Learning Objectives Week 1 Semester 3

Created by Tara Menon

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What are the characteristics and clinical implications of Spina bifida occulta?

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FeatureDescription/Implication
Affected StructureVertebral arch only
Skin CoveringIntact
Clinical SignsTuft of hair or dimple
Neurologic SymptomsTypically none
CSF LevelsNormal

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Neural Tube Development and Defects

What are the characteristics and clinical implications of Spina bifida occulta?

FeatureDescription/Implication
Affected StructureVertebral arch only
Skin CoveringIntact
Clinical SignsTuft of hair or dimple
Neurologic SymptomsTypically none
CSF LevelsNormal
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Neural Tube Development and Defects

What defines Meningocele and its clinical outcomes?

FeatureDescription/Outcome
Herniated StructureMeninges only
Clinical PresentationCystic mass, variable deficits
Neurologic SymptomsVariable (may be absent or mild)
CSF LevelsElevated
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Neural Tube Development and Defects

What are the key features of Myelomeningocele and its associated conditions?

FeatureDescription/Association
Herniated StructuresMeninges + spinal cord
Clinical DeficitsMotor, sensory, bowel/bladder deficits
Associated ConditionsChiari II malformation
CSF LevelsElevated
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Neural Tube Development and Defects

What is Anencephaly and its clinical significance?

FeatureDescription/Significance
CauseAnterior neuropore fails to close
Main FindingAbsence of brain/calvarium
Associated ConditionPolyhydramnios
CSF LevelsElevated
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Neural Tube Development and Defects

What are the implications of Encephalocele in neural development?

FeatureDescription/Implication
DefectSkull defect + brain herniation
Clinical OutcomesSeizures, hydrocephalus, intellectual disability
CSF LevelsVariable
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Neural Tube Development and Defects

What are the major events in neural tube development and their timeline?

DayEvent
18SHH induces neural plate formation
19-20Neural plate begins folding; hinge points form
21-22Neural groove deepens; neural folds elevate
22-23Fusion begins at cervical region
~Day 25Anterior neuropore closes
~Day 27Posterior neuropore closes
Week 4-5Neural crest migration begins
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Micronutrients in Neural Development

What are the key micronutrients involved in normal neural development and their clinical consequences of deficiencies?

  • Micronutrients:

    • Zinc: Important for DNA synthesis and cell division.
    • Thiamine: Essential for energy metabolism in neural tissues.
    • Iron: Crucial for oxygen transport and neurotransmitter synthesis.
    • Copper: Involved in myelination and neurotransmitter release.
    • Iodine: Necessary for thyroid hormone production, affecting brain development.
    • Choline: Important for neurotransmitter synthesis and cell membrane integrity.
  • Macronutrients:

    • Carbohydrates: Provide energy for brain function.
    • Fats: Essential for brain structure and function.
    • Proteins: Necessary for neurotransmitter and enzyme production.
  • Clinical consequences of deficiencies can include developmental delays, cognitive impairments, and increased risk of neural tube defects.

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Neural Tube Development and Defects

What is the pathogenesis of Anencephaly?

Anencephaly is caused by the failure of the rostral (cranial) neuropore to close on day 25 of development.

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Neural Tube Development and Defects

What are the key features of Encephalocele?

Key features of Encephalocele include protrusion of brain/meninges through the occipital region or other cranial sites, leading to neurological deficits, seizures, and developmental delay.

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Neural Tube Development and Defects

What clinical consequences are associated with Craniosynostosis?

Craniosynostosis can lead to increased intracranial pressure, developmental delay, and syndromic forms such as Crouzon syndrome.

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Neural Tube Development and Defects

What is the description of Iniencephaly?

Iniencephaly is a rare neural tube defect characterized by extreme retroflexion of the head, often associated with anencephaly.

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Neural Tube Development and Defects

What is the consequence of Spina Bifida?

Spina Bifida can result in lower extremity paralysis, hydrocephalus (via Chiari II), and neurogenic bladder and bowel incontinence.

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Micronutrients in Neural Development

What is the role of Folic Acid in neural development and what are the consequences of its deficiency?

Folic Acid is essential for DNA synthesis and the closure of the neural tube. Its deficiency can lead to neural tube defects (NTDs).

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Micronutrients in Neural Development

How does Zinc contribute to neural development and what are the effects of its deficiency?

Zinc acts as a cofactor for over 100 enzymes, playing a role in neurogenesis and synaptic signaling. Deficiency can result in poor memory, delayed mental development, and NTDs in utero.

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Micronutrients in Neural Development

What are the consequences of Thiamine (B1) deficiency in neural development?

Thiamine (B1) is a cofactor for pyruvate dehydrogenase, crucial for glucose metabolism in neurons. Its deficiency can lead to Wernicke-Korsakoff syndrome, infantile beriberi, and impaired myelination.

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Micronutrients in Neural Development

What role does Iron play in neural development and what are the consequences of its deficiency?

Iron is important for myelination, dopamine synthesis, and oxygen transport. Deficiency can cause poor cognitive development, learning deficits, and microcytic anemia.

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Micronutrients in Neural Development

What is the significance of Copper in neural development and what are the effects of its deficiency?

Copper serves as a cofactor for enzymes involved in neurotransmitter biosynthesis and myelin formation. Deficiency can lead to Menkes disease, characterized by hypotonia, seizures, and neurodegeneration.

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Micronutrients in Neural Development

What is the role of Iodine in brain development and what are the consequences of its deficiency?

Iodine is critical for the synthesis of thyroid hormones (T3/T4), which are essential for brain development. Its deficiency can result in cretinism, leading to intellectual disability and growth retardation.

