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Holoprosencephaly

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Holoprosencephaly

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Holoprosencephaly

  1. 1. HOLOPROSENCEPHALIES, RELATED DISORDERS & MIMICS Dr. Vishnu Dakshin Dr. Rudresh Hiremath
  2. 2. HOLOPROSENCEPHALY • Rare congenital brain malformation resulting from incomplete separation of the two hemispheres. • “Holo” – Single ventricle • “pros” – Prosencephalon • “encephaly” - Brain
  3. 3. EMBRYOLOGY
  4. 4. TYPES - DEMYER • CLASSIC - Alobar - Semilobar - Lobar • VARIANTS - Syntelencephaly. - Septopreoptic HPE. • Minimal HPE. • Microform HPE.
  5. 5. CLASSIC • Alobar HPE. • Semilobar HPE. • Lobar HPE. • The distinction between these 3 forms is based primarily on the presence or absence of a midline fissure separating the hemispheres.
  6. 6. ALOBAR HPE • Most severe. • No midline fissure, no identifiable lobes. • Fused basal ganglia. • Agyric /disordered gyri /shallow sulci. • Single crescent monoventricle - opening dorsally into a large CSF filled dorsal cyst.
  7. 7. ALOBAR HPE Small rim of cortex surrounds "horseshoe" central monoventricle. Thalami are fused. More cephalad scan in the same patient shows a large dorsal cyst and central monoventricle with thin rim of surrounding brain.
  8. 8. SEMILOBAR HPE • Intermediate form. • Primitive ventricular horns, third ventricle. • Fused basal ganglia&hypothalami, thalami often separated. • Rudimentary falx, posterior IHF. • Posterior CC forms while anterior aspects are absent.
  9. 9. SEMILOBAR HPE H-shaped central ventricle with primitive- appearing temporal horns, fused basal ganglia, and rudimentary interhemispheric fissure. Axial T2WI - Rudimentary posterior interhemispheric fissure, primitive ventricular horns, and anterior midline fusion.
  10. 10. SEMILOBAR HPE Sagittal T1WI shows sHPE with partial differentiation of third ventricle, occipital horns. Axial T2WI in the same patient- Rudimentary temporal and occipital horns. The third ventricle is partially formed. The thalami are separated, but the hypothalamus remains fused.
  11. 11. SEMILOBAR HPE More cephalad T2WI in the same patient shows fused basal ganglia, rudimentary posterior interhemispheric fissure, and absence of anterior interhemispheric fissure with the brain fused across the midline. More cephalad scan shows the upper aspect of a poorly differentiated central monoventricle
  12. 12. LOBAR HPE • Best-differentiated. • IHF & Falx are clearly developed, with shallow and dysplastic-appearing anterior aspects. • Third & lateral ventricles – well formed. • Cavum septum pellucidum is always absent. • Rudimentary frontal horns are typical , and only the most inferior portions of the frontal lobes are fused.
  13. 13. LOBAR HPE Sagittal T2WI of lobar HPE shows well-differentiated brain, nearly normal-appearing third ventricle & azygous ACA Axial T2WI shows well- developed occipital horns, third ventricle, and minimal anterior midline fusion. Coronal T2WI shows that the anteroinferior frontal cortex is fused across the midline.
  14. 14. VARIANTS • Syntelencephaly aka middle interhemispheric variant of HPE. • Septopreoptic HPE - Solitary median maxillary central incisor syndrome. - Congenital nasal pyriform aperture stenosis.
  15. 15. SYNTELENCEPHALY • CC genu, splenium present, middle absent. (Only brain malformation with that morphology) • Mid-sections of falx, interhemispheric fissure absent. • Posterior frontal gray/white matter fused across midline.
  16. 16. SYNTELENCEPHALY Axial graphic-Absent midsection of the IHF, upward extension of an anomalous sylvian fissure across the midline and foci of both gray & white matter that bridge the hemispheres. Axial NECT- Midportions of the hemispheres appear fused across the midline with bridges of both white and gray matter.
  17. 17. SYNTELENCEPHALY Corpus callosum genu and splenium are present without an intervening body. Note dysplastic gray matter deforming the lateral ventricle. Coronal T2- fused,"notched" lateral ventricles with a nodule of gray matter perched on top of the fused lateral ventricle.
  18. 18. SOLITARY MEDIAN MAXILLARY CENTRAL INCISOR SYNDROME. • Single midline incisor. • Often coexists with nasal anomalies. • Brain anomalies of fornix, septi pellucidi, CC. common.
  19. 19. SMMCI Axial bone CT in a 3d infant with breathing difficulty shows a single midline maxillary incisor. Coronal bone CT in the same patient shows the central incisor and narrowed pyriform aperture stenosis.
  20. 20. SMMCI Axial T2WI in the same patient at age 7 months shows lobar HPE with mild hypotelorism and fusion across the ventral frontal lobes. More cephalad scan shows absent septi pellucidi and thickened dysplastic-appearing fused fornices.
  21. 21. CONGENITAL NASAL PYRIFORM APERTURE STENOSIS • Choanal atresia, mid-nasal stenosis, pyriform aperture stenosis. • Often coexists with SMMCI. • HPA axis dysfunction common.
