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56 Cards in this Set
- Front
- Back
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When does the midline of the neural tube close?
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~22 days
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When does the rostral neural tube close?
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~24 days
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When does the caudal neural tube close?
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~26 days
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What forms from the neural crest cells?
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The peripheral nervous system:
DRG Autonomic ganglion Adrenal chromaffin Melanocytes |
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What are the lateral/dorsal signals for regionalisation in the developing neural plate?
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BMP
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What is the signal for ventral regionalisation of the developing neural plate?
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Sonic Hedgehog - released from notochord
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What does the telencephalon form from? What structures form from the Telencephalon?
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Prosencephalon
> cerebral cortex, amygdala, hippocampus, striatum, lateral ventricle |
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What does the diencephalon derive from? What structures does it give rise to?
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Prosencephalon
>thalamus, retina, 3rd ventricle |
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What forms from the mesencephalon?
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Midbrain and cerebral aqueduct
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What does the metencephalon derive from? What does it go on to form?
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Rhombencephalon
>pons, cerebellum, 4th ventricle |
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What structure does the myelencephalon derive from? What does it go on to form?
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Rhombencephalon
>medulla and 4th ventricle |
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What is the name for the single layer of deep neuroepithelial cells that undergo mitosis and eventually migrate superficially in CNS development?
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Ventricular zone
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How does the CNS account for the surplus of neurons generated in development?
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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.
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Where is CSF produced?
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choroid plexus (~80%) and ependyma
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Where are the choroid fissures located?
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All ventricles except the anterior and posterior horns of the lateral ventricles
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What is the mechanism of CSF secretion?
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Active: Na-K-ATPase and CO2 metab
Passive: facilitated diffusion |
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What are the determining factors of CSF absorption?
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CSF pressure
Venous pressure Resistance across arachnoid villi |
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What is normal CSF pressure in adults?
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5-12 mmHg
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What is the definition of hydrocephalus?
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Increased CSF volume (not pressure)
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What are the signs and symptoms of acute hydrocephalus?
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Signs:
Headache, nausea, vomiting, lethargy, stupor Symptoms: Papilledema, diplopia, "setting sun", false localising, decreased level of consciousness |
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What are the characteristic signs of normal pressure hydrocephalus?
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Gait disturbance, dementia, urinary incontinence
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What are the causes of normal pressure hydrocephalus?
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Idiopathic: elderly
Secondary: trauma, SAH, meningitis |
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What is pseudotumour cerebri? Who is generally affected?
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Increased ICP in the absence of a mass lesion or hydrocephalus.
Young, overweight females |
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Which drug is used to reduce CSF production?
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Acetazolamide
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What is the course of CSF?
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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 |
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What substances pass easily through the BBB?
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LMW
Lipid soluble |
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What are the embryonic layers 18 days after conception?
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Ectoderm - nervous system
Mesoderm - mesenchyme (CT) Endoderm - epithelium |
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What is the prevalence of spina bifida occulta? Where does it usually occur?
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~10%
L5-S1 |
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When does the defect leading to myelomeningocele generally occur?
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Around week 4 of gestation
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What are the risk and preventative factors for spina bifida?
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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 |
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Which malformation is associated with spina bifida?
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Chiari II Malformation due to
small posterior fossa or spinal tethering Causes cerebellum to be pushes anterior and inferiorly |
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What are the area of cells lining the neural tube called?
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Ventricular zone
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T/F Most neurons of the cerebral cortex form between weeks 22-28
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False
Weeks 7-16 |
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What cells are used by the proliferating neurons in the ventricular zone to migrate superficially?
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Radial glial cells
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T/F Neurons don't begin to differentiate until they have migrated from the ventricular zone of the neural tube
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True
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When do the first synapses in the cerebral cortex occur?
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Third trimester
However, most develop postnatally in the first two years |
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What are the average brain weights at birth and in adulthood? What is the reason for this difference?
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300g and 1400g
Mostly due to myelination |
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During what period of gestation is the male embryo exposed to testosterone?
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Weeks 8-20 of gestation
Causes genital development and gender identity |
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When does the process of neurulation occur?
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Days 18-26 of gestation
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What are the facies of fetal alcohol syndrome?
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Microcephaly, short palpebral fissure, short nose, long philtrum, thin upper lip
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What is ARND?
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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 |
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What is required to diagnose epilepsy?
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Two or more seizures occurring on multiple occasions
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What is the prevalence of epilepsy? What percentage of people who experience a seizure will have epilepsy?
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Prevalence around 1%
1/3 of people who have seizures will be due to epilepsy |
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What is the definition of a generalised seizure?
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Those in which the first clinical changes indicate the involvement of both hemispheres
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What are the characteristics of a tonic-clonic seizure?
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Sudden onset no warning
May see myoclonic jerks first Tonic phase with tremor Interrupted by brief atonia Clonic phase Unconscious/confused after |
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What is the definition of a partial seizure?
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The first clinical and EEG changes indicate the initial activation of a system of neurons limited to one hemisphere
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What percentage of epileptics will have an identifiable cause for the syndrome?
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25-30%
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What is the major identifiable cause for epilepsy?
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Vascular (11%)
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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 |
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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 |
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T/F Idiopathic epilepsies often show a family history and display a complex inheritance pattern
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True
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Name four common seizure precipitants
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Low glucose (high glucose less often)
Low Na, Ca, Mg Stimulant or other proconvulsant intox Sedative withdrawal Severe sleep deprivation |
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What is the rate of recurrence after a first seizure?
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Around 50%
More common if symptomatic or shows abnormal EEG |
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What are the key differentials of seizure from convulsive syncope?
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Seizure:
Postictal confusion/unconscious Tonic/clonic evolution Aura can be associated Incontinence Duration longer (minutes) Muscle soreness/tongue bite Abnormal EEG |
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What are the key differentials of syncope from seizure?
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Syncope:
Precipitating events (fear, gore etc) Limp fall Brief (seconds) Rapid recovery Normal EEG |
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Which surgical remedy for epilepsy has the best success rate?
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Temporal lobectomy (60-70% seizure freedom) better than focal extratemporal resection (40-60%)
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