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17.1 Skull Base
pophysis) derived from neuroectoderm as an extension of the
hypothalamus, from the oor of the
third ventricle. The anterior lobe
secretes thyroid stimulating harmone (TSH), leutinizing harmone
(LH), follicle stimulating harmone
(FSH), adrenocorticotropin harmone (ACTH), growth harmone
(GH) and prolactin but posterior
lobe does not secret any hormone
but stores vasopressin and oxytocin.
Relation of pituitary gland
Superiorly—The pituitary gland is
attached to the hypothalamus by
pituitary stalk, related to optic chiasma, and diaphragma sellae (it is a
fold of meningeal layer of dura
mater that covers the pituitary
gland).
Laterally—It is related to cavernous sinus and structures within the
meningeal layer of dural covering.
Posteriorly—It is bounded posteriorly by posterior intercavernous
sinus, dorsum sellae, Basilar arteryalong with dural covering.
Anteriorly—Tuberculum sella and
sphenoid sinus; there is covering of
periosteal and meningeal layer of
dura.
Inferiorly—sphenoid sinus; there is
covering of periosteal and meningeal layer of dura.
Blood supply—The anterior pituitary
gland is supplied by the superior
hypophyseal artery, a branch of the
ICA.The anterior hypophyseal artery
forms the primary network of capillaries around the hypothalamus and
the secondary network around the
anterior pituitary known as the
hypophyseal portal system to supply
the anterior pituitary gland. The posterior part of the gland is supplied by
the superior hypophyseal artery,
infundibular artery and inferior
hypophyseal artery.
451
Diaphragma sellae—This is a sheet of
meningeal layer of dura mater that
forms the roof of the pituitary fossa. The
two layers of dura mater of diaphragma
sellae merge anteriorly with the dura
covering the planum sphenoidale and
the anterior cranial fossa and posteriorly
with the dura covering the dorsum sellae
and the clivus. At the centre, it has an
opening for a stalk of the pituitary gland.
– Cavernous sinus—The cavernous
sinuses are paired dural venous
sinuses of head, 1×2cm in size in
an adult, located in parasellar space
lateral to pituitary gland and sella
turcica in the middle cranial fossa.
On both sides, they extend from the
superior orbital ssure to the petrous
part of the temporal bone. They are
enclosed by an endosteal and meningeal layer of dura mater. It is
bounded anteriorly by superior
orbital ssure, posteriorly by petrous
temporal bone, medially by the body
of the sphenoid, laterally by the
meningeal layer of dura, roof by the
meningeal layer of the dura that
attaches to the anterior and middle
clinoid process and oor by an endosteal layer of dura mater that overlies the base of the greater wing of
the sphenoid bone. The internal
carotid artery and cranial nerves VI
pass through this blood- lled space
and cranial nerves III, IV, V, V1 and
V2 run on the lateral wall. The lling
tributaries of the cavernous sinus are
superior and inferior orbital veins,
pterygoid plexus, Sylvian vein, and
emptying tributaries are superior
and inferior petrosal sinuses.
– Internal carotid artery—The
internal carotid arteries arise from
the common carotid arteries, at the
level of cervical vertebrae C3 or C4
452
17 History andExamination ofSkull Base
where these bifurcate into the internal and external carotid arteries.
The internal carotid artery is
located posterior and deep in contrast to the external carotid artery.
In the neck, it runs vertically
upward in the carotid sheath and
enters the skull through the carotid
canal. The petrous part of ICA runs
in the petrous temporal bone up to
the foramen lacerum, where it
ascends and ends at petrolingual
ligament; this segment is known as
paraclival segment or lacerum segment. Next segment is cavernous
or sellar; it starts at the petrolingual
ligament and runs anteriorly in the
cavernous sinus up to the proximal
dural ring. The proximal dural ring
is formed by the medial and inferior periosteum of anterior clinoid
process. The ICA runs superome-
dial to abducent nerve and
medial to CN III, CN IV, CN V1
and CN V2 inside the cavernous
sinus. The next segment is a clinoi-
dal segment which extends from
the proximal dural ring to the distal
dural ring. This segment lies outside the dura. The next segment is
supraclinoid or ophthalmic which
gives ophthalmic artery on lateral
side. The last segment is communicating or cerebral. The internal
carotid artery supplies the brain
and eye (Fig.17.1e, f).
