CNS Semester 1: Cerebrospinal Fluid
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Questions and Answers

What type of injury is characterized by damage to brain tissue on the side opposite to the initial impact?

  • Cerebral contusion
  • Depressed skull fracture
  • Contrecoup injury (correct)
  • Concussion

Which component is NOT found in high concentration in cerebrospinal fluid (CSF) compared to blood?

  • Protein (correct)
  • Sodium
  • Glucose
  • Chloride

What is one of the key functions of cerebrospinal fluid (CSF)?

  • Transport oxygen
  • Maintain thermal balance
  • Remove waste products (correct)
  • Protect against bacterial infection

Which of the following solutes is present in cerebrospinal fluid at lower concentrations than in blood?

<p>Protein (A)</p> Signup and view all the answers

What type of skull fracture occurs when bone is driven into brain tissue?

<p>Depressed skull fracture (A)</p> Signup and view all the answers

Which electrolyte is present in cerebrospinal fluid at a higher concentration than in blood?

<p>Sodium (Na+) (B)</p> Signup and view all the answers

Which of the following is NOT considered a function of cerebrospinal fluid (CSF)?

<p>Support neuronal regeneration (C)</p> Signup and view all the answers

Which of these substances is primarily found in higher concentrations in cerebrospinal fluid but lower in blood?

<p>Lactate (A)</p> Signup and view all the answers

What facilitates the movement of larger water-soluble solutes across the cell membrane?

<p>Specific transporter (A)</p> Signup and view all the answers

What property allows lipid soluble molecules to easily traverse the cell membrane?

<p>Lipid solubility (D)</p> Signup and view all the answers

Which component's concentration is typically lower in cerebrospinal fluid (CSF) compared to plasma?

<p>Potassium (B)</p> Signup and view all the answers

What role does ATP play in the function of P-glycoprotein?

<p>Drives the efflux pump (A)</p> Signup and view all the answers

What is the typical sodium concentration range in plasma?

<p>135-145 mmol/L (C)</p> Signup and view all the answers

What happens to P-glycoproteins when they interact with lipid-soluble molecules?

<p>They change shape and expel the molecules (B)</p> Signup and view all the answers

Which of these ions typically has a higher concentration in CSF compared to plasma?

<p>Chloride (B)</p> Signup and view all the answers

What is the characteristic of permeability at the choroid plexus compared to the blood-brain barrier?

<p>Similar permeability to water-soluble substances (D)</p> Signup and view all the answers

What does the opening pressure of cerebrospinal fluid (CSF) indicate?

<p>The pressure within the CSF system (A)</p> Signup and view all the answers

Which characteristic is typical of a normal cerebrospinal fluid (CSF) sample?

<p>Colorless and clear fluid (A)</p> Signup and view all the answers

In a sub-arachnoid hemorrhage, what change is expected in CSF composition?

<p>Discoloration and yellowish appearance (B)</p> Signup and view all the answers

What is NOT a characteristic of the blood-brain barrier (BBB)?

<p>Allows unrestricted movement of water-soluble substances (D)</p> Signup and view all the answers

What is a primary function of the blood-brain barrier?

<p>To separate circulating blood from the brain and extracellular fluid (A)</p> Signup and view all the answers

In cases of bacterial infection, which of the following changes occur in the CSF?

<p>Increase in lactate levels (D)</p> Signup and view all the answers

How do endothelial cells in the blood-brain barrier differ from those in peripheral capillaries?

<p>They are tightly packed with tight junctions (A)</p> Signup and view all the answers

What happens to CSF lactate levels in cases of CNS infections?

<p>They increase (B)</p> Signup and view all the answers

What is the primary cause of increased CSF pressure leading to hydrocephalus?

<p>Obstruction to CSF circulation (A)</p> Signup and view all the answers

Which condition is characterized by the swelling of the optic disc due to increased intracranial pressure?

<p>Papilledema (A)</p> Signup and view all the answers

What condition results from the brain becoming flattened against the skull due to increased CSF volume?

<p>Hydrocephalus (A)</p> Signup and view all the answers

What is a common cause of hydrocephalus in older adults?

<p>Clogged arachnoid granulations (C)</p> Signup and view all the answers

At what pressure is CSF typically measured in healthy individuals?

