06. venous sinuses.ppt treatment an repair

Venous sinuses are the most important sinuses in our body

1. Venous Blood Sinuses
They are blood-filled spaces situated
between the layers of the duramater.
They are lined by endothelium.
Their walls are thick and composed
of fibrous tissue. They have no
musculartissue. They have no valves.
They receivetributariesfrom the
brain; the diploic veins of the skull;
the orbit and the internal ear.
Inferior Sagittal Sinus
It occupies the free lowermargin of
the falx cerebri.
It runs backward andjoinsthe great
cerebral vein which is formed by the
union of the 2 internal cerebral veins
at the freemargin of the tentorium
cerebelli to formthe straight sinus.
It receivescerebral veins from the
medialsurface of the cerebral hemisphere.
N.B:
Veins have no valves; no muscular tissue
in their wall and drain intovenous
sinuses

2. Superior Sagittal Sinus
It occupiesthe upperfixedborder of the
falx cerebri. It beginsin the front at the
foramencecumwhere it receives a vein
from the nasal cavity.
It runs backward,grooving the vault of
the skull and at the internal occipital
protuberanceit deviates to one side
( usually the right) and becomes
continuous with the transverse sinus.
It communicatesthrough small openings
with 2 or 3 venous lacunaeon each side.
Numerous arachnoid villi and
granulations projectinto these lacunae
which also receivethe diploic; emissary
and meningeal veins.
It receivesthe superior cerebral veins .
At the internal occipital protuberanceit is
dilatedto form the confluence of the
sinuses which is connected tothe
opposite transverse sinus and receives
theoccipital sinus.

3. Straight Sinus
It occupiesthe line of
junction of the falx cerebri
with the tentorium cerebelli.
It is formedby the union of
the inferior sagittal sinus with
thegreat cerebral vein.
It endsby turning to theleft
( sometimes to the right ) to
form the transverse sinus.

4. Occipital Sinus
It is a small sinus occupying the attached marginof the falx cerebelli.
It communicates with the vertebral veinsnear the foramen magnum.
Superiorly it drains into theconfluence of sinuses.

5. Transverse Sinus
They are paired and begin at the internal occipital protuberance.
The right sinus usually continuous with the superior sagittal sinus.
The leftis continuous with the straight sinus.
Each sinus occupies the attached marginof the tentorium cerebelli , groovingthe occipital
bone and posteroinferior angleof the parietal bone.
They receive the superior petrosal sinuses; inferior cerebral and cerebellar veins and diploic
veins.
They endby turning downward as the sigmoid sinuses.

6. Superior and Inferior Petrosal Sinuses
They are small and situated on the superior and inferior borders of the petrous
part of the temporal bone on each side.
Each superiorsinus drains the cavernous sinusinto the transverse sinus.
Each inferiorsinus drains the cavernous sinusinto the internal jugular vein.

7. Sigmoid Sinuses
They are a direct continuationof the transverse sinuses. Each sinus turns
downward and medially and grooves themastoid part of the temporal bone.
Here it lies behindthe mastoid antrum.
It then turns downward through the posterior partof the jugular foramen to
become continuous withthe superior bulb of the internal jugular vein.

8. Cavernous Sinuses
They are situatedinthe middle cranial fossa on each side of the body of the
sphenoidbone.
Each sinus extends fromthe superior orbital fissure in front to the apex of the
petrouspart of the temporal bone behind.
The 3
rd
; 4
th
cranial nerves and the ophthalmic & maxillarydivisions of the
trigeminal nerve run forward in the lateral wallof this sinus. They lie betweenthe
endothelial and the dura mater .
The internal carotid artery, its sympathetic nerve plexusand abducent nerve run
forward through it. They are separated from the bloodby an endothelial
covering.

9. The tributaries are 1-Superior ophthalmic vein which communicates it with thefacial V
2-Inferior ophthalmic vein. 3-Cerebral veins
4-Central vein of the retina 5-Sphenopareital sinus.
The sinus drains posteriorlyinto the superior and inferior petrosal sinuses and
inferiorlyinto the pterygoid venous plexus.
The 2 sinuses communicatewith one another by means of the anterior and
posterior intercavernous sinuses which run in the diaphragma sellaein front and
behind the stalk of the hypophysis cerebri.
1
5
5

10. Hypophysis Cerebri
The pituitary gland is an edocrinegland. It is
small, oval and attached tothe undersurface
of the brainby infundibulum.
It is located inthe sella turcicaof the
sphenoid bone.
It is divided intoan anterior lobe or
adenohypophysisand posterior lobe or
neurohypophysis.
Relations
Superiorly: The diaphragma sellaewhich has
a central aperture that allows the
passage of the infundibulum.This
sellae separatesthe anterior lobe
from the optic chiasma. Inferiorly: The
body of the sphenoidwith its
sphenoid air sinuses. Laterally: The
cavernous sinus and its
contents. Posteriorly: The
dorsum sellae; basilar artery and
pons.
Blood supply: The superior and inferior
hypophyseal arteries the branches of the
internal carotid artery.
Veins drain into the intercavernous sinuses.

12. Extradural Hemorrhage
It results from injuries of the meningeal
arteries or veins.The most common is
the anterior branchof the middle
meningeal artery.
A minor blow to the sideof the head
result in fracture of theanteroinferior
portion of the parietal bone ( pterion ).
The intracranial pressure rises. The
blood clot exerts local pressureon the
underlying motor areain the precentral
gyrus.
Blood may pass outthrough the
fracture line to form a soft swelling
under the temporalis muscle.
The burr hole through the skull wall
should be placed 2.5 to 4 cm above the
midpoint of the zygomaticarch to ligate
or plug the torn artery or vein.

13. Subdural Hemorrhage
It is more common than the middle meningeal artery hemorrhage. It results from tearing of
the superior cerebral veinsat their entrance into thesuperior sagittal sinus.
The cause is a blow on the front or back of the head causing anteroposterior displacement
of the brain within the skull. Blood under low pressure begins to accumulate in the space
between the dura and arachnoid. The case is bilateral in 50 %.
Acutesymptoms in the form of vomiting dueto rise in the venous pressure may be present.
In the chronicform, over a several months, the small blood clot will attract fluid byosmosis
so a hemorrhagic cystis formed and gradually expandsproduces pressure
symptoms.

14. Intracranial Hemorrhage in the Infant
It occurs during birth and from excessive moldingof the head. Bleeding occurs
from cerebral veinsor venous sinuses
Excessive anteroposterior compressionoften tears the anterior attachment ofthe
falx cerebri from the tentorium cerebelli.
bleeding then takes place from the great cerebral veins; straight sinus or inferior
sagittal sinus.

15. Subarachnoid Hemorrahage
It results from leakage or rupture ofa
congenital aneurysm onthe circle of Willis or
less commonly from an angioma.
The sudden symptoms include severe
headache; stiffness of the neckand loss of
consciousness.
The diagnosis is established by withdrawing
heavily blood-stained CSF fluidthrough a
lumbar puncture ( spinal tap ).
Cerebral Hemorrhage
It is caused rupture of the thin-walled
lenticulostriate artery, a branch of the middle
cerebral artery. The hemorrhage involves the
vital corticobulbar & corticospinalfibers in
the internal capsule and produceshemiplegia
on the opposite sideof the body.
The patient immediately loses consciouness
and paralysis is evidentwhen consciousness
regained.