Neuro - Brain and Environments

CSF provides _ so that the brain does not sit on the base of the skull

Buoyancy

The foramen magnum is at the

Base of the skull

Where does the spinal cord transition to the medulla

Cervicomedullary junction

The cervicomedullary junction is located at the

Foramen magnum

The pyramidal decussation is where

The lateral corticospinal tract crosses to the other side of the spinal cord

What is located in the foramen ovale

CNV3

What is located in the foramen spinosum

Middle meningeal artery

The fossa compartments in the base of the skull include the

- Anterior

- Middle

- Posterior

The layers of the meninges are (PAD)

- Pia mater

- Arachnoid mater

- Dura mater

The 2 layers of the dura mater are the

- Periosteal layer (outer)

- Meningeal layers (inner)

The meningeal (inner) layer of the dura mater folds into the cranial cavity to form

- Falx cerebri

- Tentorium cerebelli

The tentorial notch is an opening in the tentorium cerebelli where

The midbrain passes through

CSF freely flows in the

Subarachnoid space

The arachnoid mater is loosely adherent to the

Inner dura (meningeal layer)

The pia mater is a very thin layer that adheres to the

Surface of the brain

The epidural space (potential space) exists between the

Inner skull and dura

Which artery supplies the epidural space

Middle meningeal artery

The middle meningeal artery supplies the _ and comes off the _

Dura; external carotid artery

The subdural space (potential space) lies between the

Dura and arachnoid mater

A venous sinus is

A large channel formed between 2 layers of dura where used blood is deposited

In the subdural space, bridging veins cross over to drain in the

Dural venous sinuses

The subarachnoid space (actual space) lies between the

Arachnoid and pia mater

CSF lies in the

Subarachnoid space

The subarachnoid space contains the major _ of the brain

Arteries

There is _ lateral ventricle within each cerebral hemisphere

1

The third ventricles lie within

The diencephalon

The fourth ventricle is surrounded by the

Pons and cerebellum

Since the lateral ventricle is so large, it extends into

Every lobe

CSF leaves the ventricular system via foramen in the _ and flows to the _

Fourth ventricle; Spinal cord

What are the foramen that CSF reaches the spinal cord from

- Foramina of Luschka (lateral)

- Foramen of Magendie (midline)

CSF is reabsorbed by arachnoid granulations into the

Venous sinuses

New CSF is produces _ a day

3-4 times

A cistern is a

Widened area of the subarachnoid space that contains CSF

Spinal taps occur at

Lumbar cistern

The blood brain barrier exists because

Capillary endothelial cells in the brain are joined at the edges

What kinds of molecules can clear the blood brain barrier

Most fat soluble and smaller molucles

The blood brain barrier restricts what kinds of molecules

Water soluble and larger molecules

In addition to the BBB there also exists a

Blood-CSF barrier between the choroid plexus and CSF

In the brain there are _ where there is no BB

Specialized regions

Why are there areas of the brain where the BBB does not exists

So that the blood can be monitored and the brain can respond to changes in chemical environment