– Tuberculum sella—This is a verti-
cal bony elevation that forms the
anterior boundary of sella turcica
and posterior boundary of chiasmatic sulcus.
– Dorsum sellae—It is a square-
shaped bone that forms the posterior boundary of sella turcica and
separates the middle cranial fossa
and sphenoid sinus from the posterior cranial fossa.
– Optic nerve—The optic nerve,
responsible for vision, is a bundle
of bres that starts at the optic disc
at the posterior aspect of the eye. Its
intraocular portion is located at the
optic disc, and its intraorbital portion extends from the optic disc to
the optic canal; the intracanalicular
portion passes inside the optic
canal, and the intracranial portion
passes superior to the diaphragma
sellae and cavernous sinus to form
the optic chiasma.
– Chiasmatic sulcus/groove—This
is a groove or sulcus located on the
cranial side or superior surface of
the body of sphenoid bone/sphenoid
sinus, posterior to planum sphenoidale and anterior to tuberculum
sella. Anteriorly on both sides, it
ends in optic foramen, which transmits the optic nerve and ophthalmic
artery. It houses optic chiasma.
– Optic chiasma—Optic chiasma is
formed by fusion of two optic
nerves, superior to sphenoid sinus
and anterior to sella turcica in chiasmatic sulcus. The optic chiasm or
optic chiasma is an X-shaped structure located in the forebrain,
directly in front of the hypothalamus and pituitary stalk. Two optic
nerves meet and intersect at the
optic chiasma. At the decussation
point, bres from one side eye’s
nasal eld cross over and enter the
other side of the optic tract, but
bres from the temporal eld do
not cross and go through the same
optic tract. Therefore, visual input
from the left nasal visual eld and
right temporal visual eld travel in
the right optic tract.
– Superior orbital ssure—This is a
cleft or ssure located between the
lesser and greater wing of the sphenoid, lateral to the optic canal. The
17.1 Skull Base
453
structures transmitting from the
middle cranial fossa to orbit
through the superior orbital ssures
are CN III, CN IV, CN V1, CN VI,
superior ophthalmic vein, superior
branch of the inferior ophthalmic
vein and sympathetic nerve bres.
– Foramen rotundum—The fora-
men rotundum is foramen of the
skull base located at the junction
of the greater wings and the body
of the sphenoid bone. It connects
the middle cranial fossa to the
pterygopalatine fossa. The maxil-
lary division of the trigeminal
nerve passes through the foramen
rotundum.
– Abducent nerve—This is the sixth
cranial nerve that arises from the
abducent nucleus in the pons of the
brain stem. It leaves the brain stem at
the junction of the pons and medulla
and enters the subarachnoid space
and then pierces the dura mater to
travel in Dorello’s canal. At the tip of
petrous temporal bone, it enters the
cavernous sinus inferolateral to ICA
and runs forward to enter the orbit
through superior orbital ssure to
supply the lateral rectus muscle.
– Trochlear nerve—This is the
fourth cranial nerve that arises from
the trochlear nucleus within the
medial mid-brain at the level of the
inferior colliculus. Both cranial
nerves travel dorsally surrounded
by periaqueductal grey mater,
decussate before exiting the dorsal
mid-brain. It pierces the dura mater
above the trigeminal nerve and then
enters the cavernous sinus and runs
anteriorly on the outer wall of the
cavernous sinus below the oculomotor nerve and above the ophthalmic nerve in the lateral wall of the
cavernous sinus. Finally, it enters
the orbit through the superior
orbital ssure to innervate the supe-
rior oblique muscle and control the
abduction of the eyes.
– Oculomotor nerve—The oculo-
motor nerve is the third cranial
nerve that control the functions like
movement of eyes, constriction of
pupil and accommodation and position of the upper eyelid. This nerve
innervates the pupil, lens, upper
eyelid and eye muscles. This nerve
arises from two nucleus (oculomotor nucleus and Edinger-Westphal
nucleus) in the mid-brain. After
exiting the brain stem, it passes
between the superior cerebellar and
posterior cerebral artery and then
pierces the dura mater anterolaterally to the posterior clinoid process
to enter the cavernous sinus. Within
the cavernous sinus, it passes
through the other orbital nerves,
receiving a communicating branch
from the trigeminal nerve‘s ophthalmic division and one or two laments from the sympathetic
nervous system’s cavernous plexus.
