Neurology and Special Senses Flashcards
Neural development Day 18
Notochord - induces overlying ectoderm to differentiate into neuroectoderm and form neural plate
What does neural plate give rise to?
Neural tube and neural crest cells
What does notochord become?
Nucleus pulpous of intervertebral disc in adults
Dorsal vs Ventral plate in neural development
Dorsal: alar plate, sensory, regulated by TGF-B (including bone morphogenetic protein BMP)
Ventral: basal, motor, regulated by sonic hedgehog gene (SHH)
Forebrain AKA
Prosencephalon
Midbrain AKA
Mesencephalon
Hindbrain AKA
Rhombencephalon
Prosencephalon becomes
Telencephalon
Diencephalon
Rhombencephalon becomes
Metencephalon
Myelencephalon
What does telencephalon become?
Cerebral hemisphere, basal ganglia, lateral ventricles
What does diencephalon become?
Thalamus, hypothalamus, retina, third ventricle
What does mesencephalon become?
Mid brain and cerebral aqueduct
What does metencephalon become?
Pons (and upper part of fourth ventricle)
Cerebellum
What does myelencephalon become?
Medulla and lower part of fourth ventricle
What does microglia originate from?
Mesoderm
What does neural crest form?
PNS neurons, Schwann cells, glia, melanocytes, adrenal medulla
What does the neuroepithelial of neural tube produce?
CNS neurons, ependymal cells, oligodendrocytes, astrocytes
What is a neural tube defect?
Neuropores fail to fuse (4th week)= persistent connection between amniotic cavity and spinal canal
What is neural tube defects associated with?
Diabetes and folate deficiency
Neural tube defect confirmatory tests
Increased AFP in amniotic fluid and increased AChE
What neural tube defect doesn’t have an increased AFP?
Spinal bifida occult
What is spina bifida occult?
Failure of caudal neuropore to close but no herniation
Seen in lower vertebral levels
Dura is intact
Tuft of hair or skin dimple at level of bony defect
What is a meningocele?
Meninges (but no neural tissue) herniate through bony defect
What is myelomeningocecle?
Meninges and neural tissue herniate through bony defect
What is myeloschisis?
AKA rachischisis
Exposed unfused neural tissue without skin/meningeal covering
What is anencephaly?
Failure of rostral neuropore to close = no forebrain, open calvarium
Polyhydramnois
What is holoprosencephaly?
Failure of embryonic forebrain to separate into 2 cerebral hemispheres usually during weeks 5-6
What causes holoprosencephaly?
Possible mutation in SHH
What is holoprosencephaly additionally associated with?
Midline defects = cleft palate, and cyclopean, increased risk for pituitary dysfunction (diabetes insipidus)
What syndrome can present with holoprosencephaly?
Patau
Trisomy 13
MRI of holoprosencephaly
Monoventricle and fusion of basal ganglia
What is lishencephaly
Failure of neuronal migration resulting in “smooth” brain that lacks sulci and gyri
What is a chairi I malformation ?
Ectopia of cerebellar tonsils inferior to foramen magnum
Congenital, asymptomatic in childhood, headaches and cerebellar syndromes in adulthood
What causes chiari I malformation?
Syringomyelia
What is a Chiari II malformation?
Herniation of cerebellar vermin and tonsils through foramen magnum with aqueduct stenosis
Aqueductal stenosis causes what kind of hydrocephalus?
Noncommunicating
What is Chiari II malformations associated with?
Meylomeningocele (may present with paralysis/sensory loss at and below the level of the lesion)
What Chiari malformation appears in childhood?
II
What is Dandy-Walker malformation?
Agenesis of cerebellar vermis -> cystic enlargement of 4th ventricle that fills the enlarged posterior fossa
What is DW malformation associated with?
Noncommunicating hydrocephalus, spina bifida
What is a syringomyelia?
Cystic cavity within central canal of spinal cord
What is damaged first in syringomyelia?
Anterior white commissure (spinothalamic tract)
= Cape like bilateral loss of pain and temperature sensation in upper extremities
Most common for syringomyelia? C?T?L?
C>T>L