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Micronutrients in Neural Development

How does Choline contribute to neural development and what are the effects of its deficiency?

Choline is a precursor to acetylcholine and plays a role in neurogenesis and cell membrane synthesis. Deficiency can lead to memory deficits and impaired fetal brain development.

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Macronutrients in Neural Development

What is the primary role of carbohydrates in neural development and what are the consequences of their deficiency?

Carbohydrates serve as the main energy source for the brain (glucose) and are essential for cell division. Deficiency can lead to hypoglycemia, resulting in seizures and impaired brain growth in infancy.

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Macronutrients in Neural Development

What role do fats, especially DHA, play in neural development and what are the consequences of their deficiency?

Fats, particularly DHA, are crucial for myelin synthesis and the structure of neuronal membranes. Deficiency can impair myelination and lead to poor visual and cognitive development.

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Macronutrients in Neural Development

What is the significance of proteins in neural development and what are the effects of their deficiency?

Proteins provide amino acids necessary for neurotransmitter synthesis, structural proteins, and receptors. Deficiency can result in microcephaly, cognitive delay, and reduced synapse formation.

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Neural Tube Development and Defects

What are the major risk factors for neural tube defects (NTDs)?

Major risk factors for NTDs include maternal diabetes, anticonvulsants (such as valproate), and folate deficiency.

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Neural Tube Development and Defects

What does elevated AFP in maternal serum and amniotic fluid acetylcholinesterase indicate?

Elevated AFP and acetylcholinesterase suggest open neural tube defects such as anencephaly and myelomeningocele.

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Neural Tube Development and Defects

How can periconceptional folic acid impact neural tube defects?

Periconceptional folic acid may prevent many neural tube defects, which are detectable on prenatal ultrasound.

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Cerebrospinal Fluid (CSF) Diagnostics

What are the normal and abnormal findings associated with cerebrospinal fluid (CSF) opening pressure?

Normal opening pressure is 90-180 mmH2O. It is elevated in infections like meningitis, subarachnoid hemorrhage (SAH), and tumors, and decreased in CSF leaks.

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Cerebrospinal Fluid (CSF) Diagnostics

What does a turbid appearance of CSF indicate?

A turbid appearance of CSF suggests bacterial infection, while xanthochromia indicates red blood cell breakdown, often seen in SAH.

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Cerebrospinal Fluid (CSF) Diagnostics

What is the significance of elevated protein levels in CSF?

Elevated protein levels (15-45 mg/dL) in CSF are associated with infections, inflammation, and conditions like Guillain-Barré syndrome.

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Cerebrospinal Fluid (CSF) Diagnostics

What does the presence of oligoclonal bands in CSF suggest?

The presence of oligoclonal bands in CSF is associated with Multiple Sclerosis (MS).

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Cerebrospinal Fluid (CSF) Diagnostics

What is the clinical significance of a positive India Ink stain in CSF?

A positive India Ink stain in CSF indicates the presence of Cryptococcus neoformans, a fungal infection.

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Hydrocephalus Types and Mechanisms

What are the different causes and types of hydrocephalus?

Hydrocephalus can be caused by obstruction of CSF flow, overproduction of CSF, or impaired absorption. Types include communicating and non-communicating hydrocephalus.

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Cerebrospinal Fluid (CSF) Diagnostics

What is the production rate of cerebrospinal fluid (CSF) and its total volume in the human body?

The production rate of cerebrospinal fluid (CSF) is approximately 500 mL/day, with a total volume of about 150 mL.

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Cerebrospinal Fluid (CSF) Diagnostics

Describe the circulation pathway of cerebrospinal fluid (CSF) in the brain.

The circulation pathway of cerebrospinal fluid (CSF) is as follows:

  1. Lateral ventricles
  2. Foramen of Monro
  3. 3rd ventricle
  4. Cerebral Aqueduct
  5. 4th ventricle
  6. Foramina of Luschka (lateral) and Magendie (medial)
  7. Subarachnoid space
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Cerebrospinal Fluid (CSF) Diagnostics

What are the main functions of cerebrospinal fluid (CSF)?

The main functions of cerebrospinal fluid (CSF) include:

  • Cushioning the brain (buoyancy)
  • Removing waste
  • Transporting nutrients
  • Maintaining ionic homeostasis
  • Shock absorption
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Hydrocephalus Types and Mechanisms

What is hydrocephalus and what are its main consequences?

Hydrocephalus is defined as the abnormal accumulation of cerebrospinal fluid (CSF) in the ventricles, leading to an increase in intracranial pressure (ICP).

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Hydrocephalus Types and Mechanisms

What are the characteristics of communicating hydrocephalus?

Communicating hydrocephalus is characterized by:

  • Pathophysiology: Decreased CSF absorption by arachnoid granulations
  • Causes: Meningitis, subarachnoid hemorrhage (SAH), post-infectious fibrosis
  • Features: Increased ICP, headache, papilledema, and risk of herniation
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Hydrocephalus Types and Mechanisms

What distinguishes non-communicating (obstructive) hydrocephalus from other types?

Non-communicating (obstructive) hydrocephalus is distinguished by:

  • Pathophysiology: Obstruction in CSF flow within ventricles or foramina
  • Causes: Aqueductal stenosis, tumors (e.g., colloid cyst), Arnold-Chiari malformation, Dandy-Walker malformation
  • Features: Enlarged ventricles upstream from the blockage
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Hydrocephalus Types and Mechanisms

What is Normal Pressure Hydrocephalus (NPH) and its classic triad of symptoms?

