Meninges And Cerebrospinal Fluid

Front 1

What is the innermost layer of the connective tissue membranes around the CNS?

Back 1

The pia mater which closely adheres to the brain and spinal cord into every sulci and depression on the surface of the CNS.

Front 2

What connective tissue membrane around the brain is vascular and carries the blood vessels that supply the CNS?

Back 2

The pia mater

Front 3

B/e what connective tissue membranes are the cisterna magna and lumbar cistern located b/e?

Back 3

In the subarachnoid space which lies in b/e the pia mater and the arachnoid.

Front 4

Where is the cisterna magna located?

Back 4

Posterior to the medulla below the cerebellum

Front 5

Where is the lumbar cistern located?

Back 5

Below L1-2 where the spinal chord terminates.

Front 6

What are the arachnoid trabeculae?

Back 6

Thin threads of connective tissue that extend through the subarachnoid space connecting the arachnoid w/ the pia mater.

Front 7

What space contains the CSF?

Back 7

The subarachnoid space

Front 8

Where do ruptured vessels in the pia mater bleed into?

Back 8

The subarachnoid space.

*called a subarachnoid hemorrhage.

Front 9

What causes inflammatory cells to be found in the subarachnoid space?

Back 9

Meningitis (an infection of the meninges)

Front 10

B/e what vertebral levels do you insert the needle during a lumbar puncture?

Back 10

L4-5

Front 11

What is the outermost membrane surrounding the brain? what does it contain?

Back 11

The dura mater which contains dense connective tissue and is very strong.

Front 12

What layers does the dura mater contain?

Back 12

An outer periosteal layer and an inner meningeal layer.

Front 13

What does the periosteal layer of the dura mater contain? what does it attach to?

Back 13

Contains blood vessels and nerves and is attached to the inner surface of the cranium.

Front 14

What is the subdural space?

Back 14

The potential space b/e the arachnoid and the dura.

Front 15

What causes blood to collect in the subdural space or a subdural hematoma?

Back 15

Venous in origin from head trauma that caused shearing of the bridging veins.

Front 16

What is the epidural space?

Back 16

The space b/e the dura mater and bone

Front 17

What causes a epidural hemorrhage?

Back 17

Arterial in origin from a laceration of the middle meningeal artery. These are more likely to be associated w/ a skull fracture.

Front 18

What is the function of the dura mater?

Back 18

Covers the entire brain and spinal cord all the way down to the second sacral vertebrae and helps anchor the spinal chord to the meninges

Front 19

What do the denticulate ligaments do?

Back 19

Anchor the spinal chord to the meninges.

Front 20

What's the dx?

Back 20

Subdural hematoma; notice the characteristic crescent shape b/c it is a venous hemorrhage.

Front 21

Where is the falx cerebri? what does it do?

Back 21

Extends into the interhemispheric fissure and divides the left and right halves of the brain.

Front 22

What does the falx cerebri divide into?

Back 22

The cerebellar tentorium

Front 23

What is the cerebellar tentorium?

Back 23

The two divisions of the falx cerebri that extends over the surface of the cerebellum

Front 24

Where in the dura is the opening for the spinal chord located?

Back 24

In the anterior edge of the cerebellar tentorium

Front 25

What effect on the brain would increased intracranial pressure from a tumor or hemorrhage w/in the brain have?

Back 25

Cause the temporal lobe to herniate through the opening of the cerebellar tentorium. the most medial portion of the temporal lobe (the uncus) will compress the ipsilateral oculomotor nerve (CNIII) resulting in 3rd nerve palsy.

Front 26

What are the presenting symptoms of 3rd nerve palsy?

Back 26

A dilated pupil w/ the eye deviated laterally. This is an ominous finding in comatose patients.

Front 27

Where are the lateral ventricles located? what processes does it contain?

Back 27

in the cerebral hemispheres w/ an anterior (frontal) horn, a posterior (occipital) horn, and an inferior (temporal) horn.

Front 28

What borders the frontal horn of the lateral ventricle medially?

Back 28

The septum pellucidum.

Front 29

What bulges into the lateral aspect of the frontal horn?

Back 29

The caudate nucleus.

Front 30

What forms the medial wall of the inferior horn of the lateral ventricle?

Back 30

The hippocampus.

Front 31

What is the foramen of Monro?

Back 31

CSF from each lateral ventricle communicates w/ the third ventricle through this foramen

Front 32

What surrounds the third ventricle?

Back 32

The two thalami

Front 33

How does CSF from the third ventricle reach the fourth ventricle?

Back 33

Via the cerebral aqueduct

Front 34

What does the cerebral aqueduct divide?

Back 34

The tegmentum from the tectum in the midbrain

Front 35

Where is the 4th ventricle located?

Back 35

B/e the pons and medulla (anteriorly) and the cerebellum posteriorly

Front 36

How does CSF exit the 4th ventricle?

Back 36

Via the two lateral foramens of Luschka and via the single middle foramen of Magendie.

Front 37

What is the cisterna magna?

Back 37

The outlet of the two foramen of Luschka and the foramen of Magendie.

Front 38

Once leaving the brain through the cisterna magna where does CSF go?