It splits into superior and inferior
branches after entering the orbit
through the superior orbital ssure.
– Muscles supplied by oculomotor
nerve
Levator palpebrae superioris—Raise the
upper eyelid.
Superior rectus muscle—Rotate the eyelid
backward on looking up.
Medial rectus—Adduct eye on looking
towards the nose.
Inferior rectus muscle—Rotate the eyeball
forward on looking downward.
Inferior oblique muscle—Rotate the eye
backward on adduction of the eye.
Ciliary muscle—Control lens shape while
focussing on close objects.
Sphincter muscles—Pupillary
constriction.
454
17 History andExamination ofSkull Base
– Opthalmic nerve—This is the rst
branch of the trigeminal nerve originating from the trigeminal ganglion in Meckel Cave. This is a
sensory nerve that provides the sensation of the eyes, face and head. It
runs from the posterior to the anterior direction in the lateral wall of
the cavernous sinus to enter the
orbit through the superior orbital
ssure. In orbit, it divides into frontal, nasociliary and lacrimal nerves.
It provides sensory supply to the
forehead, scalp, upper eyelid, conjunctiva, cornea, dorsum of the
nose and lacrimal gland.
– Maxillary nerve—This is the sec-
ond branch of the Gasserian/trigeminal ganglion that runs in the
lateral wall of the cavernous sinus
to exit the cranial cavity through
the foramen rotundum to enter into
the pterygopalatine fossa to give
sensory supply to the upper lip and
upper alveolus.
Contents of extracranial side/
inferior side of the skull base of
the central compartment
– Sphenoid bone—This is a most
complex bone that forms the central
and lateral compartment of the
middle skull base. It has four parts:
the body, lesser wing, greater wing
and pterygoid process. The body is
located at the centre of the sphenoid
bone which houses the sphenoid
sinus and forms the central compartment of the middle skull base.
The greater wings extend both sides
from the sphenoid body in lateral,
superior and posterior directions
and form the oor of the middle
cranial fossa, the lateral wall of the
skull and the posterolateral wall of
orbit. It contains foramen rotundum, foramen ovale and foramen
spinosum through which various
neurovascular structures pass. The
lesser wings extend from the anterior aspect of the body in superolateral direction. It separates the
anterior cranial fossa from the middle cranial fossa and forms the lateral border of the optic canal and
the anteromedial wall of the superior orbital ssure. The pterygoid
process descends inferiorly from
the junction of the body with the
greater wing.
– Sphenoid sinus—The sphenoid
sinus is housed inside the body of
the sphenoid bone. It has six walls
superior, inferior, lateral, medial
anterior and posterior. The superior
wall is formed from anterior to posterior by planum sphenoidale, chiasmatic sulcus, tuberculum sellae,
hypophyseal fossa and dorsum sellae. The chiasmatic sulcus houses
optic chiasma, and the hypophysis
fossa houses the pituitary gland.
Anteriorly, the sphenoid sinus connects to the nasal cavity via the
sphenoid sinus ostia medial to
superior turbinate. Laterally, the
optic nerve and internal carotid
artery lie in close relation with the
sphenoid wall. The posterior wall
forms the clivus which separates
the sphenoid sinus from the posterior cranial fossa.
Content of lateral compartment
of skull base
Contents of the superior side or
the intracranial side of the lateral
compartment-
– Meckel’s cave/trigeminal cave—
Meckel’s cave is a natural mouthshaped aperture in the
postero-medial portion of the middle cranial fossa next to cavernous
sinus, within the petrous apex’s
meningeal and periosteal layers of
dura mater. It measures around
4×9 mm wide at its opening and
15 mm in length. Mackel’s cave
17.1 Skull Base
455
houses only posterior half of the
ganglion which is surrounded by
the subarachnoid space lled with
the cerebrospinal uid, whereas the
anterior half is located outside. It
acts as a key conduit for the largest
cranial nerve, the trigeminal nerve.
