Exam 1 Flashcards
Neuronal cell differentiation
the process during which young, immature (unspecialized) cells take on individual characteristics and reach their mature (specialized) form and function
Baby’s brain is fully developed by…
Baby brains are fully developed by 9 mo
Neuronal cell death (apoptosis)
a type of cell death in which a series of molecular steps in a cell lead to its death
5 months after conception
baby’s lobes are fully developed ready for differentiation
Synaptogenesis
a process involving the formation of a neurotransmitter release site in the presynaptic neuron and a receptive field at the postsynaptic partners, and the precise alignment of pre- and post-synaptic specializations.
infant viability
in the 3rd trimester
Extracorporeal Membrane Oxygenation
blood is pumped outside of your body to a heart-lung machine that removes carbon dioxide and sends oxygen-filled blood back to tissues in the body
Synaptic refinement
he reorganization of synapses and connections without significant change in their number or strength
A newborns preference for mutual, rather than unilateral, gaze shows…
that babies are designed for reciprocity(communication between child and parent)
Neurulation
the folding process in vertebrate embryos, which includes the transformation of the neural plate into the neural tube
What part of development takes the longest time?
Development of the Brain
40 days after conception
spinal develops(when?)
Dr. Coubey’s Premature Baby Shows
obtained six incubators in 1896 in France to demonstrate the new technology for saving infants. To add drama, six preterm infants from Virchow’s maternity unit in Berlin were brought and exhibited inside the incubators at the 1896 Berlin Exposition
35 days after conception
the pituitary gland forms
25 days after conception
the forebrain, hindbrain, and the midbrain develop
Attempts to stimulate and revive apparently dead newborns include:
beating, shaking,yelling, fumigating, and dipping in ice-cold water(shocking)
50 days after conception
the cerebral hemispheres form
US ranks 30th in world infant mortality (why?)
- more teen births
- more obese moms
- more unplanned pregnancies
- US count all births as live births
100 days after conception
development of the cerebellum, pons, midbrain, and medulla take place along with cell migration
Historical attempts at resuscitation of newborns
- beating
- shaking
-yelling - fumigating
- dipping in ice-cold water
consequences of prematurity
Underdeveloped infants lead to illness and disability
ex. cerebral palsy
A newborn’s preference for mutual, rather than unilateral, gaze shows…
that babies are designed for reciprocity(communication between child and parent)
Extracorporeal Membrane Oxygenation
blood is pumped outside of your body to a heart-lung machine that removes carbon dioxide and sends oxygen-filled blood back to tissues in the body
Function and responsibility of the NICU
to care for ill preterm and term infants born in the hospital
Dr. Couney’s Premature Baby shows
obtained six incubators in 1896 in France to demonstrate the new technology for saving infants.
Reasons why the US ranks 30th in world infant mortality(tied with Slovakia)
- more teen births
- more obese moms
- more unplanned pregnancies (40%)
- the US counts all births as live births
NICU
department in charge of the care of ill preterm and term infants born in that hospital
Autism (synaptogenesis problem)
cause by the over population of neuroconnections
Synaptogenesis
the creation of synapses between neurons in the nervous system
Apoptosis
programmed cell death
Astrocytoma
a tumor that begins in the CNS in a star shaped cell that supports nerve cells
double band cortex
a disorder in neuronal migration that usually present with seizures and intellectual impairment (almost exclusive in females)
consequences of premature birth
abnormal development of the posterior fossa, some lesions may be overlooked or missed, diagnosis could be delayed due to subtle or silent early postnatal clinical features
Autism (synaptogenesis problem)
cause by the over population of neuroconnections
cell migration
the direct movement of a single cell or group of cells in response to chemical and/or mechanical signal
Six stages of CNS development
Neurogenesis, migration, differentiation, synaptogenesis, neuronal cell death, synaptic refinement
The shortest and most intense stages in development…
Neurogenesis and Migration
Central Nervous System (CNS) Develops…
Central Nervous System (CNS) Develops…
Neurogenesis
mitosis produces neurons and glial cells in the area next to the central canal
migration
Neuronal cell migration
Microcephaly
condition where a baby’s head is smaller than expected
neurogenesis
the process by which new neurons are formed in the brain
Differentiation
final stage in development of neurons where neurons develop according to the need of their system by creating connections with other cells, ect.
