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29 Cerebrospinal Fluid Rhinorrhea
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Anterior andMidline Central Skull
Данная книга находится в списке для перевода на русский язык сайта https://meduniver.com/
Base Tumors
SaraAshkanani andAbhishekMenon
30
Key Points
• Mainstay of treatment for sinonasal
squamous cell CA is surgical resection.
Radiotherapy may be used as adjuvant
therapy, except in nonresectable tumors,
where they are used as mainstay.
• Perineural invasion is more common in
adenocarcinoma.
• Clinical presentation and examination
of olfactory neuroblastoma can mimic
inammatory polyps.
• Pituitary adenomas are usually seen in
the third decade of life. MRI with gadolinium enhancement is the single best
radiological test for midline central skul
base tumor diagnosis. Treatment is usually surgical excision.
• Chordomas and chondrosarcomas are
derived from embryonic remnants of the
notochord.
S. Ashkanani (*)
Otolaryngology-Head and Neck Surgery Division,
Department of Surgery, Hamad Medical Corporation,
Doha, Qatar
Department of Otolaryngology-Head and Neck
Surgery Division, Weill Cornell Medicine-Qatar,
Doha, Qatar
e-mail: sashkanani@hamad.qa
30.1 Introduction
The skull base refers to the most inferior part of
the neurocranium, on which the brain rests, and
it is the major bony and soft tissue interface for
the intracranial and extracranial compartments.
Its anatomy is complex, containing multiple traversing foramina that act as conduits for various
neurovascular structures. They are divided into
anterior, central, and posterior parts (Fig.30.1).
In this chapter, we will be dealing with the anterior skull base and midline aspect of the central
skull base and its pathologies. The various foramen and the structures passing through them
are mentioned in Tables 30.1, 30.2, and 30.3.
30.2 Anatomy
The anterior skull base proper is formed medially
by the cribriform plate, making up the roof of the
nasal cavity, laterally by the orbital plates of the
frontal bone which form the roof of the orbits and
ethtmoid air cells and, posteriorly, by the planum
sphenoidale and lesser wings of the sphenoid.
A. Menon
Otolaryngology-Head and Neck Surgery Division,
Department of Surgery, Hamad Medical Corporation,
Doha, Qatar
e-mail: AMenon1@hamad.qa
© Springer Nature Switzerland AG 2021
A. Al-Qahtani et al. (eds.), Textbook of Clinical Otolaryngology,
https://doi.org/10.1007/978-3-030-54088-3_30
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337
338
S. Ashkanani and A. Menon
Fig. 30.1 Skull base showing the different parts and ssures within them
Table 30.1 The foramina of the anterior skull base and
their traversing neurovascular structures
Foramen Nerve Vessel
Foramen
caecum
Cribriform
plate
Optic canal Optic nerve Ophthalmic artery
Olfactory
nerve
Emissary vein to superior
sagittal sinus
Table 30.2 The foramina of the central skull base and
their traversing neurovascular structures
Foramen Nerve Vessel
Superior orbital
ssure
Foramen
rotundum
Foramen ovale Mandibular nerve
The central skull base comprises the body and
greater wing of sphenoid bone and squamous
temporal bones, and is demarcated from the posterior skull base by the petrous temporal bone.
They are divided into:
• Midline Central Skull base Compartment:
Foramen
spinosum
Vidian
(pterygoid)
canal
Meckel’s canal Trigeminal nerve
Includes the pituitary (sella), sphenoid body, and
clivus, and abuts the extracranial nasopharynx.
• Paramidline Central Skull Base Compartment:
Includes a cluster of neurovascular foramina,
the cavernous sinuses, and Meckel’s caves.
lopontine angle, internal auditory meatus, petromastoid, jugular foramen, and hypoglossal canal.
The dura is particularly closely attached to the
anterior skull base and so is prone to injury fol-
This posterior skull base compartment
includes the anatomical structures of the cerebel-
lowing a skull base fracture, potentially with
pneumocephalus or cerebrospinal uid (CSF)
CN III, IV, V
Maxillary nerve
(CN V2)
(CN V3)
Meningeal
branch of
mandibular nerve
Vidian nerve Vidian artery/vein
ganglion
, VI Superior and
1
inferior
ophthalmic vein
Accessory
meningeal artery
Middle meningeal
artery
30 Anterior andMidline Central Skull Base Tumors
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339
Table 30.3 The foramina of the posterior skull base and
their traversing neurovascular structures
Foramen Nerve Vessel
Facial nerve
canal
Internal
auditory
meatus
Petrous
carotid canal
Foramen
lacerum
Jugular
foramen
Foramen
magnum
Hypoglossal
canal
Facial nerve (CN
VII)
Facial (CN VII) and
vestibulocochlear
(CN VIII) nerves
Vidian nerve leaves
its anterior aspect
Glossopharyngeal
(CN IX)
Vagus (CN X)
Spinal accessory
nerve
(CN XI)
Medulla oblongata Vertebral artery
Hypoglossal nerve
Labyrinthine
artery
Petrous segment
of the internal
carotid artery
Artery of
pterygoid canal
Emissary veins
(carotid artery is
immediately
superior)
Inferior petrosal
sinus
Jugular bulb
Anterior and
posterior spinal
arteries
rhinorrhoea. The anterior skull base also has a
rich plexus of valveless venous perforations (e.g.,
the vein of Breschet) and so paranasal sinus
infection can spread either into the frontal bones
as osteomyelitis or traverse the anterior skull
base giving intracranial sepsis.