It is shaped like an open-ended
three-ngered glove pointing
antero-supero-medially, and the
palm of the glove rests within a
bony indentation of the petrous
apex. The ngers of the glove,
superior to inferior, contain the
three postganglionic bres of ophthalmic (V1), maxillary (V2) and
mandibular (V3) accordingly. The
cuff of the glove or the entrance of
the cave, the porus trigeminus, is
located between the superior and
inferior petrosal sinuses and contains the trigeminal nerve with an
arachnoid sheath. The precavernous or lacerum or paraclival segment of the internal carotid artery
lies inferomedial to the Mackel’s
Cave.
– Trigeminal/Gasserian/semilunar
ganglion—The prominent sensory
ganglion of cranial nerve V is the
semilunar; it is also known as the
Gasserian or trigeminal ganglion.
This ganglion houses the sensory
cell bodies for the mandibular,
maxillary and ophthalmic divisions—the three branches of the
trigeminal nerve. The mandibular
nerve carries both sensory and
motor functions, whereas the ophthalmic and maxillary nerves are
purely sensory. Nestled within a
dural fold called the Meckel’s Cave,
the Gasserian ganglion sits in a
depression at the petrous apex. The
sensory roots of the three branches
of cranial nerve V attach anteriorly
to the ganglion, which then connects posteriorly to the pons.
Additionally, the Gasserian ganglion receives sympathetic bres
from the carotid plexus.
– Trigeminal nerve—The trigeminal
nerve arises from three sensory
nuclei (spinal, principal sensory
and mesencephalic) and one motor
nucleus (extending from the midbrain to the medulla). It exits the
brainstem through a small motor
root and a large sensory root. The
motor root passes under the ganglion to merge with the sensory
division of the mandibular nerve
and exits the skull via the foramen
ovale, while the sensory root moves
laterally to connect with the
Gasserian ganglion. Its three
branches are the ophthalmic, maxillary and mandibular nerves.
Contents on the extracranial side/
inferior surface of the skull
base—lateral part
– Infratemporal fossa—The infra-
temporal fossa is limited above by
the greater wing of sphenoid and
squamous temporal bone, medially
by the lateral pterygoid plate and
anteriorly by the posterior wall of
the maxilla. Laterally, this is
bounded by the zygoma and temporalis muscle and posteriorly by the
petrous part of the temporal bone
and Eustachian tube.
The infratemporal fossa communicates at the superolateral corner
with the orbit via the inferior orbital
ssure. Between the lower temple
and the zygomatic arch, the fossa
communicates laterally with the
temporal fossa. Inferiorly, it communicates with the neck but is partially closed by the medial pterygoid
muscle and its fascial covering.
Medially, it communicates to the
pterygopalatine fossa through the
pterygomaxillary ssure anterosuperiorly. Superiorly, the foramen
456
17 History andExamination ofSkull Base
ovale is located just posterior to the
junction of the lateral pterygoid
plate with the body of the sphenoid
and postero-laterally to the foramen
ovale is foramen spinosum.
Medially it is communicated by
with parapharyngeal space posterior to medial pterygoid muscle.
The internal jugular vein and internal carotid artery are not located in
this space because they are on the
posterior plane.
The contents are medial pterygoid,
lateral pterygoid and temporalis
muscle located in the space from
medial to lateral. The maxillary
artery traverses this space from lateral to medial direction and the
mandibular nerve and its branches
from the superior to inferior
direction.
Contents of infratemporal fossa
Maxillary artery—Maxillary
artery, a terminal branch of external
carotid artery, originates posterior
to the mandibular neck and runs
forward between the ramus of the
mandible and the sphenomandibular ligament then either supercial
or deep to lateral pterygoid muscle
in the infratemporal fossa to the
pterygopalatine fossa. It is divided
into three parts by the lateral pterygoid muscle: lateral, posterior and
medial. The rst or lateral part runs
between the ramus of the mandible
and the sphenomandibular ligament
and has ve branches: deep auricular artery, anterior tympanic artery,
middle meningeal artery, inferior
alveolar artery and accessory meningeal artery. The second part runs
behind the lateral pterygoid muscle
and gives masseteric artery, pterygoid artery, buccal artery and anterior and posterior deep temporal
artery. The third part that runs
medial to the lateral pterygoid mus-
cle is not a content of infratemporal
fossa. It runs in the pterygopalatine
fossa and has ve branches:
Descending palatine artery, infraorbital artery, posterior superior alveolar artery, artery to pterygoid canal
and nal branch is sphenopalatine
artery.