Sarnat Stage 1 (mild encephalopathy)
✓ Hyperalert
✓Normal muscle tone, active suck, strong Moro, normal grasp, normal doll’s-eye reflex ✓Increased tendon reflexes
✓Hyper-responsiveness to stimulation
✓Dilation of pupils, reactive
✓Usually lasts <24 hours
Sarnat Stage 2 (moderate encephalopathy)
✓Hypotonia and lethargy
✓Increased tendon reflexes
✓Diminished brainstem reflexes - weak suck, incomplete Moro reflex, varying respiration ✓Possible clinical seizures
Recovery to Stage 1
✓No further seizure activity
✓Transient jitteriness
✓Improvement in level of consciousness
Sarnat Stage 3 (severe encephalopathy)
another name: acute phase
Sarnat Stage 3 (severe encephalopathy)
✓Apnea/bradycardia; mechanical ventilation needed
✓Brainstem: Pupils unequal; variable reactivity & poor light reflex
✓Level of consciousness deteriorates to coma ✓Seizures in first 12 hours: multifocal clonic seizures
Sarnat Stage 3 (severe encephalopathy): deterioration
✓Occurs within 24 to 72 hours
✓Severely affected infants worsen, then death maybe
ways of intervention to delay neuronal death
Therapeutic hypothermia
Therapeutic hypothermia
cooling to 33 degrees celsius is the only neuroprotective treatment in HIE term infants
Treatment of ischemic brain injury aims:
- Slow release of excitatory neurotransmitters
- Decrease caspase-3 activation and apoptosis
- Reduce oxygen free-radicals
- Block inflammatory mediators and inhibit apoptotic pathways
When hypothermia is started
by 6 hours of birth and continued for 72 hours
Why is hypothermia used?
Cooling reduces death or major neurodevelopmental disabilities in neonates with moderate to severe HIE
32-year-old woman whose first baby was delivered via CS attempted vaginal birth this pregnancy. During labor, she had sudden severe abdominal pain, became hypotensive, and fetal heart rate was undetectable. Emergent CS is performed and baby is brought to the resuscitaire
Initial exam reveals an unresponsive floppy infant with no respiratory effort and heart rate of 80 bpm. Apgar scores are 1, 4, and 7 at 1, 5 and 10 minutes
Weight 3720 gms (>90%), T 96.5o , HR 190 bpm, BP 37/23 mmHg (low)
Pale and poorly perfused. On ventilator with periodic respiration effort
Level of consciousness: poor eye opening to stimulation, no sustained alertness Movements and Tone: minimal spontaneous activity, hypotonia Brainstem/Autonomic Function: pupils constricted but reactive, no suck, no gag Reflexes: incomplete Moro, no DTRs
Dx?
HIE (diagnosis)
Good news: immature brain is more resistant to HI than brain of a term neonate, due to the immature brain’s:
✓ Lower cerebral metabolic rate
✓ Lower cerebral O2 demand
✓ Lower sensitivity to neurotransmitters with potential neurotoxicity ✓ Greater plasticity
OTOH: premature birth
✓ Any injury disrupts areas of active neural development
✓ Glucose uptake mechanisms are underdeveloped
✓ Autoregulation of increased cerebral blood flow is immature
A 2-month-old infant is brought to ER by her mother who fears her daughter had a stroke. An hour ago, she was breastfeeding when she began to repeatedly kick her right foot in the air. After 2 minutes, her right arm and leg ‘went limp’. The infant has returned to baseline.