MRI can clearly delineate the olfactory bulbs,
which may have reduced volume in some neurodegenerative processes. The foramen caecum is
generally blind ended or transmits an emissary
vein in adulthood, but is also the site of a dural
diverticulum in early life. If this diverticulum
persists in the context of midline nasal developmental anomalies such as dermoid cysts, then it
may predispose to ascending meningitis.
30.3 Tumors oftheAnterior
SkullBase
Pathologic processes affecting the anterior skull
base may arise from the bones of the skull base
proper, intracranially from the meningeal cover-
ings, or exocranially from the sinonasal mucosa
investing the nasal cavity, ethmoid and frontal
sinuses, from the olfactory mucosa covering the
roof of the nasal cavity, from the orbit, from cranial nerves and vessels, from the chondro-
vomerian
synchondrosis, or from embryonic remnants.
30.3.1 Sinonasal Neoplasms
Most sinonasal neoplasms are epithelial in origin
and include, in decreasing order of frequency,
squamous cell carcinoma, intestinal type adenocarcinoma, and minor salivary gland neoplasms.
The remainder comprise neoplasms arising from
the olfactory mucosa, (esthesioneuroblastomas),
nasal lymphoma, melanoma, and a variety of mesenchymal tumors including rhabdomyossarcoma,
the most common in the pediatric age group.
30.3.1.1 Squamous Cell Carcinoma
• Most common sinonasal tumor.
• Constitute 70% of all malignancies.
• Presents with nasal congestion, blockage, frequent epistaxis, headache.
• Imaging features are non-specic and include
intermediate signal intensity on T2W images
reecting high cellularity and aggressive bone
destruction occasionally with small bony fragments engulfed within the lesion [1, 2].
• Mainstay of treatment is surgical resection.
• Radiotherapy may be used as adjuvant therapy, except in nonresectable tumors, where
they are used as mainstay.
30.3.1.2 Adenocarcinoma
• Comprises 10% of all sinonasal neoplasms.
• Perineural invasion more common.
• Three types:
– Minor salivary gland tumors
– Intestinal type adenocarcinoma
– Neuroendocrine neoplasms
• Distinctive imaging features include T2W
prolongation [3–5] and, in low-grade tumors,
a less aggressive pattern of bone involvement,
usually with remodelling and thinning rather
than permeative destruction of surrounding
bone (Fig.30.2).
• Treatment is surgical resection.
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S. Ashkanani and A. Menon
a
b
c
Fig. 30.2 (a) Coronal CT sinus showing adenocarci-
noma extending from the roof of the left ethmoid sinus
distally and medially through the olfactory recess eroding
the nasal septum crossing into the contralateral side. (b)
Coronal T1W MRI sinus showing intermediate signal
intensity lesion mildly expanding predominantly left
nasal roof and olfactory recess mass lesion inseparable
from medial lamella of left middle turbinate, and inltrating the nasal septum crossing to and expanding contralat-
eral olfactory recess, with remodelling of cribriform plate
with no denite intracranial extension. (c) Coronal T2W
MRI sinus showing inhomogeneous mixed signal intensity lesion mildly expanding predominantly left nasal roof
and olfactory recess mass lesion inseparable from medial
lamella of left middle turbinate, and inltrating the nasal
septum crossing to and expanding contralateral olfactory
recess, with remodelling of cribriform plate with no denite intracranial extension
ab
30 Anterior andMidline Central Skull Base Tumors
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341
30.3.1.3 Olfactory Neuroblastoma
• Also known as esthesioneuroblastoma.
• It is a rare tumor of neural crest origin which
arises from the olfactory mucosa lining the
nasal vault and cribiform plate and therefore is
a site specic neoplasm.
• Clinical presentation and examination mimics
inammatory polyps.
• Intracranial extension through cribriform
plate and orbital invasion through lamina papyracea are common.
