L11 - Cerebrospinal fluid pathway and disorders

Question 1

What are the meninges?

Answer 1

Three layers of protective tissue:
1. Dura mater
2. Arachnoid mater 
3. Pia mater 
Meninges of brain and spinal cord are continuous, being linked through the magnum foramen.

Question 2

What is the primitive streak?

Answer 2

• Linear band of thickened epiblast
• first appears at the caudal end of the embryo and grows cranially
• cells proliferate forming primitive node

Question 3

Where is CSF produced?

Answer 3

• Modified ependymal cells in choroid plexus: structure in ventricles of brain where CSF is produced.
• BV , along ventricular walls

Question 4

Describe the flow of CSF?

Answer 4

1. Lateral ventricles
2. Foramen of Monro (interventricular foramen)
3. Third ventricle
4. Aqueduct of sylvius (Cerebral aqueduct)
5. Fourth ventricle
6. Foramen of Magendie
7. Foramen of Luschka
8. Subarachnoid space over brain and spinal cord

Question 5

How is CSF reabsorbed?

Answer 5

Reabsorbed into venous sinus blood via arachnoid granulations.

Question 6

What is a disadvantage of the cerebral aqueduct and foramina?

Answer 6

They are very small hence easily blocked.

• causing high pressure in the lateral ventricles
• hydrocephalus

Question 7

How is the circulation of CSF driven by?

Answer 7

arterial pulsation through this pathway.

Question 8

What does the Monro Kellie Hypothesis state?

Answer 8

Sum of :

1. volume of the brain
2. arterial blood
3. venous blood
4. CSF

• should be constant.

Question 9

In regards to Intracranial pressure, what would an increase in any of the intracranial systems result in?

Answer 9

ICP tries to remain constant.
Hence
- initial compensatory decrease in vol and pressure in another system
- eventually compensation will fail and pressure within skull builds up, may lead to brain deformation (brain herniation)

Question 10

What structures within the brain are most adaptable to compensate?

Answer 10

CSF and blood flow in veins

Question 11

Describe the relationship between volume change and pressure within cranium?

Answer 11

NOT LINEAR.

• Initial vol changes cause small pressure differences
• subsequent changes in vol cause large changes

Question 12

When measuring CSF it is important to take a corresponding…

Answer 12

blood sample

- if glucose high in blood there is a high change glucose will be high in CSF.

Question 13

What are fontanel’s?

Answer 13

Soft spots on babies head where sutures will intersect.

- soft membranous gaps in infant skull between cranial bones

Question 14

What is Valsalva?

Answer 14

Moderately forceful attempted exhalation against a closed airway.
- closing ones mouth, pinching ones nose shut while pressing out as if blowing a balloon

Question 15

State briefly some symptoms of raised pressure in the brain? (4)

Answer 15

1. Headache
2. vomiting
3. change in alertness and consciousness
4. dysfunction of cranial nerves (esp II, III, IV and VI)

Question 16

Damage to the optic nerve may bring about?

Answer 16

Blurring or brief loss of vision

- obscurations

Question 17

What is the name given to swollen optic disc

Answer 17

Papilloedema

• swelling usually bilateral
• patients may get visual symptoms like transient binocular visual obscurations which last for a few seconds and are often triggered by changes in posture.

Question 18

Damage to cranial nerves II, III and IV may bring about?

Answer 18

Disorders of eye movement and double vision

Question 19

Rapid changes in ICP may cause?

Answer 19

Cushings reflex/triad

1. systemic hypertension
2. bradycardia
3. irregular respiration

Question 20

What is tinnitus?

Answer 20

Sensation of sound in the absence of an external source

e.g. ringing, whistling or rushing sound

Question 21

What is pulsatile tinnitus?

Answer 21

• Rhythmical noise usually the same as the heart.

- Check it by feeling the pulse at the same time as listening to the tinnitus.

Question 22

What causes pulsatile tinnitus?

Answer 22

Change in BF in vessels near ear.

Question 23

Define hydrocephalus and the two types?

Answer 23

Accumulation of CSF within brain, hence increased pressure in skull.
Can either be:
1. Communicating
2. Non-communicating

Question 24

Describe communicating hydrocephalus?