<p>10 mm Hg (B)</p> Signup and view all the answers

What is one of the associated conditions that can cause hydrocephalus in infants?

<p>Neural tube defects (A)</p> Signup and view all the answers

Which imaging techniques are typically used for diagnosing hydrocephalus?

<p>CT scan and MRI (A)</p> Signup and view all the answers

What is the goal of cerebral perfusion?

<p>Maintain a constant supply of oxygen and nutrients (B)</p> Signup and view all the answers

What primarily determines the pressure gradient driving cerebral blood flow?

<p>Mean arterial pressure (MAP) (B)</p> Signup and view all the answers

Which condition is likely to decrease cerebral perfusion pressure (CPP)?

<p>Increased intracranial pressure (ICP) (B)</p> Signup and view all the answers

According to the Monro-Kellie Doctrine, what must occur if there is an increase in brain swelling?

<p>Balancing change in another component (A)</p> Signup and view all the answers

What is the effect of elevated intracranial pressure (ICP) on the brain?

<p>Can lead to brain ischemia (C)</p> Signup and view all the answers

For proper cerebral blood flow to occur, which condition must be true?

<p>MAP must exceed ICP (B)</p> Signup and view all the answers

What does central venous pressure (CVP) reflect in relation to blood flow?

<p>Pressure of blood exiting the brain (A)</p> Signup and view all the answers

What can an increase in cerebrospinal fluid (CSF) lead to within the skull?

<p>Increased intracranial pressure (ICP) (B)</p> Signup and view all the answers

What primarily opposes blood flow into the brain?

<p>Intracranial pressure (ICP) (D)</p> Signup and view all the answers

What is the relationship between ICP and CPP?

<p>A decrease in CPP occurs when ICP approaches or exceeds MAP. (A)</p> Signup and view all the answers

What does a Cerebral Perfusion Pressure (CPP) of less than 50 mmHg indicate?

<p>Cerebral ischemia due to insufficient blood flow. (D)</p> Signup and view all the answers

Which factor is NOT affected by high ICP?

<p>Barometric pressure. (D)</p> Signup and view all the answers

What primary physiological adjustment does the body make when CPP is critically low?

<p>Prioritizing blood perfusion to the brain. (D)</p> Signup and view all the answers

Which condition can lead to an increase in ICP?

<p>Trauma. (D)</p> Signup and view all the answers

How does high ICP affect blood vessel function in the brain?

<p>It compresses cerebral vessels, reducing blood flow. (A)</p> Signup and view all the answers

What happens when CPP exceeds 100 mmHg?

<p>It signals potential tissue damage due to excessive perfusion. (B)</p> Signup and view all the answers

Which of the following best describes how the body responds to rising ICP?

<p>Failure of autoregulation to maintain consistent blood flow. (B)</p> Signup and view all the answers

What is the primary site of cerebrospinal fluid (CSF) production?

<p>Choroid plexus (C)</p> Signup and view all the answers

Which structure directly influences the circulation of CSF through the brain's ventricles?

<p>Ependymal cells (B)</p> Signup and view all the answers

How often is cerebrospinal fluid (CSF) replaced in the human body?

<p>Every 6-8 hours (A)</p> Signup and view all the answers

What is the approximate total volume of cerebrospinal fluid (CSF) at any given time?

<p>140 mL (A)</p> Signup and view all the answers

What is the correct sequence of CSF flow from the lateral ventricles to the fourth ventricle?

<p>Lateral ventricles → Third ventricle → Cerebral aqueduct → Fourth ventricle (B)</p> Signup and view all the answers

What is one of the primary consequences of increased intracranial pressure (ICP)?

<p>Decreased blood flow to the brain (C)</p> Signup and view all the answers

Which manifestation is closely associated with a significant rise in ICP?

<p>Cushing's triad (B)</p> Signup and view all the answers

Which of the following is NOT a typical cause of increased ICP?

<p>Pulmonary embolism (B)</p> Signup and view all the answers

What role does cerebrospinal fluid (CSF) volume play in managing increased ICP?

<p>Reducing CSF volume can lower ICP (D)</p> Signup and view all the answers

Which imaging technique is essential for diagnosing conditions associated with raised ICP?

<p>CT or MRI (C)</p> Signup and view all the answers

What can happen to the brainstem if ICP rises excessively?

