Brain and Spinal Cord Meninges
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Questions and Answers

What are the three layers covering the brain and spinal cord, from outside to inside?

The three layers are the dura mater, arachnoid mater, and pia mater.

How does the dura around the brain differ from the dura around the spine?

The dura in the skull is like a double-layered sandwich, while in the spine, the dura is just a single layer and is not attached to the vertebrae.

The epidural space is the same in the head and spine.

False (B)

Where is the subdural space located?

<p>Between the dura and arachnoid.</p> Signup and view all the answers

Where is the subarachnoid space located?

<p>Under the arachnoid, right above the pia.</p> Signup and view all the answers

How does the spinal cord stay put inside the dura?

<p>Both A and B (C)</p> Signup and view all the answers

Why are lumbar punctures done below L2?

<p>To avoid spearing the spinal cord.</p> Signup and view all the answers

What is the target space for lumbar punctures?

<p>The subarachnoid space.</p> Signup and view all the answers

What is the function of arachnoid granulations?

<p>To drain CSF into the bloodstream.</p> Signup and view all the answers

What is the likely diagnosis for a head injury patient with a lens-shaped bleed on a CT scan?

<p>Epidural hematoma.</p> Signup and view all the answers

How does an epidural hematoma appear on imaging?

<p>Bright, biconvex (lens-shaped), stays within suture lines (B)</p> Signup and view all the answers

What is a "bloody tap" during a lumbar puncture?

<p>When the CSF starts bloody but clears as you collect more tubes indicating you poked a vein in the epidural space.</p> Signup and view all the answers

How does the pia mater relate to the blood-brain barrier?

<p>The pia helps keep things sealed, though the blood-brain barrier itself is mostly from tight junctions in capillary endothelial cells and astrocyte foot processes.</p> Signup and view all the answers

Which of the following is a scenario where the subarachnoid space is critically important?

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

What is the falx cerebri?

<p>The falx is that sickle-shaped curtain of dura that splits the brain into left and right halves.</p> Signup and view all the answers

Why are spinal epidural hematomas an emergency?

<p>Even a small bleed in the epidural area can crush the spinal cord.</p> Signup and view all the answers

How does CSF get back into the blood?

<p>CSF drains trough those arachnoid granulations into the dural sinuses.</p> Signup and view all the answers

In a trauma patient, what condition is indicated by a crescent shaped bleed on a CT scan?

<p>Subdural hematoma.</p> Signup and view all the answers

Why are lumbar punctures performed below L2?

<p>To avoid spearing the spinal cord.</p> Signup and view all the answers

What does a lens-shaped bleed on a CT scan of a head injury patient indicate?

<p>Epidural hematoma.</p> Signup and view all the answers

Match the hematoma type:

<p>Epidural = Bright, biconvex (lens-shaped), stays within suture lines. Associated with artery and skull fracture. Common in young patients with a temporal bone fracture. Subdural = Crescent-shaped, crosses sutures (but not midline). Caused by torn bridging veins. Common in elderly or chronic alcoholics.</p> Signup and view all the answers

During a lumbar puncture, what does a 'bloody tap' indicate?

<p>Poking a vein in the epidural space (traumatic tap) or subarachnoid hemorrhage.</p> Signup and view all the answers

Give two scenarios where the subarachnoid space is a big deal clinically. (Select two)

<p>Meningitis (B), Aneurysm rupture (D)</p> Signup and view all the answers

What is the falx cerebri made of?

<p>The meningeal dura layer (not the periosteal part).</p> Signup and view all the answers

How does CSF get back into the blood, and what if it can't?

<p>CSF drains through those arachnoid granulations into the dural sinuses.</p> Signup and view all the answers

Trauma patient with a crescent-shaped bleed on CT—what's the diagnosis?

<p>Subdural hematoma.</p> Signup and view all the answers

Flashcards

Dura Mater

The tough, outer layer of the meninges.

Arachnoid Mater

The web-like, middle layer of the meninges.

Pia Mater

The thin, inner layer of the meninges that clings to the brain and spinal cord.

Dura Mater Layers

In the skull, it's a double layer; in the spine, it's single.

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Spinal Epidural Space

A space filled with fat and veins between the dura and vertebrae in the spine.

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Cranial Epidural Space

Non-existent unless there's bleeding, as the dura adheres tightly to the skull.

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Epidural Hematoma Artery

The middle meningeal artery, often torn in skull fractures.

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Subdural Space

The space between the dura and arachnoid mater.

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Subarachnoid Space

The space between the arachnoid and pia mater, containing CSF and major arteries.

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Bridging Veins

Small veins that run from the brain surface to the dura, prone to tearing.

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Subdural Hematoma

A blood collection between the dura and arachnoid, often crescent-shaped.

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Thunderclap Headache

A headache caused by bleeding into the subarachnoid space.

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Denticulate Ligaments

Structures that anchor the spinal cord to the dura mater.

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Filum Terminale

A thin strand of pia that anchors the spinal cord to the tailbone.

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Conus Medullaris

The lower end of the spinal cord, usually at L1-L2 in adults.

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Why LP Below L2?

To avoid damaging the conus medullaris.

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LP Target Space

To obtain CSF for analysis.

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Arachnoid Granulations

One-way valves that drain CSF into the dural sinuses.

