Anatomy 4 - Space occupying lesions

Question 1

What is the problem with space occupying lesions and define what a SOL is ?

Answer 1

Space occupying lesions (SOL) = abnormal tissue taking up space in the skull

The problem with SOL’s is that the base of skull foraminae do not readily permit ‘escape’ of contents ==> Acute or sub acute (expanding) intracranial pathologies can result in increased ICP, in turn the increased ICP can result in herniation

Question 2

What are the 5 layers of the scalp and how do you remember them ?

Answer 2

SCALP:

1. Skin
2. Connective tissue
3. Aponeurosis
4. Loose connective tissue
5. Pericranium

Question 3

What does layer 2 of the scalp contain and why is this important ?

Answer 3

Contains the named arteries of the scalp

The scalp arteries form a rich anastomotic network just deep to the skin – scalp lacerations & incisions can bleed excessively

Question 4

What are the 4 main sutures of the skull and what is their function ?

Answer 4

1. Coronal
2. Sagittal
3. Lamboid
4. Squamous - joins the parietal and temporal bones

Function is to stop fractures spreading (they are fibrous joints)

Question 5

What are the main bones of the skull ?

Answer 5

Question 6

What are the main bones of the skull (face)

Answer 6

Question 7

What are the main bones of the base of the skull

Question 8

Go over some of the features of the skull

Answer 8

Question 9

What is the pterion and why is it significant ?

Answer 9

It is the thinnest part of the skull formed between the Frontal, parietal, temporal and sphenoid bones

The middle meningeal artery courses deep to it ==> it is at risk to damage

Question 10

State the following meningeal layers shown

Answer 10

Question 11

What is the intracranial dura mater mainly innervated by ?

Answer 11

CN V

Question 12

What is the dura mater adherent to ?

Answer 12

All of the bones of the skull

Question 13

What is the tentorium cerebelli and the diaphragm sellae ?

Answer 13

Tentorium cereblli = a tough sheet of dura mater ‘tenting’ over the cerebellum

Diaphragm sellae = a tough sheet of dura mater forming a roof over the pituitary fossa

Question 14

What is the falx cerebelli ?

Answer 14

A midline structure of dura mater splitting the brain into the left and right cerebral hemispheres

Question 15

Label the venous drainage of the brain

Answer 15

Main veins to remember:

• Superior sagittal sinus
• Cerebral veins
• Left sigmoid sinus
• Opthalamic veins
• Internal jugular vein
• Facial vein

The dural venous sinuses lie between the periosteal and meningeal layers of the dura mater. They are best thought of as collecting pools of blood, which drain the central nervous system, the face, and the scalp. All the dural venous sinuses ultimately drain into the internal jugular vein

Question 16

Label the arteries indicated

Answer 16

Note that the external carotid arteries remain external to the cranium and supply the face, scalp and neck

Question 17

What does the internal carotid and what does the vertebral arteries pass through to enter the cranial cavity ?

Answer 17

• Internal jugular arteries pass through the carotid canal
• Vertebral arteries pass through the foramen magnum

Question 18

Label the arteries of the circle of willis

Answer 18

Question 19

What do each of the following arteries supply:

1. Anterior cerebral
2. Middle cerebral
3. Posterior cerebral

Answer 19

1. Anterior cerebral - supplies the anteromedial portion of the cerebrum
2. Middle cerebral - supply the majority of the lateral part of the brain.
3. Posterior cerebral - supply both the medial and lateral parts of the posterior cerebrum.

Question 20

Describe the clinical relevance of the danger triangle of the face

Answer 20

• The danger triangle of the face consists of the area from the corners of the mouth to the bridge of the nose, including the nose and maxilla.
• Due to the special nature of the blood supply to the human nose and surrounding area, it is possible, albeit extremely unlikely, for retrograde infections from the nasal area to spread to the brain, causing cavernous sinus thrombosis, meningitis or brain abscess.
• This is possible because of venous communication (via the ophthalmic veins) between the facial vein and the cavernous sinus.

Question 21

Describe the anatomy of the subarachnoid space in terms of:

• What is surrounds
• Where is it located
• What is contains
• Its function

Answer 21

Found between arachnoid mater and pia mater:

• completely surrounds both brain & spinal cord
• continuous
• cushions and protects the brain and spinal cord

Contains circulating cerebrospinal fluid (CSF)

Question 22

Where is CSF produced and how is it reabsorbed ?

Answer 22

• Produced in the choroid plexus of the ventricles
• Reabsorbed into the dural venous sinuses via arachnoid granulations

Question 23

Where is the circle of willis located ?

Answer 23

Inferior to the midbrain, closely related to the pituitary stalk & the optic chiasm, within the subarachnoid space

Question 24

Label the indicated structures

Answer 24

Question 25

Describe the pathway of CSF from production to reabsorption

Answer 25

1. CSF produced in the choroid plexus of the lateral ventricles 2. The passes through the R and L foramina of monro (the interventricular foramina) into the 3rd ventricle 3. The through the cerebral aqueduct into the 4th ventricle 4. The passess mainly into the subarachnoid space but also some passes into the central canal of the spinal cord 5. CSF is then absorbed from the subarachnoid space via arachnoid granulations into the dural venous sinuses

Question 26

Where does the bleeding within the cranial cavity occur in each of the following and give an example of a common cause of each: 1. Extradural haematoma 2. Subdural haemoatoma 3. Subarachnoid haematoma

Answer 26

1. Extradural haematoma - bleeding occurs between the dura and bone, commonly due to a ruptured middle meningeal artery due to trauma to the pterion 2. Subdural haemoatoma - bleeding occurs between the dural and subarachnoid mater, commonly due to torn cerebral veins due to falls in the elderly or people with alcohol problems 3. Subarachnoid haematoma - bleeding occurs in the subarachnoid space commonly due to a ruptured berry aneurysm

Question 27

What layers does the needle pass through in a lumbar puncture ?

Answer 27

1. supra- and then interspinous ligaments 2. ligamentum flavum 3. epidural space (fat & veins) the destination of the epidural catheter 4. then the lumbar puncture (spinal) needle continues.. 5. through the dura mater & 6. arachnoid mater simultaneously …to reach the… 7. subarachnoid space …to obtain the CSF sample

Question 28

What is the appropriate level for a lumbar puncture and why ?

Answer 28

L3/4 * This is because its safer to access the subarachnoid space which surrounds the cauda equina than the subarachnoid space surrounding the spinal cord * Since the cord cord ends at L2 and then the cauda equina continues on and the subarachnoid space continues on also until S2 ==\> best the access it at L3/4 level

Question 29

What are the different herinations which can occur in the brain as a result of raised ICP ?

Answer 29

Supratentorial herinations: 1. Cingulate (subfalcine) - In cingulate or subfalcine herniation, the most common type, the innermost part of the frontal lobe is scraped under part of the falx cerebri 2. central 3. uncal - the uncus (medial part) of the temporal lobe herniates inferior to the tentorium cerebelli 4. transcalvarial Infratentorial herniations: 1. upward 2. downward or tonsillar herniation (herniation of the cerebellar tonsils): the cerebellar tonsils herniate into the foramen magnum

Question 30

What clinical sign can an uncal herniation result in ?

Answer 30

Ipsilateral fixed dilated pupil due to compression of the oculomotor nerve