<p>Loss of blood supply (A)</p> Signup and view all the answers

Which type of brain herniation is associated with compression of the temporal lobe?

<p>Uncal herniation (C)</p> Signup and view all the answers

What is a critical concern when performing a lumbar puncture if elevated ICP is suspected?

<p>Risk of herniation (A)</p> Signup and view all the answers

What is one major function of cerebrospinal fluid (CSF) that directly impacts brain protection?

<p>Acts as a shock absorber (B)</p> Signup and view all the answers

Which characteristic best describes the relative impact of cerebrospinal fluid (CSF) on brain weight?

<p>Decreases effective brain weight to approximately 50g (B)</p> Signup and view all the answers

Where is cerebrospinal fluid (CSF) primarily formed in the brain?

<p>Choroid plexus (B)</p> Signup and view all the answers

What are the consequences of increased intracranial pressure (ICP) on the brain?

<p>Decreased blood flow to the brain (B)</p> Signup and view all the answers

Which statement about cerebrospinal fluid (CSF) function as a cushion is true?

<p>CSF cushions the brain from both gravity and lateral impacts (D)</p> Signup and view all the answers

What role does cerebrospinal fluid (CSF) play in relation to the spinal cord?

<p>Prevents contact with vertebral bones (A)</p> Signup and view all the answers

Cushing's reflex is a response to what condition within the cranial cavity?

<p>Increased intracranial pressure (ICP) (B)</p> Signup and view all the answers

What is the primary purpose of the blood-brain barrier in relation to cerebrospinal fluid (CSF)?

<p>To limit substances entering the brain from blood (D)</p> Signup and view all the answers

What is a potential consequence of untreated hydrocephalus?

<p>Physical flattening of the brain against the skull (D)</p> Signup and view all the answers

How does increased intracranial pressure (ICP) typically affect a patient neurologically?

<p>Confusion and drowsiness (C)</p> Signup and view all the answers

What is one common cause of aqueductal stenosis in infants?

<p>Congenital neural tube defects (D)</p> Signup and view all the answers

What is a typical method for diagnosing increased cerebrospinal fluid (CSF) pressure?

<p>Lumbar puncture (D)</p> Signup and view all the answers

What specific condition in older adults can lead to Normal Pressure Hydrocephalus (NPH)?

<p>Clogged arachnoid granulations (A)</p> Signup and view all the answers

Which sign could indicate increased ICP during a clinical examination?

<p>Papilledema (A)</p> Signup and view all the answers

What can the enlargement of the ventricles indicate in a neurological assessment?

<p>Increased CSF volume leading to hydrocephalus (D)</p> Signup and view all the answers

Which of the following conditions could potentially lead to neural tube defects in infants?

<p>Congenital aqueductal stenosis (D)</p> Signup and view all the answers

What primarily drives cerebral perfusion pressure (CPP)?

<p>Mean arterial pressure (MAP) (A)</p> Signup and view all the answers

According to the Monro-Kellie Doctrine, what must happen when there is an increase in brain swelling?

<p>There must be a decrease in another component such as blood volume. (C)</p> Signup and view all the answers

How does elevated intracranial pressure (ICP) affect cerebral perfusion pressure (CPP)?

<p>It decreases CPP by reducing the pressure gradient. (A)</p> Signup and view all the answers

What role does mean arterial pressure (MAP) play in blood flow to the brain?

<p>It is the pressure of blood entering the brain through arteries. (B)</p> Signup and view all the answers

What explains the relationship between mean arterial pressure (MAP) and intracranial pressure (ICP) for proper cerebral blood flow?

<p>MAP must exceed ICP for cerebral blood flow to occur. (B)</p> Signup and view all the answers

Which component is NOT included in the determination of intracranial pressure (ICP)?

<p>Mean arterial pressure (MAP) (A)</p> Signup and view all the answers

What could potentially result from a decrease in cerebral perfusion pressure (CPP)?

<p>Brain ischemia and insufficient oxygen. (C)</p> Signup and view all the answers

What is the relationship between the pressure gradient and the components influencing cerebral blood flow?

<p>The pressure gradient is influenced by both MAP and ICP. (D)</p> Signup and view all the answers

What physiological response characterizes Cushing’s Reflex as a reaction to increased intracranial pressure?