Normal Pressure Hydrocephalus (NPH) is characterized by a slow increase in CSF with normal opening pressure. Its classic triad of symptoms includes:

  • Wet: Urinary incontinence
  • Wobbly: Gait disturbances
  • Wacky: Dementia
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Hydrocephalus Types and Mechanisms

What is Ex Vacuo Hydrocephalus and how does it differ from true hydrocephalus?

Ex Vacuo Hydrocephalus is characterized by ventricular enlargement due to brain atrophy, often seen in conditions like Alzheimer's disease and advanced neurodegeneration. It differs from true hydrocephalus in that it has normal ICP and is related to atrophy rather than an actual accumulation of CSF.

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Hydrocephalus Types and Mechanisms

What are the congenital anomalies associated with hydrocephalus?

The congenital anomalies associated with hydrocephalus include aqueductal stenosis (X-linked), Chiari II malformation, and Dandy-Walker malformation. Symptoms may include macrocephaly in infants, sunsetting eyes, and bulging fontanelle.

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Hydrocephalus Types and Mechanisms

What are the alterations in hydrocephalus related to CSF production, circulation, resorption, and function?

The alterations in hydrocephalus are as follows:

ProcessAlteration in Hydrocephalus
ProductionUsually normal, except in choroid plexus papilloma (overproduction)
CirculationBlocked in obstructive hydrocephalus
ResorptionImpaired in communicating hydrocephalus
FunctionDisrupted: CSF buildup leads to ↑ICP, compressed brain parenchyma, herniation risk
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Hydrocephalus Types and Mechanisms

What is the mnemonic for the triads of Normal Pressure Hydrocephalus (NPH)?

The mnemonic for the triads of Normal Pressure Hydrocephalus (NPH) is 'Wet, Wobbly, Wacky':

  • Wet = urinary incontinence
  • Wobbly = ataxic gait
  • Wacky = dementia (reversible!)
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Hydrocephalus Types and Mechanisms

What clues indicate obstructive hydrocephalus based on ventricular enlargement?

If only part of the ventricular system is enlarged, it suggests obstruction at that level. If all ventricles are enlarged with no obstruction, consider communicating hydrocephalus or Normal Pressure Hydrocephalus (NPH).

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Pharmacology of Antiepileptic Drugs

What is the mechanism of action of the drug that binds to synaptic vesicle protein SV2A?

It modulates neurotransmitter release, especially glutamate and GABA, leading to decreased neuronal excitability.

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Seizure Types and Treatment Approaches

What types of seizures is the drug that binds to SV2A effective against?

It is effective against focal (partial) seizures, generalized tonic-clonic seizures, and myoclonic seizures.

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Pharmacology of Antiepileptic Drugs

What are the hepatic effects of the drug that binds to SV2A?

It has minimal hepatic metabolism and is mostly excreted renally; it does not induce or inhibit CYP enzymes.

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Pharmacology of Antiepileptic Drugs

What are the adverse effects associated with the drug that binds to SV2A?

Adverse effects include somnolence, fatigue, behavioral changes (agitation, depression), and dizziness.

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Pharmacology of Antiepileptic Drugs

What is the mechanism of action of Valproic Acid (Valproate)?

Valproate increases GABA levels by inhibiting GABA transaminase, blocks voltage-gated Na+ channels, and may inhibit T-type Ca²⁺ channels.

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Seizure Types and Treatment Approaches

What seizure types is Valproic Acid effective against?

Valproic Acid is effective against generalized tonic-clonic seizures, absence seizures (as a second line if ethosuximide fails), myoclonic seizures, and focal seizures; it is broad-spectrum and useful in mixed seizure disorders.

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Pharmacology of Antiepileptic Drugs

What are the hepatic effects of Valproic Acid?

Valproic Acid inhibits CYP450 enzymes, especially CYP2C9, and carries a risk of hepatotoxicity, particularly in children under 2 or those with mitochondrial disorders.

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Pharmacology of Antiepileptic Drugs

What are the adverse effects of Valproic Acid?

Adverse effects include GI upset, hepatotoxicity, neural tube defects (teratogenic), pancreatitis, weight gain, tremor, alopecia, and thrombocytopenia.

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Pharmacology of Antiepileptic Drugs

What mnemonic can help remember the characteristics of Valproate?

The mnemonic is 'Valproate = Very broad, but Very Bad for Babies & the liver.'

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Pharmacology of Antiepileptic Drugs

What is the drug class of Midazolam?

Short-acting benzodiazepine

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Pharmacology of Antiepileptic Drugs

How does Midazolam enhance GABA-A receptor activity?

It increases the frequency of Cl channel opening, leading to hyperpolarization and CNS depression.

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Pharmacology of Antiepileptic Drugs

What are the primary uses of Midazolam?

  • Status epilepticus (acute seizures) (IV/IM) - Sedation for procedures - Anesthesia induction
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Pharmacology of Antiepileptic Drugs

What are the pharmacokinetic properties of Midazolam?

  • Rapid onset, short half-life (good for procedures) - High lipid solubility for quick CNS entry - Metabolized by CYP3A4 in the liver
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Pharmacology of Antiepileptic Drugs

What are the key adverse effects associated with Midazolam?

  • Respiratory depression (especially with opioids) - Hypotension - Amnesia - Paradoxical agitation (especially in elderly/kids)
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Pharmacology of Antiepileptic Drugs

What is the reversal agent for Midazolam and its mechanism of action?

Flumazenil - a competitive GABA-A antagonist, but carries a risk of seizures if the patient is benzodiazepine-dependent.

