Skull base lesions

1. IMAGING OF SKULL BASE
LESIONS
Presentor: Apoorva Kankane
Guide : Dr Pravin Lamdhade

2. Normal skull base
• When viewed from above, it is divided into
anterior, middle and posterior cranial fossa
• Concept of fossa does not work well for the
skull base when viewed from below,
because the bony anatomy spills over from
one fossa to the next.

4. Normal skull base- 5 bones

5. Occipital bone
• Floor of the posterior
fossa
• 3 distinct areas:
– Basilar (clivus)
– Condylar (lateral)
portion
– Squamous (posterior)
portion

6. Temporal bone
• Petrous pyramid and mastoid
process form most of the skull
base between the posterior and
middle skull base.
• Apex of the petrous pyramid joins
the anterolateral margin of the
clivus (i.e., basiocciput) and the
posteromedial aspect of the
greater wing of sphenoid along
the basisphenoid synchondrosis.

7. Sphenoid bone
• 3 compartments:
– Basisphenoid:
• Dorsum sella, posterior
clinoids, sella turcica,
tuberculum sella, sphenoid
sinus
• Fused to clivus in adult
– Greater wing of sphenoid
• Medial two-thirds and anterior
wall of the middle cranial fossa
floor
– Lesser wing of sphenoid
• Medial and superior aspects of
the anterior wall of the middle
cranial fossa and the anterior
clinoids
• Superior and medial edges of
the superior orbital fissure

8. Frontal bone
• Anterior cranial fossa is
anteriorly and laterally
bound by frontal bone;
majority by orbital plate
of frontal bone

9. Ethmoid bone
• Cribriform plate is
perforated by approx 20
holes on each side of the
crista galliNerve fibres of
olfactory nerve (CN I)
pass from nasal mucosa
to olfactory bulb
• Crista galli serves as the
anchor for anterior margin
of the falx cerebri

23. Submento-vertical
Jugular foramina: Submento-vertical 20 degrees caudad

24. Role of imaging
• Diagnosis
• Extend of disease – criteria of surgical
resectability
• Treatment planning
• Follow up – recurrence vs post ttreatment
changes

25. Contra-indications for surgical
resection
Invasion of
1. Cavernous sinus
2. Bilateral optic nerve or optic chiasm
3. Nasopharynx
4. Prevertebral fascia
5. Lateral or superior wall of sphenoid.

26. Utility of CT and MR in evaluation
skull base lesions
CT
1. Fine bony details
2. Walls of skull base and
neurovascular foramina
3. Pattern of bone destruction
4. Depiction of Calcifiation
MRI
1. Assessment of soft tissue
component
2. Intracranial extensions,
invasion of dura,
leptomeninges, cranial
nerves and brain
parenchyma
3. Detecting perineural and
perivascular spread
4. Bone marrow involvement

30. • Lesions arise:
– Extracranially
• From the nasal vault, frontal and ethmoid sinuses
– Intrinsically
• From the skull base itself
– Intracranially
• From the brain, meninges and CSF spaces
ANTERIOR SKULL BASE LESIONS

31. ANTERIOR SKULL BASE LESIONS
• LESIONS ARISING
EXTRACRANIALLY
SINONASAL LESIONS
• Esthesioneuroblastoma
• SCC
• Adenocarcinoma
• Adenoid cystic Carcinoma
• Lymphoma
• Sarcoma
• Melanoma
• JNA
• Mucocoele
• Sinonasal polyposis, osteomyelitis,
fungal sinusitis
ORBITAL LESIONS
• Lacrimal gland tumors
• Neurogenic tumors, lymphoma
sarcomas, metastais
LESIONS ARISING
FROM ABOVE
• Olfactory nerve
meningioma
• Schwanoma
• Encephalocoele
LESONS FROM
SKULL BASE
PROPER
• Trauma and
CSF leak
• Osteoma

32. Esthesioneuroblastoma - imaging
• Olfactory neuroblastoma
• Bipolar sensory receptor cells
in the olfactory mucosa. (neuralcrest origin)
• Any age – bimodal peak
(2nd and 4th/5th decade)
• Often confined to nasal cavity; may
extend to PNS or anterior cranial fossa
(through cribriform plate)
• High nasal vault with focal bone
destruction
• Variable signal intensity on MR
• Moderate but
inhomogenous
enhancement
• CNS dissemination as a late
manifestation

33. TRAUMA AND CSF LEAK

36. Osteoma
• Benign bony tumor
• Mature well delineated
cortical bone as their
primary component.
• Most common site:
frontal sinus
• Expands and erodes the
posterior and superior
frontal sinus walls

37. Meningioma
• Most common meningeal lesion to involve
anterior skull base
• Planum sphenoidale and olfactory groove – 10-
15% of all meningiomas
• Broad based, anterior basal subfrontal mass that
enhances strongly and relatively uniformly after
contrast administration is typical.
• Presence of tumor-brain interface or cleft with
compressed cortex and white matter buckling
indicate extraaxial location.
• Blistering and hyperostosis of the adjacent bone.