Back 38

Travels around the spinal chord to eventually come back around and empty into the superior sagittal sinus (the venous sinus over the interhemispheric fissure)

Front 39

What are arachnoid villi?

Back 39

Small evaginations in the wall of the arachnoid that protrude through the meningeal layer of the dura into the SSS that allow CSF to travel into the SSS.

Front 40

What are arachnoid granulations?

Back 40

Several arachnoid villi together

Front 41

Why is CSF able to pass through the arachnoid villi?

Back 41

B/c the hydrostatic pressure is higher in the subarachnoid space than in the venous sinus.

Front 42

What does the SSS eventually drain into? where do both the venous blood and CSF exit the intracranial cavity?

Back 42

Through the internal jugular vein

Front 43

What is the continuation of the ventricular system in the spinal chord?

Back 43

The central canal of the spinal chord.

Front 44

What produces CSF?

Back 44

The choroid plexus

Front 45

Where is the choroid plexus located?

Back 45

In the lateral ventricles, third ventricle and fourth ventricles.

Front 46

What is the composition of CSF?

Back 46

It is similar to blood except it has no RBCs or WBCs, the glucose is 2/3 that in blood and the CSF protein is ~0.5% that of blood.

Front 47

What is the importance of the fact that the weight of the nervous tissue is only slightly greater than water?

Back 47

1. It means the brain and spinal chord almost float in the CSF, this buoyancy reduces the weight of the nervous tissue and results in less traction on vessels and nerves.

2. It also minimizes the impact of external forces on the brain and spinal chord by serving as a cushion.

3. It also filters out potentially toxic substances from the brain.

SO it reduces friction, reduces impact forces and filters the brains environment.

Front 48

What is the path of CSF circulation?

Back 48

Lateral ventricles x2 => interventricular foramen of Monro x2 => Third ventricle => cerebral aqueduct => fourth ventricle => Foramen of Luschka x2 and foramen of Magendie => Cisterna Magna/Subarachnoid space => arachnoid villi => superior Sagittal Sinus => Cerebral Venous System => Internal Jugular vein

Front 49

What is the total volume of CSF in the ventricular system and the subarachnoid space?

Back 49

~150 mL in adults.

Front 50

How much CSF is produced by the choroid plexus per day?

Back 50

~500 mL, so the total amount of CSF is therefore renewed several times every day.

Front 51

If there is a blockage of the cerebral aqueduct what will happen to the brain?

Back 51

The third ventricle and lateral ventricles will dilate since the CSF produced in these ventricles cannot drain, but the fourth ventricle will not change in size.

Front 52

What is the end-result of increased intracranial pressure in adults if it is not repaired? infants/children?

Back 52

In adults it will result in herniation of the brain through the foramen magnum.

In infants/children (if the sutures have not closed) it will result in increased head circumference.

Front 53

What are the types of hydrocephalus?

Back 53

1. non-communicating hydrocephalus
2. communicating hydrocephalus
3. hydrocephalus ex-vacuo

Front 54

What is a non-communicating hydrocephalus?

Back 54

The CSF of some part of the ventricular system does not "communicate" w/ the subarachnoid space CSF.

Front 55

What disorders produce a non-communicating hydrocephalus?

Back 55

Anything that compresses the interventricular foramen of Monro, cerebral aqueduct or the outlets from the fourth ventricle.

Front 56

In what kind of hydrocephalus should a lumbar puncture NOT be performed? why?

Back 56

A non-communicating hydrocephalus b/c it lowers the pressure in the lumbar cistern and creates a greater pressure gradient b/e the ventricular CSF and subarachnoid CSF this can result in brain herniation.

Front 57

What is communicating hydrocephalus?

Back 57

The CSF of the ventricular system and subarachnoid space "communicate", but there is a blockage in the arachnoid granulations.

Front 58

What diseases can cause a communicating hydrocephalus?

Back 58

An old sub-arachnoid hemorrhage or meningitis which results in scarring and closure of the arachnoid villi.

Front 59

What is hydrocephalus ex-vacuo?

Back 59

As the brain atrophies (especially in neurodegenerative conditions like Alzheimer's) the ventricles appear larger. This is not the case! It is an optical illusion due to a loss of the normal brain tissue around the ventricles.

This is not a true hydrocephalus and is diagnosed by the presence of "hydrocephalus" on MRI or CT associated w/ a significant amount of atrophy present in the rest of the brain.

Front 60

What's the dx?

Back 60

Normal

Front 61

What's the dx?

Back 61

Hydrocephalus

Front 62

What's the dx?

Back 62

Hydrocephalus ex vacuo

Front 63

What is the blood-brain barrier?

Back 63

The BBB separates the brain from the blood.

Front 64

What are the three main components of the BBB?

Back 64

1. endothelial cells
2. basement membrane
3. astrocyte foot processes.

Front 65

What is the most important component of the BBB?

Back 65

The tight junctions b/e the endothelial cells b/c it forms the wall of brain capillaries.

Front 66

What are circumventricular organs? what do they do?

Back 66

Areas of specialized tissue located in the midline ventricular system that lack a BBB.

