Coverings of brain & spinal cord

Wednesday, April 12, 2023 1

COVERINGS OF BRAIN & SPINAL CORD/ DURAL VENOUS SINUSES

BYPROF. DR. ANSARI

( FOR DENTAL STUDENTS SEMESTER-II)


A clinical caseA 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 spaceB. Subdural spaceC. Epidural spaceD. Subpial spaceE. Cranial Dural sinuses


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.


The dural folds


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.



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

1. Intervertebral disc 2. Vertebral body 3. Dura mater 4. Extradural /epidural space 5. Spinal cord 6. Subarachnoid space


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.


1=falx cerebri2=Tentorium cerebelli

Wednesday, April 12, 2023 10Anterior


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.

http://www.gsat.tv/index.php?option=com_awiki&view=mediawiki&article=Sellar_diaphragm?qsrc=3044


Falx cerebriContaining superior sagittal sinus


Blood supply to the dura

• Middle meningeal artery 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.




1=layers of scalp;2=occipital bone;3=lacuna lateralis;4=middle meningeal vessels;

5=superior sagital sinus

http://upload.wikimedia.org/wikipedia/commons/9/91/Human_brain_dura_mater_description.JPG


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.

http://www.gsat.tv/index.php?option=com_awiki&view=mediawiki&article=Trigeminal_nerve?qsrc=3044


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 veinB. Inferior alveolar veinC. Pterygoid plexus of veinsD. inferior ophthalmic veinE. External jugular vein


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.


• 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

http://www.meddean.luc.edu/lumen/MedEd/Grossanatomy/h_n/cn/dvs/dvs2B.htm


Cavernous sinuses


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


All dural venous sinuses end up into Jugular foramen, as internal jugular vein

http://www.meddean.luc.edu/lumen/MedEd/Grossanatomy/h_n/cn/dvs/dvs1B.htm


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 boneB. Ethmoid boneC. Temporal honeD. Basioccipital boneE. Sphenoid bone


A clinical caseA 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 sinusB. Maxillary sinusC. Ethmoid air cellsD. Mastoid air cellsE. Sphenoid sinus


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.



Epidural hemorrhage or extradural hemorrhages are usually caused by tears in arteries

http://www.ask.com/wiki/Artery?qsrc=3044


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 12, 2023 30resulting from tears in bridging veins which cross the subdural space

SUB DURAL HEMORRAGE

http://www.ask.com/wiki/Bridging_veins?qsrc=3044

http://www.ask.com/wiki/Subdural_space?qsrc=3044


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.


Subarachnoid hemorrhage: The blood is under the arachnoid so it can enter the sulci


Epidural hemorrhage




Filum terminale


Applied anatomy

• Meningitis• Epidural hemorrhage• Sub dural hemorrhages• Subarachnoid hemorrhages



40

References

• Essential Clinical Anatomy- Keith Moore, 4th Edition (pages 503-511).

• Clinically Oriented Anatomy-Keith moore, 6th 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-ven

ous-drainage/• http://www.becomehealthynow.com/article/body

nervousadvanced/813/• http://www.medicallecturenotes.com/page/21/

http://www.medicallecturenotes.com/page/21/

http://antranik.org/protection-for-the-brain-meninges-csf-blood-brain-barrier/

http://antranik.org/protection-for-the-brain-meninges-csf-blood-brain-barrier/

http://vetsci.co.uk/2010/02/10/meninges-csf-venous-drainage/

http://vetsci.co.uk/2010/02/10/meninges-csf-venous-drainage/

http://www.becomehealthynow.com/article/bodynervousadvanced/813/

http://www.becomehealthynow.com/article/bodynervousadvanced/813/




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

Health & Medicine

Coverings of brain & spinal cord