39. Cephalocoele
• The most common
anterior skull base
lesion that arises from
the brain is
nasoethmoidal
cephalocoele.
• 15% of basal
cephalocoeles occur in
the frontonasal area.
• Sinciput and basal
types

41. MIDDLE SKULL BASE LESIONS
Midline(medial to
petroclival junction)
1. Sphenoid mucocoele
2. Chordoma
3. Craniopharyngioma
4. Meningioma
5. Encephalocoele
6. Nasopharyngeal
infections and
carcinoma
Parasaggital
(between petroclival
fissue and foramen
ovale)
1. Perineural spread
2. Peripheral nerve
sheath tumor.
3. JNA
4. Cavernous sinus
lesions
5. Chondroid tumors
Lateral
1. Meningioma
2. TMJ lesions

42. Cephalocoele
• Axial CT scan (b)
photographed with bone
window and coronal CT
scan (c) photographed with
soft-tissue window reveal
the presence of a persistent
craniopharyngeal canal
(arrow) in the sphenoid
bone.
• Coronal (d) and midsagittal (e)
Ti - weighted MR images
through the central skull base
demonstrate herniation of
the pituitary gland into the
craniopharyngeal canal
through the sphenoidal
defect (arrow) . Note the
proximity of the pituitary
gland to the roof of the
nasopharynx.

43. Fractures
• Most commonly occur as extensions
of cranial- vault fractures.
• Petrous temporal bone
> orbital surface of the frontal bone
> basiocciput.
Multiple skull-base fractures in a 23-year-old
man after an automobile accident.

45. Chordoma
• Slowly growing destructive tumor
• Histologically benign, but locally invasive
- Originate from embryonic remnants of
primitive notochord
- Extradural, as they arise from bones
- Adults-30-70 years
- cause mass effect on adjacent structures
- HPE: conventional/chondroid/poorly
differentiated
- Saccro-coocygeal/spheno-
occipital/vertebral body
- Clival is the second most common
location, typically mass projects in midline
indenting the pons—Thumb sign
• One-third in sphenooccipital region – Most
in midline;
primarily involve clivus
– Other – petrous apex and Meckel’s
cave

46. - CT:

47. Chondrosarcoma
• Rare in skull base
• Location: petro-occipital synchondrosis >
sphenoethmoid junction > sella tursica
• Located off-midline as compared to chordoma
• Slow growing, locally invasive tumors
• Soft tissue mass with focal bone destruction is
typical.
• CT: ring and arc calcification
• MR:
– low to intermediate signal on T1
– Hyperintense on T2
– Strong but heterogeneous enhancement

49. Posterior Skull Base Lesions
Jugular foramen lesions
1. Glomus jugulare paraganglioma
2. Nerve sheath tumors
3. Lesions extending into the jugular
foramen
4. Jugular bulb pseudolesions
5. Large or high riding bulb
Petrous apex lesions
1.Non aggressive cystic expansile
lesion—Cholesterol granuloma,
carotid artery aneurysm, mucocoele,
arachnoid cyst
2.Aggressive appearing solid lesions-
Cholesteatoma, petrous apicitis,
petrous osteomyelitis
Foramen magnum lesions:
1 chordoma
2. Chondrosarcoma
3.Neurogenic tumors
4.Infections and inflammatory
process of CV junction
• Largest and the deepest of the 3
cranial fossae.
• Roughly two-fifths of the
base of skull.
• Surrounds the foramen magnum

50. Jugular foramen
Jugular foramen:
– Located in the floor of
the posterior fossa,
between the petrous
temporal bone
anterolaterally and the
occipital bone
posteromedially.
– Anterior and inferior to it
is the hypoglossal canal
• Hypoglossal nerve
• Pars nervosa
(smaller anteromedial
compartment)
CN IX, Inferior petrosal sinus
• Pars vascularis
(larger posterolateral
compartment)
• CN X and XI
• Jugular vein

51. Glomus Jugulare
• Paraganglioma
• MC tumor of this region
• Females-4th to 6th decade
• Arises from pars vasculari
• CT: moth eaten pattern of
bone destruction, jugular
spine eroded
• T1 : low signal
• T2 : high signal
• T1 C+ (Gd) : marked
intense enhancement
• Salt and pepper
appearance is seen on
both T1 and T2
• Carotid arteriography is
necessary for
preoperative evaluation
and/or embolization

53. Nerve Sheath Tumors
• Jugular foramen is
uncommon location for
nerve sheath tumors.
• smooth well delineated
rounded or lobulated
soft tissue masses that
expand the jugular
foramen.
• Pressure erosion is
common (frank
invasion is rare; c.f.
paragangliomas)
• Isointense to brain
on T1; hyperintense
on T2
• Strong homogenous
contrast enhancement

54. Prominent jugular bulb
• Normal variant
• Most common “pseudomass” in the jugular
foramen.

55. HIGH RIDING JUGULAR BULB
• Normal variant
• Jugular bulb roof extending
above the inferior margin
of basal turn of cochlea
• MC on right side
• May lead to superior
jugular plate dehicense
with protrusion of bulb into
hypotympanum

56. Cholesterol granulomas
• Expansile cystic lesions
of petrous apex that
contain haemorrhage
and cholesterol crystals.
• Hyperintense on T1 and
T2

57. Gradenigo’s Syndrome
• Osteomyelitis of
petrous apex with sixth
nerve palsy, otorrhea,
and retroorbital pain.
• NECT:
– Destructive lesion of the
petrous apex with fliud
in the adjacent middle
ear and mastoid.

