skull base Flashcards

1
Q

What is the skull divided into?

A
  1. Anterior cranial fossae
  2. Middle cranial fossae
  3. Posterior cranial fossae
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2
Q

Where does the frontal lobe of the brain sit?

A

anterior cranial foassae

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3
Q

Where does the cerebellum sit?

A

Posterior cranial fossae

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4
Q

What are the fossae divided by?

A

Ridges

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5
Q

What are the components of the Anterior cranial fossae?

A
  1. Foramen caecum
  2. Crista Galli
  3. Cribrifoirm plate
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6
Q

What is the role of foramen caecum?

A
  1. Transmit emissionary vein

2. Drain nasal cavity into superior sagittal sinus

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7
Q

What is the role of cribriform plate?

A
  1. Transmit sensory nerve fibre from nasal mucosa transmitting smell to olfactory bulb of CN I
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8
Q

What are the components of middle cranial fossae?

A
  1. Optic Canal
  2. Superior Orbital fissure
  3. Foramen Rottundum
  4. Foramen Ovale
  5. Foramen Spinosum
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9
Q

What are the 2 structures that the optic canal transmit?

A
  1. CN II - Optic nerve

2. Opthalmic artery

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10
Q

What is the superior orbital fissure?

A

Transmit structure from cranial cavity to orbit

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11
Q

What are the cranial nerves of superior orbital fissure?

A
  1. CN III - Occulomotor nerve
  2. CN IV - Trochlear nerve
  3. CN VI - Trigeminal
  4. CN VI - Abducens

Superior opthalmic vein

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12
Q

What structure passes through the superior orbital fissure?

A

Superior opthalmic vein

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13
Q

What is the superior orbital fissure?

A

Communication between cavernous sinus and apex of orbit

It is a cleft lying between lesser and greater wings of sphenoid bone

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14
Q

What cranial nerve is found in the foramen Rotundum, and what is the vein called?

A

CN V2 - Trigmeninal

Maxillary nerve

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15
Q

What are the structures found in the Foramen Ovale?

A
O - Otic Ganglion
V - V3 (Trigeminal)
A - Accessory Meningeal Artery
L - Lesser petrosal nerve
E - Emissary vein
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16
Q

Where is Foramen Spinsosum found and what is it’s role?

A

More lateral to the foramen ovale

Transmits middle meningeal artery

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17
Q

What is the role of Foramen Spinosum?

A

Allows the passage of middle meningeal artery, the middle meningeal vein and meningeal branch of CN V3

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18
Q

What are the 5 bones of normal skull base?

A
  1. Frontal
  2. Ethmoid
  3. Sphenoid
  4. Temporal
  5. Occipital
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19
Q

What does Ethmoid bone form?

A

Part of nasal cavity + orbits

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20
Q

What is the role of Ethmoid bone?

A

Main mechanical support structure of nasal cavity

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21
Q

What does Lesser wing of sphenoid separate?

A

Anterior cranial fossa from middle cranial fossa

It forms the lateral border of optic canal

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22
Q

What do Anterior Cranial Fossa contain?

A
  1. Orbital plate of frontal bone
  2. Ethmoid bone
  3. Lesser Wing of Sphenoid
  4. Frontal Crest
  5. Crista Galli
  6. Foramen caecum
  7. Cribriform plate
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23
Q

What does the middle cranial fossa contain?

A
  1. Sphenoid bone
  2. Squamous temporal
  3. Petrous temporal
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24
Q

What anatomical structures does the middle cranial fossa accomodate?

A
  1. Pituitary gland

2. Temporal lobes of the cerebral cortex

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25
Q

What are examples of openings in the middle cranial fossa?

A
  1. Optic canal
  2. Superior orbital fissure
  3. Foramen rotundum
  4. Foramen ovale
  5. Foramen spinosum
  6. Foramen lacerum
  7. Carotid canal
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26
Q

What is the role of foramen lacerum in middle cranial fossa?

A

Transmits artery and nerve of pterygoid canal

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27
Q

What is the sphenoid bone?

A
  1. Mid-section of the skull base

2. Anterior wall of middle cranial fossa

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28
Q

What are important for identifying structures?

A
  1. The petrous portion of the temporal bone

2. Greater wings of sphenoid bone

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29
Q

What are 3 distinct areas of occipital bone of posterior fossa?

A
  1. Basiocciput
  2. Condylar
  3. Squamous
30
Q

What are the apertures of occipital bone of posterior cranial fossa?

A
  1. Foramen magnum
  2. Posterior condylar canal
  3. Hypoglossal canal
31
Q

What is the petrous part of temporal bone?

A

Pyramid-shaped and is wedged in at the base of skull between sphenoid and occipital bone

32
Q

What is temporal bone?

A

Bone located bilaterally on either side of the skull

Part of the cranium

part of the middle cranial fossa

33
Q

What are the components of the posterior cranial fossa?

A
  1. Internal acoustic meatus
  2. Jugular foramen
  3. Hypoglossal canal
  4. Foramen magnum
34
Q

Internal acoustic meatus of PCF?

A

Transmits 2 cranial nerve
CNVII - facial
CN VIII - Vestibulocochlear nerve

35
Q

Jugular foramen of the PCF?

A

cavity formed by the petrous part of temporal bone anteriorly and occipital bone posteriorly

36
Q

What is the main function of jugular foramen?