<p>Elevation of arterial pressure to maintain cerebral perfusion (D)</p> Signup and view all the answers

Which of the following is NOT a component of Cushing’s Triad?

<p>Hypotension (B)</p> Signup and view all the answers

What is the main danger associated with the manifestation of Cushing's Reflex in a patient?

<p>It can lead to brain ischemia if not addressed promptly. (A)</p> Signup and view all the answers

What compensatory mechanism causes bradycardia during Cushing’s Reflex?

<p>Response of baroreceptors to elevated blood pressure (A)</p> Signup and view all the answers

Which intervention is NOT typically used to manage increased intracranial pressure?

<p>Medications to increase blood pressure (C)</p> Signup and view all the answers

What primary change occurs to respiration due to increased ICP as it compresses the brainstem?

<p>Irregular breathing patterns develop (A)</p> Signup and view all the answers

What underlying problem must be addressed to manage Cushing's Reflex effectively?

<p>Reducing intracranial pressure (A)</p> Signup and view all the answers

How does Cushing’s Reflex help maintain cerebral perfusion?

<p>By ensuring arterial pressure is above ICP (A)</p> Signup and view all the answers

Flashcards

Contrecoup injuries

Brain injuries on the opposite side of the initial impact, caused by head movement and brain sloshing in the CSF.

Depressed skull fracture

Skull fracture where the bone is driven into brain tissue.

Cerebrospinal Fluid (CSF)

Fluid that surrounds and cushions the brain and spinal cord, maintaining chemical stability, and removing waste products.

Components of CSF (organic):

Glucose, albumin, urea, amino acids, globulins, immunoglobulins, lactate, enzymes, and neurotransmitters.

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Components of CSF (inorganic)

Sodium (Na+), Chloride (Cl-), Potassium (K+), Bicarbonate (HCO3-), and Calcium (Ca2+).

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CSF vs. Blood Solutes

CSF has higher levels of sodium, chloride, and magnesium compared to blood.

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CSF's Function 1

Maintain an optimal ionic concentration for neuronal functioning.

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CSF's Function 2

Helps buffer pH and remove waste products.

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Cell membrane permeability

The ability of substances to pass through the cell membrane, varying depending on size and charge (lipid solubility).

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P-glycoprotein

A transporter protein that actively pumps lipid-soluble molecules out of cells (efflux pump).

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Lipid solubility

A substance's ability to dissolve in lipids (fats).

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Blood-brain barrier

A barrier that regulates the movement of substances between blood and brain.

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Sodium concentration

Sodium concentration in plasma (blood) is similar to Cerebrospinal fluid.

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Potassium concentration

Potassium concentration is lower in Cerebrospinal Fluid compared to plasma.

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Chloride concentration

Higher in cerebrospinal fluid than blood.

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Choroid Plexus

Specialized tissue producing Cerebrospinal fluid (CSF).

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Opening CSF pressure

The initial pressure of cerebrospinal fluid (CSF) measured during a lumbar puncture.

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Normal CSF characteristics

Clear, colorless fluid with a few white blood cells, no red blood cells, and low protein and glucose level similar to plasma glucose.

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CSF change in Sub-arachnoid hemorrhage

CSF discolors to yellowish due to blood and shows increased WBCs (especially neutrophils).

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CSF changes with bacterial infection

Increased protein, decreased glucose, increased lactate, presence of bacteria, and increased CSF pressure.

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Blood-Brain Barrier (BBB)

A selective barrier that separates blood from brain cells, protecting the brain from harmful substances.

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BBB structure

Tight junctions between endothelial cells of capillaries, along with astrocytes and other glia, forming a continuous barrier.

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BBB function

Regulates the entry and exit of substances into and out of brain cells, maintaining a constant environment.

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BBB vs Peripheral Capillary

BBB endothelial cells have tight junctions, lack fenestrations,minimal pinocytic vesicular transport and have p-glycoproteins.

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What is intracranial pressure?

The total pressure inside the skull, including the pressure from brain tissue, cerebrospinal fluid (CSF), and blood.

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How is CSF pressure measured?

Cerebrospinal fluid (CSF) pressure is measured by a lumbar puncture, which involves inserting a needle into the spinal canal to collect CSF.

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What happens when CSF circulation is obstructed?

