posterior cranial fossa-decamber2009
TRANSCRIPT
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 1/47
POSTEIOR CRANIALFOSSA
Mohammed issa al-oqaily
261100003112/21/09 Mohammed issa al-oqaily 261100003 POSTEIOR
CRANIAL
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 2/47
12/21/092
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 3/47
12/21/09Mohammed issa al-oqaily 261100003
POSTEIOR CRANIAL3
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 4/47
The inside view of cranium is known as
cranial cavityThe cranial cavity containsthe brain and its surroundingmeninges, portions of thecranial nerves, arteries,veins, and venous sinuses.
412/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 5/47
Cranial cavity is contained by thefrontal, parietal, sphenoid,
temporal and occipital bones, and
in part the ethmoid, all covered by
endosteal layer of dura mater
Bones that make up the cranial cavity
512/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 6/47
Anatomy of the lateral aspects of the skull
(b)
Parietal boneCoronal suture
Frontal bone
Frontal sinus
Sphenoid bone(greater wing)
Crista galli
Nasal bone
Sphenoid sinus
Ethmoid bone(perpendicular plate)
Vomer bone
Maxilla
Mandible
Alveolar margins
Incisive fossa
Lambdoid suture
Occipitalbone
Occipitomastoidsuture
External occipitalprotuberance
Internal acousticmeatus
Sella turcicaof sphenoid
bone
Pterygoidprocess of sphenoid
bone
Mandibularforamen
Palatinebone
Squamoussuture
Temporalbone
Palatineprocess of
maxilla
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 7/47
1. Anterior cranial fossa which accommodates the
anterior lobe of brain.
2. Middle cranial fossa, much wider than the anterior
cranial fossa contain the 2 temporal lobes of brain.
3. Posterior cranial fossa is much shallower and wider
than the middle cranial fossa and it accommodates the
occipital lobes of the brain.
The cranial cavity is divided into three
cranial fossa
712/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 8/47
8 12/21/09Mohammed issa al-oqaily 261100003POSTEIOR CRANIAL
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 9/47
Posterior cranial fossa
•It is the deepest and most capacious of the 3
cranial fossae.
•It contains the cerebellum, pons, and medulla
oblongata.
912/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 10/47
12/21/09Mohammed issa al-oqaily 261100003POSTEIOR CRANIAL
10
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 11/47
Continue . . .
a The foramen magnum is located centrally
and inferiorly in the posterior fossa. The
posterior fossa is surrounded by deep
grooves containing the transverse sinuses
and sigmoid sinuses
1112/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 12/47
12/21/09Mohammed issa al-oqaily 261100003POSTEIOR CRANIAL
12
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 13/47
Boundaries:
AnteriorlySuperior border of the petrous part of temporal bone
and dorsum sallae.
PosteriorlyInternal surface of squamous part of the occipital bone.
Floor Basilar, squamous & condylor parts of the occipital
bone & mastoid part
foramen magnum forms the central part of the floor.1312/21/09 Mohammed issa al-oqaily
261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 14/47
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 15/47
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 16/47
Tumors of theposterior cranial
fossa
12/21/09 16Mohammed issa al-oqaily 261100003 POSTEIOR CRANIAL
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 17/47
a Tumors in the posterior fossa are
considered critical brain lesions. This is, primarily, because of the limited space
within the posterior fossa and the potential
involvement of vital brain stem nuclei.
1712/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 18/47
Frequency
a Posterior fossa tumors are more common
in children than the adults.a Between 54% and 70% of all childhood
brain tumors originate in the posterior
fossa.a About 15-20% of brain tumors in adults
occur in the posterior fossa
1812/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 19/47
Continue . . .
a Certain types of posterior fossa tumors,
such as medulloblastoma, pineoblastoma,
ependymomas, primitive neuroectodermaltumors (PNETs), and astrocytomas of the
cerebellum and brain stem, occur more
frequently in children.
1912/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 20/47
Continue . . .
a Some glial tumors, such as mixed gliomas,
are unique to children. They are located
more frequently in the cerebellum (67%)
and are usually benign.
