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INRC > Skull Base > Flashcards

Skull Base Flashcards

1
Q

What are paragangliomas?

A

Neoplasm that originated from chromaffin cells

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2
Q

Where do jugular foramen schwannomas arise from?

A

CN9 and 10 > 11 or sympathetic chain

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3
Q

What are the boundaries of the jugular foramen?

A

Junction between the petrous temporal and occipital bones

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4
Q

What are the segments of the jugular foramen?

A 
Anterior = IPS
Middle = CN9, 10 & 11
Posterior = Sigmoid sinus and Jugular bulb with meningeal branches from the occipital and ascending pharyngeal arteries
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5
Q

What are the contents of the pars nervosa of the jugular foramen?

A

CN9, tympanic nerve (branch of CN9) and IPS

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6
Q

What are the contents of the pars venosa of the jugular foramen?

A

CN10, auricular branch of CN10, CN11, Jugular bulb and posterior meningeal branch of the ascending pharyngeal artery

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7
Q

What separates the pars venosa from the pars nervosa of the jugular foramen?

A

The jugular spine (fibrous septum in 80% and bony in 20%)

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8
Q

Which cranial nerve is completely separate from the others in the Jugular foramen?

A

CN9 lies within a connective tissue sheath

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9
Q

What is the grading system for Jugular foramen tumours?

A 
A = Intracranial
B = Intraosseous
C = Extracranial
D = Saddle shaped tumours spanning the above
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10
Q

What is the approach of choice for Jugular foramen tumours with large intradural components?

A

Retrosigmoid approach - but cannot access the Intraosseous or Extracranial components;
This can be extended via the transcondylar approach by removing the occipital condyle and jugular tubercle

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11
Q

What is the approach of choice for dumbbell tumours of the jugular foramen?

A

Presigmoid, transcondylar infra labyrinthine approach

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12
Q

What is the aim of surgery for glomus jugulare tumours?

A

Total surgical resection

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13
Q

Should the sigmoid sinus and jugular bulb be ligated if the veins are occluded?

A

No as they will recannalise once the tumour has been removed

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14
Q

How would you approach a jugular foramen tumour extending intracranially to the CP angle?

A

Retrosigmoid +/- transcondylar route

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15
Q

How would you approach an Extracranial jugular foramen tumour?

A

Cervical approach

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16
Q

How are dumbbell tumours of the jugular foramen approached?

A

Presigmoid, transcondylar, infralabyrinthine approach

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17
Q

What % of meningiomas are at the foramen magnum?

A

2%

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18
Q

Where do most foramen magnum tumours have their dural attachment?

A

Anterior-lateral in 75%

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19
Q

What are the approaches for anterior foramen magnum meningiomas?

A

Transoral, far lateral or the extreme / anterio-lateral approach

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20
Q

What is the main difference between the far lateral and the extreme lateral approaches?

A

The extreme lateral approach requires transposition of the vertebral artery to allow occipital condyle drilling

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21
Q

What are the factors that influence resection of foramen magnum meningiomas?

A

Anterior location, tumour size (larger tumours are easier due to bigger surgical corridor), invasion, extradural extension, vertebral artery encasement and arachnoid plane.

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22
Q

Which tumours can affect the optic nerves?

A 
Meningioma
Optic Gliomas
Pituitary adenoma
Craniopharyngioma
Chordoma
Fibrous dysplasia
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23
Q

What is the most common histology for an optic nerve sheath Glioma?

A

Pilocytic astrocytoma

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24
Q

Which patients are most likely to develop optic nerve sheath Gliomas?

A

NF 1

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25
Q

Bilateral optic nerve sheath gliomas are pathognomonic for which condition?

A

NF1

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26
Q

How do optic nerve sheath Gliomas present?

A

Proptosis if unilateral or visual deterioration if bilateral

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27
Q

When is surgery undertaken for optic nerve sheath Glioma?

A

Once vision is lost and if the tumour is growing towards the chiasm

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28
Q

What is the rate of malignant transformation of fibrous dysplasia?

A

1%

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29
Q

What is fibrous dysplasia?

A

Where normal bone is replaced with fibrous connective tissue

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30
Q

When is surgery undertaken with fibrous dysplasia?

