Meninges of brain & spinal cord

A lecture for undergraduate medical students

1. Meninges of brain & SPINAL CORD DR. ABDUL QADEER

2. MENINGES OF BRAIN Three membranous covering ( Meninges ) Dura mater (Outer) = Pachymeninx Arachnoid mater (Middle) Pia mater (Inner) = Leptomeninges CSF in subarachnoid space

3. Dura mater Two layers around brain Endosteal layer Meningeal layer

4. Scalp

5. Dura mater ( Endosteal layer) Firmly tethered with endosteum of the skull Attached to foramen magnum Attached to all foramina of skull Continuous upto to the periosteum of skull outside Continuous with sutural ligaments at the sutures

6. Dura mater ( Meningeal layer) Also called dura mater proper Dense, strong fibrous membrane Continuous through the foramen magnum with the dura mater of spinal cord Provides tubular sheaths for the cranial nerves Sheaths fuse with the epineurium of the nerves outside the skull

7. Septa of meningeal layer of dura Falx cerebri Tentorium cerebelli Falx cerebelli Diaphragma sellae

8. Falx cerebri Sickle-shaped fold Partitions both cerebral hemispheres of brain Anterior end = narrow, attached to crista galli Posterior end = broad, blends with upper surface of tentorium cerebelli

9. Venous sinuses within falx cerebri Superior sagittal sinus (SSS) Inferior sagittal sinus (ISS) Straight sinus (SS)

10. Tributaries of SSS Superior cerebral veins Venous lacunae on each side, in which, arachnoid villi and granulations project Diploic veins Emissary veins SSS drains into confluence of the sinuses

11. Tentorium cerebelli Crescent shaped fold of dura mater Forms roof over the posterior cranial fossa Covers the upper surface of cerebellum Tentorial notch = It is a gap in the anterior edge for the passage of midbrain Therefore inner border is free while outer is fixed

12. Tentorium cerebelli (Attachments) Posterior clinoid processes Superior borders of the petrous bones Margins of the grooves on occipital bone Anterior clinoid processes (Free border)

13. Venous sinuses within tentorium cerebelli Superior petrosal sinus Straight sinus: it is formed by (a) ISS (b) Great cerebral vein Transverse sinus – continues as sigmoid sinus & then as internal jugular vein Confluence of sinuses, which also recieves occipital sinus from falx cerebelli

14. Transverse sinuses Paired It recieves SSS in right T. sinus SS in left T. sinus Make confluence of the sinuses Superior petrosal sinuses Inferior cerebral veins Cerebellar veins Diploic veins It continues as sigmoid sinus

15. Sigmoid sinus Paired Direct continuation of transverse sinus on each side Lies posterior to the mastoid antrum Makes superior bulb before passing through jugular foramen Continues down as internal jugular vein

16. Falx cerebelli Small, sickle-shaped Attached to internal occipital crest Partitions two cerebellar hemispheres Its posterior fixed margin contains occipital sinus

17. Venous sinuses in falx cerebelli Occipital sinus (un-paired) It commences near the foramen magnum, where it communicates with the vertebral veins It drains into the confluence of sinuses

18. Diaphragma sellae Small, circular fold of dura mater Forms roof of sella turcica A small opening in its center allows passage of the stalk of the hypophysis cerebri (Pituitary gland) Anterior and posterior inter-cavernous sinuses run infront and behind the stalk of h.cerebri

19. Cavernous sinus Situated in middle cranial fossa On each side of the body of sphenoid bone The sinus drains into the superior and inferior petrosal sinuses and to the pteregoid venous plexus The cavernous sinuses of both sides communicate with each other by anterior & posterior inter-cavernous sinuses Facial vein communicates with cavernous sinus via superior ophthalmic vein. Therefore, infection of skin of face can travel to the sinus

20. The cavernous sinus

21. Tributaries & drainage of cavernous sinus Tributaries: Superior ophthalmic vein Inferior ophthalmic vein Inferior cerebral veins Spheno -parietal sinus Central vein of retina Drainage: Superior petrosal sinus Inferior petrosal sinus Pteregoid venous plexus Communication : Both cavernous sinuses unite by anterior & posterior inter-cavernous sinuses

22. Structures passing through cavernous sinus Internal carotid artery Sympathetic nerve plexus Abducent nerve (VI)

23. Structures passing in the lateral wall of cavernous sinus Occulomotor nerve (III) Trochlear nerve (IV) Ophthalmic division of trigeminal nerve (V 1 ) Maxillary division of trigeminal nerve (V 2 )

24. Nerve supply of dura mater Trigeminal nerve Vagus nerve First three cervical spinal nerves Headache occurs if dura is stretched

25. Arterial supply of dura mater Internal carotid artery Maxillary artery Ascending pharyngeal artery Occipital artery Vertebral artery Middle meningeal artery

26. Meningeal veins These veins lie in the endosteal layer of dura mater Middle meningeal vein accompanies the artery of same name and drains into: Pteregoid venous plexus Spheno -parietal sinus

27. Arachnoid mater Sub- arachnoid space contains CSF It bridges over the sulci on the surface of brain Arachnoid villi are the projections into the venous sinuses Arachnoid granulations are the aggregations of arachnoid villi There function is to diffuse the CSF into the blood stream

28. Arachnoid mater Structures passing to and from the brain to the skull or its foramina must pass through the subarachnoid space Arachnoid mater forms a sheath over the OPTIC NERVE, which extends into the orbital cavity through the optic canal and fuses with the sclera of eyeball Thus subarachnoid space extends around the optic nerve as far as the eyeball

29. Optic nerve & its meninges

30. Cerebro -spinal fluid (CSF) It is produced by choroid plexus within the ventricles of brain It surrounds brain and spinal cord upto S2 vertebra. It gives buoyancy to brain & spinal cord, so that brain floats and protected from trauma It removes waste products associated with neuronal activity Provides transport medium for drugs & hormones

31. Pia mater Pia mater is a vascular membrane Covers gyri and descends into sulci It extends out over the cranial nerves & fuses with their epineurium Pia mater forms tela choroidea of the roof of 3 rd & 4 th ventricles of brain, and it fuses with the ependyma to form the choroid plexus in the lateral, 3 rd & 4 th venticles

32. Meninges of the spinal cord Dura mater is dense, and encloses spinal cord and cauda equina Continues up as meningeal layer of dura through foramen magnum over the brain Ends on the filum terminale at S2 vertebral level Lies loosely within vertebral canal and makes epidural space, which contains loose areolar tissue & internal vertebral venous plexus. Continues with epineurium of every spinal nerve

33. Meninges of the spinal cord Arachnois mater of spinal cord lies on pia mater It has sub- arachnoid space filled with CSF It ends at filum terminale at the level of lower border of S2 vertebra Covers the roots of spinal nerves

34. Meninges of the spinal cord Pia mater of spinal cord is vascular It is thickened on either side between the nerve roots to form the ligamentum denticulatum (denticulate ligament)

35. Denticulate ligament

36. Clinical notes Hemorrhages: Epidural & subdural hematoma Sub- arachnoid hemorrhage Headaches: Meningeal headache Headache caused by cerebral tumors Migraine Alcoholic headache Due to diseases of teeth, PNSs, eyes

37. The end