brain lab briefing

Question 1

describe the layers of the scalp

Answer 1

Skin: where hair grows, nutrients for hair follicles are found here

Connective tissue: dense subcutaneous layer of fat and fibrous tissue. contains nerves and vessels of scalp.

epicranial Aponeurosis: tough layer of dense connective tissue which runs from frontalis muscle anteriorly to occipitalis posteriorly

Loose connective tissue: areolar connective tissue, made up of random collagen bundles, separates the upper 3 layers of scalp of pericranium, and allows them to move in realign to pericranium.

Periosteum: provides nutrition to the cranium capacity to repair

Question 2

if there is an infected scalp wound, how is there potential for it to spread intracranially?

Answer 2

via emissary veins into cranial cavity

Question 3

why is the convex shape of the skull important?

Answer 3

it dissipates injury by distributing and minimising the effects fo a blow to the head so the head is able to take more force without fracturing

Question 4

what important structures are found the base of the skull?

Answer 4

cranial nerves and blood supply

Question 5

what bones make up the base of the skull?

Answer 5

orbital plate of frontal bone, sphenoid bone, squamous and petrous temporal bones, occipital bone

Question 6

describe a depressed skull fracture

Answer 6

bone fragments depress inwards with damage/compression of brain

Question 7

describe a linear skull fracture

Answer 7

a break in cranial bone resembling a thin line. it occurs at site of impact but the fracture lines radiate away

Question 8

what is battle’s sign?

Answer 8

bruising over the mastoid process (purplish bruising)

Question 9

what is periorbital ecchymosis also known as?

Answer 9

raccoon or panda eyes

Question 10

what causes panda eyes?

Answer 10

basal skull fracture that ruptures meninges and causes venous sinuses to bleed into arachnoid vill and cranial sinuses.

Question 11

what clinical features are seen in panda eyes beside bruising around the eyes?

Answer 11

blood or csf coming out of the ear or nose which indicates breach of the meninges

Question 12

what diagnostic test should be carried out if panda eyes are present?

Answer 12

CT scan

Question 13

what is the pterion?

Answer 13

region of skull behind the temple, where the frontal, parietal, temporal, and sphenoid bones join together.

Question 14

why is there a high chance of fracture of the pterion and what consequences would a fracture have?

Answer 14

It is translucent and very thin

There are branches of meningeal arteries underneath so fracture could lead to intracranial haematoma.

Question 15

what are the 2 layers of the dura mater and where are they attached and separated?

Answer 15

endosteal and meningeal layers

they are closely attached and only separate to form venous sinuses and at reflections

Question 16

what are the 2 main dural reflections and what do reflections do?

Answer 16

falx cerebri and tentroium cerebellum

They divide the cranial cavity into compartments by forming partitions

Question 17

list 3 types of intracranial haematomas

Answer 17

epidural/extradural
subdural
intracerebral

Question 18

describe an epidural haematoma including causes and shape

Answer 18

When blood collects between periosteal layer of dura and skull, the blood strips the dura away from the periosteum.

Related to a skull fracture, caused by arterial bleeding usually of middle meningeal artery. It forms a lens shaped swelling because it cannot swell along suture lines

Question 19

describe a subdural haematoma

Answer 19

when blood collects between dura and arachnoid

Blood is of venous origin = slower bleeding

Question 20

what features can be seen in an acute extradural/epidural haematoma CT scan?

Answer 20

lens shaped haematoma
“white” area = fresh blood in context of head injury
ventricular shift - swelling of brain closes the ventricles and shifts the ventricle away from midline

Question 21

what features can be seen in an acute subdural haematoma CT scan?

Answer 21

crescent shaped haematoma as there are no suture limitations so blood can spread all the way around the brain
middling shift of ventricles

Question 22

what re the 3 components of intracranial volume?

Answer 22

blood, csf, brain

Question 23

what happens in response to raised cranial pressure due to presence of a mass? what happens I this mass keeps increasing?

Answer 23

compensatory mechanisms eg removing venous blood and csf

after a critical point, there is decompensation which causes ICP to rise rapidly

Question 24

what is the equation for cerebral perfusion pressure?

Answer 24

CPP = MAP - ICP

Question 25

how does a normal brain auto regulate its blood flow to maintain perfusion pressure?

Answer 25

by altering the resistance of cerebral blood vessels

Question 26

if homeostatic mechanisms fail after a head injury, what effect does a rising ICP have?

Answer 26

can lead to reduced CPP and ischaemic damage

Question 27

what are signs of increasing ICP?

Answer 27

decreasing Glasgow coma scale
diminished pupil response to light
lateralising signs eg weakness on one side

Question 28

if there is uncontrolled rise in ICP, what are the types of herniation that occur? describe them

Answer 28

1st: cingulate herniation occurs
cingulate gyrus slips under the flax cerebri and this causes a midline shift which is seen on CT scan

2nd: uncal herniation occurs
uncal of temporal lobe slips under tentorium cerebellum and this ipsilaterally compresses oculomotor nerve (CN3) which affect pupils reflexes = fixed and dilated pupil

if it progresses further: brainstem could be compressed