Overview of Traumatic Brain Injury (TBI)

oh right you guys welcome back to

another lesson this lesson here is gonna

be a lesson that's near and dear to my

heart for a few different reasons and

that is to talk about the complex world

of traumatic brain injury so there's a

lot of stuff to talk about with this

topic so make sure you guys hang in

there and I'm gonna start breaking this

down with an overview all right you guys

welcome back let's go and get started

with this lesson here today on traumatic

brain injury and my name is Eddie Watson

and this is ICU advantage and my goal

here with ICU advantage is to take these

complex critical care topics and really

break them down and make them easy to

understand for you guys I really hope

that I'm able to do just that and if I

have hopefully by the end of this lesson

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release a new lesson alright and so

let's go ahead and start off talking

about traumatic brain injury or

something that we refer to as TBI and so

what this is is essentially when we have

some sort of external force that's going

to be causing damage to the brain and

this can really be the result of many

different types of forces so things from

mechanical thermal chemical electrical

even radiation can technically cause

damage to the brain

but more often when we're talking about

this we're referring to the physical

mechanical forces these are they're

gonna be the most common type and so our

attention has really been brought to TBI

over the last decade or so primarily as

a result of some of the sports related

injuries most notably the the big NFL

controversy as well as TBI amongst our

military given the wars in Iraq and

Afghanistan and seeing higher rates of

TBI as a result and so because of these

we've learned quite a lot in regards to

this injury

now unfortunately TBI is a very common

thing in fact the CDC estimates that we

have 2.5 million traumatic brain

injuries that occur every year in the US

alone and TBI is a major cause of our

preventable death

and disability within the United States

and in fact it makes up over 30% of all

the injury related deaths and really we

estimate that there's probably fifty

thousand plus deaths per year as a

result of this and half of those are

actually dying within the initial two

hours after the injury all right and so

with that said let's take a quick look

at the etiology of this particular brain

injury as I said all of this is a result

of those external forces really being

transferred to the brain tissue so I'm

going to take you guys back a little bit

to high school physics and if you

remember we have our equation force

equals mass times acceleration and so

logically we just know that the force

that's going to be exerted is going to

partially be dependent on the size of

the particular object as well as the

acceleration of the speed or sometimes

even deceleration and some of our

injuries the speed that something is

going and ultimately the impact that

these forces have are going to be

dependent on factors such as the amount

of the force the direction of that force

the duration of the force as well as the

rate and other things like that and so

knowing that we have these different

factors that are going to play into the

impact of this force this actually leads

pretty nicely into talking about our

mechanisms of injury now before I get

started here I really am interested to

see what you guys know about this so

head down in the comments below let me

know some examples of different

mechanisms of injury that really you

guys can think of like I said I'm truly

interested to see what you guys know and

then afterwards let's go ahead and

compare answers all right so hopefully

you took the time to head down there and

leave that comment so let's go and talk

about these mechanisms of injury and

there's really two different major types

of mechanisms of injury the first is

going to be what we call blunt injury

and the other is going to be penetrating

so first let's actually talk about our

penetrating injuries so this is going to

result when an object actually has

penetrated the skull and these

penetrating injuries are most commonly

caused by guns which are our number one


common cause and this includes both high

and low velocity which will actually

have some importance here in just a

minute as well as knives and then other

penetrating objects and these other

penetrating objects can really be a

whole wide variety of things I mean I've

seen things from big long pieces of

rebar that have caused injury I've seen

things from rocks being kicked up from a

lawn mower as well as they've even seen

things as crazy as like a machete

although I guess that technically could

be classified as a knife so again the

key takeaway here is the object is going

to penetrate the skull causing injury to

the brain and so now let's talk about

these blunt injuries and so when we talk

about these these are really gonna be

resulting from one of the following six

reasons we have our acceleration injury

which is when a moving object makes

contact with the head and this is going

to cause acceleration of the head so

here think baseball bat hitting a head

the next is going to be our deceleration

and so this is where we have a moving

head that strikes a stationary object so

here think of someone who's fallen off

the ladder and then hits their head in

the process we also have something that

we call acceleration deceleration and so

this is where the brain quickly goes

from rest to moving and then back to

rest again and this is really most

commonly seen in our motor vehicle

accidents we also have what we call

rotation injury and this is going to be

twisting of the brain inside of the

skull this is most commonly caused by

some sort of side impact to the head and

then finally apparently I can't count

this is number five finally we have our

compression or deformation and this is

really where we have a change in the

shape of the skull that's ultimately

causing injury to the brain tissue and I

think this one's pretty self-explanatory

here all right and so next i want to

talk about the different ways in which

we classified these brain injuries and

we can really classify these injuries

one of two ways the first is based on

the severity and then the other is going