A

With visual deterioration, rapid growth or cosmesis. There is no preventative surgery for fibrous dysplasia!

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31
Q

Where do chordomas arise?

A

In the Clivus and sacrum

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32
Q

What do chordomas arise from?

A

Notochord remnants

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33
Q

What is the treatment of choice for chordomas?

A

Maximal resection and proton beam therapy

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34
Q

How do chordomas present?

A

Classically with headache and CN6 palsy. Visual deterioration if optic nerves are compressed.

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35
Q

How can hearing be improved in patients with an intact CN8?

A

Cochlear implant

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36
Q

How can hearing be improved in patients with a deficient CN8?

A

Brainstem auditory implant

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37
Q

How do brainstem auditory implants work?

A

Through direct stimulation of the cochlear nucleus in the brainstem

38
Q

What are the outcomes of auditory brainstem implants?

A

50% have >50% average correct sentence recognition which improves to 70% with lip reading

39
Q

Why were penetrating electrodes now used for auditory brainstem implants?

A

Different tone pitches are represented in different layers of the cochlear nucleus so penetrating electrodes allows access to these but overall does not improve hearing

40
Q

How can hearing be improved in patients with damaged cochlear nuclei?

A

Inferior colliculus stimulation via auditory midbrain implants

41
Q

When should a spontaneous CSF leak be suspected?

A

In cases of recurrent meningitis

42
Q

What is a Hyrtl’s fissure?

A

A pseudo typano-meningeal duct in which there is an intracranial-Extracranial CSF connection along the CN9 to the tympanic canal.

43
Q

What proportion of pituitary tumours occur in children?

A

5% are

44
Q

What genetic conditions are most likely to result in paediatric pituitary tumours?

A

MEN1, Carney complex and familial isolated pituitary adenoma (FIPA)

45
Q

What is the most common paediatric pituitary region tumour?

A

Craniopharyngioma (90%)

46
Q

What is the age specific incidence of craniopharyngioams?

A

Bimodal between 5-14 years and then >50 years

47
Q

What is the treatment for Craniopharyngioma?

A

Surgical resection followed by radiotherapy

48
Q

What is the incidence of craniosynostosis?

A

1:2500

49
Q

What are the incidences of single suture synostosis?

A

Sagittal (Scaphocephaly) 50%
Coronal (brachycephaly) 30%
Metopic (Trigonocephaly) 10%
Lamdoid (Posterior plagiocephaly) 1%

50
Q

What environmental factors predispose to craniosynostosis?

A

Valproate use during pregnancy
Uterine anomaly
Multiple pregnancies

51
Q

What is the inheritance pattern of most syndromic craniosynostosis?

A

Autosomal dominant (Except Carpenter’s syndrome which is recessive)

52
Q

Which gene mutations are most commonly involved with craniosynostosis?

A

FGFR3 , FGFR2, TWIST1 and EFNB1

53
Q

Which patients with craniosynostosis should undergo genetic testing?

A

FGFR3, FGFR2 and TWIST1 should be tested in all patients with coronal and multi suture synostosis

54
Q

What lesions occurs at the petrosphenoid junction?

A

Chondrosarcoma

55
Q

What lesions can occur at the bony petrous apex?

A

Cholesterol granuloma, Trigeminal schwannomas and Epidermoid cyst

56
Q

What is the differential diagnosis of a jugular foramen tumour?

A 
Paraganglioma (glomus jugulare) (80%)
Schwannoma (10%)
Meningioma
Epidermoid
Clival chordoma
57
Q

Where is the petrolingual ligament?

A

Underneath the Trigeminal ganglion overlying the petrous ICA

58
Q

What is the differential diagnosis of a petrous apex lesion?

A

Within the bone - cholesterol granuloma
Extradural - Trigeminal schwannoma, Chondrosarcoma, meningioma
Intradural - (look it up)

59
Q

Which syndrome is associated with endolymphatic sac tumorus?

A

VHL

60
Q

Which nerve is found exiting the suboccipital triangle?

A

The greater occipital nerve

61
Q

Where does the hypoglossal nerve lie during the far lateral approach?

A

Above the V3 segment of the vertebral artery

62
Q

What is the differential diagnosis of a cystic pituitary region lesion?

