L11 - Cerebrospinal fluid pathway and disorders Flashcards
1. Describe normal CSF circulation 2. Communicating hydrocephalus 3. Non-communicating hydrocephalus 4. Developmental abnormalities of skull base 5. Syringomyella 6. Idiopathic intracranial hypertension 7. Abnormal eye movements 8. False localising 9. Venous sinus thrombis
What are the meninges?
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.
What is the primitive streak?
- Linear band of thickened epiblast
- first appears at the caudal end of the embryo and grows cranially
- cells proliferate forming primitive node
Where is CSF produced?
- Modified ependymal cells in choroid plexus: structure in ventricles of brain where CSF is produced.
- BV , along ventricular walls
Describe the flow of CSF?
- Lateral ventricles
- Foramen of Monro (interventricular foramen)
- Third ventricle
- Aqueduct of sylvius (Cerebral aqueduct)
- Fourth ventricle
- Foramen of Magendie
- Foramen of Luschka
- Subarachnoid space over brain and spinal cord
How is CSF reabsorbed?
Reabsorbed into venous sinus blood via arachnoid granulations.
What is a disadvantage of the cerebral aqueduct and foramina?
They are very small hence easily blocked.
- causing high pressure in the lateral ventricles
- hydrocephalus
How is the circulation of CSF driven by?
arterial pulsation through this pathway.
What does the Monro Kellie Hypothesis state?
Sum of :
- volume of the brain
- arterial blood
- venous blood
- CSF
- should be constant.
In regards to Intracranial pressure, what would an increase in any of the intracranial systems result in?
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)
What structures within the brain are most adaptable to compensate?
CSF and blood flow in veins
Describe the relationship between volume change and pressure within cranium?
NOT LINEAR.
- Initial vol changes cause small pressure differences
- subsequent changes in vol cause large changes
When measuring CSF it is important to take a corresponding…
blood sample
- if glucose high in blood there is a high change glucose will be high in CSF.
What are fontanel’s?
Soft spots on babies head where sutures will intersect.
- soft membranous gaps in infant skull between cranial bones
What is Valsalva?
Moderately forceful attempted exhalation against a closed airway.
- closing ones mouth, pinching ones nose shut while pressing out as if blowing a balloon
State briefly some symptoms of raised pressure in the brain? (4)
- Headache
- vomiting
- change in alertness and consciousness
- dysfunction of cranial nerves (esp II, III, IV and VI)
Damage to the optic nerve may bring about?
Blurring or brief loss of vision
- obscurations
What is the name given to swollen optic disc
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.
Damage to cranial nerves II, III and IV may bring about?
Disorders of eye movement and double vision
Rapid changes in ICP may cause?
Cushings reflex/triad
- systemic hypertension
- bradycardia
- irregular respiration
What is tinnitus?
Sensation of sound in the absence of an external source
e.g. ringing, whistling or rushing sound
What is pulsatile tinnitus?
- Rhythmical noise usually the same as the heart.
- Check it by feeling the pulse at the same time as listening to the tinnitus.
What causes pulsatile tinnitus?
Change in BF in vessels near ear.
Define hydrocephalus and the two types?
Accumulation of CSF within brain, hence increased pressure in skull.
Can either be:
1. Communicating
2. Non-communicating
Describe communicating hydrocephalus?
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
Describe non-communicating hydrocephalus?
Obstructive.
Flow of CSF blocked along one or more of the narrow passages connecting the ventricles.
Where does the 2nd cranial nerve arise from?
Anterior bottom cranial fossa.
Give an example of a developmental defects that can occur?
- Arnold Chiari malformation
- hind brain malformation
- can cause hydrocephalus
- can cause syringomyelia - Spina bifida, Meningocoele
- neural tube defects
What is syringomyelia?
Disorder where cyst develops within spinal cord.
Cyst = Syrinx
Syrinx expand and elongate over time, destroying spinal cord
What are some of the symptoms of syringomyelia?
- Loss of feeling
- paralysis
- weakness
- stiffness in the back, shoulders and extremities
What is the corpus callosum?
- Wide, thick nerve tract
- consisting of a flat bundle commissural fibres,
- beneath the cerebral cortex in brain.
In older adults, hydrocephalus is known as?
Normal pressure hydrocephalus
- presents with triad of symptoms
What are some of the symptoms that a patient with NPH may present with? (4)
*normal pressure hydrocephalus
- Gait disturbance
- Changes in cognition
- Urinary incontinence
- Disproportionately enlarged ventricles.
- remember as we get older, brain shrinks and lateral ventricles will appear bigger.
Describe idiopathic intracranial hypertension?
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.
Describe some symptoms of raised pressure? (4)
- Headaches
- Visual obscurations
- Double vision
- Pulsatile tinnitus
What are some possible causes of chronic IH?
Loads of them (8)
- Chronic subdural haematoma
- Brain tumour
- Meningitis
- Encephalitis
- Hydrocephalus
- Arteriovenous malformation
- Arteriovenous fistula
- Venous sinus thrombis
State what a chronic subdural haematoma is?
A blood clot on the surface of the brain
A clot formation within the venous sinuses of the brain is known as?
Cerebral venous sinus thrombosis
What is often the treatment for CVST?
*cerebral venous sinus thrombosis
Anticoagulants
- heparin / warfarin
What is intracranial hypotension?
Low pressure syndrome due to dural tear and leak of CSF
- spontaneous or after procedures
Postural headache - goes away completely on lying down
What is papilloedema?
Optic disc swelling caused by increased intracranial pressure.
What is 6th nerve palsy?
Abducens
Prevents some of the muscles that control eye movement from working properly.
- affected people cannot turn the eye outwards toward the ear.
What are some signs / symptoms of 6th nerve palsy?
- Double vision
- headaches
- pain around the eye.
Give examples of causes of 6th nerve palsy?
loads
- Stroke
- brain aneurysm
- diabetic neuropathy
- trauma
- infections
- inflammation
- tumours
- migraine headaches or intracranial pressure.
What is diabetic neuropathy?
categories (3)
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.
Describe false localising?
Dysfunction is reflected distant from the expected anatomical position.
e.g. False localising more common in patients with raised intracranial pressure.
