Anatomy of Space Occupying Lesions Flashcards

1
Q

What is a space occupying lesion?

A

Abnormal tissue taking up space in the skull

Both acute and subacute (expanding) intracranial pathologies can be considered as SOLs

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2
Q

How and why does a space occupying lesion cause raised ICP, which may cause brain herniation?

A

The skull has limited space and holds many structures
Usually only capable of slow rate expansion. Acute and subacute SOLs can result in increase ICP and cause herniation through foramen magnum

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3
Q

What are layers of the scalp from superficially to skull bone?

A
SCALP
Skin
Connective tissue
Aponeurosis
Loose connective tissue
Pericranium
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4
Q

Which layer of the scalp has a rich anastomotic arterial blood supply?

A

Layer 2- connective tissue

Lacerations can cause excessive bleeding

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5
Q

What is the clinical significance of sutures in the skull?

A

Prevent fractures from spreading

N.B. Fibrous joints

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6
Q

What is the significance of the ‘H-shaped’ pterion?

A

This is where frontal, parietal, temporal and sphenoid bones meet
Thinnest part of skull

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7
Q

Why is the pterion clinically relevant?

A

Close proximity to middle meningeal artery

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8
Q

What is meningitis?

A

Bacterial or viral infection of the meninges

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9
Q

Name the meninges from superficial to deep

A
Dura Mater (Hard mother)
Arachnoid Mater (Spidery mother)
Subarachnoid space (contains CSF)
Pia Mater (Faithful mother)
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10
Q

What is the role of dura mater?

A

Tough/fibrous
Has sensory nerve supply mainly from CN V
Encloses the dural venous sinuses

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11
Q

What is the role of arachnoid mater?

A

Arachnoid granulations reabsorb CSF

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12
Q

What is the role of Pia mater?

A

Adherent to the brain and the blood vessels & nerves entering or leaving brain

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13
Q

What is the name of the dura mater covering the cerebellum?

A

Tentorium cerebelli

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14
Q

Where does the tentorium cerebella attach?

A

Attaches to ridges of petrous temporal bones

Has central gap to permit the brainstem to pass through

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15
Q

What is the name of the dura mater forming a roof (diaphragm) over the pituitary fossa?

A

Diaphragm sellae

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16
Q

How are the dural venous sinuses formed?

A

Split between dura mater layers

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17
Q

The dura mater forms a midline structure that separates the right & left cerebral hemispheres, what is the name of it?

A

Falx cerebri

18
Q

Where does the flax cerebri attach to the skull?

A

The crista galli of the ethmoid bone anteriorly

Internal occipital protuberance of the occipital bone posteriorly

19
Q

What are sinuses that drain the brain?

A
Superior sagittal sinus
Left sigmoid sinus- drains into internal jugular at jugular foramen
Confluence of the sinuses
Inferior sagittal sinus
Cavernous sinuses
20
Q

What is the clinical significance of the danger triangle?

A

Potenital for venous spread of infection in facial vein
Facial vein is atypical- much thicker walls that remain open rather than collapse and have no valves allowing spread of bacteria

21
Q

Which veins of the face connect with the cavernous sinus?

A

Ophthalmic veins

22
Q

Which arteries supply the brain?

A

Right vertebral artery passes through cervical vertebrae then foramen magnum
Right common carotid gives rise to right external carotid artery and right internal carotid artery

23
Q

Circle of Willis

24
Q

Where does the subarachnoid space lie?

A

Between arachnoid mater and pia mater

25
What is the role of the subarachnoid space?
Cushions and protects
26
How many mls of CSF are produced per day?
400-500mls
27
Where is CSF produced?
Inside the brain | Choroid plexus of the ventricles
28
Where is CSF reabsorbed?
In the dural venous sinuses via arachnoid granulations
29
Where can CSF be samples from?
Via lumbar puncture at L3/L4 or L4/5 IV disc levels to obtain a sample of CSF
30
Where does the subarachnoid space end?
Level of S2 in sacrum
31
How does CSF move through the ventricles?
1. Secreted by choroid plexus 2. Lateral ventricles via foraminae of Monro 3. Midline of 3rd ventricle 4. Via cerebral aqueduct into.. 5. 4th ventricle then.. 6. Subarachnoid space of brain & spinal cord 7. Reabsorbed from subarachnoid space via arachnoid granulations 8. Into dural venous sinuses
32
What is hydrocephalus?
Excessive production, obstruction to flow or inadequate reabsorption leads to an increased CSF volume
33
How can hydrocephalus be treated surgically?
Shunt catheter "tunnelled" beneath the skin of the neck and chest then sited within the peritoneal cavity
34
What is an extradural haemorrhage?
Between bone and dura | Example: ruptured middle meningeal artery, trauma to the pterion
35
What is a subdural haemorrhage?
Separates dura from arachnoid Torn cerebral veins Common in falls in the elderly and those with drinking problems
36
What is a subarachnoid haemorrhage?
Haemorrhage into CSF of subarachnoid space Ruptured circle of Willis ("berry") aneurysm Congenital aneurysm
37
Describe the pathway of an epidural catheter vs lumbar puncture as it passes through the skin
``` Supra and then interspinous ligaments Ligamentum flavus Epidural space (fat + veins) ``` Lumbar puncture then continues through the dura mater + arachnoid mater to reach subarachnoid space to obtain CSF sample
38
Damage to the extradural venous plexus can result in what?
Epidural haematoma compressing spinal cord or cauda equina
39
What are the two directions of an infratentorial herniation?
Upward Downward or tonsillar herniation (herniation of cerebellar tonsils into foramen magnum)
40
What are the four types of supratentorial herniation?
Cingulate (subfalcine) Central Uncal- the uncut (medial part) of temporal lobe herniates inferior to tentorium cerebella Transcalvarial
41
What is the clinical sign seen when the oculomotor nerve is compressed by an uncle herniation?
Ipsilateral fixed dilated pupil (a "blown" pupil)