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56 Cards in this Set

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When does the midline of the neural tube close?
~22 days
When does the rostral neural tube close?
~24 days
When does the caudal neural tube close?
~26 days
What forms from the neural crest cells?
The peripheral nervous system:
DRG
Autonomic ganglion
Adrenal chromaffin
Melanocytes
What are the lateral/dorsal signals for regionalisation in the developing neural plate?
BMP
What is the signal for ventral regionalisation of the developing neural plate?
Sonic Hedgehog - released from notochord
What does the telencephalon form from? What structures form from the Telencephalon?
Prosencephalon
> cerebral cortex, amygdala, hippocampus, striatum, lateral ventricle
What does the diencephalon derive from? What structures does it give rise to?
Prosencephalon
>thalamus, retina, 3rd ventricle
What forms from the mesencephalon?
Midbrain and cerebral aqueduct
What does the metencephalon derive from? What does it go on to form?
Rhombencephalon
>pons, cerebellum, 4th ventricle
What structure does the myelencephalon derive from? What does it go on to form?
Rhombencephalon
>medulla and 4th ventricle
What is the name for the single layer of deep neuroepithelial cells that undergo mitosis and eventually migrate superficially in CNS development?
Ventricular zone
How does the CNS account for the surplus of neurons generated in development?
Axons compete for neurotrophic substances. They are guided towards targets by attractant and repellent molecules. Only those neurones that reach the target are sustained by neurotrophins.
Where is CSF produced?
choroid plexus (~80%) and ependyma
Where are the choroid fissures located?
All ventricles except the anterior and posterior horns of the lateral ventricles
What is the mechanism of CSF secretion?
Active: Na-K-ATPase and CO2 metab
Passive: facilitated diffusion
What are the determining factors of CSF absorption?
CSF pressure
Venous pressure
Resistance across arachnoid villi
What is normal CSF pressure in adults?
5-12 mmHg
What is the definition of hydrocephalus?
Increased CSF volume (not pressure)
What are the signs and symptoms of acute hydrocephalus?
Signs:
Headache, nausea, vomiting, lethargy, stupor
Symptoms:
Papilledema, diplopia, "setting sun", false localising, decreased level of consciousness
What are the characteristic signs of normal pressure hydrocephalus?
Gait disturbance, dementia, urinary incontinence
What are the causes of normal pressure hydrocephalus?
Idiopathic: elderly
Secondary: trauma, SAH, meningitis
What is pseudotumour cerebri? Who is generally affected?
Increased ICP in the absence of a mass lesion or hydrocephalus.
Young, overweight females
Which drug is used to reduce CSF production?
Acetazolamide
What is the course of CSF?
Choroid plexus/Ependyma>
Lateral ventricles>
Foramen of munro>
Third ventricle>
Cerebral aqueduct>
Fourth ventricle>
Foramen of Magendie and foramina of Luschka>
SaS cisterns>
Arachnoid villi>
Subdural space sinuses>
Sigmoid sinus (mostly)>
Internal Jugular Vein
What substances pass easily through the BBB?
LMW
Lipid soluble
What are the embryonic layers 18 days after conception?
Ectoderm - nervous system
Mesoderm - mesenchyme (CT)
Endoderm - epithelium
What is the prevalence of spina bifida occulta? Where does it usually occur?
~10%
L5-S1
When does the defect leading to myelomeningocele generally occur?
Around week 4 of gestation
What are the risk and preventative factors for spina bifida?
RF:
anticonvulsants valproic acid and carbamazepine (but only increases risk from 1:1000 to 1:100)
prepregnacy obesity

Preventative:
folic acid 400ug daily for three months before contraception - doesn't attenuate risk due to anticonvulsants or pregnancy though
Which malformation is associated with spina bifida?
Chiari II Malformation due to
small posterior fossa or spinal tethering
Causes cerebellum to be pushes anterior and inferiorly
What are the area of cells lining the neural tube called?
Ventricular zone
T/F Most neurons of the cerebral cortex form between weeks 22-28
False
Weeks 7-16
What cells are used by the proliferating neurons in the ventricular zone to migrate superficially?
Radial glial cells
T/F Neurons don't begin to differentiate until they have migrated from the ventricular zone of the neural tube
True
When do the first synapses in the cerebral cortex occur?
Third trimester
However, most develop postnatally in the first two years
What are the average brain weights at birth and in adulthood? What is the reason for this difference?
300g and 1400g
Mostly due to myelination
During what period of gestation is the male embryo exposed to testosterone?
Weeks 8-20 of gestation
Causes genital development and gender identity
When does the process of neurulation occur?
Days 18-26 of gestation
What are the facies of fetal alcohol syndrome?
Microcephaly, short palpebral fissure, short nose, long philtrum, thin upper lip
What is ARND?
Alcohol Related Neurodevelopmental Disorder
Children without full FAS features but whom may show learning and developmental problems
It is around 3 times more common than FAS
What is required to diagnose epilepsy?
Two or more seizures occurring on multiple occasions
What is the prevalence of epilepsy? What percentage of people who experience a seizure will have epilepsy?
Prevalence around 1%
1/3 of people who have seizures will be due to epilepsy
What is the definition of a generalised seizure?
Those in which the first clinical changes indicate the involvement of both hemispheres
What are the characteristics of a tonic-clonic seizure?
Sudden onset no warning
May see myoclonic jerks first
Tonic phase with tremor
Interrupted by brief atonia
Clonic phase
Unconscious/confused after
What is the definition of a partial seizure?
The first clinical and EEG changes indicate the initial activation of a system of neurons limited to one hemisphere
What percentage of epileptics will have an identifiable cause for the syndrome?
25-30%
What is the major identifiable cause for epilepsy?
Vascular (11%)
Describe the following for childhood absence epilepsy:
Peak onset
Gender association
Remission
Treatment
Peak onset: 6-7 years
Gender: girls>boys
Remission: 80% by adolescence
Treat: ethosuxide, valproate, lamotrigine
Describe the following for juvenile myoclonic epilepsy:
Peak onset
Seizures
Prognosis
Treatment
Peak onset: 12-16 years
Seizures: early morning, tonic-clonic in 95%, sensitive to sleep dep and EtOH
Prognosis: good response to VPA
Treatment: lifelong VPA
T/F Idiopathic epilepsies often show a family history and display a complex inheritance pattern
True
Name four common seizure precipitants
Low glucose (high glucose less often)
Low Na, Ca, Mg
Stimulant or other proconvulsant intox
Sedative withdrawal
Severe sleep deprivation
What is the rate of recurrence after a first seizure?
Around 50%
More common if symptomatic or shows abnormal EEG
What are the key differentials of seizure from convulsive syncope?
Seizure:
Postictal confusion/unconscious
Tonic/clonic evolution
Aura can be associated
Incontinence
Duration longer (minutes)
Muscle soreness/tongue bite
Abnormal EEG
What are the key differentials of syncope from seizure?
Syncope:
Precipitating events (fear, gore etc)
Limp fall
Brief (seconds)
Rapid recovery
Normal EEG
Which surgical remedy for epilepsy has the best success rate?
Temporal lobectomy (60-70% seizure freedom) better than focal extratemporal resection (40-60%)