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Pharmacology of Antiepileptic Drugs

What is the mechanism of action (MOA) of Midazolam?

It enhances GABA-A receptor activity, leading to increased chloride ion influx, resulting in CNS depression.

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Pharmacology of Antiepileptic Drugs

What seizure coverage does Midazolam provide?

It is used for acute seizures, particularly in status epilepticus.

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Pharmacology of Antiepileptic Drugs

Which hepatic enzymes metabolize Midazolam?

Midazolam is metabolized by CYP3A4 in the liver.

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Pharmacology of Antiepileptic Drugs

What are the key side effects of Midazolam compared to other antiepileptic drugs?

Key side effects include respiratory depression and amnesia, which are significant compared to other drugs like Levetiracetam and Valproic Acid.

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Seizure Types and Treatment Approaches

What is the difference between a seizure and epilepsy?

A seizure is a transient, abnormal excessive or synchronous electrical discharge of neurons in the brain, which can be provoked or unprovoked. Epilepsy is a chronic disorder characterized by having ≥2 unprovoked seizures >24 hours apart, or one unprovoked seizure with a high risk of recurrence due to underlying brain dysfunction.

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Seizure Types and Treatment Approaches

What are the key differences in the origin of focal and generalized seizures?

Seizure TypeOrigin
FocalLocalized area of one hemisphere (often temporal lobe)
GeneralizedBilaterally and diffusely across both hemispheres
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Seizure Types and Treatment Approaches

How does consciousness differ between focal and generalized seizures?

Seizure TypeConsciousness
FocalCan be preserved (focal aware) or altered (focal impaired awareness)
GeneralizedTypically impaired from onset (except myoclonic seizures)
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Seizure Types and Treatment Approaches

What are some clinical features of focal seizures?

Clinical features of focal seizures include:

  • Jacksonian march (motor spread)
  • Déjà vu or rising epigastric sensation
  • Automatisms (e.g., lip smacking, hand wringing)
  • An aura is often present.
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Seizure Types and Treatment Approaches

What are the different types of generalized seizures and their clinical features?

Generalized seizures include:

  • Tonic-clonic (grand mal): characterized by stiffening followed by convulsions.
  • Absence: presents as a blank stare with a 3Hz spike on EEG.
  • Myoclonic: involves brief jerks.
  • Atonic: results in a sudden loss of muscle tone.
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Seizure Types and Treatment Approaches

What is the typical onset and timeline for focal seizures compared to generalized seizures?

Seizure TypeOnset/WarningDuration
FocalOften preceded by auraSeconds to minutes
GeneralizedAbrupt onset, no warningVaries by type: Absence <15s, Tonic-clonic 1-2min, Myoclonic <1s
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Seizure Types and Treatment Approaches

What is the postictal state like for focal versus generalized seizures?

Seizure TypePostictal State
FocalOften present (confusion, fatigue)
GeneralizedPresent in tonic-clonic; absent in absence and myoclonic seizures
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Seizure Types and Treatment Approaches

What are the EEG findings associated with localized spike or sharp waves in focal epilepsy?

EEG findings can be frequent in focal epilepsy, commonly associated with etiologies such as stroke, tumor, trauma, and cortical dysplasia.

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Seizure Types and Treatment Approaches

What are the common etiologies for generalized discharges in epilepsy?

Common etiologies include genetic epilepsy syndromes, metabolic derangements, and idiopathic causes, with generalized discharges like 3 Hz spike-and-wave seen in absence seizures occurring multiple times daily.

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Pharmacology of Antiepileptic Drugs

What is the treatment approach for focal epilepsy?

The treatment approach involves narrow-spectrum drugs such as:

  1. Carbamazepine
  2. Phenytoin
  3. Gabapentin
  4. Phenobarbital
  5. Lacosamide
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Pharmacology of Antiepileptic Drugs

What is the treatment approach for generalized epilepsy?

The treatment approach involves broad-spectrum drugs such as:

  1. Valproic acid
  2. Levetiracetam
  3. Lamotrigine
  4. Topiramate
  5. Ethosuximide (for absence only)
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Pharmacology of Antiepileptic Drugs

What are the key differences between narrow-spectrum and broad-spectrum antiepileptic drugs?

Drug TypeNarrow-Spectrum (Focal only)Broad-Spectrum (Generalized + Focal)
ExamplesCarbamazepine, Oxcarbazepine, Phenytoin, GabapentinValproate, Lamotrigine, Levetiracetam, Topiramate
Avoid inGeneralized epilepsy (may worsen)Focal-only epilepsy if other safer options exist
Special NotesGood for temporal lobe epilepsyValproate is contraindicated in pregnancy due to neural tube defects
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Seizure Types and Treatment Approaches

What does the mnemonic 'TAMAA' stand for in generalized seizure types?

The mnemonic 'TAMAA' stands for:

  • Tonic-clonic: full body convulsion
  • Absence: 3 Hz, blank stare
  • Myoclonic: quick jerks
  • Atonic: drop attacks
  • Atonic: Associated with Lennox-Gastaut
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Cerebrospinal Fluid (CSF) Diagnostics

How does glucose level in CSF vary in different types of meningitis?

Glucose levels in CSF are approximately 60% of serum glucose. They decrease in bacterial, fungal, and TB meningitis but remain normal in viral meningitis.

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Cerebrospinal Fluid (CSF) Diagnostics

What do increased white blood cells (WBCs) in CSF indicate?

Increased WBCs in CSF indicate bacterial infections if polymorphonuclear cells (PMNs) are elevated, and viral, TB, or fungal infections if lymphocytes are elevated.

