ACRANIA (Absent
Cranial Vault) |
|
Exencephaly
|
Iniencephaly
|
|
Flat bones of calvarium |
Absent |
Partial or Complete absence |
*
Partial or complete absence. Clausus = without encephalocele |
|
|
|
|
Skull base
|
N |
N |
*
Dysraphic defect in occiput. |
Fetal neck
|
N |
N |
*
Persistent hyperextension. |
Cervical |
N |
N |
*
Hyperextended |
|
|
|
|
Cerebral tissue |
Absent - occasional remnants of
forebrain |
Present but: |
Normal
or absent if associated with anencephaly or abundant and disorganized if
associated with exencephaly. |
|
|
|
|
Brainstem
|
Partially
present esp medulla. |
Present. |
Usually
present. |
Other signs
|
* Frogs eye: |
|
|
|
|
|
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Pathology
|
Primary
non closure of ant. neuropore or secondary
degeneration of closed neuropore |
?
Failure of mesenchymal migration |
Unknown |
REFERENCES |