A

Act as a conduit for essential structures to pass through

CN 9-11

Internal jugular vein

37
Q

Hypoglossal canal of PCF

A

CN 12 - Hypoglossal nerve

38
Q

Foramen magnum of PCF

A

Spinal root CN X1
(spinal accessory)

Anterior and posterior spinal arteries

Spinal cord - medulla oblongata

Vertebral arteries

39
Q

What are the 4 parts of the temporal bone?

A
  1. Petrous
  2. Mastoid
  3. Tympanic
  4. Squamous part
40
Q

Petrous Carotid Canal

A

A passage within petrous temporal bone and transmits internal carotid artery and sympathic plexus

41
Q

What is foramen lacerum?

A

Triangular-shaped hole in the base of the skull

located between sphenoid bone, the apex of the petrous part of temporal bone and basilar part of occipital bone

42
Q

Internal auditory canal

A

A canal within the petrous part of the temporal bone of skull between posterior cranial fossa and inner ear

43
Q

What are the components of the midline of sphenoid bone?

A
  1. sulcus chiasmaticus
  2. Tuberculum sella
  3. Sella Turcica
  4. Dorsum Sellae
44
Q

What are the components of paramedian of sphenoid bone?

A
  1. Optic canal
  2. Anterior clinoid process
  3. Superior orbital fissure
  4. Foramen rotundum
  5. Foramen vesalius
  6. Foramen ovale
  7. Formane spinosum
45
Q

What does the pterygoid process contain?

A
  1. Pterygopalatine fossa

2. Infratemporal fossa

46
Q

What is Pterygopalatine fossa?

A

pyramidal space located inferior to the orbital apex and posterior to the maxillary sinus

47
Q

What is the function of pterygopalatine fossa?

A

communicates with the infratemporal fossa via the pterygomaxillary fissure

48
Q

What are the compontents of greater wing of sphenoid?

A
  1. Inferior orbital fissure
  2. Pterygopalatine fossa
  3. Nasal cavity
  4. Vividian canal
  5. F. Ovale V3
  6. F. Spinosum
49
Q

What are used to image the skull base?

A
  1. CT

2. MRI

50
Q

What are the characteristic of CT

A
Planes : Axial & Coronal
Thin slices : <3mm 
Algorithm : bone &amp; soft tissue
Windows : wide bone / narrow soft tissue
MDCT: Reformats in multiple planes
IV Contrast : ? CTA / CTV
IT Contrast : Cisternography
51
Q

What are the characteristic of MRI?

A
Planes : Axial / Coronal / Sagittal
Thin slices : <3mm 
Sequences : 
		T2 FSE 
		T1 pre; 
		T1 fat sat post C 
		\+/- MRA/MRV
52
Q

What are the skull base pathology?

A

Most tumours are benign -m but can be fatal due to site

53
Q

What are the presentation for skull base pathology?

A
  1. Neurovascular
  2. Compression
  3. Brain invasion
54
Q

Skull Base pathology

A

Difficult to access surgically

Often require combined Neuro / ENT surgeon

55
Q

What are the lesions from below?

A
  1. Inflammatory
  2. Benign tumour
  3. Malignant tumour
56
Q

What are examples of inflammatory lesion?

A
  1. Osteomyelitis from sinus
  2. Otitis externa
  3. Facial abscess
  4. Aggressive sinonasal polyposis
57
Q

What are examples of Benign tumour?

A
  1. Nasal: Juvenile angiofibroma, inverting papilloma, dermoid sinus osteoma
58
Q

What are examples of malignant tumour?

A

NP Carcinoma, NH Lymphoma, Esthaesioneuroblastoma, SCC (perineural spread), parotid malignancies

59
Q

What are examples of lesions that are intrinsic to skull base?

A
  1. Pseudomass
  2. Congenital
  3. Inflammatory
  4. Trauma
  5. Benign Tumour
  6. Malignant Tumour
  7. Metabolic/Dysplastic
60
Q

What are examples of Pseudomass?

A
  1. Jugular bulb complex flpw

2. Petrous apex air cell fluid

61
Q

What is an example of congenital lesion?

A

Primary cholesteatoma

62
Q

What is an example of inflammatory lesion intrinsic to skull base?

A

Apical petrositis, mucocele, cholesterol granuloma

63
Q

Trauma

A

Fracture +/- dural tear

64
Q

Benign tumour

A

Paraganglioma (glomus) tumour, nerve sheath tumour, meningioma, chordoma, benign primary bone tumour

65
Q

Malignant Tumour

A

Metastasis, NH Lymphoma / Leukaemia, Myeloma, malignant primary bone tumour

66
Q

Metabolic / Dysplastic

A

Fibrous dysplasia, Paget’s, Anaemias, Histiocytosis X

67
Q

What are examples of lesions from above?

A
  1. Congenital
  2. Vascular lesion
  3. Benign tumour
  4. Malignant tumour
68
Q

Congenital lesion

A
  1. Cephalocele (meningocele/encephalocele

2. Arachnoid cyst

69
Q

Vascular lesion

A
  1. Carotid aneurysm

2. Dural AVF

70
Q

Benign tumour (above lesion)

A
  1. Meningioma
  2. Nerve sheath tumour
  3. Dermoid
  4. Pituitary tumour
  5. Rathe’s cleft cyst
71
Q

Malignant tumour (above lesion)

A

Primary brain tumour

Dural metastasis