Answer for BIR CoW 16 Jan 2022
Corpus callosum agenesis
Findings
T1 sagittal complete abscence of corpus callosum sun burst gyral pattern flair coronal -moose head appearance (viking helmet) T2 axial racing car sign bat wing appearance of lateral ventricles(widely spaced ventricles ) lateral convex frontal horn colpocephaly anterior interhemispheric fissure adjoins 3rd ventricle dilated foramen of monro absence of normal convergence of parieto occipital and calcarine sulcus
MRV –loss of U shaped vein of Gallen
Discussion
Callosal Dysgenesis Spectrum : The corpus callosum can be completely absent (agenesis) or partially formed (hypogenesis). Complete CC agenesis is almost always accompanied by the absence of the hippocampal commissure (HC). The anterior commissure (AC), which forms 3 weeks earlier than the CC, is usually present and normal. If the CC is hypogenetic, the posterior segments and the inferior genu and rostrum are usually absent Pathology In complete CC agenesis, all five segments are missing. The cingulate gyrus is absent on sagittal sections, whereas the hemispheres demonstrate a radiating "spoke-wheel" gyral pattern extending perpendicularly to the roof of the third ventricle . On coronal sections, the "high-riding" third ventricle looks as if it opens directly into the interhemispheric fissure. It is actually covered by a thin membranous roof that bulges into the interhemispheric fissure, displacing the fornices laterally. The lateral ventricles have upturned, pointed corners. A prominent longitudinal WM tract called the Probst bundle is situated just inside the apex of each ventricle . These bundles consist of the misdirected commissural fibers, which should have crossed the midline but instead course from front to back, indenting the medial walls of the lateral ventricles The septi pellucidi often appear absent but actually have widely separated leaves that course laterally—not vertically—from the fornices to the Probst bundles. Axial sections show that the lateral ventricles are parallel and nonconverging. The occipital horns are often disproportionately dilated, a condition termed colpocephaly. The gross pathology of CC hypogenesis varies according to which segments are missing. The splenium is usually small or absent. CC dysgenesis is the most common CNS malformation and is found in 3-5% of individuals with neurodevelopmental disorders. It has a prevalence of at least 1:4,000 live births. Nonsyndromic CC dysgenesis is found in patients of all ages Minor CC dysgenesis/hypogenesis is often discovered incidentally on imaging studies or at autopsy. Major commissural malformations are associated with seizures, developmental delay, and symptoms secondary to disruptions of the hypothalamic-pituitary axis CT Findings : Axial NECT scans show parallel, nonconverging, widely separated lateral ventricles. Disproportionate enlargement of the occipital horns is common. MRI Imaging findings: Sagittal • Partial or complete CC agenesis • Third ventricle appears "open" to interhemispheric fissure Cingulate gyrus absent → gyri "radiate" outward from third ventricle Axial • Lateral ventricles parallel, nonconverging, widely separated Probst bundles = WM along medial margins of lateral ventricles Coronal • "Viking helmet" or "moose head" appearance • "High-riding" third ventricle • Pointed, upcurving lateral ventricles • Probst bundles Corpus Callosum Hypogenesis: In partial agenesis, the rostrum and splenium are usually absent and the remaining genu and body often have a "blocky," thickened appearance The hippocampal commissure is typically absent, but the AC is generally preserved and often appears quite normal or even larger than usual. Angiography: In complete CC agenesis, CTA, DSA, and MRA demonstrate an azygous ACA that courses directly upward within the interhemispheric fissure . Differential Diagnosis The major differential diagnosis of CC dysgenesis is destruction caused by trauma, surgery (callosotomy), or ischemia. Occasionally, if the hippocampal commissure forms but the CC is absent, the HC may mimic a remnant portion of the CC on sagittal images. Coronal views show that the HC connects the fornices, not the hemispheres. Ultrasound Findings of Agenesis : SECOND TRIMESTER Axial Views Cavum septi pellucidi (CSP) is absent or appears atypical (consider also holoprosencephaly, septo-optic dysplasia, hydrocephalus, schizencephaly) Mild ventriculomegaly with pointed anterior horns (teardrop shape colpocephaly) Ventricles are parallel Widening of interhemispheric space (the normal single line becomes 3 lines = falx + medial surface of each hemisphere) Coronal Views : Anterior horns have a U configuration (Viking helmet or steer horn) CSP is not visible above the fornices Possible high-riding third ventricle in 50%-60% (which may mimic CSP) Midsagittal Views Corpus callosum absent, short, or deformed Circular loop of pericallosal artery is not present THIRD TRIMESTER On axial view, many sulci perpendicular to the interhemispheric fissure (hairy midline) Midsagittal view shows radial orientation of sulci from the thalamus (sunburst appearance) OTHER Interhemispheric cyst or lipoma Additional anomalies, especially of midline and posterior fossa structures Malformations Associated With Callosal Dysgenesis: Chiari 2 malformation, Dandy-Walker spectrum, frontonasal dysplasia, median cleft face syndromes, syndromic craniosynostoses, hypothalamicpituitary anomalies, cerebellar hypoplasia/dysplasia, and malformations of cortical development all have an increased prevalence of CC anomalies. CC agenesis and regional increases in cortical thickness are the most common brain morphologic defects in fetal alcohol syndrome.