She was born at 40 weeks’ gestation after an uncomplicated pregnancy, with no postnatal complications or recent illnesses
The infant now has normal vital signs and is a well-appearing, playful infant who shows no weakness.
dx?
seizure(dx)
Seizure
Stereotypic spell of abnormal neurologic function (behavior, motor, and/or autonomic function)
Seizures are…
✓More likely than in older patients
✓Behavioral expression is different
✓They reflect rapid ontogeny of ion channel expression
✓Long-term development consequences are worse
✓Need different drug treatment than adults
Neonatal seizures- unusual presentations
Electrographic seizures
Clinical seizures * Subtle
* Tonic
* Clonic
* Myoclonic
Case
Term girl born to a 28-year-old mother. Labor and delivery were notable for tight nuchal cord. She was delivered vaginally. Apgar scores were 7 (-1 tone, -2 color) and 9 (-1 color) at 1 and 5 minutes. The infant had no respiratory distress and fed well overnight. Early on 2nd DOL, she had a 1-minute bilateral clonic seizure.
* She is taken to nursery, where her rapid glucose is 60mg%. An IV is started and phenobarbital is given. She is transferred to NICU, where she has a second seizure, starting in the right arm.
* Exam: VS T36.8, P140, R60, BP 90/50, birth weight 3300g. Length and head circumference are 50th percentile. She is sleepy. There is mildly decreased generalized tone. DTRs are 1-2+ and symmetric.
* A second dose of phenobarbital is given, and no further seizures are noted.
* Serum electrolytes and glucose are normal. CBC is remarkable for hematocrit 36%
(anemic), normal WBC, normal platelet count. Lumbar puncture shows normal CSF.
* Brain MRI scan shows increased signal in left hippocampus.
Dx?
seizures dx
Electrographic seizures
Abnormal electrocortical activity - EEG
✓No behavioral change
✓Cannot be provoked by tactile
stimulation
✓Cannot be suppressed by restraint of infant
Hypersynchronous discharge of a critical mass of neurons
Neonatal seizures (Etiology)
❖85% - Most neonatal seizures are acute provoked seizures Hypoxic-ischemic encephalopathy
Structural brain injuries, especially stroke Transient glucose and electrolyte abnormalities CNS infections
❖15% - Genetic epilepsy syndromes Channelopathies
Brain malformations IEMs
Subtle seizures
✓ More in preterm than in term infants
✓ Gaze deviation (term)
✓ Blinking, fixed stare (preterm)
✓ Repetitive mouth/tongue movements
✓ Pedaling/posturing of limbs
Tonic seizures (Clinical Seizure Classification)
- Primarily in preterm infants with ICH
- Focal or generalized
- Sustained extension of limbs (decerebrate posturing)
- Sustained flexion of upper/extension of lower limbs (decorticate posturing)
Clonic seizures (Clinical Seizure Classification)
✓Primarily in term
✓Focal or multifocal
✓Clonic limb movements (may migrate)
✓Consciousness may be preserved
Myoclonic seizures
✓ Rare, usually bad
✓ Focal, multifocal or generalized
✓ Single jerks of extremities (upper > lower)
Myoclonic movements
rapid, isolated jerks that can be generalized, multifocal, or focal in a trunk or limb distribution
Prognosis of Neonatal Seizures (term)
Mortality and morbidity
Normal= 60%
Dead= 20%
Prognosis of Neonatal Seizures (<2500g)
normal= 35%
dead= 40%
Prognosis of Neonatal Seizures (<1500g)
normal=20%
dead=60%
Two ways to predict the outcome of neonatal seizures
✓ EEG
✓ Underlying neurological disease
Prognosis of neonatal seizures in relation to EEG
(EEG Background Normal)
normal = </= 10%
Prognosis of neonatal seizures in relation to EEG
(EEG Background Moderate abnormal)
~50 Voltage asymmetry, severe immaturity
Prognosis of neonatal seizures in relation to EEG
EEG Background (Neurologic Sequelae)
90 Discontinuity
Neonatal Seizures and Outcome by Cause(poor=0-10)
Cause=
Brain malformations(% Normal Development = 0
Neonatal Seizures and Outcome by Cause(Good=100)
hypocalcemia 100
Benign familial neonatal seizures ~100
Neonatal Seizures and Outcome by Cause(fair=50)
50% normal development
Hypoglycemia
Bacterial meningitis
Hypoxia-ischemia
Neonatal seizures (prognosis)
best if the cause is transient, or has a genetic cause with otherwise normal metabolism and brain formation
newborn brain is biased toward excitation (why?)