  22. 22. CRANIOFACIAL
  23. 23. RELATED MIDLINE DISORDERS • Septooptic dysplasia. - SOD plus – associated with other anomalies ( Schizencephaly / callosal agenesis) • Arrhinencephaly.
  24. 24. SEPTOOPTIC DYSPLASIA • Aka De Morsier syndrome. • Absence of septi pellucidi. - Squared-off frontal horns, pointed inferiorly on coronal T2WI • Hypoplastic optic nerves, chiasm. • Look for ○ Malformations of cortical development ○ Thin stalk, small gland, ectopic posterior pituitary
  25. 25. SEPTOOPTIC DYSPLASIA Absent cavum septi pellucidi with flat-roofed anterior horns and small optic chiasm. Cavum septi pellucidi are absent ; boxlike lateral ventricles with inferiorly pointed frontal horns. Coronal T2WI in newborn- absent cavum septi pellucidi, schizencephaly,extensive polymicrogyria, fused fornices.
  26. 26. SEPTOOPTIC DYSPLASIA Empty-appearing lateral ventricle with low-lying fornix. The optic chiasm appears small. Hypoplastic optic chiasm, absent septi pellucidi & the peculiar box-like or squared- off" appearance of the frontal horns.
  27. 27. SEPTOOPTIC DYSPLASIA Extreme hypoplasia of the optic chiasm, small pituitary gland with inapparent stalk, and low-lying fornices that give a striking "empty“ appearance to the lateral ventricle. Coronal IR in the same case- unilateral schizencephaly with dysplastic gray matter lining the cleft. Note contralateral polymicrogyria.
  28. 28. ARRHINENCEPHALY • Absent olfactory bulb and tracts. • Often seen in association with other midline facial abnormalities (cleft lip/palate,…) • Kallman syndrome. • CHARGE syndrome – in 25% with olfactory agenesis.
  29. 29. ARRHINENCEPHALY Normal Arrhinencephaly
  30. 30. MIMICS • HYDRANENCEPHALY - Consequence of severe brain destruction in utero. - “Water bag" brain. - Small nubbins of remnant brain with a normal falx cerebri and posterior fossa. - Hemihydranencephaly.
  31. 31. HYDRANENCEPHALY Large head with striking transillumination indicating that most of the cranium is water-filled. The hemispheres are absent ("water-bag brain"), and only the basal ganglia are present. Note separation.
  32. 32. HYDRANENCEPHALY A falx cerebri and tentorium are present, as are the separated basal ganglia. The hemispheres are absent. Both hemispheres are replaced by CSF. BG/thalami are separated, falx is present. No brain is visible over CSF-filled cavities.
  33. 33. HYDRANENCEPHALY Sagittal T1WI - hydranencephaly with macrocephaly; CSF fills virtually all of the supratentorial spaces. Coronal T1WI in the same case- expanded, CSF-filled cranial vault, only tiny remnants of brain. A falx is present.
  34. 34. D/D • Severe obstructive hydrocephalus (OH) Sagittal T1–massively enlarged lateral ventricles & tectal dysplasia causing aqueductal stenosis. Thin rim of compressed but normally formed cortex and subcortical WM lying under the calvarium.
  35. 35. D/D • Alobar holoprosencephaly Almost the entire calvarium is occupied by the CSF-filled monoventricle covered by a very thin rim of featureless brain. The basal ganglia are fused. Note absent falx, thin rim of smooth dysplastic appearing brain.
  36. 36. D/D • Severe bilateral "open lip" schizencephaly Axial T2WI- Severe "open lip" schizencephaly, another cause of "water-bag brain" appearance. Coronal T2WI- falx and tentorium are normal. The massive "open lip" schizencephalic clefts are lined by dysplastic-appearing gray matter.
  37. 37. PRENATAL DIAGNOSIS • As early as 6 weeks from the LMP. • 10 - 14 weeks -- abnormal facial morphology and absence of the “butterfly” sign. • Early closure of the metopic suture. • Absence of the cavum septum pellucidum – Hallmark.
  38. 38. BUTTERFLY SIGN • Normal appearance of the choroid plexuses on axial imaging of the normal first-trimester brain.
  39. 39. SUMMARY • Incomplete separation of the two hemispheres. • Types - Classic – Alobar, Semilobar, Lobar. D/D – Hydranencephaly. D/D – Alobar/ Lobar HPE, depending on severity of sHPE. D/D - SOD,Arrhinencephaly , Syntelencephaly
  40. 40. SUMMARY • Variants- mivHPE, Septopreoptic HPE.
  41. 41. SUMMARY • Related midline disorders – SOD, Arrhinencephaly. D/D – Well-differentiated Lobar HPE.
  42. 42. SUMMARY • Mimics – Hydranencephaly.
  43. 43. CONCLUSION • HPE is not uniformly lethal, as is commonly thought. • Survival depends on the severity of the brain and facial malformations, the presence of chromosomal abnormalities, the involvement of other organs, and the presence of a multiple anomaly syndrome.
  44. 44. REFERENCES • Osborn’s Brain Imaging, Pathology, and anatomy – Second edition. • Holoprosencephaly: A Survey of the Entity, with Embryology and Fetal Imaging - Thomas C. Winter , Anne M. Kennedy, Paula J. Woodward. • Holoprosencephaly: A Guide to Diagnosis and Clinical Management - Manu S Raam, Benjamin D Solomon and Maximilian Muenke.
  45. 45. THANK YOU! Visit www.jssmcradiology.com for more Radiology Education

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