
the bodies of the lateral ventricles parallel to
each other and shifted laterally.
• Dorsal elevation of the third ventricle can be also
present.

13. Axial planes

14. Axial planes

15. Axial planes

16. ACC: Lateral ventricle in the case of agenesis of corpus callosum, with
the “teardrop sign.” The distance between the medial border of the
lateral ventricle and the falx cerebri is larger in the part of the sharply
pointed anterior horn than that fromthe posterior horn. The third
ventricle is seen centrally; the septum pellucidum cannot be seen.

17. Coronal plane
• The frontal horns separated more than usual
with inner walls that are concave medially
because of the longitudinal bundle of Probst
that fail to cross the hemispheres and instead
are rerouted parasagittally, parallel to the
midline.
• Absence of the CC.

18. Coronal plane

19. • ACC. Frontal view of the anterior part of the
brain in agenesis of corpus callosum: “three
lines sign.” The longitudinal fissure separating
the cerebral hemispheres is widened.

20. The midsagittal plane
• Direct signs: absence of the CC (still see in the
coronal plane)
• And, in advanced gestation or postnatally, an
atypical radiating appearance of the median
sulci, which converge toward the third
ventricle. In this view, usually no cingulate
gyrus can be recognized, or it appears
incomplete.

21. The midsagittal plane

22. Partial ACC
• Usually the posterior portion is affected (the posterior
body and the splenium);
• The CSP can be present, and often the only indirect US
sign is a mild colpocephaly.
• Sometimes the indirect signs of partial ACC may also
be completely absent.
• A sagittal view is the only way to make the diagnosis,
visualizing a small CC that is lacking the posterior part
and only partially surrounds the 3rd ventricle.
• Less frequently, the remaining structure is the genu; it
can appear thin and barely discernible with gray-scale
imaging and can be identified only when highlighted by
the course of the pericallosal artery.

23. Partial ACC

24. Color Doppler
• The semicircular loop, normally formed by the
pericallosal artery along the superior surface of
the CC, is lost.
• Its value is even greater in the case of partial ACC.
• In partial ACC, the pericallosal artery closely
follows and depicts the small anterior part of the
CC, often discernible with difficulty on gray-scale
imaging. Its course is then lost, being usually
absent in the posterior part of the CC.

25. Color Doppler

26. Color Doppler

27. Differential diagnosis
• Lobar holoprosencephaly

28. Associated with ACC
• (1) Interhemispheric cysts: two main
categories:
– the cysts are herniations of the ventricular system,
representing the dorsal expansion of the roof of
the 3rd ventricle.
– clearly separated from the ventricles.
• (2) Intracranial lipoma: visible only in the 3rd
trimester as a hyperechogenic image under
the inferior part of the interhemispheric
scissure.

29. Associated with ACC

30. Fetal MRI
• Fetal MRI allows good visualization of the corpus
callosum and its anomalies.
• The main advantage of MRI is the recognition of
possible additional cerebral anomalies, such as
late sulcation, migration anomalies, and
heterotopias. In these cases, it is more sensitive
than US.
• However, the presence of these anomalies
usually can be recognized only from the late
second trimester onward, when advanced
development of the sulci and gyri has occurred.

31. Fetal MRI

32. Association with other malformations
• Cerebral and/or extracerebral malformations,
including a number of syndromes and metabolic
diseases.
• The risk of associated brain anomalies is
extremely high (up to 80%) including Dandy–
Walker complex, gyral anomalies, and neuronal
heterotopia.
• The risk of associated extra-CNS abnormalities is
high (up to 60%), including congenital heart
disease and skeletal and genitourinary defects.

33. Risk of chromosomal anomalies
• .This is relatively high (20% of cases): trisomy
13 and 18, deletions [del(4)(p16), del(l6)(q23),
del(X)(p22)], and duplications [dup(8)(p21–
23), dup(11)(q23–qter)].

34. Risk of nonchromosomal syndromes

35. Obstetric management.
• Mandatory karyotyping
• Full family hystory
• Careful search for additional structural anomalies
(hematologic diseases, asplenia, anophthalmia,
cleft lip/palate, albinism, bone lesions, congenital
megacolon, and camptodactyly).
• Fetal MRI: late sulcation, migration anomalies,
and heterotopia, with late development of the
sulci and gyri.

36. Prognosis
Prognosis of ACC is controversial.
The presence of additional anomalies a worse
prognosis.
Isolated ACC a better prognosis.
BUT
Neurodevelopmental delay is present in about 25%
of cases of isolated ACC at 3 years AND subtle
neuropsychologic, perceptual, and motor defects
can emerge later in life.
Follow up to 6 years of age to update status of
these patients.

37. Prognosis, survival, and quality of life
• Most of individuals with ACC suffered from
developmental delay and often from seizures.
• Several postnatal case series suggest a direct
relationship between the occurrence of
associated brain abnormalities and poor
neurodevelopmental outcome.
• With isolated ACC, caution must be adopted
when assessing the fetal/neonatal prognosis.
• Significant neurodevelopmental delay develops in
a consistent proportion of cases (20%–30%), even
if ACC is confirmed postnatally to be isolated.
The same also applies to isolated partial ACC.

38. Prognosis, survival, and quality of life
• Even when the outcome is good, subtle
neuropsychologic, perceptual, and motor defects
can emerge later in life, because all individuals
with CACC/PACC have some neuropsychological
symptoms.
• Considering the presence of neurosensorial
information transfer defects, no differences seem
to exist between PACC and CACC in terms of the
performance accuracy of the somatosensory
functions.
• The functions of the CC are not completely
understood and it is difficult to assess correctly
the neuropsychologic status of individuals with
CACC/PACC and normal-range IQs, and the role of
possible compensatory mechanisms

39. Prognosis, survival, and quality of life
• The recurrence risk is 5% when syndromes are
excluded.

40. Postnatal care
• MRI is considered the best method of
confirming the diagnosis and excluding other
central nervous system anomalies.
• Treatment is symptomatic and includes
physiotherapy, psychotherapy, speech therapy,
and antiepileptic drugs for seizures.

41. Information for the patient
• Up to 1% of adults have congenital agenesis of
the corpus callosum, without their knowledge
and without symptoms.
• In the absence of associated anomalies,
mental development is normal.

42. Summary
• Incidence. From 0.3%–0.7% in the general population
to 2%–3% in the developmentally disabled population.
• Ultrasound diagnosis. Midsagittal view: Complete or
partial absence of the corpus callosum. Axial views:
Colpocephaly, absence of the CSP (in complete
agenesis). Coronal views: lateral convexity of and
increased distance between the frontal horns.
• Risk of chromosomal anomalies. High: 20%.
• Risk of nonchromosomal syndromes. High.
• Outcome. About 20%–30% rate of significant
neurodevelopmental delay in isolated forms has been
reported; in nonisolated form the prognosis is poor.

43. Thank you