NMDA/AMPA receptors are transiently overexpressed in developing cortex; coincides with increased seizure susceptibility
In an immature brain…
NMDA receptor makeup is developmentally regulated
predominant NR2 subunit is NR2B - (longer current decay time than NR2A subunit on mature neurons)
NR2C, NR2D, and NR3A subunits are increased - reduces magnesium sensitivity and thus increases excitability
In immature forebrain…
GABA receptor activation causes depolarization rather than hyperpolarization
KCC2 is virtually absent in first months of life, whereas Cl- importer NKCC1 is overexpressed
In immature forebrain…
Cl- equilibrium potential is positive to the
resting membrane potential
Activation of GABAA receptors results in Cl- efflux
and depolarization
In immature forebrain…
Glutamate is overactive and GABA is excitatory until about 6 weeks of life
An otherwise normal-term boy started having seizures at age 3 days. He had 4–8 seizures per 24 hours, which started with tonic limb posturing with apnea for ~10s followed by vocalizations, eye-rolling, chewing, and asymmetric jerks of the limbs
All relevant tests including interictal EEG were normal
Recommended treatment with valproate was vigorously rejected by the grandmother, the dominant member of the family, who herself, her father, and two of her 4 children had similar neonatal seizures without consequence in their successful lives
He had seizures up to age of 6 weeks but was normal in between seizures. On follow-up at age 2 years, he is a normal child
‘Granny was right again’ the family admitted
Dx?
Severe Myoclonic Epilepsy of Infancy
Severe Myoclonic Epilepsy of Infancy
A SCN1A channelopathy
Begins during first year of life with myoclonic seizures Development arrests
Partial and generalized seizures also occur
Pyridoxine-dependent seizure- Clinical seizure
Clinical seizure - eye deviation to right and asymmetric clonic movements of extremities, associated with widely distributed high voltage electrographic seizures
Pyridoxine-dependent seizure- Clinical seizure (lasts)
Five minutes after the patient received 100mg pyridoxine by IV infusion. EEG shows normal background.
Cranial sonography is best for…
high-risk and unstable premature infants (US type)
Cranial sonography is best for high-risk and unstable premature infants (why?)
Rapid evaluation of infants in NICU without need for sedation and with no risk
A good imaging modality due to its portability, lower cost, speed, with no radiation
Cranial sonography is best for…(dx?)
Most useful for
✓intracranial hemorrhage
✓ hydrocephalus
✓periventricular leukomalacia (PVL)
Triplets are born at 24 weeks gestation to a G1P0 mother for premature labor. Triplet C dies on DOL3 of lung prematurity. Triplets A and B are stable until DOL4 when they become suddenly hypertensive and anemic. Stat head ultrasounds are done. Dx?
