Week 1 - J - Anatomy 5 - Meninges, SOLs, Herniations - Includes Subdural and extradural haematoma

Question 1

What are the 5 layers of the scalp and which layer contains the named arteries of the scalp?

Answer 1

S - skin

• C - connective tissue (dense)
• A - aponeurosis
• L - loose connective tissue
• P - pericranium

Question 2

Which layer of the scalp is the highly vascular layer hence scalp incisions can continually bleed?

Answer 2

This would be the connective tissue layer of the scalp Loss subaponeurotic layer is the loss areolar connective tissue layer of the scalp

Question 3

What is the layer of the scalp that runs from frontalis anteriorly to occipitalis posteriorly?

Answer 3

This would be the aponeurois layer - dense fibrous tissue

Question 4

Why is it that scalp lacerations & incisions can bleed excessively?

Answer 4

This is due to the highly anastamotic network from the branches of the ECA and ICA that supply the scalp with blood

Question 5

Sutures of skull (fibrous joints) help prevent skull fractures from spreading What are the main sutures of the skull and what do they separate?

Answer 5

Coronal suture - frontal and parietal bones Saggital suture - the right and left parietal bones Squamous suture - temporal bone from parietal bones Lamboid suture (black circle posteriorly) - occipital bone from the right and left parietal bones

Question 6

What is the thinnest part of the skull known as and what bones form it? What shape is it?

Answer 6

This is the Pterion Formed by the frontal, parietal, temporal and sphenoid bones It is an H shaped structure

Question 7

What artery courses over the deep aspect of the pterion? If a fracture occurs here and bleeding occurs, what is the bleed known as?

Answer 7

The middle meningeal artery runs along this apsect If a fracture occurs here, it causes an extradural (epidural) haemorrhage

Question 8

What foramen in the skull is for the middle meningeal artery?

Answer 8

This would be the foramen spinosum - tiny hole situated next to the ovale shaped foramen ovale

Question 9

What is the groove between the temporal and occipital bone caused by? What is the hole between the temporal and occipital bones known as? What cranial nerves pass here?

Answer 9

Caused by teh sigmoid sinus Hole is known as the jugular foramen Glossopharngeal, vagus and spinal accessory

Question 10

usually a bacterial or viral infection of the meninges What is this? What is the purpose of the meninges?

Answer 10

This is meningitis The meninges serve to protect the brain and spinal cord

Question 11

the brain and spinal cord are surrounded by three layers of membrane (“meninx” = membrane) What are the three layers of the meninges from superficial to deep? Which layers are usually joined to one another? Which layer is though to appear like a spiders web?

Answer 11

Dura mater Arachnoid mater Pia mater Dura and arachnoid are often joined to one another Arachnoid mater is often known as the spider web layer

Question 12

What is the main nerve supply to the meninges?

Answer 12

This would be mainly a sensory nerve supply from CN V (TRIGEMNIAL NERVE)

Question 13

The entire cranial cavity is lined by dura mater which is adherent to the bones of the skull What is the sheet of dura mater that forms a roof over the pituitary gland sitting in the pituitary fossa? What does the small hole in this sheet allow to pass through?

Answer 13

This is the diaphragm sellae Small hole to allow the pituitary stalk to pass through and attach to the hypothalamus

Question 14

a tough sheet of dura mater “tenting” over the cerebellum What is this? and what does it attach to? What does the central gap in this sheet allow to pass throguh?

Answer 14

Tentorium cerebelli - attaches to the ridges of petrous temporal bone Central gap to allow brainstem to pas through

Question 15

What is the opening in the tentorium cerebelli that allows passage of the brainstem known as? What is the midline structure of dura mater that separates the right and left hemispheres of the brain?

Answer 15

This is the tentorial notch Falx cerebri separates right and left hemispheres of the brain

Question 16

What are the attachment points of the falx cerebri?

Answer 16

Attaches anteriorly to the crista galli Attaches to the internal aspect of the saggital suture Attaches to the internal occipital protuberance of occipital bone posteriorly

Question 17

What is the crista galli a projection from?

Answer 17

It is a projection from the cribriform plate of the ethmoid bone

Question 18

The venous drainage of the brain drains into sinuses What are the veins that drain from the brain known as? What are the three sinuses that join to form the confluence of sinuses?

Answer 18

The cerebral veins drain the blood from the brain to sinuses The superior sagittal (dural venous) sinus, straight sinus and occipital sinus join to form the confluence of sinuses

Question 19

Where is the confluence of sinuses located and how does this sinus become the internal jugular vein?

Answer 19

Confluence of sinuses is located at the internal occipital protuberance It drains into the transverse sinus which drains into the sigmoid sinus The sigmoid sinus exits the skull at the jugular foramen to become the internal jugular vein

Question 20

Bacteria that enter a facial vein can travel directly back via the ophthalmic veins to the cavernous sinus The reason the bacteria can travel freely is due to the unique structure of the veins of the face, what is this unique structure?

