Dural folds and cavernous sinus

1. DURAL FOLDS AND CAVERNOUS SINUS M.ARAVIND

2. MENINGES The interior of the cranial cavity is lined by the durameter. The surface of the brain is covered by the piameter. The dura is separated from the arachnoid by subdural space. The arachnoid is separated from the pia by subarachnoid space. (CSF) Between these two lies the arachnoid mater. T hese three together constitute the meninges of the brain.

3. DURAMATER The cerebral duramater consisting of the outermost thickest and toughest membrane consisting of two layers. Outer endosteal layer (endocranium) periosteum lining the inner surfaces of the skull bones. Inner meningeal layer (duramater proper) encloses the brain and at the foramen magnum becomes continuous with the duramater surrounding the spinal cord .

4. DURAL FOLDS At places, the meningeal layer is folded on itself to form dural folds(dural septa). Falx cerebri Tentorium cerebelli Falx cerebelli Diaphragma sella

5. Falx cerebri Tentorium cerebelli Falx cerebelli Diaphragma sella Shape & location Large sickle shaped Median longitudinal fissure Tent shaped Cerebellum & occipital lobes Sickle shaped Posterior cerebellar notch Small circular Roof of the hypophyseal fossa Attachments Crista galli Median plane of upper surface of tentorium cerebelli Transverse sulcus Petrous temporal bone, post. Clinoid process Inf surface of tentorium cerebelli on median plane Tuberculum sellae, dorsum sellae Dura middle cranial fossa Margins Upper-Convex saggital sulcus Lower-Concave free U-shaped ant free margin ant clinoid process. bears tentorial notch Apex -foramen magnum convex-internal occipital crest -------- Surface Medial surface of cerebral hemisphere Superiorly –occipital lobe of cerebrum inferiorly-superior cerebellum ------- hypophysis cerebri Sinus Superior & inferior saggital Straight sinus Transverse Superior petrosal Occippital ---------

6. TRIGEMINAL OR MECKEL’S CAVE It is a recess of the dura mater present in relation to the attached outer margin of the tentorium cerebelli It is formed by the evagination of the meningeal layer of duramater by two roots of the trigeminal nerve below the superior petrosal sinus over the trigeminal impression on the anterior surface of the petrous temporal bone near its apex

7. BLOOD SUPPLY OF DURA The vault- supplied by middle meningeal artery The anterior cranial fossa and the dural lining- supplied by anterior ethmoidal, posterior ethmoidal and ophthalmic arteries The middle cranial fossa- supplied by middle meningeal arteries, accessory meningeal and internal carotid arteries, and meningeal branches of ascending pharyngeal artery. The posterior cranial fossa- supplied by meningeal branches of vertebral, occipital and ascending pharyngeal arteries

8. NERVE SUPPLY OF DURA The dura of the vault is supplied by sensory nerves derived from ophthalmic division of trigeminal nerve The dura of the floor has rich nerve supply and is sensitive to pain: - anterior cranial fossa- supplied by anterior ethmoidal nerve and partly by maxillary nerve - middle cranial fossa- supplied by maxillary nerve in the anterior part and by branches of mandibular nerve and from the trigeminal ganglion in the posterior part - posterior cranial fossa- supplied by recurrent branches of 1 st , 2 nd and 3 rd cervical spinal nerves and by meningeal branches of 9 th and 10 th cranial nerves

9. CLINICAL ANATOMY EXTRA DURAL AND SUBDURAL HAEMORRHAGES Common Distinguished by Extradural Haemorrhage is arterial (injury to middle meningeal artery) Subdural Haemorrhage- venous Extradural Haemorrhage - symptoms of cerebral compression are late Extradural Haemorrhage- paralysis appears first in the face and then spreads to lower parts of the body. Subdural Haemorrhage - haphazard Extradural Haemorrhage- no blood in the CSF. - Subdural Haemorrhage- it is a common feature.

10. CAVERNOUS SINUS Large venous space Situation- Middle cranial fossa on either side of body of sphenoid bone Divided into caverns (spaces) by trabeculae (prominent in dead) Floor & medial wall – endosteal duramater Lateral wall & roof – meningeal duramater EXTENSION Anteriorly- superior orbital fissure Posteriorly- apex of petrous temporal bone 2cm long, 1cm wide

11. RELATIONS SUPERIORLY Optic chiasma Optic tract Olfactory tract Internal carotid artery INFERIORLY Foramen lacerum Junction of the body and the greater wing of sphenoid MEDIALLY Hypophysis cerebri Sphenoidal air sinus LATERALLY Temporal lobe with uncus BELOW LATERALLY Mandibular nerve ANTERIORLY Superior orbital fissure Apex of the orbit POSTERIORLY Apex of the petrous temporal bone Crus cerebri of mid brain

12. TRIBUTARIES FROM THE ORBIT Superior ophthalmic vein Inferior ophthalmic vein Central vein of retina FROM THE BRAIN Superficial middle cerebral vein Inferior cerebral vein FROM THE MENINGES Sphenoparietal sinus Frontal trunk of middle meningeal vein STRUCTURES PASSING THROUGH LATERAL WALL Occulomotor Trochlear Ophthalmic maxillary MEDIAL WALL Internal carotid artery Abducent nerve

13. COMMUNICATIONS With transverse sinus - via superior petrosal sinus With internal jugular vein – through inferior petrosal sinus and a plexus of veins around internal carotid artery With pterygoid venous plexus – through emissary veins passing through foramen ovale, emissary sphenoidal foramen and foramen lacerum With opposite cavernous sinus- via anterior and posterior intercavernous sinus With facial vein by two routes- - Superior ophthalmic vein and angular vein - Pterygoid venous plexus and deep facial vein

14. CAVERNOUS SINUS THROMBOSIS Septic thrombosis of cavernous sinus -by communication from dangerous area of face, orbit and pharynx -severe pain in eye and forehead -ophthalmoplegia due to involvement of 3 rd , 4 th and 6 th cranial nerves - Marked oedema of eyelids - exophthalmos

15. PULSATING EXOPHTHALMOS Pulsating exophthalmos- internal carotid artery is ruptured as a result of fracture of base of skull – arterio- venous communication is established - ligation of inernal carotid artery may be helpful, but patient may develop contralateral hemiplegia