PVL
Grade I IVH
Germinal matrix hemorrhage with no or minimal IVH (bilateral germinal matrix hemorrhage)
Grade II IVH
IVH (10–50% of the ventricular area without hydrocephalus)
Grade III IVH
IVH (>50% of the ventricular area) with hydrocephalus)
Grade IV IVH
Periventricular hemorrhage
HUS grading levels
Normal
Grade 1
Grade 2
Cystic PVL
Normal HUS grading
echogenicity of periventricular white matter (PVWM) (brightness of PVWM is same as choroid plexus)
Grade 1(HUS)
slightly increased echogenicity of PVWM, the affected region as bright as the choroid plexus)
Grade 2(HUS)
very increased echogenicity of PVWM, the affected region obviously brighter than the choroid plexus
Cystic PVL(HUS)
holes in the PVWM
PVL grade 1
areas of increased periventricular echogenicity without any cyst formation
PVL grade 2
the echogenicity has resolved into small periventricular cysts
Cerebral edema
Gray-white matter blurring
Neonatal EEG 24-26 wks
hypersynchronous/discontinuous (EEG)
Neonatal EEG 29-30 weeks
synchronous/ discontinuous (EEG)
Neonatal EEG 40 weeks
Dysynchronuous/ continuous (EEG)
Synchronicity is achieved(when)
eeg is reactive and synchronous by 32 weeks
discontinuity is…(eeg)
common early, but by term should only be in quiet sleep
Neonates’ states of consciousness
Awake, active sleep, and quiet sleep
In neonatal eeg(by term)
awake and active sleep look similar
In neonates’ quiet sleep is marked by…
marked by attenuated periods in prematurity, after which it evolves to slow wave sleep
Concern for epileptic activity
discharges that are extremely frequent, persistently in one area, or become rhythmic
Neonatal seizures (evolve)
evolve just like adult seizures, but are usually focal rather than generalized
normal 40.5 weeks PMA
the tracing is continuous with multiple admixed frequencies, and of moderate amplitude
- chaotic appearing wavelengths are normal for neonates when awake
Quiet sleep
trace alternant in quiet sleep starts around 34 weeks PMA and gradually evolves into slow-wave sleep
trace alternant
characterized by quiet periods of voltage over 25 μV, alternating with bursts of 100- to 200-μV amplitude
Active sleep
in a normal 41 week PMA neonate the continuous tracing with a mixture of frequencies, as well as lateral eye movements
How can a neonatal EEG be abnormal?
✓Asymmetric – left and right sides look different
✓Seizing – a focal rhythmic wave
✓Flat - flat
✓(Dysmature) - normal for a younger infant
Asymmetric
left and right sides look different
Seizing
a focal rhythmic wave
Flat
flat
(Dysmature)
normal for a younger infant
formal testing is seldom needed(why?)
information can usually be gleaned from talking to parents and watching, handling, and listening to the baby carefully throughout the exam
Testing during the first few days after delivery
newborns may be neurologically labile
when testing a baby(consider what?)
gestational and postnatal age(considered when?)
Neonates’ first movement occurs…
movement occurs @ 2 months gestation (development of brainstem)
Neonates’ first movements
hiccup, breath, swallow, startle, partial movement
28 week mental status
needs gentle rousing to awaken
28 week cranial nerves
pupils: blinks to light
hearing: pauses, no orientation to sound
suck + swallow: weak suck, no synchrony with swallow
28 week motor function
minimally flexed
28 week reflexes
MORO: weak, incomplete, hand opening
ATNR:
Palmer grasp: present, but weak
32 week mental status
opens eyes spontaneously, sleep-wake cycle is apparent
32 week cranial nerves
consistent pupillary reflex, suck is strong with better synchrony with swallow
32 week motor
flexed hips and knees
32 week reflexes
MORO: complete extension and abduction
34 week cranial nerves
fix and follow (ability to focus and follow an object with eyes)
34 week motor
increased flexion at hips and knees
34 week palmar grasp
grasp is stronger
40 week mental status
at 36 weeks alertness increases and cries when awake
40 week cranial nerves
head and eyes turn to sound
coordinated suck and swallow at 37 weeks
40 week motor
flexed in all extremeties
40 week MORO
full MORO with ant. flexion
40 week ATNR
Appears at 35 wks
40 week palmar grasp
strong grasp, able to be lifted out of bed
Red flag mental status
irritable infant or lethargic infant
Red flag cranial nerves