to be based on the pathological features

that present and so if we talk about the

severity scale this is where we're going

to see three different severa levels we

have what we call mild moderate and


the way that we really grade somebody

based on this score is there's a couple

of different things that we can look at

but the most common of these is going to

be to use what we call the Glasgow Coma

Scale as our primary assessment tool for

classifying this severity of TBI now if

you're wondering what the Glasgow Coma

Scale is and you haven't already watched

my video that I've already put together

on this

I'm actually gonna link to that right

here right up above and head on over and

watch that video right now that way

you'll really understand what I'm

talking about with this assessment and

so the big takeaway here is the higher

GCS score that we have is that's

actually going to be associated with

better outcomes for our patients but

don't discount the effects of even a

mild traumatic brain injury because even

this injury can potentially last a

lifetime although the majority of people

that do have this mild injury will fully

recover within just a few weeks all

right so now if we actually talked about

the pathological features as a

classification there's two different

types when it comes to classifying this

way and the first of these is what we

call focal and this is where we're gonna

be producing symptoms that are related

to functions of the specific damaged

areas so you can almost think about this

as being localized now these particular

focal injuries do take up space in the

skull and they ultimately can cause

compression of the surrounding tissue

leading to edema elevated ICPs brain

shifts and even herniation so just

because they're focal or localized

doesn't mean that they can't have an

effect on the entire brain now the other

classification here is something that we

call diffuse and this is as the name

suggests it's a widespread injury often

with very little apparent damage on

imaging studies now with these injuries

you certainly can have either/or but

more common is you're actually gonna see

both of these in our patients all right

so let's go ahead and move on from here

and I'm gonna talk real quickly about

something that we call head injury this

is basically a more broad term and

technically does encompass the brain

injury that we're going to talk about

here in a minute but things that we also

consider a head injury that we don't

consider a brain injury are going to be

things like a skull

injury and our skull fractures now for a

scalp injury this is where we're gonna

have things like an abrasion which is

gonna be that top layer of skin that's

removed with maybe a little bit of

bleeding to a contusion which is the

skin isn't broken and we have a hematoma

and then finally a laceration in which

we have the scalp which is actually torn

now the scalp is well supplied with

blood so if you do see a scalp

laceration you truly might have

extensive bleeding and is probably gonna

require some sort of suturing now when

it comes to skull fractures

there's actually four and I believe I

can count this time there's four

different skull fractures that we're

gonna talk about the first is going to

be our linear fracture where this is

essentially just a single fracture line

or a crack in the bone so next is going

to be our comminuted this is basically

splintered and shattered into pieces

next is going to be the depressed skull

fracture which actually goes in line

with what we had talked about previously

with the mechanism of injury being that

compression or deformation so in the

depressed skull fracture we're gonna

have bone fragments that become inwardly

depressed into the brain tissue and this

can either be open or closed and then

finally the last fracture is going to be

something that we call the basal er

which is essentially a linear fracture

along the base of the skull now our

basal skull fracture this is where

you're gonna see some of these classic

signs like like our periorbital

ecchymosis or something we call raccoon

eyes the mastoid ecchymosis or battle

sign you can also have a dural tear

resulting in either rhinorrhea which is

CSF or blood from the nose or Oda Riya

which is CSF or blood from the ears as

well as the hemotympanum which is where

we have blood in the tympanic cavity

behind that tympanic membrane alright so

with those out of the way let's actually

get in and start to talk about our brain

injuries and specifically something that

we refer to as our primary brain injury

now this is going to be a really quick

overview as I'm actually going to have

another lesson coming up here where I'm

going to cover this stuff in much more

depth but our primary brain injury is

going to be something that occurs at the

time of the impact and the result is

either a focal defeat

or combination of the two injury there's

actually seven different types of

primary brain injury that I'm going to

talk about so the first thing the least

severe is going to be our concussion and

this is essentially our mildest form

really this is considered a diffuse

injury and someone with a concussion can

often have a brief loss of consciousness

a headache dizziness and possibly nausea

and vomiting alright next is going to be

something that we call a contusion this

is where we're gonna have small bleeds

or bruising in the brain tissue now this

is where we can start to see things like

ku versus counter-coup which is

essentially seeing injury on the same

which is ku or the opposite side which

is counter-coup of the impact symptoms

that you can see what this are going to

be changes in our patients level of

consciousness you can have central

nervous system dysfunction seizures

hemiparesis hemiplegia really kind of

dependent on where this particular focal

injury is occurring all right the next

injury that I'm going to talk about is

something that we call a epidural

hematoma and this is where we have

bleeding between the dura mater and the

skull and this one's often associated

with skull fractures now the epidural

hematomas are usually the result of an

arterial bleed most associated with the

middle meningeal artery that's located

right under the temporal bone but sort

of our classic presentation for this and