At the circumventricular organs, hormones and large peptides can be exchanged b/e the blood-brain-CSF.

Front 67

What is the area postrema?

Back 67

A circumventricular organ that is sometimes called the "vomiting center" b/c it detects toxins such as the chemotherapeutic medication cisplatin.

Front 68

Where is the area postrema?

Back 68

Along the caudal wall of the 4th ventricle in the medulla.

Front 69

What are the circumventricular organs?

Back 69

1. Area postrema
2. Pineal gland
3. Subcomissural organ
4. Subfornical gland
5. Organum vasculosum of the lamina terminalis
6. Median eminence
7. neurohypophysis

Front 70

What is meningitis?

Back 70

An infectious process involving the meninges and CSF.

Front 71

What do pts w/ meningitis present with?

Back 71

Severe headache and fever which typically progresses over hours, patients generally have pain w/ neck flexion which stretches the meninges.

Occasionally there will be a petechial skin rash in meningococcal infections.

Front 72

What should you do if you have a pt w/ meningitis?

Back 72

make a RAPID dx!!! b/c there are many forms of meningitis which are treatable.

Front 73

What are the differences in prognosis b/e bacteria, viral and fungal meningitis?

Back 73

*bacterial meningitis is rapidly fatal.

*viral meningitis is generally benign and pts have a good recovery.

*fungal meningitis results in chronic meningitis which presents more slowly and requires long-term treatment.

Front 74

What is the most likely cause of meningitis in pts who are 0-2 months old?

Back 74

1. Gram-negative bacilli (ESPECIALLY E. Coli)

2. group B streptococcus

3. Listeria

Front 75

What is the most likely cause of bacterial meningitis in a patient who is 3 months- years old?

Back 75

1. H. influenza (not as big a prob. anymore)

2. N. meningitides

3. S. pneumonia

Front 76

What is the most likely cause of meningitis in a patient who is 3 years old - adults?

Back 76

1. S. pneumonia

2. N. meningitides

Front 77

What is encephalitis?

Back 77

An invasion of the brain parenchyma itself by an organism that is almost always viral.

Front 78

What do pts w/ encephalitis present with?

Back 78

headache and fever like meningitis but also have symptoms suggestive of cortical involvement such as: seizures, lethargy -> coma, aphasia and sometimes focal weakness if motor cortex is involved.

Front 79

What is the most important (specific) organism to consider in a pt presenting w/ encephalitis?

Back 79

Herpes Simplex Encephalitis (HSE)

Front 80

What age group does HSE typically affect?

Back 80

Any age can be affected.

Front 81

What are the most common Sys of HSE infection?

Back 81

rapidly progressive headaches, fever, seizures, personality changes, encephalopathy and aphasia if language area is involved.

Front 82

What is important in diagnosing HSE infection?

Back 82

CSF analysis.

Front 83

What would neuroimaging reveal in a pt w/ HSE infection?

Back 83

Edema in the temporal lobe and most often in both temporal lobes.

Again, RAPID dxing is critical since untreated HSE results in death in at least 2/3rds of pts.

Front 84

What change in concentration of WBCs, RBCs, glucose, proteins would be seen in the CSF in bacterial meningitis? what other changes could be detected?

Back 84

WBCs: LARGELY increased
RBCs: no change (zero)
Glucose: drastically decreased
Protein: drastically increased

There would also be a positive culture.

Front 85

What change in concentration of WBCs, RBCs, glucose, proteins would be seen in the CSF in viral meningitis?

Back 85

WBCs: inc.
RBCs: no change (zero)
Glucose: normal
Protein: inc.

Front 86

What change in concentration of WBCs, RBCs, glucose, proteins would be seen in the CSF in HSE? what other changes can be detected?

Back 86

WBCs: inc.
RBC: inc. (more than zero)
Glucose: normal or dec.
protein: increased

The CSF would also be PCR positive. (which is amplifying foreign DNA content to detect small things like viruses)

Front 87

What change in concentration of WBCs, RBCs, glucose, proteins would be seen in the CSF in subarachnoid hemorrhage? what other change would be detected?

Back 87

WBCs: inc. proportional to RBCs
RBCs: DRASTICALLY inc.
Glucose: dec.
Protein: inc.

There would also xanthochromia (or the CSF would be yellowish)

Front 88

What change in concentration of WBCs, RBCs, glucose, proteins would be seen in the CSF in fungal meningitis? what other things could be detected?

Back 88

WBCs: inc.
RBCs: zero
Glucose: drastically dec.
Protein: inc.

There would be a positive culture of fungus from the CSF.

Front 89

What is a "traumatic tap"? how can you tell whether a traumatic tap occurred?

Back 89

During a lumbar puncture a missed stab of the needle results in and elevated RBC count but the number of RBCs decreases w/ each tube in a traumatic tap.

Front 90

How can you distinguish b/e a subarachnoid hemorrhage and a traumatic tap?

Back 90

The number of RBCs will dec. in a traumatic tap w/ each successive test tube.

Checking for xanthochromia, in sub-arachnoid hemorrhages the RBCs will lyse during centrifuging and turn the CSF yellow b/c of bilirubin. In a traumatic tap there is no xanthochromia.