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Hydrocephalus

A backup of CSF due to blocked drainage.

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Epidural Hematoma (Shape)

A lens-shaped blood collection between the dura and skull.

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Epidural Hematoma (Imaging)

Bright and biconvex, within suture lines.

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Subdural Hematoma (Imaging)

Crescent-shaped, crosses suture lines.

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Traumatic Tap

CSF clears as more is collected.

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Subarachnoid Hemorrhage (LP)

CSF uniformly bloody, doesn't clot, xanthochromia.

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Xanthochromia

Yellow tinge to CSF after RBC breakdown.

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Blood-Brain Barrier

Is mostly from capillary endothelial cells but the pia contributes.

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Meningitis

Bugs inflame the arachnoid and pia mater.

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Falx Cerebri

Sickle-shaped dura separating the brain hemispheres.

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Spinal Epidural Hematoma

Rapid decompression is needed to prevent permanent damage.

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Hydrocephalus (Cause)

CSF builds up due to blocked drainage route.

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Dura Layers

In the skull, it consist of two layers, while in the spine, it is a single layer.

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Epidural Hematoma

A collection of blood that is in Biconvex shape that occurs between the dura and skull.

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Study Notes

Brain and Spinal Cord Coverings

  • The three layers that cover the brain and spinal cord are the dura mater, arachnoid mater, and pia mater.
  • The dura mater in the skull has two layers (periosteal and meningeal), which split to form dural sinuses for blood drainage.
  • The dura mater in the spine only has one layer, creating an epidural space filled with fat and veins.
  • There is no natural epidural space in the brain, unless there's a bleed.
  • In the spine, the epidural space where anesthesia is injected is packed with fatty cushioning and veins, including Batson's plexus.
  • Blood in the epidural space indicates a torn middle meningeal artery from a skull fracture.

Subdural vs. Subarachnoid Spaces

  • The subdural space is between the dura and arachnoid. Trauma can lead to subdural hematomas via torn bridging veins.
  • On a CT scan, subdural hematomas appear crescent-shaped and can cross skull sutures but not the midline.
  • The subarachnoid space is under the arachnoid, containing CSF and major brain arteries.
  • Subarachnoid hemorrhage (e.g., a ruptured aneurysm) causes "thunderclap headaches."
  • Meningitis inflames the subarachnoid space.
  • The spinal cord is secured by denticulate ligaments (21 pairs) and the filum terminale (a skinny thread of pia).
  • These structures are primarily embryonic pia tissue.

Lumbar Punctures

  • Lumbar punctures should be performed below L2 (e.g., L3-L4) to avoid hitting the spinal cord, targeting the subarachnoid space for CSF collection.
  • A traumatic tap occurs from hitting an epidural vein. If CSF is uniformly bloody it indicates subarachnoid hemorrhage.
  • Xanthochromia (yellowish CSF) indicates broken down red blood cells.

Arachnoid Granulations

  • Arachnoid granulations act as one-way valves that protrude into the dural sinuses, particularly the superior sagittal sinus, facilitating CSF drainage.
  • Arachnoid granulations blockage can cause hydrocephalus.
  • The arachnoid contains arachnoid trabeculae to hold blood vessels.

Epidural Hematoma

  • On a CT scan, lens-shaped bleed may mean epidural hematoma.
  • Arterial blood strips the dura off the skull, forming a high-pressure pocket.
  • Immediate surgery may be needed and these do not cross skull sutures.

Subdural Hematoma

  • On imaging, subdural hematomas appear crescent-shaped, cross sutures but not the midline, and arise from torn bridging veins.
  • If CSF starts bloody but clears up during collection, suspect a traumatic tap from accidentally puncturing a vein in the epidural space.
  • uniformly bloody CSF could be a sign of subarachnoid hemorrhage.
  • Red blood cells in the CSF can cause Xanthochromia (yellow supernatant) after a few hours

Pia Mater

  • The pia mater follows the brain's surface, diving into sulci, and helps the blood-brain barrier seal.
  • The arachnoid and pia mater can become inflamed by bacteria or viruses (bugs) in cases of meningitis.
  • CSF can become cloudy with white cells in cases of meningitis .
  • In cases of an Aneurysm rupture the subarachnoid space is flooded causing headaches.

Falx Cerebri

  • The falx cerebri is a sickle-shaped structure made of the meningeal dura layer that separates the brain into left and right halves.
  • A midline shift on a scan occurs when a mass pushes the falx.
  • Spinal epidural hematomas are emergencies due to compression of spinal cord resulting in back pain and leg weakness or paralysis.

Hydrocephalus

  • The CSF drainage can become blocked resulting in Hydrocephalus due to a subarachnoid hemorrhage or infection
  • The blockage may be in the ventricles leading to non-communicating hydrocephalus.
  • A blockage at the arachnoid granulations leads to communicating hydrocephalus
  • Subdural hematomas result from slow venous oozing from bridging veins, common in older individuals.
  • Epidural bleeds are arterial, rapid, and results from skull fractures.

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Description

The meninges are the protective layers covering the brain and spinal cord. These include the dura mater, arachnoid mater, and pia mater. The dura mater has structural differences in the skull versus the spine, impacting epidural space and potential pathways for infection.

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