Answer 20

The veins of the face are thick walled and therefore if punctured will not collapse and due to not having valves bacteria can flow freely into the ophthalmic veins to the cavernous isnus

Question 21

What is the area of trauma of the face where if bacteria enters, then these veins can transport infection known as?

Answer 21

This is the danger triangle of the face

Question 22

What do the vertebral arteries pass through to enter the cranial cavity? What do the right and left vertebral arteries become? What are the vertebral arteries a branch of?

Answer 22

They pass through the foramen magnum to become the basilar artery The vertebral arteries are branches of the right and left subclavian arteries

Question 23

What do the cervical veretbraes posses to allow the vertebral arteries to pass through on their way to the skull?

Answer 23

They posses transverse foramina

Question 24

The internal carotid artery also enters the cranial cavity to give off branches to supply the brain What foramen does it enter the cranial cavity via?

Answer 24

Via the carotid canal

Question 25

The right and left vertebral arteries join to form the basilar artery What does this divide into?

Answer 25

This divides into the right and left posterior cerebral arteries

Question 26

What arteries does the internal carotid artery give rise to?

Answer 26

Gives rise to the middle cerebral, anterior cerebral (at its bifurcation) and the ophthalmic artery

Question 27

Label each artery Green? (what joins the green in the middle) Red? Purple? Black? (and black circle with blue line) Yellow? Pink?

Answer 27

Green - anterior cerebral arteries (joined by the anterior communicating artery) Red - ophthalmic artery Purple - Middle cerebral artery Black - Black line - posterior inferior cerebellar artery - Blue line - anterior inferior cerebellar artery Yellow - posterior cerebral artery Pink - internal carotid artery

Question 28

Which artery gives rise to the anterior, middle and posterior cerebral arteries?

Answer 28

Anterior and middle cerebral arteries come from the internal carotid artery Posterior cerebral arteries come from the basilar artery

Question 29

Which parts of the hemispheres do the cerebral arteries each supply?

Answer 29

Anterior cerebral artery - medial of hemispheres with small portion of lateral Middle cerebral artery - lateral apsect of hemisphere Posteiror cerebral artery - mainly occiput (but also the inferior temporal gyrus)

Question 30

What layers of dura mater does the subarachnoid space lie between? What is the function of CSF? Where is CSF produced? How is it reabsorbed into the dural venous sinus? How much CSF is produced per day?

Answer 30

Lies between the arachnoid and pia mater CSF function is to cushion and protect the brain It is reabsorbed into the dural venous sinus via arachnoid granulations (villi) Roughly 500mls of CSF is produced daily

Question 31

At what vertebral levels can the CSF be accessed? At what vertebra level does the spinal cord end and the subarachnoid space end?

Answer 31

Lumbar puncture via L3/4 or L4/5 vertebra levels Spinal cord ends at L2 Subarachnoid space ends at S2

Question 32

What glial cells line the wall of the ventricles?

Answer 32

These are the ependymal cells

Question 33

Describe the flow of CSF

Answer 33

CSF is produced in the ventricles Flows from the lateral ventricles into the interventricular foramen (of Monroe) where it reaches the 3rd Ventrcile, then passes down the cerebral aqueduct (Sylvian aqueduct) to reach the 4th ventricle (located between the pons and cerebellum) Once at the 4th ventricle flow out through medial and lateral apertures to enter the subarachnoid space, then drains through arachnoid granulations into the dural venous sinuses

Question 34

What are the two midline ventricles? Where do the horns of the lateral ventricles lie?

Answer 34

The 3rd and fourth ventricle Anterior horn - frontal lobe Body of ventricle - parietal lobe Posterior horn - occipital lobe Lateral horn - temporal lobe

Question 35

What is the canal of subarachnoid space that runs in the centre of the spinal cord known as?

Answer 35

This is the central canal of the spinal cord

Question 36

excessive production, obstruction to flow or inadequate reabsorption leads to an increased CSF volume: What is this condition known as? What is the most common cause of this condition?

Answer 36

This is hydrocephalus Most commonly due to obstruction of flow of the CSF

Question 37

Blockage of where in the CSF circulation will cause hydrocephalus of one ventricle?

Answer 37

Blockage occuring at the interventricular foramen leading to distension of one of the lateral ventricles

Question 38

What is the treatment used to treat hydrocephalus and how does this work?

Answer 38

It is known as a ventricular peritoneal shunt A catheter is tunnel beneath the skin of the neck and chest and then situated within the peritoneal cavity to drain the fluid

Question 39

Extradural haemorrhage occurs between the bone and dura mater Which artery is ruptured and what bit of bone does this lie beneath?

Answer 39

Middle meningeal artery lying beneath the pterion (the anterior branch)

Question 40

What is the pathophysilogy of extradural haematomas?