• Meningeal spread and parenchymal invasion
of the olfactory bulbs and inferior frontal
lobes are often seen in advanced tumors.
• Typical imaging presentation is that of a solitary, polypoid, expansile soft tissue mass centered in the nasal vault and cribiform plate.
• This radiographic grading scale is as follows:
– A—limited to nasal cavity.
– B—nasal and paranasal cavity.
– C—beyond nasal and paranasal cavity
(invades cribriform plate, anterior cranial base
or orbit, intracranial, and maxillary sinus).
• They tend to be slightly hyperdense on CT and
of intermediate signal intensity on both T1W
and T2W MR images (Fig.30.3) [6, 7].
• Treatment is surgical enbloc resection.
30.3.1.4 Others
• Less common tumors include:
– Malignant melanoma
– B Cell lymphoma
– T Cell lymphoma
30.3.2 Orbital Tumors
• Although less commonly, a variety of neo-
plasms arising from the orbital contents may
affect the anterior skull base from below.
These include lacrimal gland neoplasms, neurogenic tumors, lymphoma, rhadomyosarcoma, chloroma, and metastasis to name the
most common.
• Benign lacrimal gland tumors manifest as
mass lesions originating in the superior and
outer aspect of the orbit, the normal anatomic
location of the lacrimal gland. When large
enough, they displace the globe and extraocular muscles inferiorly and medially and
remodel and erode the orbital roof.
Fig. 30.3 (a) T1W MRI showing low T1 lesion with small bright patches in a post-op patient. (b) T2W MRI showing
mixed signal, heterogenously enhancong lesion in a post-op patient
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342
S. Ashkanani and A. Menon
• Malignant neoplasms arising in the orbital
compartment show aggressive features and
may extend posteriorly through the orbital
apex and orbital ssures into the medial cranial fossa.
30.4 Tumors Arising fromAbove
theAnterior Skull Base
Besides meningiomas and their malignant counterparts, the skull base is rarely affected by other
tumors arising from the intracranial compartment. Only rarely do primary CNS tumors grow
outside the brain and when this occurs it is often
along the path of a surgical defect.
30.4.1 Olfactory Groove Meningioma
• Most common intracranial lesion affecting the
anterior skull base from above.
• Does not cause symptoms until tumor has
grown to large size.
• Symptoms include anosmia, blurred vision,
loss of memory, headache, nausea, vomiting,
and personality changes.
• They are best characterized with magnetic
resonance imaging.
• They are usually isointense to brain on both
T1W and T2W images, well-circumscribed
and show intense and homogeneous gadolinium enhancement.
• Treatment is usually surgical resection.
30.5 Pseudotumors
Many infectious inammatory conditions such as
mucoceles, sinonasal polyposis, abscesses, fungal infection, osteomyelitis and several granulomatous diseases including Wegener’s can affect
the skull base and even grow intracranially mimicking tumoral lesions. Correlation with clinical
history and laboratory ndings is mandatory to
reach the diagnosis. Imaging features that might
suggest inammatory pseudotumor include the
presence of MR signal changes, particularly on
long TR images, in excess to the amount of soft
tissue mass seen on CT and the presence of vessel
occlusion. Whereas neoplasms invading the cavernous sinus tend to narrow or compress the
internal carotid artery, rarely leading to a complete occlusion, infection and inammation
reaching the skull base may rapidly extend to the
petrous or cavernous segments of the carotid
artery, leading to inammation of the vessel wall
(endarteritis) and occlusion.
30.6 Tumors oftheMidline
Central Skull Base
Midline central skull base tumors may arise from
the sphenoid sinus and clivus, sella or the extracranial tissues (nasopharynx). Most (>90%) sellar lesions are pituitary in origin, and the
remaining can be meningiomas and
craniopharyngiomas.
30.4.2 Subfrontal Schwannomas
• Rare neoplasms of unclear origin, thought to
arise from the olfactory nerve or from a meningeal branch of cranial nerve V.
• Benign slow-growing lesions which tend to
remodel adjacent bone and may be associated to
bone sclerosis and intratumoral calcications.
• Often misdiagnosed for olfactory groove meningomas or olfactory neuroblastomas due to
their particular location imaging features.
• Treatment is surgical excision.
30.6.1 Pituitary Adenomas
• They are the most common causes of midline
central skull base tumors [8].
• Pituitary adenomas are benign tumors of the
adenohypophysis.
• Usually seen in the third decade of life.
• MEN1, Gs-alpha and AIP mutations have
been shown to play a role in the development
of the tumor.