References
Callosal Dysgenesis Spectrum Unterberger I et al: Corpus callosum and epilepsies. Seizure. 37:5560, 2016 Filippi CG et al: Lesions of the corpus callosum and other commissural fibers: diffusion tensor studies. Semin Ultrasound CT MR. Valery N. Kornienko, I.N. Pronin. Diagnostic Neuroradiology. (2008) ISBN: 9783540756521 Tang P, Bartha A, Norton M, Barkovich A, Sherr E, Glenn O. Agenesis of the Corpus Callosum: An MR Imaging Analysis of Associated Abnormalities in the Fetus. AJNR Am J Neuroradiol. 2009; L.M. Ketonen, A. Hiwatashi, R. Sidhu et al. Pediatric Brain and Spine. (2004) Gebarski S, Gebarski K, Bowerman R, Silver T. Agenesis of the Corpus Callosum: Sonographic Features. Radiology.
Findings
T1 sagittal complete abscence of corpus callosum sun burst gyral pattern flair coronal -moose head appearance (viking helmet) T2 axial racing car sign bat wing appearance of lateral ventricles(widely spaced ventricles ) lateral convex frontal horn colpocephaly anterior interhemispheric fissure adjoins 3rd ventricle dilated foramen of monro absence of normal convergence of parieto occipital and calcarine sulcus
MRV –loss of U shaped vein of Gallen
Discussion
Callosal Dysgenesis Spectrum : The corpus callosum can be completely absent (agenesis) or partially formed (hypogenesis). Complete CC agenesis is almost always accompanied by the absence of the hippocampal commissure (HC). The anterior commissure (AC), which forms 3 weeks earlier than the CC, is usually present and normal. If the CC is hypogenetic, the posterior segments and the inferior genu and rostrum are usually absent Pathology In complete CC agenesis, all five segments are missing. The cingulate gyrus is absent on sagittal sections, whereas the hemispheres demonstrate a radiating "spoke-wheel" gyral pattern extending perpendicularly to the roof of the third ventricle . On coronal sections, the "high-riding" third ventricle looks as if it opens directly into the interhemispheric fissure. It is actually covered by a thin membranous roof that bulges into the interhemispheric fissure, displacing the fornices laterally. The lateral ventricles have upturned, pointed corners. A prominent longitudinal WM tract called the Probst bundle is situated just inside the apex of each ventricle . These bundles consist of the misdirected commissural fibers, which should have crossed the midline but instead course from front to back, indenting the medial walls of the lateral ventricles The septi pellucidi often appear absent but actually have widely separated leaves that course laterally—not vertically—from the fornices to the Probst bundles. Axial sections show that the lateral ventricles are parallel and nonconverging. The occipital horns are often disproportionately dilated, a condition termed colpocephaly. The gross pathology of CC hypogenesis varies according to which segments are missing. The splenium is usually small or absent. CC dysgenesis is the most common CNS malformation and is found in 3-5% of individuals with neurodevelopmental disorders. It has a prevalence of at least 1:4,000 live births. Nonsyndromic CC dysgenesis is found in patients of all ages Minor CC dysgenesis/hypogenesis is often discovered incidentally on imaging studies or at autopsy. Major commissural malformations are associated with seizures, developmental delay, and symptoms secondary to disruptions of the hypothalamic-pituitary axis CT Findings : Axial NECT scans show parallel, nonconverging, widely separated lateral ventricles. Disproportionate enlargement of the occipital horns