Obstruction to CSF flow leads to an increase in CSF pressure, known as intracranial hypertension, which can cause various symptoms like confusion and headache.

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What is papilledema?

Swelling of the optic disc, which can occur due to increased intracranial pressure, and is often a sign of hydrocephalus.

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What is hydrocephalus?

A condition where there is an excess of cerebrospinal fluid (CSF) in the brain, leading to an enlargement of the ventricles.

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What causes hydrocephalus in infants?

Common causes in infants include aqueductal stenosis (narrowing of the aqueduct of Sylvius) and neural tube defects like spina bifida.

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What causes hydrocephalus in older adults?

In older adults, hydrocephalus can be caused by clogged arachnoid granulations, which are responsible for draining CSF.

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What is the role of cerebral perfusion?

Cerebral perfusion is the process of delivering oxygen and nutrients to the brain. It is crucial for brain function.

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Cerebral Perfusion

The flow of blood through the brain, driven by the pressure gradient between mean arterial pressure (MAP) and intracranial pressure (ICP).

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Mean Arterial Pressure (MAP)

The average pressure of blood entering the brain, representing the driving force for cerebral perfusion.

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Intracranial Pressure (ICP)

The pressure inside the skull, resisting blood flow into the brain.

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Monro-Kellie Doctrine

States that the total volume within the skull (brain, blood, and cerebrospinal fluid) must remain constant. An increase in one component requires a decrease in another to maintain normal pressure.

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Elevated ICP

Increased pressure within the skull, reducing the pressure gradient between MAP and ICP, potentially leading to brain ischemia.

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Brain Ischemia

Insufficient oxygen and nutrients reaching brain tissue, caused by reduced blood flow.

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Central Venous Pressure (CVP)

Pressure in veins as blood exits the brain, reflecting the ease of blood drainage.

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Cerebral Blood Flow Gradient

The difference in pressure between MAP (arterial inflow) and CVP (venous outflow), driving blood flow into and out of the brain.

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What is Cerebral Perfusion Pressure (CPP)?

The pressure gradient that drives blood flow to the brain. It ensures the delivery of oxygen and nutrients to brain tissue. Calculated as: CPP = MAP - ICP.

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What is the normal range for CPP?

Normal CPP range is between 60-80 mmHg.

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What happens when CPP is below 50 mmHg?

Cerebral ischemia (insufficient blood flow) can occur.

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How does high ICP affect CPP?

High ICP compresses cerebral vessels, reduces blood flow, obstructs venous outflow, narrows the difference between MAP and ICP, and can even cause mechanical brain compression.

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What is the body's priority when CPP is critically low?

Preserving blood perfusion to the brain takes precedence.

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What is the relationship between ICP and CPP?

ICP is the resistance to blood flow within the skull, while CPP is the pressure driving blood to the brain. High ICP decreases CPP, leading to brain ischemia.

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What are the consequences of a reduced CPP?

Hypoxia (lack of oxygen) and hypercapnia (CO2 buildup) occur due to restricted cerebral blood flow.

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What is the primary cause of increased ICP?

Increased ICP can arise from trauma, haemorrhage, tumours, or other conditions.

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CSF Circulation

The continuous flow of cerebrospinal fluid (CSF) through the ventricles and around the brain and spinal cord.

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CSF Production Rate

The rate at which cerebrospinal fluid (CSF) is produced, which is around 500 mL per day.

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CSF Replacement Rate

The rate at which CSF is replaced, which is about 3-4 times a day.

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CSF Volume

The total volume of cerebrospinal fluid (CSF) in the body, which is about 140 mL.

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CSF Functions

Cerebrospinal fluid (CSF) is the protective fluid surrounding the brain and spinal cord. It provides buoyancy, cushioning, chemical stability, waste removal, and helps in regulating brain volume.

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CSF Formation

CSF is predominantly formed in the choroid plexus, a specialized tissue found in the brain's ventricles. This process involves filtering blood and secreting CSF into the ventricular system.

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What is the Blood-Brain Barrier (BBB)?

The BBB is a selective barrier that protects the brain from harmful substances in the bloodstream. It controls what can enter and leave the brain's delicate environment.

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Increased ICP Consequences

Elevated ICP can squeeze the brain, reduce blood flow, and cause various problems like headaches, vomiting, confusion, and even brain damage.