Otic ganglion—This is the smallest
of all four parasympathetic ganglia
of the head neck region and is situated inferior to the foramen ovale in
the infratemporal fossa. It has four
roots: sensory, motor, sympathetic
and parasympathetic. The parasympathetic roots are preganglionic
bres which originate in the inferior
salivatory nucleus of the glossopharyngeal nerve, leave the nerve by its
tympanic branch and pass via the
tympanic plexus and then the lesser
petrosal nerve to the otic ganglion.
These bres synapse in the otic ganglion, and from here, the postganglionic bre is carried by the
auriculotemporal nerve to provide a
secretomotor supply to the parotid
gland. The sympathetic bres of the
otic ganglion are postganglionic
bres derived from the plexus
around the middle meningeal artery
which travel through the otic ganglion without relaying. From the
otic ganglion, they are carried by
the auriculotemporal nerve to provide a vasomotor supply to the
parotid gland. The sensory root is
also carried by the auriculotemporal
nerve to supply the parotid gland.
The motor bre of otic ganglion
supplies medial pterygoid muscle,
tensor veli palatini and tensor tympani. These bres also do not relay
in otic ganglion.
Pterygoid venous plexus—
Pterygoid venous plexus is a vast
valveless plexus of veins, located in
the infratemporal fossa on the lat-
17.1 Skull Base
457
eral aspect of the medial pterygoid
muscle. It surrounds the medial
two- thirds of the maxillary artery
so tributaries go along the branches
of the artery. The pterygoid plexus
anastomoses anteriorly with the
facial vein via the deep facial vein
and inferior ophthalmic vein. The
pterygoid venous plexus is connected superiorly with the cavern-
ous sinus via emissary veins which
pass through the sphenoidal emissary foramen (of Vesalius), fora-
men ovale and foramen lacerum;
anteriorly, the veins of pterygoid
plexus converge to form the maxillary vein, which conveys the blood
from the plexus into the retromandibular vein. The main tributaries
of pterygoid venous plexus are
sphenopalatine vein, deep temporal
vein (anterior and posterior), pterygoid vein, masseteric vein, buccal
vein, alveolar vein (superior and
inferior), infraorbital vein and middle meningeal vein.
Muscles of mastication—The primary muscles of mastication are
temporalis, medial pterygoid, lateral pterygoid and masseter.
Sphenomandibular ligament
(SML)—It is a ligament of tem-
poromandibular (TM) joint that
presents medial to the mandible. It
spreads from the spine of the sphe-
noid bone superiorly to lingula of
the mandible. The structures that
(c) Posterior skull base
pass lateral to SML are lateral pter-
ygoid muscle, auriculotemporal
nerve, maxillary artery and maxillary vein; medial is the chorda tym-
pani nerve and medial pterygoid
muscle is inferolateral
Mandibular nerve—This is the
third and only branch of the trigem-
inal nerve that contains both motor
root and sensory. After exiting the
cranial cavity through the foramen
ovale, the main trunk immediately
gives off the sensory meningeal
branch and motor muscular
branches to the medial pterygoid,
tensor tympani and tensor veli palatini muscle. The main trunk divides
into anterior and posterior branches.
The anterior branch gives the motor
nerve; masseteric, deep temporal
and lateral pterygoid and sensory
nerve; and buccal nerve. The posterior branch gives motor and sensory
(inferior alveolar nerve) and sensory (auriculotemporal, lingual,
mental nerve) motor (nerve
mylohyoid).
Foramen ovale—It is one of the
larger of the several foramina in the
middle skull base, located posterolateral to the root of the medial
pterygoid plate in the posterior part
of the greater wing of the sphenoid
bone. The mandibular nerve, acces-
sory meningeal artery, lesser
petrosal nerve and emissary vein
transmit through this.
Foramen spinosum—It is a small
circular foramen of the skull base,
located posterolateral to the foramen ovale in the greater wing of the
sphenoid. The middle meningeal
artery, a branch of the maxillary
artery, passes through this.
• Anatomy—The posterior skull base is
bounded anteriorly dorsum sallae, clivus, petrous part of temporal bone and
posteriorly by occipital bone. It has
one central and two lateral compartments. The lateral compartment is also
known as the lateral skull base that
contains the cerebellopontine angle,
458
17 History andExamination ofSkull Base
IAC, VII nerve, VIII nerve and posterior inferior cerebellar artery (PICA)
(Fig.17.1c).