is common. MRI Imaging findings: Sagittal • Partial or complete CC agenesis • Third ventricle appears "open" to interhemispheric fissure Cingulate gyrus absent → gyri "radiate" outward from third ventricle Axial • Lateral ventricles parallel, nonconverging, widely separated Probst bundles = WM along medial margins of lateral ventricles Coronal • "Viking helmet" or "moose head" appearance • "High-riding" third ventricle • Pointed, upcurving lateral ventricles • Probst bundles Corpus Callosum Hypogenesis: In partial agenesis, the rostrum and splenium are usually absent and the remaining genu and body often have a "blocky," thickened appearance The hippocampal commissure is typically absent, but the AC is generally preserved and often appears quite normal or even larger than usual. Angiography: In complete CC agenesis, CTA, DSA, and MRA demonstrate an azygous ACA that courses directly upward within the interhemispheric fissure . Differential Diagnosis The major differential diagnosis of CC dysgenesis is destruction caused by trauma, surgery (callosotomy), or ischemia. Occasionally, if the hippocampal commissure forms but the CC is absent, the HC may mimic a remnant portion of the CC on sagittal images. Coronal views show that the HC connects the fornices, not the hemispheres. Ultrasound Findings of Agenesis : SECOND TRIMESTER Axial Views Cavum septi pellucidi (CSP) is absent or appears atypical (consider also holoprosencephaly, septo-optic dysplasia, hydrocephalus, schizencephaly) Mild ventriculomegaly with pointed anterior horns (teardrop shape colpocephaly) Ventricles are parallel Widening of interhemispheric space (the normal single line becomes 3 lines = falx + medial surface of each hemisphere) Coronal Views : Anterior horns have a U configuration (Viking helmet or steer horn) CSP is not visible above the fornices Possible high-riding third ventricle in 50%-60% (which may mimic CSP) Midsagittal Views Corpus callosum absent, short, or deformed Circular loop of pericallosal artery is not present THIRD TRIMESTER On axial view, many sulci perpendicular to the interhemispheric fissure (hairy midline) Midsagittal view shows radial orientation of sulci from the thalamus (sunburst appearance) OTHER Interhemispheric cyst or lipoma Additional anomalies, especially of midline and posterior fossa structures Malformations Associated With Callosal Dysgenesis: Chiari 2 malformation, Dandy-Walker spectrum, frontonasal dysplasia, median cleft face syndromes, syndromic craniosynostoses, hypothalamicpituitary anomalies, cerebellar hypoplasia/dysplasia, and malformations of cortical development all have an increased prevalence of CC anomalies. CC agenesis and regional increases in cortical thickness are the most common brain morphologic defects in fetal alcohol syndrome.
References
Callosal Dysgenesis Spectrum Unterberger I et al: Corpus callosum and epilepsies. Seizure. 37:5560, 2016 Filippi CG et al: Lesions of the corpus callosum and other commissural fibers: diffusion tensor studies. Semin Ultrasound CT MR. Valery N. Kornienko, I.N. Pronin. Diagnostic Neuroradiology. (2008) ISBN: 9783540756521 Tang P, Bartha A, Norton M, Barkovich A, Sherr E, Glenn O. Agenesis of the Corpus Callosum: An MR Imaging Analysis of Associated Abnormalities in the Fetus. AJNR Am J Neuroradiol. 2009; L.M. Ketonen, A. Hiwatashi, R. Sidhu et al. Pediatric Brain and Spine. (2004) Gebarski S, Gebarski K, Bowerman R, Silver T. Agenesis of the Corpus Callosum: Sonographic Features. Radiology.
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!