Answer 40

They are often due to fractured temporal or parietal bone (in the pterion of the skull - where the frontal, shphenoid, temporal and parietal meet - weakest part of skull) and this fracture causes laceration of the middle meningeal artery A tear in dural venous sinus will also result in an extra dural bleed Blood then accumulates between the bone and the dura

Question 41

When should you be suspect of an extradural haematoma?

Answer 41

Suspect in patient with deteriorating consciousness after a head injury that initially produced no loss of consciousness or after initial drowsiness that seems to have resolved. The lucid interval is typical of extradural bleeds.

Question 42

How does an extradural haematoma present?

Answer 42

USually with severe headache, vomiting , confusion and fits can follow If bleeding continues, can show upper motor neurone signs with brisk reflexes and plantar reflexes

Question 43

How is diagnosis made?

Answer 43

CT shows a lens shaped haematoma LUMBAR PUNCTURE CONTRAINIDCATED This is seen often in rugby player histories

Question 44

subdural haemorrhage: separates the dura from the arachnoid - torn cerebral veins What type of people are these likely to occur in?

Answer 44

falls in the elderly & those with problem drinking

Question 45

What is the cause of the subdural haemorrhage? (pathophysiology)

Answer 45

It is due to a bleeding in your bridging veins - between the cortex and venous sinuses- in the head causing an accumulating haematoma between dura and arachnoid leading to a gradually increasing ICP. This can cause midline shift of the brain away from the side of bleed. Elderly are most susceptible as the bridging veins are weak. The subdurals are most often due to trauma but this can have happened a while ago

Question 46

WHat types of patients is it most commonly seen in? What are the symptoms and signs?

Answer 46

* Seen in elderly as the bridging veins are weak so are very susceptible * Seen in patients with falls ie alcoholics and patients on anticoagulant Fluctuating level of consciousness, insidious physical or intellectual slowing, headache, personality change and unsteadiness Also can have seizures presenting and focal neurological symptoms

Question 47

What is seen on CT in subdural haemorrhage?

Answer 47

Crescent/sickled shaped collecting of blood over 1 hemisphere - biconcave shape is what it is also known as on CT

Question 48

What is the treatment of a subdural haematoma?

Answer 48

Referral to neuro / neurosurgery +/- burr hole decompression

Question 49

Subarachnoid haemorrhage spreads into the CSF of the the subarachnoid space It is most commonly caused by a brain aneursym bursting What type of brain aneursym can be invlved? it is associated with a kidney condtiion

Answer 49

Berry aneurysms associated with autosomal dominant polycysitc kidney disease (ADPKD)

Question 50

During a lumbar puncture, damage to the extradural venous plexus can result in what?

Answer 50

this can result in an epidural haematoma

Question 51

The catheter needle goes through supraspinous, infraspinous ligaments and the ligamentum flavum before reaching epidural space to then continue through the meninges and into the CSF What do these ligaments attach? Does the pedicle or lamina connect with the spinous processes?

Answer 51

Supraspinous ligament - attaches tips of spinous processes Interspinous ligaments - attaches the bodies of the spinous processes Ligamentum flavum - attaches adjacent laminae Lamina attaches to spinous process Pedicles - vertebral body

Question 52

the needle is most safely inserted into the region where: the subarachnoid space surrounds the cauda equina, NOT the spinal cord (the spinal nerve roots of the cauda equina are less easily damaged than the conus medullaris) the vertebrae are not fused (i.e. not the sacrum) Why does it make sense to do it at this level? what is the level of choice again?

Answer 52

L3/4 or L4/5 Cauda equina isnt a solid structure and therefore less chance of penetrating wound Non-fused vertebra allows access into the CSF

Question 53

Supratentorial and infratentorial herniations can occur in the skull dependent on whether or not the herniations arise above the tentorium cerebelli

• What are the four types of supratentorial herniation?
• What are the two types of infratentorial herniation?

Answer 53

• 1. Cingulate (subfalcine)
• 2. Central
• 3. Uncal (tentorial)
• 4. Transcalvarial

Infratentorial - either upward or downwards cerebellar tonsillar herniation

Question 54

In a cingulate (subfacline) herniation, one of the cerebral hemispheres is forced under the falx cerebri WHat happens in an uncal herniation? What happens in a transcalvarial herniation?

Answer 54

Uncal herniation - medial aspect of temporal lobe (uncus) herniates through the tentorial notch Transcalvarial - aka external herniation - part of the brain herniates through a fracture site

Question 55

What happens in cerebellar herniation? (upwards and downwards)

Answer 55

Upwards cerebellar herniation is where the tonsils herniate up through the tentorial notch Downwards is where the tonsils herniate down through the foramen magnum

Question 56

compression of the oculomotor nerve can happen during which type of herniation? What are the features of this herniation if affecting the oculomotor nerve?

Answer 56

UNcal (tentorial) herniation affects the oculomotor nerve Will have a blown pupil as there are no parasympathetics going to the sphincter pupillae of the eye May also have a drooping eyelid and eye down and out