Coverings of brain & spinal cord

1. COVERINGS OF BRAIN & SPINAL CORD/ DURAL VENOUS SINUSES BY PROF. DR. ANSARI ( FOR DENTAL STUDENTS SEMESTER-II) Wednesday, April 24, 2013 1

2. A clinical case A 25-year-old man is involved in an automobile accident and slams his head into a concrete wall of a bridge. His computed tomography (CT) scan reveals that the middle meningeal artery has ruptured but the meninges remain intact. Blood leaking from this artery enters which of the following spaces ? A. Subarachnoid space B. Subdural space C. Epidural space D. Subpial space E. Cranial Dural sinuses Wednesday, April 24, 2013 2

3. The protective coverings of central nervous system There are three coverings that protect the brain and spinal cord. Apart from protection they carry venous blood/sinuses. They constitute the blood brain barrier. They drain (CSF) the cerebrospinal fluid. The outer layer is Dura, intermediate layer is arachnoid and inner layer is pia mater. Wednesday, April 24, 2013 3

4. Wednesday, April 24, 2013 4 The dural folds

5. The cranial Dura It is double layered, periosteal layer and menningeal layer. The meningeal layer continues as the spinal dural. The falx cerebri separates the right from the left cerebral hemisphere, the tentorium cerebelli separates the occipital lobe of the cerebrum from the underlying cerebellum, and the diaphragma sellae forms a circular partition around the stalk of the pituitary gland. The medial edge of the tentorium cerebelli is called the tentorial incisure. The falx cerebelli separates the two cerebellar hemisphere, and attached to the inner surface of tentorium cerebelli. Wednesday, April 24, 2013 5

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7. The spinal dura is single layered It extends below the spinal cord and ends as a sac at the level of lower border of second sacral vertebra Intervertebral disc Vertebral body Dura mater Extradural /epidural space Spinal cord Subarachnoid space Wednesday, April 24, 2013 7

8. The falx cerebri is a sickle shaped fold of dura mater It has an attached border enclosing superior sagittal sinus. It has a free border enclosing inferior sagittal sinus. The falx separates the right from left cerebral hemispheres. It is attached anteriorly to crista galli and frontal crest. Posteriorly it is inserted into tentorium cerebelli, enclosing straight sinus. Wednesday, April 24, 2013 8

9. Wednesday, April 24, 2013 9 1= falx cerebri 2= Tentorium cerebelli

10. Wednesday, April 24, 2013 10 Anterior

11. The diaphragma sellae The sellar diaphragm is the smallest dural infolding and is a circular sheet of dura that is suspended between the clinoid processes, forming a partial roof over the hypophysial fossa. The sellar diaphgram covers the pituitary gland in this fossa and has an aperture for passage of the infundibulum (pituitary stalk) and hypophysial veins. Wednesday, April 24, 2013 11

12. Wednesday, April 24, 2013 12 Falx cerebri Containing superior sagittal sinus

13. Blood supply to the dura Middle meningeal arter y is a branch from maxillary, enters the cranial cavity via foramen spinosum. Accessory middle meningeal artery branch from maxillary. Meningeal branches from internal carotid and vertebral arteries. Posterior & anterior ethmoidal arteries , branches of ophthalmic artery. Wednesday, April 24, 2013 13

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16. 1=layers of scalp;2=occipital bone;3=lacuna lateralis;4=middle meningeal vessels; 5=superior sagital sinus Wednesday, April 24, 2013 16

17. Innervations of dura Sensory innervations of the supratentorial dura mater is via small meningeal branches of the trigeminal nerve (V1, V2 and V3). The innervations for the infratentorial dura mater are upper cervical nerves . The dura of posterior cranial fossa is supplied by glossopharyngeal, vagus and cervical nerves. Wednesday, April 24, 2013 17

18. A clinical case A 63 year old man has thrombosis of the cavernous sinus. Three days earlier he developed an infection after the extraction of an upper molar tooth. The most likely route through which the infection reached the cavernous sinus is through which of the following venous channels :- A. Angular vein B. Inferior alveolar vein C. Pterygoid plexus of veins D. inferior ophthalmic vein E. External jugular vein Wednesday, April 24, 2013 18

19. The dural venous sinuses are spaces between the endosteal and meningeal layers of the dura. They contain venous blood that originates for the most part from the brain or cranial cavity. The sinuses contain an endothelial lining that is continuous into the veins that are connected to them. There are no valves in the sinuses or in the veins that are connected to the sinuses, their tunica lacks muscular layer. The vast majority of the venous blood in the sinus drains from the cranium via the internal jugular vein. Wednesday, April 24, 2013 19