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Meninges Structure and Function

What are the three layers of the meninges and their primary functions?

Meningeal LayerLocationPrimary Function
Dura MaterOutermostMechanical protection, contains venous sinuses
Arachnoid MaterMiddleSupports blood vessels, contains CSF
Pia MaterInnermostClosely adheres to CNS, involved in CSF circulation
p.1
Meninges Structure and Function

What is the structure and function of the dura mater?

Structure of Dura Mater:

  • Outermost and toughest layer of the meninges.
  • Composed of dense irregular connective tissue.
  • In the cranial cavity, it has two layers:
    • Periosteal layer: Adheres to the inner surface of the skull.
    • Meningeal layer: Deeper layer, continuous with the spinal dura.
  • In the spinal canal, only the meningeal layer is present.
  • Contains venous sinuses between the two layers in the cranial cavity (e.g., superior sagittal sinus).

Functions of Dura Mater:

  • Provides mechanical protection to the CNS.
  • Forms infoldings (dural reflections) that separate parts of the brain:
    • Falx cerebri: Separates the cerebral hemispheres.
    • Tentorium cerebelli: Separates the cerebrum from the cerebellum.
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Meninges Structure and Function

What is the function of the falx cerebelli in the brain?

The falx cerebelli separates the cerebellar hemispheres and encloses venous sinuses that drain cerebral blood. It is innervated by the trigeminal nerve (CN V) and is pain-sensitive.

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Meninges Structure and Function

What is an epidural hematoma and how does it appear on CT imaging?

An epidural hematoma is usually due to the rupture of the middle meningeal artery between the skull and dura mater. It appears as a biconvex/lentiform hyperdensity on CT imaging.

p.2
Meninges Structure and Function

What causes a subdural hematoma and how is it characterized on imaging?

A subdural hematoma is caused by the tearing of bridging veins between the dura and arachnoid. It is characterized by a crescent-shaped hemorrhage on imaging.

p.2
Meninges Structure and Function

What is the role of arachnoid villi in the central nervous system?

Arachnoid villi (or granulations) protrude into dural venous sinuses, facilitating the absorption of cerebrospinal fluid (CSF) into the venous system.

p.2
Meninges Structure and Function

Describe the structure and function of the arachnoid mater.

The arachnoid mater is the middle meningeal layer, thin and avascular, lying just deep to the dura mater. It encloses the subarachnoid space, which contains cerebrospinal fluid (CSF) and cerebral arteries and veins. It is connected to the pia mater via fine, web-like arachnoid trabeculae and does not follow the contours of sulci but bridges over them.

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Meninges Structure and Function

What is subarachnoid hemorrhage and how does it typically present?

Subarachnoid hemorrhage is bleeding into the subarachnoid space, often from ruptured berry aneurysms, particularly in the Circle of Willis. It typically presents with a sudden, severe headache known as a 'thunderclap headache'.

p.3
Cerebrospinal Fluid (CSF) Diagnostics

What is the procedure for a lumbar puncture and where is it performed?

A lumbar puncture involves accessing cerebrospinal fluid (CSF) from the subarachnoid space at the L3-L4 or L4-L5 levels of the spine.

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Hydrocephalus Types and Mechanisms

What can cause hydrocephalus in relation to the arachnoid villi?

Hydrocephalus can occur if the arachnoid villi are damaged, such as from post-infectious scarring, leading to impaired CSF reabsorption and resulting in communicating hydrocephalus.

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Meninges Structure and Function

What are the key structural features of the pia mater?

The pia mater is the innermost meningeal layer, delicate and highly vascularized, closely adhering to the surface of the brain and spinal cord, and following the contours of gyri, sulci, and fissures.

p.3
Meninges Structure and Function

What are the functions of the pia mater?

The pia mater provides a supportive layer for blood vessels supplying the brain and spinal cord, helps form the perivascular (Virchow-Robin) spaces, and in the spinal cord, continues as the filum terminale, anchoring the cord to the coccyx.

p.3
Meninges Structure and Function

What is meningitis and how does it relate to the pia mater?

Meningitis is the inflammation of the pia and arachnoid (leptomeninges) and can be caused by bacterial, viral, or fungal infections.

p.3
Meninges Structure and Function

What are the relationships between the epidural space and the dura mater?

The epidural space is located between the skull and dura mater; it is only a potential space in the cranium but is a real space in the spinal canal.

p.3
Meninges Structure and Function

What is the significance of the subdural space in relation to the dura and arachnoid layers?

The subdural space is a potential space between the dura and arachnoid layers, which becomes a real space in cases of subdural hemorrhage.

p.4
Meninges Structure and Function

What is the subarachnoid space and what does it contain?

The subarachnoid space is a real space located between the arachnoid and pia mater. It contains cerebrospinal fluid (CSF), blood vessels, and cranial nerves.

p.4
Developmental Origins of Germ Layers

What are the derivatives of the surface ectoderm?

The surface ectoderm gives rise to several structures, including:

  1. Epidermis of skin, hair, nails
  2. Sebaceous, sweat, and mammary glands
  3. Lens of the eye
  4. Anterior pituitary (from Rathke pouch)
  5. Inner ear structures (including external auditory meatus and tympanic membrane - outer layer)
  6. Oral epithelium, including enamel of teeth
  7. Anal canal above the pectinate line
p.5
Neural Tube Development and Defects

What are the derivatives of the neuroectoderm?