• Contents
– Brain stem and cerebellum are the
contents of the central compartment of the posterior cranial fossa.
– Cerebellopontine angle—It is a
wedge-shaped/triangular subarachnoid space (cisternal space) in the
lateral compartment of the posterior cranial fossa located between
the cerebellum and the pons. It is
bounded by the tentorium cerebelli
and trigeminal nerve superiorly,
brainstem and pons medially, cerebellum posteriorly, petrous part of
temporal bone and IAC anterolaterally and inferiorly lower cranial
nerves. The contents of the cerebellopontine angle are VII, VIII nerves
and AICA.
– Basilar artery—Two vertebral
arteries unite at the pontomedullary
junction to form the basilar artery.
The vertebral artery rises in the
neck from the subclavian artery to
the posterior cranial fossa: primarily as the blood vessel that forms
the brain’s posterior circulation and
as the supplying element of the vertebrobasilar vascular system. It
splits into three posterior cerebral
arteries: the superior cerebellar
artery, the labyrinthine artery and
the anterior inferior cerebellar
artery.
– Anteroinferior cerebellar artery
(AICA)—It arises from the proximal part of the basilar artery at the
pontomedullary junction. The vessel
takes a posterolateral course as it
goes to supply the inferior aspect of
the cerebellum and anastomoses
with the posterior inferior cerebellar
artery and superior cerebellar artery.
It also gives off labyrinthine arteries.
– Internal auditory canal—The
internal auditory canal (IAC) or
internal acoustic meatus located in
the petrous part of the temporal
bone and in between the inner ear
and posterior cranial fossa. It has
the vestibulocochlear nerve (CN
VIII), facial nerve (CN VII), the
labyrinthine artery and the vestibular ganglion. The internal auditory
meatus provides a passage through
which the vestibulocochlear nerve
(CN VIII), the facial nerve (CN VII)
and the labyrinthine artery can pass
from inside the skull to inner ear
and face. The falciform crest rst
divides the meatus into superior and
inferior sections and a vertical crest
(Bill’s bar, named by William
F. House) and then divides the
upper passage into anterior and posterior sections. The anterosuperior
part contain facial nerve, anteroinferior part cochlear nerve, posterosuperior part superior vestibular
nerve and posteroinferior part contain inferior vestibular nerve.
– Foramen magnum—It is a size-
able, oval-shaped aperture in the
occipital bone of the skull. The
spinal cord passes through the
foramen magnum as it exits the
cranial cavity. It also transmits the
vertebral arteries, the anterior and
posterior spinal arteries and the
tectorial membranes and alar
ligaments.
– Jugular foramen—The jugular
foramen is a cavity with an opening
formed by the petrous part of the
temporal bone anteriorly and the
occipital bone posteriorly. Its major
function is to act as a conduit for
essential structures to pass through.
The internal jugular vein and 9th,
10th and 11th cranial nerves pass
through this.
17.1 Skull Base
459
2. Tumours/lesions of skull base
(a) Tumours/lesions of skull base—The skull
base is a complex region from which
many different diseases can arise. The
diagnosis of these various diseases
requires a multidisciplinary approach.
• Classications of skull base tumours/
lesions
– Location of tumour/Lesions
(Table17.1)
– Central middle skull base lesions
(Table17.2)
– Sites of origin of tumour
(Table17.3)
3. Chief complaints/symptoms of skull base
lesions/tumour
(a) Site-specic symptoms
• Symptoms of anterior skull base
lesions and tumour
– Nasal mass/nasal obstruction
– Watery rhinorrhea
– Anosmia/hyposmia
– Telecanthus
– Vision loss
– Epistaxis
• Symptoms of middle skull base dis-
eases and tumour
– Problem in vision—blurred or dou-
ble vision, ptosis
– Headaches—Frontal headache,
headache at the vertex.
– Nausea or vomiting
– Impaired sense of smell—It may be
impaired or lost
(hyposmia/anosmia).