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Cushing's Reflex

Cushing's reflex is a physiological response to increased ICP, involving elevated blood pressure, slowed heart rate, and irregular breathing.

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Increased intracranial pressure (ICP)

The pressure within the skull, caused by the brain tissue, cerebrospinal fluid, and blood. When this pressure rises, it can compress vessels and reduce blood flow to the brain.

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What is intracranial pressure (ICP) caused by?

ICP can be caused by various factors including traumatic brain injury, brain tumours, bleeding within the skull, hydrocephalus (fluid buildup in the brain), and infections.

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What are the dangers of increased ICP?

Increased ICP can compress cerebral vessels, reducing blood flow to the brain, leading to cerebral ischemia (lack of oxygen) and potential brain damage.

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What are the consequences of increased ICP?

Consequences include brain herniation (brain tissue being pushed out of its normal space), impaired consciousness, respiratory depression, and potential death.

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What are some manifestations of increased ICP?

Symptoms include headache, nausea and vomiting, altered consciousness, pupillary abnormalities, seizures, and Cushing's triad (high blood pressure, slow heart rate, irregular breathing).

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How is increased ICP diagnosed?

Diagnosis involves a clinical examination (including fundoscopy for papilledema), imaging tests such as CT or MRI, and a lumbar puncture (if ICP is not too high).

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What is the role of cerebral perfusion pressure (CPP)?

CPP is the pressure gradient driving blood flow to the brain. It is calculated as CPP = MAP (mean arterial pressure) - ICP (intracranial pressure).

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What is the goal of managing increased ICP?

The goal is to prevent secondary brain injury by improving cerebral blood flow, and reduce ICP by lowering CSF volume. This is achievable through various treatment strategies.

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What is Intracranial Pressure (ICP)?

The overall pressure within the skull, including the pressure from brain tissue, cerebrospinal fluid (CSF), and blood.

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What is CSF Pressure?

The pressure exerted by the cerebrospinal fluid specifically within the subarachnoid space and the brain's ventricular system.

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Cerebral Perfusion Pressure (CPP)

The pressure difference that drives blood flow to the brain. It's calculated by subtracting ICP from MAP: CPP = MAP - ICP.

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Cushing's Triad

A set of three signs indicating increased intracranial pressure (ICP) that include high blood pressure, a slow heart rate, and irregular breathing.

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Hypertension in Cushing's Reflex

The body raises blood pressure to overcome the high ICP, trying to force blood into the brain and maintain perfusion.

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Bradycardia in Cushing's Reflex

The heart rate slows down as a compensatory mechanism to the increased blood pressure, preventing the pressure from getting too high.

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Irregular Respiration in Cushing's Reflex

Increased ICP puts pressure on the brainstem, affecting the respiratory center, leading to abnormal breathing patterns.

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Clinical Perspective of Cushing's Reflex

The appearance of Cushing's reflex in a patient is a critical sign of potentially life-threatening ICP, usually indicating an emergency requiring immediate action.

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Management of Cushing's Reflex

Addressing the cause of high ICP is critical. This involves methods like lowering ICP using osmotic therapy, draining CSF, or surgical decompression, to reduce pressure and restore equilibrium.

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Consequences if Cushing's Reflex is Unmanaged

If the high ICP is not treated, it can lead to brain ischemia, brain tissue displacement (herniation), and even death.

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Study Notes

Course Information

  • Course: CNS
  • Year: 2
  • Semester: 1
  • Code: CNS
  • Title: Blood Brain Barrier, Cerebrospinal fluid, Intracranial Pressure
  • Lecturer: Dr. Melanie Föcking (RCSI-IE), Dr. Colin Greengrass (RCSI-BH)
  • Date: November 2024

Cerebrospinal Fluid (CSF)

  • CSF is a clear, colorless fluid
  • Found in the brain and spinal cord
  • Acts as a cushion
  • Provides basic mechanical and immunological protection to the brain

Functions of CSF

  • Buoyancy: Counteracts brain weight, ensuring it is neutrally buoyant, protecting from gravity injury
  • Protection: Acts as a cushion against impacts and blows
  • Cushioning: Allows the brain to withstand minor traumas of everyday living
  • Circulation: Transports and removes nutrients and waste products