Normal ICP is around

15 mmHg

Elevated ICP can cause

Decreased cerebral perfusion and brain ischemia

Cerebral perfusion pressure needs to be above

~50 mmHg

Placing someone in a medically induced coma reduces

The metabolic demands of the brain

ICP can be lowered to maintain

Cerebral perfusion

Large increases in ICP can happen

Suddenly or slowly

S/s of increased ICP include

- HA

- Altered mental status*

- Nausea and vomiting

- VIsual loss

- Diplopia

Papilledema is

Edema of the optic disc, usually due to elevated ICP

Small masses in the brain can be compensated for by a

Decrease in CSF and blood volume

Brain herniation syndromes include

- Subfalcine

- Central

- Uncal

- Tonsilar

A subfalcine brain herniation occurs

At the cingulate gyrus under the falx cerebri

A subfalcine brain herniation can compress the

ACA

A central brain herniation causes

Central and downward displacement of the brainstem

What nerve is involved in a central brain hernation

CN VI, can also lead to uncal herniation

An uncal brain herniation occurs at

The medial temporal lobe through the tentorial notch

In an uncal brain herniation the _ can be compressed causing _

CN III (dilated pupil); Contralateral hemiplegia and coma

A tonsilar brain herniation occurs

At the cerebellar tonsils through the foramen magnum

A tonsilar herniation can lead to

- Respiratory arrest

- BP instability

- Death

A sudden explosive onset of severe headache can be the first indication of

Subarachnoid hemorrhage or CVA

Intracranial hemorrhages are either

Traumatic or non-traumatic

An epidural hematoma occurs

In the potential space between the dura and skull

Epidural hematomas are usually caused from

A rupture of the middle meningeal artery due to temporal bone fx

Epidural hematomas usually present with _ initially, and _ within a few hours

No symptoms; elevated ICP and herniation

A subdural hematoma occurs in

The potential space between dura and arachnoid

Subdural hematomas are usually caused by

Rupture of bridging veins as they cross the arachnoid into the dura

What happens in a subdural hematoma

Venous blood spreads out over a large area and forms crescent shaped hematoma

Chronic subdural hematomas are more common in

Elderly patients

Since venous blood collects slowly in a chronic subdural hematoma, symptoms can be

Vague (cognitive impairment, HA, unsteady gait)

Chronic subdural hematomas can be caused from

Minimal trauma

In patients with a chronic subdural hematoma, the brain moves

Freely due to atrophy and bridging veins more susceptible to shear injury

In order for an acute subdural hematoma to appear right after an injury, there must be

A high impact velocity

Since acute subdural hematomas are caused by high impact velocity, prognosis is generally

Poor

A subarachnoid hemorrhage occurs between the

Arachnoid and pia

On a CT, a subarachnoid hemorrhage appears as

Blood pooling in the contours of brain sulci

What key structures lie in the subrachnoid space

CSF and blood vessels of the brain

A spontaneous subarachnoid hemorrhage is generally caused by rupture of arterial aneurysms including

- Acomm

- Pcomm

- MCA

- AVM

The main symptom of a spontaneous subarachnoid hemorrage is

A sudden catastrophic headache

Other symptoms of a spontaneous subarachnoid hemorrhage includes

- Neurological deficits

- Impaired LOC

- Coma

- Progression to death

The overall mortality rate of a spontaneous subarachnoid hemorrhage is

50%

A traumatic subarachnoid hemorrhage is caused by

Bleeding into CSF from damaged vessels

A traumatic subarachnoid hemorrhage is more common than

Spontaneous

The headache in a traumatic subarachnoid hemorrhage is severe due to

Meningeal irritation from blood in the CSF

An intracerebral hemorrhage occurs within

Brain parenchyma in cerebral hemispheres, brainstem, cerebellum, or spinal cord

Traumatic intracerebral hemorrhages are

Contusions of cerebral hemispheres

Traumatic intracerebral hemorrhages occur at

Temporal and frontal poles

A coup-countercoup injury can lead to

Subarachnoid and acute subdural hemorrhaging

Non-traumatic intracerebral hemorrhages are caused by

- HTN

- Brain tumors

- Secondary hemorrhage after infarction

- AVMs

- Coagulation abnormalities

- Infections

A HTN hemorrhage is the most common type of

Non-traumatic intracerebral hemorrhage

HTN hemorrhages typically involve

Small, penetrating vessels such as those at the basal ganglia, thalamus, cerebellum, and pons

Head trauma can cause

- Hemorrhage behind ear drum

- Hemorrhage into subcutaneous tissue

- Hemorrhage between external periosteum and galea aponeurotica

When you have head trauma, you should rule out

Skull fx

A basilar skull fracture often appears with

Battle's sign or "raccoon eyes"