The derivatives of the neuroectoderm include:

  1. CNS neurons and glia (brain and spinal cord)
  2. Retina and optic nerve
  3. Pineal gland
  4. Posterior pituitary
  5. Oligodendrocytes and astrocytes
  6. Ependymal cells (line ventricles and central canal)
p.5
Developmental Origins of Germ Layers

What structures are derived from neural crest cells?

Neural crest cells give rise to a variety of structures, including:

  • Peripheral nervous system:
    • Dorsal root ganglia
    • Autonomic ganglia
    • Schwann cells
    • Sensory neurons
  • Adrenal medulla (chromaffin cells)
  • Melanocytes (pigment cells)
  • Parafollicular (C) cells of the thyroid
  • Pia and arachnoid mater
  • Bones/cartilage of the face and skull (e.g., maxilla, mandible)
  • Odontoblasts (form dentin of teeth)
p.6
Developmental Origins of Germ Layers

What are the contributions of the aorticopulmonary septum in heart development?

The aorticopulmonary septum contributes to the outflow tract of the heart by dividing the truncus arteriosus and bulbus cordis.

p.6
Developmental Origins of Germ Layers

What is Hirschsprung disease and what causes it?

Hirschsprung disease is caused by the failure of the enteric nervous system, specifically the Meissner and Auerbach plexuses, to migrate properly during development.

p.6
Developmental Origins of Germ Layers

What are the main divisions of the mesoderm?

The mesoderm is divided into four main divisions:

  1. Paraxial mesoderm
  2. Intermediate mesoderm
  3. Lateral plate mesoderm
  4. Axial mesoderm (notochord)
p.6
Developmental Origins of Germ Layers

What are the derivatives of the paraxial mesoderm?

The derivatives of the paraxial mesoderm (somites) include:

  1. Skeletal muscles (except head and some pharyngeal arch muscles)
  2. Axial skeleton (vertebrae and ribs)
  3. Dermis of skin (dorsal)
p.6
Developmental Origins of Germ Layers

What structures are derived from the intermediate mesoderm?

The intermediate mesoderm primarily gives rise to the urogenital system, which includes the kidneys and ureters.

p.7
Developmental Origins of Germ Layers

What are the derivatives of the lateral plate mesoderm?

The derivatives of the lateral plate mesoderm include:

  1. Cardiovascular system:

    • Heart (including myocardium)
    • Blood vessels
  2. Lymphatics

  3. Body wall (parietal layer)

  4. Smooth muscle of GI and respiratory tract

  5. Serous linings (pleura, pericardium, peritoneum)

  6. Spleen (intraperitoneal mesoderm-derived organ)

  7. Adrenal cortex

p.7
Developmental Origins of Germ Layers

What is the role of the notochord in development?

The notochord, which is part of the axial mesoderm, plays a crucial role in development by:

  • Inducing neural tube formation.
  • Its remnants become the nucleus pulposus of intervertebral discs.
p.7
Developmental Origins of Germ Layers

What is the VACTERL association and its significance?

The VACTERL association refers to a group of congenital anomalies that include:

  • Vertebral defects
  • Anal atresia
  • Cardiac defects
  • Tracheoesophageal fistula
  • Renal anomalies
  • Limb anomalies

This association is significant as it highlights the impact of mesodermal derivatives in developmental anomalies.

p.7
Developmental Origins of Germ Layers

What does the endoderm form in the body?

The endoderm forms the epithelial lining of internal structures and contributes to some glands, playing a vital role in the development of the gastrointestinal and respiratory systems.

p.8
Developmental Origins of Germ Layers

What are the key derivatives of the endoderm germ layer?

The key derivatives of the endoderm germ layer include:

  • Epithelial lining of the GI tract (except mouth and anal canal below pectinate line)
  • Epithelial lining of the lower respiratory tract (trachea, bronchi, alveoli)
  • Bladder (except trigone) and urethra
  • Auditory tube and middle ear cavity
  • Parenchyma of the liver
  • Parenchyma of the pancreas (both exocrine and endocrine)
  • Thyroid follicular cells
  • Parathyroid glands
  • Submandibular and sublingual glands
  • Thymus
  • Eustachian tube
p.8
Developmental Origins of Germ Layers

What are the key derivatives of the ectoderm germ layer?

The key derivatives of the ectoderm (surface) germ layer include:

  • Epidermis
  • Hair
  • Nails
  • Lens of the eye
  • Anterior pituitary
p.8
Developmental Origins of Germ Layers

What are the key derivatives of the neuroectoderm?

Germ Layer/RegionKey Derivatives
NeuroectodermCNS neurons, Retina, Posterior pituitary
Neural CrestSee neural crest derivatives table
MesodermSee mesoderm derivatives table
p.8
Developmental Origins of Germ Layers

What are the key derivatives of the neural crest?

Germ Layer/RegionKey Derivatives
Neural CrestPNS, Melanocytes, Adrenal medulla, Craniofacial bones, C-cells
NeuroectodermSee neuroectoderm derivatives table
MesodermSee mesoderm derivatives table
p.8
Developmental Origins of Germ Layers

What are the key derivatives of the mesoderm?

Germ Layer/RegionKey Derivatives
MesodermMuscle, Bone, Heart, Blood vessels, Urogenital tract, Spleen
NeuroectodermSee neuroectoderm derivatives table
Neural CrestSee neural crest derivatives table
p.9
Developmental Origins of Germ Layers

What are the key mechanics involved in the fertilization stage of embryonic development?

