1. CNS malformations Flashcards
1
Q
Types of CNS malformations
A
- Neural tube defects
- Forebrain anomalies
- Posterior fossa anomalies
- Syringomyelia & Hydromyelia
2
Q
Definition of neural tube defects
A
Failure of a portion of the neural tube to close, or reopening of a region of the tube after successful closure
3
Q
Types of neural tube defects
A
- Spina bifida
- Encephalocele
- Anencephaly
4
Q
Etiologies & Associations with neural tube defects
A
- Occurs during 3rd – 4th week of embryogenesis
- Environmental factors:
- Folate deficiency during initial weeks of gestation - Genetic factors:
- High concordance amongst monozygotic twins
- Overall recurrence rate of neural tube defects in subsequent pregnancies at 4-5%
- May in part be due to polymorphisms in enzymes of folic acid metabolism - Detection in utero (test maternal blood & amniotic fluid)
- Elevation of alpha-fetoprotein levels
- Acetylcholinesterase
5
Q
Definition of Spina bifida
A
Failure of closure of caudal portions of neural tube
6
Q
Types of spina bifida
A
- Spina bifida occulta: asymptomatic bony defect with hairy patch on overlying skin
- Meningocele: isolated meningeal extrusion
- Myelomeningocele: extension of CNS tissue & meninges (occurs most commonly in lumbosacral region)
- Syringomyelocele: extension of CNS tissue & meninges due to a syringomyelia
7
Q
Definition of encephalocele
A
Failure of closure of rostral portions of neural tube
8
Q
Anencephaly
A
- Absence of brain & calvarium due to disrupted forebrain development
- In its place lies area cerebrovasculosa (a flattened remnant of disorganized brain tissue with admixed ependyma, choroid plexus & meningothelial cells)
- Sparing of posterior fossa structures
- Females > Males
9
Q
Types of forebrain anomalies
A
- Microencephaly
- Polymicrogyria
- Holoprosencephaly
10
Q
Microencephaly
A
- Small brain
- Etiologies & Associations
- Chromosomal abnormalities
- Fetal alcohol syndrome
- HIV infection acquired in utero - Presentation can range from a noticeable decrease in gyri to total absence
- Lissencephaly (agyria): complete absence of gyri; brain has smooth surface
11
Q
Polymicrogyria
A
- Small, unusually numerous & irregularly formed cerebral convolutions
- Entrapment of meningeal tissue at points of fusion that
would otherwise be at the cortical surface
12
Q
Holoprosencephaly
A
- Spectrum of malformations characterized by incomplete separation of the cerebral hemispheres across the midline
- Cyclopia: severe variant with failure to divide the orbits of the eye into two separate cavities; the face is typically absent, with a non-functioning nose in the form of a proboscis in its place
- Arrhinencephaly: absence of olfactory cranial nerves
& related structures - Etiologies & Associations
- Trisomy 13
- Maternal diabetes mellitus
13
Q
Types of posterior fossa anomalies
A
- Arnold-Chiari Malformation (Chiari Type II Malformation)
2. Dandy-Walker Malformation
14
Q
Arnold-Chiari malformations (Chiari Type II Malformation)
A
- Characterized by:
- Small posterior fossa
- Misshapened midline cerebellum with downward extension of the cerebellar tonsils through the foramen magnum - Almost invariably involves:
- Hydrocephalus
- Lumbar myelomeningocele
15
Q
Dandy-Walker Malformation
A
- Characterized by:
- Enlarged posterior fossa
- Absence of cerebellar vermis or presence only in its rudimentary form
- In place of cerebellar vermis is a large midline cyst that represents an expanded, roofless fourth ventricle - Results in:
- Raised intracranial pressure & hydrocephalus
- Slow motor & mental development