Formation of CSF

  • Primary site: Choroid plexus (tufts of capillaries in the ventricles)
  • Formed by tufts of capillaries and their associated membranes
  • Majority formed in the lateral ventricles (70%)
  • Remaining 30% produced by other brain capillaries

Blood-CSF Barrier

  • Formed by choroid plexus and other brain capillaries
  • Regulates the entry of substances from blood into CSF
  • Transporters promote entry of some substances and restrict others
  • Maintains optimal ionic concentration for neuronal functioning
  • Helps in buffering pH and waste products

CSF Components (Composition)

  • Primarily water (99.13%)
  • Organic solutes (0.87%): Glucose, albumin, urea, amino acids, globulins, immunoglobulins, lactate, enzymes, neurotransmitters etc
  • Inorganic solutes: Sodium(Na+), chloride (Cl-), potassium (K+), bicarbonate (HCO3-), calcium (Ca2+), magnesium (Mg2+), trace metals

Intracranial Pressure (ICP)

  • Pressure exerted within the skull
  • Reflects pressure from brain tissue, blood, and CSF
  • Normal range: 7-15 mm Hg (in adults, supine)
  • Elevated ICP can compress cerebral vessels, reducing blood flow & causing cerebral ischemia

Causes of Increased ICP

  • Traumatic brain injury
  • Brain tumours
  • Haemorrhage (e.g., subdural, epidural, intracerebral)
  • Hydrocephalus
  • Infections (e.g., meningitis, encephalitis)

Consequences of Increased ICP

  • Brain herniation syndromes (e.g., uncal, central, tonsillar)
  • Compressed brainstem → Impaired consciousness and respiratory depression

Clinical Relevance of ISF

  • Abnormalities in ISF formation/composition can cause neurological issues
  • Alzheimer's disease: Impaired ISF dynamics can lead to beta-amyloid accumulation
  • Oedema: Brain injury can disrupt the BBB, leading to abnormal ISF accumulation & swelling

Abnormal Trauma

  • Abnormal trauma leads to brain injury
  • Examples: Contrecoup injury and depressed skull fracture

CSF Circulation

  • CSF flows from the lateral ventricles through the interventricular foramina to the third ventricle, then through the cerebral aqueduct to the fourth ventricle to the subarachnoid space.
  • CSF circulates around the brain and spinal cord and is absorbed into venous blood via arachnoid granulations.

Glymphatic System

  • The glymphatic system is a CSF-based waste clearance pathway that plays a significant role in waste removal.
  • CSF facilitates waste transportation.
  • Primarily active during sleep.

Lumbar Puncture

  • A hollow needle is inserted between the 3rd/4th or 4th/5th lumbar vertebrae in such a way that the puncture site lies in the subarachnoid space.
  • Opening pressure is the initial CSF pressure reading from the subarachnoid area.

Papilledema

  • Swelling of optic disk
  • A symptom of elevated ICP

Hydrocephalus

  • An increase in CSF volume
  • Results in enlarged ventricles
  • Can cause brain flattening and damage

CPP (Cerebral Perfusion Pressure)

  • Pressure gradient driving blood flow to brain tissue.
  • Ensures the delivery of oxygen and nutrients to brain tissue
  • CPP = MAP - ICP
  • Normal range: 60-80 mmHg
  • Low CPP can lead to brain ischemia.
  • High CPP can cause damage.

Cushing's Reflex

  • A physiological response to increased intracranial pressure (ICP).
  • Mechanism: The body attempts to increase blood pressure and slow heart rate to maintain perfusion despite the reduced pressure gradient.
  • Elevated blood pressure with bradycardia, irregular respiration
  • Important clinical sign that can indicate rising ICP.

Management of Raised ICP

  • Address the underlying causes (e.g., trauma, hemorrhage, tumour)
  • Reduce ICP: Medication, fluid removal, or surgical decompression.
  • Optimise blood flow.
  • Monitoring ICP

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RCSI CNS Phys 2024 Blood Brain Barrier CSF Intracranial Pressure PDF

Description

Test your knowledge on Cerebrospinal Fluid (CSF) and its functions, including buoyancy, protection, cushioning, and circulation. Discover how CSF is formed and its significance in the brain's mechanical and immunological protection. This quiz is designed for 2nd-year CNS students.

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