– Sexual dysfunction
– Depression
– Fatigue
– Infertility
– Growth problems
– Osteoporosis
– Unexplained weight gain/weight
loss
– Easy bruising
– Aching joints
– Carpal tunnel syndrome
– Disrupted menstruation
– Early menopause
– Muscle weakness
– Galactorrhoea (spontaneous breast-
milk ow not associated with childbirth or the nursing of an infant)
• Symptoms of posterior skull base
tumour
– Hearing loss
– Tinnitus
– Vertigo
– Nausea and vomiting
– Headache
– Gait dysfunction
(b) Lesions/tumours/disease-specific
symptoms
• Symptoms of sellar tumour/lesions
– Symptoms of pituitary tumour/
lesions—The symptoms/presentation of pituitary tumour depend on
whether the tumour is functional or
not, the size of the tumour and pattern of growth. Tumours of the pituitary gland have been classied into
microadenoma (functional) and
macroadenoma (non-functional).
The presence of three or more of
the following symptoms may indicate a pituitary tumour.
Non-functional tumour
(macroadenoma)
Symptoms due to pressure:
Headaches—It is due to pressure exerted
on the diaphragma sellae or other structures. It is a sudden onset of severe U/l
or B/L frontal headache or pain behind
the eye.
Vision problems—Bitemporal hemiano-
pia (impaired vision on outer half of the
visual eld, as a result of compression
of optic chiasma), diplopia, (as a result
of compression of cranial nerves III, IV,
or VI).
Facial pain—It is due to compression of
the trigeminal nerve.
Partial complex seizure—It is due to
compression of the temporal lobe.
Hydrocephalus—Due to compression of
the third ventricle.
460
Table 17.1 Classication of skull base lesions
Anterior skull base Middle skull base tumour Posterior skull base
Meningioma
CSF leak
Olfactory neuroblastoma
Paranasal sinus tumour
Meningoencephalocele
Dermoid cyst
Angiobroma
Malignant tumour of nose and sinuses
Fibrous dysplasia
Encephalocele
Table 17.2 Tumours of the central compartment of the middle skull base
Arising from or within bone and cartilage of the base of the skull
Chordoma
Chondrosarcoma
Arising from the intracranial compartment but involving bone
Pituitary macroadenoma/microadenoma
Craniopharyngioma
Schwannomas of cranial nerves within the cavernous sinus
Giant internal carotid artery aneurysm
Cavernous sinus haemangioma
Arising from the soft tissues below the base of skull but involving bone
Nasopharyngeal carcinoma/sinonasal carcinoma
Mucocele
Perineural extension of head and neck tumours (e.g. adenoid cystic carcinoma, squamous cell carcinoma)
Infratemporal fossa tumour
Fibrosarcoma, haemangioma, hemangiopericytoma, histocytosis X, Hodgkin’s lymphoma, meningioma,
neurobroma, osteosarcoma, schwannoma and rhabdomyosarcoma
Pituitary tumours
Craniopharyngioma
Rathke’s cyst pouch
Meningioma
Chordoma
Optic nerve compression
Angiobroma
CSF leak
Fibrous dysplasia
Skull base osteoma
Hypophysitis
Pituitary abscess
17 History andExamination ofSkull Base
Vestibular schwannoma
(acoustic neuroma)
Lipoma, haemangioma
Paraganglioma, meningioma
Intracranial epidermoid cyst
Glomus jugulare associated with ninth nerve
Lower CNs schwannoma
Petrous apex lesions
Chondrosarcoma
CSF leak
Chondroma
Epidermoid cyst and cholesteatoma
Table 17.3 Classication of skull base tumour according to site of origin
Arising from or in bone and cartilage of the base of the skull
Tumours
Chondrosarcoma, giant cell tumour, osteochondroma, osteoma
Osteosarcoma, bony metastases, multiple myeloma/lymphoma
Others
Langerhans cell histiocytosis, brous dysplasia, Paget’s disease of bone
Cephaloceles, osteonecrosis (e.g. radiation)
Arising from the intracranial compartment but involving bone
Hemangiopericytoma, meningioma, pituitary adenoma
Craniopharyngioma, cavernous sinus haemangioma
Arising from the soft tissues below the base of the skull but involving bone
Sarcomas (e.g. rhabdomyosarcoma), infection (e.g. fungal)
JNA (juvenile nasopharyngeal angiobroma), mucocele
Perineural extension of head, neck tumour