Answer 24

Flow of CSF blocked after it exits the ventricles.
CSF can still flow between the ventricles which remain open.
- pressure remains within normal or high normal

Question 25

Describe non-communicating hydrocephalus?

Answer 25

Obstructive. | Flow of CSF blocked along one or more of the narrow passages connecting the ventricles.

Question 26

Where does the 2nd cranial nerve arise from?

Answer 26

Anterior bottom cranial fossa.

Question 27

Give an example of a developmental defects that can occur?

Answer 27

1. Arnold Chiari malformation - hind brain malformation - can cause hydrocephalus - can cause syringomyelia 2. Spina bifida, Meningocoele - neural tube defects

Question 28

What is syringomyelia?

Answer 28

Disorder where cyst develops within spinal cord. Cyst = Syrinx Syrinx expand and elongate over time, destroying spinal cord

Question 29

What are some of the symptoms of syringomyelia?

Answer 29

- Loss of feeling - paralysis - weakness - stiffness in the back, shoulders and extremities

Question 30

What is the corpus callosum?

Answer 30

- Wide, thick nerve tract - consisting of a flat bundle commissural fibres, - beneath the cerebral cortex in brain.

Question 31

In older adults, hydrocephalus is known as?

Answer 31

Normal pressure hydrocephalus | - presents with triad of symptoms

Question 32

What are some of the symptoms that a patient with NPH may present with? (4) *normal pressure hydrocephalus

Answer 32

1. Gait disturbance 2. Changes in cognition 3. Urinary incontinence 4. Disproportionately enlarged ventricles. - remember as we get older, brain shrinks and lateral ventricles will appear bigger.

Question 33

Describe idiopathic intracranial hypertension?

Answer 33

Typically a disease of young women who are already overweight or put on weight. - no CSF obstruction - thought to be form a mismatch between CSF in circulation and reabosrption.

Question 34

Describe some symptoms of raised pressure? (4)

Answer 34

1. Headaches 2. Visual obscurations 3. Double vision 4. Pulsatile tinnitus

Question 35

What are some possible causes of chronic IH? Loads of them (8)

Answer 35

1. Chronic subdural haematoma 2. Brain tumour 3. Meningitis 4. Encephalitis 5. Hydrocephalus 6. Arteriovenous malformation 7. Arteriovenous fistula 8. Venous sinus thrombis

Question 36

State what a chronic subdural haematoma is?

Answer 36

A blood clot on the surface of the brain

Question 37

A clot formation within the venous sinuses of the brain is known as?

Answer 37

Cerebral venous sinus thrombosis

Question 38

What is often the treatment for CVST? *cerebral venous sinus thrombosis

Answer 38

Anticoagulants | - heparin / warfarin

Question 39

What is intracranial hypotension?

Answer 39

Low pressure syndrome due to dural tear and leak of CSF - spontaneous or after procedures Postural headache - goes away completely on lying down

Question 40

What is papilloedema?

Answer 40

Optic disc swelling caused by increased intracranial pressure.

Question 41

What is 6th nerve palsy? Abducens

Answer 41

Prevents some of the muscles that control eye movement from working properly. - affected people cannot turn the eye outwards toward the ear.

Question 42

What are some signs / symptoms of 6th nerve palsy?

Answer 42

1. Double vision 2. headaches 3. pain around the eye.

Question 43

Give examples of causes of 6th nerve palsy? loads

Answer 43

- Stroke - brain aneurysm - diabetic neuropathy - trauma - infections - inflammation - tumours - migraine headaches or intracranial pressure.

Question 44

What is diabetic neuropathy? categories (3)

Answer 44

Nerve damage caused by diabetes. May be categorised as: 1. Sensory - nerves detecting touch and temp damaged 2. Motor - nerves affecting muscle movement damaged 3. Autonomic - nerves which control involuntary actions (digestion / heart rate) affected.

Question 45

Describe false localising?

Answer 45

Dysfunction is reflected distant from the expected anatomical position. e.g. False localising more common in patients with raised intracranial pressure.