20. A. Superior Sagittal Sinus B. Great Cerebral Vein C. Ophthalmic Veins D. Facial Vein E. Cavernous Sinus F. Inferior Petrosal Sinus G. Jugular Vein H. Sigmoid Sinus I. Superior Petrosal Sinus J. Transverse Sinus K. Straight Sinus L. Inferior Sagittal Sinus Wednesday, April 24, 2013 20

21. Wednesday, April 24, 2013 21 Cavernous sinuses

22. The Cavernous Sinuses A. Carotid Artery G. Cavernous sinus. B. Trochlear Nerve H.Ophthalmic nerve. C. Maxillary Nerve I.Oculomotor nerve. D. Abducens Nerve E. Sphenoid Sinus F. Pituitary Gland Wednesday, April 24, 2013 22

23. Wednesday, April 24, 2013 23 All dural venous sinuses end up into Jugular foramen, as internal jugular vein

24. A clinical case A 14-year-old boy hits his head on the asphalt road after falling off his skateboard. His radiograph reveals damage to the sella turcica . This is probably due to fracture of which of the following bones ? A. Frontal bone B. Ethmoid bone C. Temporal hone D. Basioccipital bone E. Sphenoid bone Wednesday, April 24, 2013 24

25. A clinical case A 67-year-old woman comes to her physician complaining of visual loss. Her magnetic resonance imaging (MRI) scan shows an enlarged pituitary gland that lies in the sella turcica , immediately posterior and superior to which of the following structures ? A. Frontal sinus B. Maxillary sinus C. Ethmoid air cells D. Mastoid air cells E. Sphenoid sinus Wednesday, April 24, 2013 25

26. A clinical case A 9 year old boy was brought by his mother to the A&E department within an 18 hours of pyrexia and vomitting.When he was seen by the pediatric doctor, the child complained that the lights in the examination cubicle were hurting his eyes( photophobia). He was noted to have stiff and painful neck. Wednesday, April 24, 2013 26

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28. Epidural hemorrhage or extradural hemorrhages are usually caused by tears in arteries Wednesday, April 24, 2013 28

29. Extradural/epidural hemorrhages A blow to the head may cause instant deformation of the skull without a fracture. This, too, can cause vascular tears. Bleeding from these vessels lifts the dura off of the skull forming an epidural blood clot. Epidural hematomas develop most commonly with fractures of the squamous portions of the temporal and parietal bones that tear the middle meningeal vessels. Epidural and subdural hematomas, merely compress the brain and raise the intracranial pressure. Wednesday, April 24, 2013 29

30. Wednesday, April 24, 2013 30 resulting from tears in bridging veins which cross the subdural space SUB DURAL HEMORRAGE

31. Subarachnoid hemorrhages Subarachnoid hemorrhage is the most frequent traumatic brain lesion. It results from rupture of corticomeningeal vessels and from hemorrhagic contusions of the brain. Blood is diluted by the CSF and does not clot unless it is massive. A large subarachnoid hemorrhage raises the intracranial pressure, impairs cerebral perfusion. Hemoglobin released from RBCs in the subarachnoid space triggers vascular spasm. It also incites fibrosis of the arachnoid membrane and the subarachnoid space, which may impair CSF circulation leading to hydrocephalus. Wednesday, April 24, 2013 31

32. Subarachnoid hemorrhage: The blood is under the arachnoid so it can enter the sulci Wednesday, April 24, 2013 32

33. Epidural hemorrhage Wednesday, April 24, 2013 33

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36. Wednesday, April 24, 2013 36 Filum terminale

37. Applied anatomy Meningitis Epidural hemorrhage Sub dural hemorrhages Subarachnoid hemorrhages Wednesday, April 24, 2013 37

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40. References Essential Clinical Anatomy- Keith Moore, 4 th Edition (pages 503-511). Clinically Oriented Anatomy-Keith moore , 6 th Edn .(pages 865-878) http://antranik.org/protection-for-the-brain-meninges-csf-blood-brain-barrier/ http://vetsci.co.uk/2010/02/10/meninges-csf-venous-drainage/ http://www.becomehealthynow.com/article/bodynervousadvanced/813/ http://www.medicallecturenotes.com/page/21 / http://www.medicallecturenotes.com/page/21/ 40

41. Sample MCQS The presence of blood in a spinal tap taken from an individual with a closed head injury signals arterial bleeding into the: A. Cavernous sinus B. Epidural space C. Subarachnoid space D. Subdural space E. Maxillary sinus Wednesday, April 24, 2013 41