- no response to auditory stimulus
- chomp suck; clamps down on pacifier but no suck indicating bulbar dysfunction
chomp suck indicates…
bulbar dysfunction
Red flag motor
-hypotonia
- hypertonia
- 28 wk infant with jerky movement
- full-term infant with writhing movements
Red flag pallmar grasp
- asymmetry
- if obligatory or sustained, suggest pyramidal or extrapyramidal motor abnormality
- fixed obligate grasp (suggest B hemisphere dysfunction)
Term baby posture
when prone, the knees are often tucked under the abdomen, fists clenched, thumbs intermittently curl, when the head is midline, limbs are roughly symmetric, like boxers
32 week baby posture
infant lies in froglike position while supine. Legs are slightly flexed at hips and knees, but arms are extended and hypotonic
infant spontaneous motor activity
normal infants move their limbs in alternating fashion (like boxers)
many babies are jittery:
some are jittery only when crying and some are jittery in several behavioral states, but excessive jitter is abnormal
Arousal
Healthy-term infants move between behavioral states, mostly in quiet or active sleep; quiet or active
Visual tracking
Newborns should follow at least 90 degrees with their eyes
Mostly saccadic movement
Primitive reflexes
rooting, sucking, moro, traction, ATNR(asymmetric tonic neck reflex)
rooting(primitive reflex)
reflex helps your baby find and latch onto a bottle or your breast to begin feeding
Neonatal neurologic red flag signals
✓ Persistent irritability
✓ Difficulty in feeding
✓ Persistently deviated head and/or eyes
✓ Persistently asymmetric posture and movements
✓ Persistent adducted thumbs in a fisted hand
✓ Opisthotonos
✓ Persistent posture of flexed arms and extended legs
✓ Apathy and immobility ✓ Floppiness (hypotonia) ✓ Convulsions
✓ Abnormal cry
✓ Setting-sun sign, vomiting, rapid increase in head circumference
Neonatal neurologic exam alarm signals
Persistent:
Asymmetric posture/movements
Limb abduction
Adducted thumb in a fisted hand
Hypotonia
Opisthotonos
Opisthotonos
a condition in which a person holds their body in an abnormal position. The person is usually rigid and arches their back, with their head thrown backward
Neonatal neurologic alarm signals (hydrocephalus )
Setting-sun sign, vomiting, rapid increase in head circumference
Brain development takes the _______ time
takes the longest time
CNS develops _________ gestation (and then some)
develops throughout gestation
The shortest and most intense stages are …
Neurogenesis and Migration (which stages?)
1st stages of brain development
Neurogenesis
Neurogenesis
mitosis produces neurons and glial cells in the area next to the central canal
Error in neurogenesis (proliferation)
microcephaly (what stage of development)
microcephaly (definition)
a condition where a baby’s head is much smaller than expected.
2nd stage of band development
cell migration
cell migration (definition)
the directed movement of a single cell or a group of cells in response to chemical and/or mechanical signals
Double band cortex (what stage of development)
Error in cell migration
double band cortex (definition)
a rare neuronal migration disorder, classically present with seizures and intellectual impairment and is seen almost exclusively in females
3rd stage of brain development
Differentiation
Neuronal/ cell differentiation
a given population of neurons gives rise to subpopulations that are specific to the various parts of the nervous system
Error in differentiation
Astrocytoma (error in what step)
Astrocytoma
a type of cancer that can form in the brain or spinal cord in the star-shaped cell
Error in synaptogenesis
Autism (error in what?)
Synaptogenesis
the formation of synapses between neurons in the nervous system
Autism
A serious developmental disorder that impairs the ability to communicate and interact.
4th stage of brain development
synaptogenesis (what step?)
5th stage of brain development
Neuronal cell death (what stage?)
Apoptosis
neuronal cell death
Fragile X syndrome
error in neuronal cell death
Stage 6 of brain development
Synaptic refinement (what step?)
Synaptic refinement (allows for?)
- Make new friends; keep some of the old friends
- Lifelong
- Activity-dependent
- Allows learning
Error in synaptic refinement
Autism, ADHD, Dyslexia, ect…( error in what?)