A 
Pituitary adenoma
Craniopharyngioma
Rathke's cleft cyst
Epidermoid cyst
Germinomas
Arachnoid cyst
63
Q

Options for management of a craniopharyngioma?

A 
VP shunt
Cyst aspiration +/- reservoir
Cyst-ventricular shunt / Cyst fenestration marsupilisation
Tumour debulking
(Radiotherapy)
64
Q

What are the surgical approaches used for craniopharyngioma?

A

Pterional
Fronto-lateral
Interhemispheric (transbasal / transglabella)

65
Q

What is Sternberg’s canal?

A

Look it up:

A widening between the sphenoid body and wing which results in a connection and is a cause of a spontaneous CSF leak.

66
Q

What is a Hyrtl’s fissure?

A

A congenital connection between the posterior fossa and the middle ear which usually closes by 24 weeks. Can be a congenital cause of a spontaneous CSF leak.

67
Q

What is the most common skull base tumour?

A

Meningioma

68
Q

What meningioma types are atypical (have brain invasion)?

A

Chordoid and clear cell

69
Q

What meningioma types are anaplastic?

A

Papillary and rhabdoid

70
Q

What mutation occurs in most meningiomas?

A

Loss 22q (reason why meningiomas are common in NF2!)

71
Q

What protein is encoded by the NF2 gene?

A

Merlin

72
Q

What are the biological therapies for meningiomas?

A

Vismodegib - inhibits SHH pathway

73
Q

What proportion of chordomas metastasise?

A

40%

74
Q

What cells are found in chordomas?

A

Physaliferous cells

75
Q

What types of craniopharyngioma have a BRAF mutation?

A

Papillary (Adult) type

76
Q

What is the lowest part of the anterior cranial fossa?

A

The olfactory fossa

77
Q

Enlargement of the sella occurs with which pathology?

A

Meningioma (not adenoma)

78
Q

Patient with a tuberculum meningioma and something in the nose. What is in the nose?

A

Either growth of the meningioma into the nose or a MUCOCELE

79
Q

How do you manage an asymptomatic meningoma?

A

Monitor the lesion with serial scans to assess the natural history. Remove if growing / causing mass effect and conservative management if not.

80
Q

What is OCT?

A

Optic coherence tomography

81
Q

What approach for olfactory groove or planum meningioma can preserve smell?

A

Unilateral supra-orbital / pterional craniotomy approaching from the side where the smell is worse.
Note: Endonasal approaches are transcribiform so loss of smell always occur.

82
Q

What is the classification of vestibular schwannoma?

A

Koos classification from 1-4 based on size i.e. <10mm, 10-20mm, 20-30mm and >30mm

83
Q

What is the classification for hearing?

A

Gardener-Robertson classification:

Serviceable hearing = <50Db / >50 discrimination rule (On PTA and speech discrimination)

84
Q

What is the management algorithm for vestibular schwannoma?

A

<15mm - observe
15-25 mm - SRS (surgery if trigeminal dysfunction or disabling vertigo)
>30 or cystic or mass effect - microsurgery

85
Q

What is the hearing preservation following SRS/microsurgery for acoustic neuroma?

A

Good hearing preservation if the hearing is unaffected to begin with. If hearing is diminished to begin with, then will deteriorate with time. Overall about 50%

86
Q

When is a middle fossa approach done for vestibular schwannoma?

A

Small intra-cannalicular approach for hearing preservation

87
Q

How is facial nerve preserved during acoustic neuroma microsurgery

A

Subtotal resection of acoustic neuroma followed by SRS to remnant if >5 mm

88
Q

What medical treatment is given for vestibular schwannoma in NF2?

A

Avastin (bevacizumab) if growth rate >4mm / year; VEGF inhibitor that has to be taken longterm.

89
Q

How is hearing reconstructed following acoustic neuroma resection?

A

Auditory brainstem implant

Or cochlear nerve implant if cochlear nerve preserved

90
Q

What happens to hearing in NF2 patients?

A

Eventually will loose hearing so hearing preservation is not possible so. Work on hearing reconstruction!

91
Q

What are the causes of hydrocephalus in acoustic neuroma?

A

1) Mass effect causing obstructive hydrocephalus

2) Proteinaceous fluid release resulting in communicating hydrocephalus

INRC (7 decks)

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