• Types based on size:
– Microadenoma: less than 1cm
– Macroadenoma: more than 1cm
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343
• Types based on cell type:
– Gonadotroph adenomas: Clinically
nonfuctioning
– Thyrotroph adenomas: Clinically nonfunc-
tioning, but can cause hyperthyroidism
– Corticotroph adenomas: Can cause
Cushing’s disease
– Lactotroph adenomas: Causes
hyperprolactinemia
– Somatotroph adenomas: Causes increased
GH
• Symptoms include visual defects, diplopia,
headches, and symptoms assoicated with hormonal imbalance.
• MRI with gadolinium enhancement is the
single best radiological test for midline central skul base tumor diagnosis. Other test
include CT.
• Hormanal studies are also recommended.
• Treatment is surgical excision or debulking
(transnasal or open cranial approach), except
in the case of pituitary incidentaloma where
the patient has an incidental nding of pituitary tumor >1 cm on radiography, but no
symptoms (Fig.30.4).
30.6.2 Chordomas
andChondrosarcomas
• Chondromas are rare, locally aggressive,
slow-growing neoplasms.
• Derived from embryonic remnants of the
notochord.
• Can involve parts of the body other than skull
base such as sacrococcygeal region, and vertebral column.
• Three types of chordomas:
– Conventional: Absent cartilaginous or
mesenchymal components.
– Chondroid: Contains both chordomatous
and cartilaginous features. Usually seen in
sphenooccipital region.
– Dedifferentialted or sarcomatous type.
• Grossly they appear as gelatinous pink or
gray masses with solid and cystic areas.
• Whereas chondrosarcomas are rare malignant
cartilaginous tumors.
• Chondrosarcomas grossly appear as smooth,
lobulated, hard tumors.
• Microscopically chondrosarcomas are three
types:
– Well differentiated
– Moderately differntiated
– Poorly differntiated
• Surgical excision is preferred for both chordomas and chondrosarcomas (transnasal or
transfacial approach).
• Radiotherapy/adjuavant radiotherapy is also
used in treatment of chordomas and
chondrosarcomas.
30.6.3 Craniopharyngomas
• Craniopharyngiomas are benign epithelial
tumors that usually arise in the pituitary stalk
in the suprasellar region, adjacent to the optic
chiasm. A small percentage arise within the
sella, and a few tumors have been described
within the optic system or the third
ventricle.
• Slow growing.
• Symptoms include headache, visual symptoms, hormonal deciencies, growth failure,
nausea, and vomiting.
• MRI and CT are used for radiography.
• Characteristic niding is a cystic, calcied
suprasellar mass.
• Pretreatment requisites include adrenal, thyroid function and neuroopthalmic evaluation.
• Treatment needs multidisciplinary team with
surgical resection and radiotherapy followed
by post-op hormonal therapy if required.
30.6.4 Others
• Meningioma: Benign tumor arising from the
meninges.
• Pituicytoma: Uncommon, low-grade, indolent
glioma arising from the pituicytes of the posterior pituitary. It presents as a sellar mass,
which is usually mistaken for a pituitary adenoma, and has no known hormonal secretory
function.
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ab
S. Ashkanani and A. Menon
c
Fig. 30.4 (a) Ct head sagittal view showing sellar mass. (b) T1W MRI showing enhancing suprasellar lesion encroach-
ing the cavernous sinus. (c) T2W MRI showing intensely enhancing suprasellar lesion encroaching the cavernous sinus
30.7 Tumors ofPosterior
SkullBase
Take Home Messages
• The skull base is a highly complex region
that includes multiple bones. Eleven
• Cerebellopontine tumors
– Vestibular schwannomas
– Meningioma
– Epidermoid schwannomas
– Non-vestibular schwannoma
– Arachnoid cyst (Table30.4)
pairs of cranial nerves and the olfactory
nerves (CN I) pass through the inner
table of the skull via seven pairs of bony
foramina and the cribriform plate (CN I).
• Lesions and tumors can pose a challenge due to its location. Hence, apt
knowledge of anatomy is necessary.
30 Anterior andMidline Central Skull Base Tumors
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345
Table 30.4 CT vs. MRI for skull base imaging
CT MRI
Advantages Good for spatial
Bone
imaging
Used
specically
for
Cuts Submillimetric
resolution
Cortical bone
well imaged
Fractures,
sinonasal
disease, middle
ear and mastoid
disease
(mm) with
multiplanar
reformats
Good for soft tissue
resolution
Medullary bone is
well imaged (central
skull base)
Extracranial, central
skull base or
intracranial extension
of disease, cranial
nerve pathology
3mm sections in at
least two planes
(including coronal) or
increasingly
volumetric. STIR
(short tau inversion
recovery),
T1-weighted
precontrast and
T1-weighted
fat-saturated post
gadolinium
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