Neuronal proliferation/ migration (glutamate)
main excitatory neurotransmitter glutamate is involved in promoting and/or inhibiting the proliferation, survival, migration, and differentiation of NPCs (neuropathic progenitor cells) acting via ionotropic or metabotropic receptors
GABA Neurons
inhibit the production of glutamate
primary microcephaly (genetic)
babies are born with a small brain, which grows but always is small – a disorder of neuronal proliferation, resulting in fewer neurons
Secondary microcephaly (acquired)
from injury during rapid brain growth Environmental insults: prenatal irradiation, drugs, congenital
infections (Zika, cytomegalovirus, toxoplasmosis, HSV) In utero ischemia is a common cause
Megalencephaly - large brains
Neuroepithelial overproliferation, or insufficient apoptosis → too many cells in the brain
Megalencephaly (Familial)
individuals have normal or near-normal intelligence
megalencephaly individuals syndromes…
Syndromes include cerebral gigantism, fragile-X syndrome, autism, and neurocutaneous disorders
Hemimegalencephaly
enlargement of 1⁄2 the cerebrum. Primary symptom is refractory epilepsy, but also MR and hemiparesis
Hemimegalencephaly (FYI)
can occur alone or with neurocutaneous disorders: linear sebaceous nevus, hypomelanosis of Ito, neurofibromatosis
Hemispherectomy is most effective for…
most effective for medically refractory epilepsy
Neuronal Migration and Cortical Lamination (Neocortical migrating)
- have 2 main trajectories
- Most neurons migrate radially, along radial glial guides, from germ zone to cortical plate aka. (over the hill)
Some neurons migrate tangentially through prospective white matter from the ganglia eminences. Most will be GABA interneurons aka. (through the woods)
ganglia eminences
a transitory structure in the development of the nervous system that guides cell and axon migration. It is present in the embryonic and fetal stages of neural development and found between the thalamus and caudate nucleus.
Neuronal Proliferation Step 1
Overproduction of neuroblasts in all parts of the neural tube is followed by apoptosis of redundant neurons
Neuronal Proliferation Step 2
Neuroblast migration to cerebral cortex is complete by 16 weeks
Neuronal Proliferation Step 3
Neocortex is composed of vertical units (neuronal columns)
Neuronal Proliferation Step 5
Glutamate neurons of neocortex are generated in ventricular (VZ) and subventricular (SVZ) zones of lateral ventricles
Neuronal Proliferation Step 6
GABAergic neurons of neocortex are generated in the ganglionic eminences
diffuse lissencephaly (caused by)
Incomplete migration in the cortex causes
pachygyria
Focal lissencephaly
Mistimed arrest of neurons migrating along radial glia to cortex:
Periventricular nodular heterotopia
Periventricular nodular heterotopia
Failure of neurons to leave the ventricular zone
Subcortical laminar heterotopia
Failure of a subgroup of neurons to complete migration, while others finish their migration
Overmigration of neurons
migration of neurons beyond their intended cortical site
Lissencephaly
smooth brain - without gyri Pachygyria describes an area of broad and flat gyri, shallow sulci, and fewer foldings of the cortex
Lissencephaly (Affected infants)
Affected infants fail to thrive, microcephaly, mental retardation, severe epilepsy
Periventricular nodular heterotopia (Nodules)
grey matter located along both lateral ventricles: total failure of migration of a few mitotic neurons
Subcortical laminar heterotopia
- One population of neurons forms relatively normal cortex
- A second population arrests during migration - leading to a band of neurons beneath the cortex
micropolygyria
excessive cortical folding
ectopias
clusters of extra cells
BNFC – benign neonatal familial convulsions
- Focal seizures begin in the first week
- Are due to mutant K+ channel
- Usually resolves in a few weeks
These infants have low seizure thresholds compared with children
Neurotransmitter receptors mature
Some change their function (what?)
GABA changes from…
changes from excitatory to inhibitory about the time of birth