58. FORAMEN MAGNUM
Normal Aantomy
• Large aperture in the occipital
bone though which posterior
fossa communicates with the
cervical spinal canal.
• It transmits:
– Medulla and its meninges
– Spinal segment of CN XI
– 2 vertebral arteries
– Anterior and posterior spinal
arteries
– Vertebral veins

59. Foramen magnum lesions
• Bony lesons arising
from clivus like
chordoma and
chondrosarcoma
• Tumors arising from
nerves and meninges
• Bony tumors of atlas
and axis
• Infectious and
inflammatory
pathology of CVJ like
RA and TB

60. • Lesions that can
occur in any or all
BOS locations
DIFFUSE SKULL
BASE MASSES
Diffuse/ non site specific skull base lesions
Metastasis
Fibrous dysplasia
Paget’s Disease
Skull base osteomyelitis
Osteopetrosis

61. Metastases
• Most common malignancy
of skull base
Occurs in region of high
marrow content-petrous
apex
• Direct or haematogenous
spread
• MC primary – lung, breast
and prostate
• CT – destructive mass
infiltrating the skull base
• MRI – T1WI show a
“muscle” intensity mass
within the skull base with
loss of normal, low intensity
Metastasis to the sphenoid triangle (greater wing of
sphenoid). The tumor (T) expands in all directions,
pushing the temporalis muscle laterally, extending
into the middle cranial fossa, and impinging on the
orbit causing proptosis.

62. Fibrous dysplasia
• Among the most common skeletal
disorders.
• Adolescents and young adults
• Monoostotic (70%) or polyostotic
• Medullary bone replaced with
fibro osseus lesion
• CT is modality of choice
• Cystic spaces-ground glass-
sclerotic phase

63. • Enhancement in
active phase, non
enhancing in
quiescent phase
• MR:
– Low to
intermediate
signal on T1 and
T2; scattered
hyperintense
regions may be
present.
• Variable contrast
enhancement.
• Lesion spares cortical
bone—dd pagets

64. Paget disease
• Adults, >40 years
• Osseous lesion of
unknown etiology
• Monoostotic or
polyostotic
• Focal or diffuse
• Thickening of cortical bone
• 3 phases are identified:
– Early destructive
phaseIntermediate phase with
combined destruction
and healing
– Late sclerotic phase.

66. OSTEOPETROSIS/ MARBLE BONE DISEASE

67. Osteosarcoma
• Craniofacial osteosarcomas are uncommon - when
present, present in older patients, and commonly
affect the maxilla or mandible.
• Skull base osteosarcomas are rare.
– May occur spontaneously or
– In association with Paget disease or previous radiation
therapy.
• A soft tissue mass with tumor matrix mineralisation
and aggressive bone destruction is characteristic.
• DD:
– Radiation osteitis, metastatic carcinoma, myeloma

68. MRIs of a radiation–induced osteosarcoma in a patient with severe fibrous dysplasia of the skull
and skull base.
(A) Gadolinium–enhanced, T1–weighted axial image with fat suppression shows a large tumor in
the region of the sphenoid and sella.
(B) T2–weighted fast spin–echo, axial and (C) gadolinium–enhanced, T1–weighted coronal image
with fat suppression of the same lesion.

69. Langerhan Cell Histiocytosis
• Solitary or monoostotic
Eosinophilic Granuloma is
the most common
presentation.
• Children between 5 and
15 years; occassionally
in young to middle- aged
adults.
• Typically affects skull vault
• However, striking diffuse
osteolytic skull base and
calvarial lesions can
occur.
• Single or multiple areas of
pure osteolysis are seen in
the skull base and
calvarium of children (i.e.,
eosinophilic granuloma).
• A soft tissue mass may be
associated (i.e., Hand-
Schuller-Christian or
Letterer-Siwe disease)

71. • Kunimatsu A, Kunimatsu N. Skull Base Tumors and Tumor-Like Lesions: A Pictorial
Review. Pol J Radiol. 2017 Jul 25;82:398-409. doi: 10.12659/PJR.901937. PMID:
28811848; PMCID: PMC5540006.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5540006/#:~:text=Computed%20tomograph
y%20(CT)%20and%20magnetic,bone%20involvement%20by%20the%20lesions.
• Raut AA, Naphade PS, Chawla A. Imaging of skull base: Pictorial essay. Indian J Radiol
Imaging. 2012 Oct;22(4):305-16. doi: 10.4103/0971-3026.111485. PMID: 23833423;
PMCID: PMC3698894. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3698894/
• Gaillard F, Knipe H, Bell D, et al. Tumors of the base of skull (differential diagnosis).
Reference article, Radiopaedia.org (Accessed on 27 Jul 2023) https://doi.org/10.53347/rID-
59246
https://radiopaedia.org/articles/59246

72. THANK YOU