  • Occurs in the ampulla of the fallopian tube.
  • Sperm binds to the zona pellucida of the oocyte (glycoproteins ZP2 and ZP3 are involved).
  • Triggers the acrosomal reaction, allowing sperm to penetrate zona pellucida.
  • Fusion of sperm and oocyte membranes allows sperm nucleus to enter the oocyte.
  • Cortical reaction (release of calcium) prevents polyspermy by hardening the zona pellucida.
  • Oocyte completes meiosis II to form the ovum and second polar body.
  • Male and female pronuclei fuse to form a diploid zygote (2n, 2c).
p.10
Mechanics of Key Developmental Stages

What is the role of ZP3 in fertilization?

ZP3 is a major sperm-binding glycoprotein located on the zona pellucida, which facilitates the binding of sperm to the egg during fertilization.

p.10
Mechanics of Key Developmental Stages

What triggers the calcium wave inside the oocyte during fertilization?

The calcium wave inside the oocyte is triggered by PLCζ (phospholipase C zeta), a sperm factor that initiates this process.

p.10
Mechanics of Key Developmental Stages

What regulates early zygotic processes before the embryonic genome activates?

Maternal mRNA and proteins regulate early zygotic processes until the embryonic genome activates.

p.10
Mechanics of Key Developmental Stages

What are the characteristics of cleavage in early embryonic development?

Cleavage involves a series of mitotic divisions of the zygote without an increase in overall size, resulting in cells called blastomeres. It transitions from 2-cell to 4-cell to 8-cell to 16-cell (morula) stages.

p.10
Mechanics of Key Developmental Stages

What happens during compaction at the 8-cell stage?

During compaction at the 8-cell stage, cell-cell adhesion increases via E-cadherin, leading to the differentiation of cells into the inner cell mass (embryoblast) and outer trophoblast around the 16-cell stage.

p.10
Mechanics of Key Developmental Stages

When does zygotic genome activation (ZGA) begin in humans?

Zygotic genome activation (ZGA) begins around the 8-cell stage in humans, marking a transition in genetic regulation during early development.

p.10
Mechanics of Key Developmental Stages

What occurs during blastulation after fertilization?

Blastulation occurs approximately 5 days after fertilization, during which a fluid-filled cavity (blastocoel) forms inside the morula, creating the blastocyst.

p.11
Developmental Origins of Germ Layers

What are the two main structures formed from the blastocyst and their roles?

The blastocyst consists of the inner cell mass (ICM), which develops into the embryo proper, and the trophoblast, which forms the placenta.

p.11
Developmental Origins of Germ Layers

What is the role of the zona pellucida during implantation?

The zona pellucida is degraded to allow for implantation into the endometrium.

p.11
Developmental Origins of Germ Layers

What are the two types of trophoblasts and their characteristics?

The trophoblast differentiates into:

  1. Cytotrophoblast: Mononuclear and mitotically active.
  2. Syncytiotrophoblast: Multinucleated, invasive, and produces hCG.
p.11
Developmental Origins of Germ Layers

Which genetic factors are crucial for maintaining the pluripotency of the inner cell mass?

The genetic factors crucial for maintaining pluripotency of the inner cell mass are OCT4, SOX2, and NANOG.

p.11
Mechanics of Key Developmental Stages

What initiates gastrulation and what is its significance in development?

Gastrulation is initiated by the formation of the primitive streak on the epiblast surface, converting the bilaminar disc into a trilaminar disc with ectoderm, mesoderm, and endoderm.

p.11
Mechanics of Key Developmental Stages

What happens to epiblast cells during gastrulation?

During gastrulation, epiblast cells migrate toward the primitive streak and invaginate, with the first wave displacing the hypoblast to become the definitive endoderm.

p.12
Neural Tube Development and Defects

What is the role of the notochord in the development of the neural plate during neurulation?

The notochord induces the overlying ectoderm to form the neural plate, which is the first step in the process of neurulation.

p.12
Developmental Origins of Germ Layers

What are the key genetic factors involved in mesoderm formation?

Key genetic factors involved in mesoderm formation include:

  • Nodal (TGF-ß family): Promotes mesoderm and endoderm formation.
  • BMP4: Promotes ventral mesoderm; antagonized by chordin and noggin to allow dorsal structures.
  • Goosecoid, Brachyury (T gene): Organize mesodermal patterning and notochord formation.
  • FGF8: Drives cell migration through the primitive streak.
p.12
Neural Tube Development and Defects

Describe the process of neural tube formation during neurulation.

The process of neural tube formation during neurulation involves the following steps:

  1. The notochord induces the ectoderm to form the neural plate.
  2. The neural plate folds inward to create the neural groove.
  3. The edges of the neural groove elevate and fuse to form the neural tube, which will develop into the brain and spinal cord.
  4. Neural crest cells form at the lateral edges and migrate throughout the embryo.
p.12
Neural Tube Development and Defects

When does neural tube closure occur and what are the key time points?

Neural tube closure occurs in a cranial to caudal direction. The key time points are:

  • Cranial neuropore closes around day 25.
  • Caudal neuropore closes around day 27.
p.12
Neural Tube Development and Defects

What is the function of Sonic Hedgehog (SHH) in neural development?

Sonic Hedgehog (SHH), produced by the notochord, plays a crucial role in neural development by inducing the formation of the floor plate and promoting the development of motor neurons.

p.13
Neural Tube Development and Defects

What is the role of BMP4 in neural tube development?

BMP4 promotes dorsal neural tube structures such as sensory neurons and is derived from the ectoderm.

p.13
Neural Tube Development and Defects

What are the functions of Noggin and Chordin in neural induction?

Noggin and Chordin are BMP antagonists that facilitate neural induction by inhibiting BMP signaling.

p.13
Neural Tube Development and Defects

What is the significance of folic acid in neural development?

