2. Congenital Malformations: Failure to cleave

Question 1

Holoprocencephaly

Answer 1

a failure to perform the normal midline cleaving

Cleaving always starts back to front - So in milder fomrs, the posterior cortex is normal and the anterior cortex is fused

Question 2

• Holoprosencephaly ( HPE) types

Answer 2

Question 3

Answer 3

Lobar Holoprosencephaly

Focal areas of incomplete fusion
anteriorly (usually the fomix)

Ventricles: Variable mild fusion of
the frontal horns of the
lateral ventricles.

Thalamus: Normal

Absent structures:
- Septum pellucidum
- Corpus callosum

Survive to Adulthood

Question 4

Answer 4

Semi-Lobar Holoprocencephaly

Back is cleaved (not the fron)
>50% fused frontal lobes

Ventricles: body of lateral ventricles = 1 chamber

Fused:
* Septum Pellucidum
* Corpus Callosum (partial)
* Anterior Interhemispheric Fissure
* Anterior Falx Cerebri

Associated Horrible thinks
Cleft Lip / Palate

Survive to adulthood but terrible at jeopardy

Question 5

Answer 5

Alobar Holoprosencephaly

Cerebral hemispheres are
fused and there is a single
midline ventricle

Single Ventricle

Fused:
* Septum Pellucidum
* Corpus Callosum
* Interhemispheric Fissure
* Falx Cerebri

CYCLOPS

Stillbonr/dede < 1 year

Question 6

Possible BUZZWORDS for HPE spectrum

Answer 6

Monster Cyclops eyes
Cleft lips/Palates
Pyriform Aperture Stenosis (from nasal process overgrowth)
Solitary Median Maxillary Incisor (MEGA-Incisor)

Question 7

Arhlnencephaly

Answer 7

“Minor” HPE expression

Midline olfactory bulbs / tracts are absent.

CAN’T SMELL

Could be tested as Kallmann Syndrome
(which also has hypogonadism, & mental
retardation)

Question 8

Meckel-Gruber Syndrome

Answer 8

1. Occipital Encephalocoele
2. Multiple Renal Cysts
3. Polydactyly

Also strongly associated with
Holoprosencephaly

Question 9

Septo Optic Dysplasia

Answer 9

Minor HPE expression — “de Morsier Syndrome ”

Associated with Schizencephaly