certainly not everybody goes through

this is you may see somebody who

presented with an initial loss of

consciousness but then regained

consciousness for this period of time

something that we call the lucid period

followed by a pretty rapid decline in

their condition and that rapid decline

is really a result of that fast bleeding

hematoma since it's an arterial bleed

now again some of the symptoms that we

can see for this are again changes in

our patient's level of consciousness

headache seizure vomiting and then again

focal changes and in particular we could

see EPSA lateral pupil dilation so here

this hematoma is putting pressure on the

brain tissue causing this mass effect

and elevating our patients ICP and in

almost all cases this is going to

require emergent surgery for this

hematoma all right so now let's talk


a subdural hematoma and this is where

we're gonna see bleeding that's between

the dura mater and the arachnoid mater

now the subdural hematoma is going to be

a little bit different because this is

going to be the result of shearing of

these cortical veins that kind of bridge

between the dura and the arachnoid so

typically these are going to be the

result of an acceleration deceleration

or some sort of rotational injury so if

you think about it here now we're

actually dealing with a venous bleed as

opposed to that arterial bleed

now essentially we're gonna classify

these as either acute versus sub acute

and chronic based on if symptoms are

going to be present within the first 48

hours most often these are going to

occur a lot sooner than that now here on

these patients were going to see this

progressive decline in their level of

consciousness they could have a headache

agitation confusion seizures and once

again focal deficits depending on where

the bleed is and again here think the

symptoms are usually going to develop

slowly as a result of that slower venous

bleed now again depending on the impact

that this is having on our patient that

this could also require potentially

emergent surgery or at a minimum some

sort of drain placement all right so the

next bleed that I'm going to talk about

here is something that we call the

traumatic subarachnoid hemorrhage and

this is where we're gonna have bleeding

that's below the subarachnoid membrane

in the subarachnoid space but it's still

outside of the brain tissue now this is

actually going to be pathologically

different than a subarachnoid hemorrhage

that we see as a result of an aneurysm

rupture and in the case of these

traumatic ones there often isn't any

surgical intervention that can be done

now if we do see a decreased level of

conscious in our trauma patients that

this is actually going to be associated

with a poor prognosis and given the

nature of the space in which this

bleeding is that this may also present

itself with an intraventricular

hemorrhage as well now for these

patients the symptoms that we're going

to see our changes in level of

consciousness a headache which is often

described as the worst headache of their

life confusion seizures and once again

focal deficits

all right in the next lead that I'm

going to talk about is something that we

call our interest cerebral hemorrhage

and this is where we have bleeding in

the actual Parekh imal tissue of the

brain now this bleeding can occur in a

lot of different places throughout the

brain depending where the particular

vessel is that's injured but it's

important to know that this is not to be

confused with the intraparenchymal

hemorrhage or iph which is the result of

a non traumatic bleed inside the parent

now this bleed is usually associated

with severe acceleration deceleration

injuries or penetrating injuries and the

symptoms that we'll see here with this

is once again changes in our level of

consciousness headache focal deficits as

well as elevated ICP all right and then

finally the last injury that I want to

talk about is something that we call our

diffuse injury and this is really

something that I exist on a continuum of

severity from concussion being our least

severe diffuse injury all the way up to

something that we call diffuse axonal

injury or Dai and essentially in the

case of Dai this is where we just have

this diffuse injury this diffuse

shearing of these axons and then these

patients are gonna present with the loss

of consciousness and coma and abnormal

posturing and again as I had mentioned

earlier oftentimes these are gonna

appear normal on the CT and if anything

you just might see this diffuse edema as

a result so our patient's prognosis is

really going to be based on the severity

of this injury although for our really

severe cases that prognosis is really

poor alright so those are different

types of primary brain injuries next I

want to just move on and talk about real

quickly something that we call our

secondary brain injury now again this is

going to be a very quick overview as

again I'm gonna do another lesson

specifically looking at these secondary

brain injuries more in depth really when

I'm talking about

the management of brain injury but

essentially the secondary brain injury

is a continuation of damage to the brain

that is as a result of physiological of

from the primary brain injury and so

basically what's happening here is the

primary brain injury is going to lead to

this cascade of ischemia and cellular

level changes that are going to lead to

additional neuron cell injury and

ultimately cell death and some of the

major contributors to this are going to

be things like hypoxemia hypotension

anemia increased intracranial pressures


Auto regulation either hypo or hyper cap

Nia same thing either hypo or

hyperglycemia various biochemical

changes that are taking place as well as

our patient's metabolic demand and so

ultimately when it comes to the

management of these patients that this

is going to revolve around minimizing

these secondary injuries ultimately by

increasing the cerebral oxygen delivery

to the brain and decreasing the cerebral

metabolic demand all right and with that

said that's gonna wrap things up here I

hope this lesson was very beneficial to

you guys like I said this was a quick

overview make sure you guys are keeping

an eye out for those future lessons

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