Folic acid is critical for neural development; its deficiency can lead to neural tube defects such as anencephaly and spina bifida.

p.13
Mechanics of Key Developmental Stages

What are the three germ layers and their corresponding organ systems during organogenesis?

Germ LayerMajor Organ Systems/Derivatives
EctodermCNS, Epidermis
MesodermHeart, Kidneys, Musculoskeletal system
EndodermGI tract, Lungs, Liver, Pancreas
p.13
Mechanics of Key Developmental Stages

What is the role of HOX genes in organogenesis?

HOX genes are crucial for patterning the anterior-posterior axis during organogenesis; mutations can lead to homeotic transformations.

p.13
Mechanics of Key Developmental Stages

How do FGFs contribute to development?

FGFs (Fibroblast Growth Factors) are involved in the development of limbs and the brain, playing a key role in signaling during organogenesis.

p.13
Mechanics of Key Developmental Stages

What is the function of Wnt signaling in development?

Wnt signaling is essential for limb and axis formation, influencing various developmental processes during organogenesis.

p.13
Mechanics of Key Developmental Stages

What is the role of retinoic acid in gene expression during development?

Retinoic acid regulates the expression of HOX genes, which are vital for proper patterning and development during organogenesis.

p.13
Mechanics of Key Developmental Stages

What is the significance of apoptosis genes in development?

Apoptosis genes, such as the Bcl-2 family, are important for sculpting structures like fingers by removing interdigital webbing during development.

p.14
Neural Tube Development and Defects

What are the key stages of neural tube development during embryogenesis?

  1. Neural induction (Day 18-19): The notochord and prechordal mesoderm secrete Sonic Hedgehog (SHH), inducing the ectoderm to form the neural plate. BMP4 is inhibited by noggin, chordin, and follistatin, allowing ectodermal cells to adopt a neural fate.

  2. Neural plate shaping and folding (Day 19-21): The neural plate elongates, median hinge points (MHP) form at the midline, and the lateral edges elevate to form neural folds, assisted by dorsolateral hinge points (DLHPs).

  3. Convergence and closure (Day 22-28): Neural folds meet and fuse at the midline, forming the neural tube, starting in the cervical region. The anterior neuropore closes around day 25, and the posterior neuropore closes by day 27.

  4. Neural crest cell migration: Neural crest cells delaminate from the neural folds and migrate to form various structures, including dorsal root ganglia and Schwann cells.

p.14
Neural Tube Development and Defects

What molecular and genetic factors are involved in neural tube closure?

  • Sonic Hedgehog (SHH): Promotes ventral patterning and motor neuron development; secreted by notochord.
  • BMP4: Promotes dorsal neural tube identity; inhibited for induction of neuroectoderm.
  • Noggin, chordin, follistatin: BMP antagonists that allow neural fate.
  • PAX3: Involved in neural crest development and neural tube closure.
  • VANGL2 and PCP pathway genes: Guide cell polarity and movement required for proper tube closure.
p.14
Neural Tube Development and Defects

What are the clinical implications of disruptions during gastrulation and organogenesis?

Disruptions during gastrulation can lead to major congenital anomalies, including:

  • Neural tube defects (NTDs): Resulting from neurulation defects.
  • Structural birth defects: Such as congenital heart disease and limb malformations, caused by errors in organogenesis.
p.15
Neural Tube Development and Defects

What are the transcription factors involved in surface ectoderm closure related to neural tube defects?

Grhl2 and Grhl3 are the transcription factors involved in surface ectoderm closure.

p.15
Neural Tube Development and Defects

What is the role of folic acid in relation to neural tube defects?

Folic acid (vitamin B9) is critical for DNA synthesis and methylation; deficiency increases the risk of neural tube defects (NTDs).

p.15
Neural Tube Development and Defects

What are the two types of neural tube defects based on tissue exposure?

Neural tube defects can be classified as open (neural tissue exposed) or closed (covered by skin).

p.15
Neural Tube Development and Defects

What are some risk factors associated with neural tube defects?

Risk factors for neural tube defects include folate deficiency, maternal diabetes, anti-folate drugs (e.g., methotrexate, valproic acid), and genetic mutations in closure-related genes.

p.15
16
Neural Tube Development and Defects

What is spina bifida occulta and its clinical features?

Spina bifida occulta is a failure of vertebral arch fusion without herniation; the skin is intact, and it may present with a tuft of hair or dimple, often asymptomatic.

p.15
16
Neural Tube Development and Defects

What distinguishes myelomeningocele from meningocele?

FeatureMyelomeningoceleMeningocele
Herniated StructuresMeninges + spinal cordMeninges only
Neurologic DeficitsMotor/sensory deficits, bladder/bowel dysfunctionUsually none or mild
Associated ConditionsChiari II malformation, hydrocephalusRarely associated
Skin CoveringOften thin or absentUsually intact
p.15
Neural Tube Development and Defects

What is the clinical significance of elevated maternal serum alpha-fetoprotein (AFP) in diagnosing neural tube defects?

Elevated maternal serum alpha-fetoprotein (AFP) and acetylcholinesterase (AChE) in amniotic fluid are indicative of neural tube defects, except in spina bifida occulta; diagnosis is confirmed by prenatal ultrasound.

p.15
Neural Tube Development and Defects

What is the recommended treatment for neural tube defects?

Treatment includes prenatal folic acid supplementation (400-800 mcg daily; 4 mg if high-risk), surgical closure (postnatal or in utero), shunt placement for hydrocephalus, and multidisciplinary care including neurosurgery, neurology, orthopedics, and physical therapy.

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