2012/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 21/47
Etiology
a No specific causes for posterior fossa tumors
exist. However, genetic factors, such as
dysfunction of some tumor suppressor genes(p53 gene) and activation of some
oncogenes, may play a role in their
development.2
Environmental factors such asirradiation and toxins may also play a role.
2112/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 22/47
Common
types of posterior
fossa tumors
12/21/09
22Mohammed issa al-oqaily 261100003 POSTEIOR CRANIAL
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 23/47
Cerebellar astrocytoma
a
Cystic cerebellar astrocytoma comprisesabout 33% of all posterior fossa tumors in
children. It represents 25% of all pediatric
tumors. Average age at presentation is 9
years.
2312/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 24/47
12/21/09Mohammed issa al-oqaily 261100003POSTEIOR CRANIAL
24
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 25/47
Continue . . .
a
Typically, cerebellar astrocytoma presents as alaterally located cyst with a well-defined solid
component. The tumor may be solid or cystic
and may be located medially in the vermis or
laterally in the cerebellar hemisp.
2512/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 26/47
Primary neuroectodermal tumors
a PNETs include medulloblastomas,
medulloepitheliomas, pigmented
medulloblastomas, ependymoblastomas, pineoblastomas, and cerebral neuroblastomas.
a These tumors originate from undifferentiated cells
in the subependymal region in the fetal brain.
PNETs are second to the cerebellar astrocytoma in
frequency
2612/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 27/47
Medulloblastoma
a Medulloblastoma initially arises in the
inferior medullary velum and grow to fill
the fourth ventricle, infiltrating the
surrounding structures. Some erroneously
thought it arose from medulloblast cells,
which do not exist.
2712/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 28/47
12/21/09Mohammed issa al-oqaily 261100003POSTEIOR CRANIAL
28
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 29/47
Ependymoma and ependymoblastoma
a Ependymomas are derived from ependymal
cells. They occur more frequently in females,with 50% presenting in children younger than 3
years.
2912/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 30/47
30
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 31/47
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 32/47
Choroid plexus papilloma and carcinoma
a Choroid plexus papilloma and carcinoma
represent 0.4-0.6% of all intracranial tumors.
a They are more frequent in children than in
adults (3% of childhood brain tumors).
a Sixty percent occur in the lateral ventricle
and 30% in the fourth ventricle. The third
ventricle and cerebellopontine angle are rare
locations for this tumor.
3212/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 33/47
a Cerebrospinal fluid (CSF) overproduction
may occur, sometimes reaching more than 4
times normal volumes.a In most of cases, CSF analysis demonstrates
increased protein, xanthochromia, or both.
3312/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
Continue . . .
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 34/47
12/21/09Mohammed issa al-oqaily 261100003POSTEIOR CRANIAL
34
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 35/47
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 36/47
12/21/09Mohammed issa al-oqaily 261100003POSTEIOR CRANIAL
36
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 37/47
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 38/47
12/21/09 Mohammed issa al-oqaily261100003 POSTEIOR 38
Dermoid tumors
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 39/47
12/21/09 Mohammed issa al-oqaily261100003 POSTEIOR 39
Hemangioblastoma
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 40/47
Metastatic tumors
a Three percent of all
cranial metastatic lesions
occur in the brainstemand 18% occur in the
cerebellum.
a Originating sites include breast, lung, skin, and
kidney.
4012/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 41/47
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 42/47
a Symptoms may be caused by focal
compression of the cerebellum or brain
stem centers and increased intracranial
pressure.
4212/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
Continue . . .
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 43/47
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 44/47
Continue . . .
a Symptoms due to focal compression of the
cerebellum include characteristic eye
findings and vermian syndrome.
4412/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 45/47
Outcome and Prognosis
a The 5-year survival rates exceed 60% for
all patients and 80% for certain good-risk
individuals with posterior fossa tumors.
4512/21/09 Mohammed issa al-oqaily261100003 POSTEIOR
8/14/2019 Posterior Cranial Fossa-Decamber2009
http://slidepdf.com/reader/full/posterior-cranial-fossa-decamber2009 46/47