Neuropathology 3 Flashcards
If the brain enlarges (e.g due to an SOL), what must escape the cranial vault to avoid rise in pressure
- CSF
* Blood
What does increased brain volume lead to?
Increased ICP
Suggest causes of raised ICP.
- Increased CSF (hydrocephalus)
- Focal lesion in brain (SOL)
- Diffuse lesion in brain (e.g. oedema)
- Increased venous volume
- Physiological (hypoxia, hypercapnia, pain)
What is hydrocephalus?
An accumulation of excessive CSF with the ventricular system of the brain
What is CSF produced by?
Choroid plexus in the lateral and fourth ventricles of the brain
What is CSF absorbed by?
Arachnoid granulations
How much CSF is normal?
120-150ml
How much CSF would there be in hydrocephalus?
500ml
CSF fluid looks…
CLEAR
What does CSF contain?
Lymphocytes <4 cells/ml Neutrophils 0 cells/ml Protein <0.4g/l Glucose >2.2mmol/l No RBCs
What does CSF not contain?
RBC’s
What 3 things can hydrocephalus be due to?
- Obstruction
- Decreased resorption
- Overproduction
What can cause obstruction to CSF?
- Inflammation
- Pus
- Tumours
What can cause decreased resorption to CSF?
- Post- SAH
* Meningitis
What causes an overproduction of CSF?
Tumours of the choroid plexus
Hydrocephalus can be either?
Communicating OR Non-communicating
In non-communicating hydrocephalus, where does the obstruction to flow of CSF occur?
Within the ventricular system and CANNOT exit
In communicating hydrocephalus, where does the obstruction to flow of CSF occur?
Goes outside of the ventricular system ie. in subarachnoid space, or at the arachnoid granulations
i.e it is communicating with something outwith the ventricular system
What happens if hydrocephalus occurs before closure of the cranial sutures?
Cranial enlargement
At what age does closure of the cranial sutures occur?
2-3 years old
What happens if hydrocephalus develops after the closure of the cranial sutures?
There is expansion of ventricles and increasing ICP
What is hydrocephalus ex vacuo?
Dilatation of the ventricular system, and a compensatory increase in CSF volume, secondary to a loss of brain parenchyma
In what condition would you see hydrocephalus ex vacuo? Why?
Alzheimer’s
- due to brain atrophy
What is ‘coning’?
Tonsillar herniation of the cerebellum into the foramen magnum
Why does coning occur?
Due to raised ICP
What 5 things occur due to raised ICP?
- Intracranial shifts and herniations
- Midline shifts
- Distortion and pressure on cranial nerves and vital neurological centres
- Impaired blood flow
- Reduced level of consciousness
Name the 4 main types of herniations.
1 – Subfalcine
2 – Tentorial
3 – Cerebellar/Tonsillar
4 – Transcalvarial
Describe subfalcine herniations.
Displacement of the brain (typically the cingulate gyrus) beneath the free edge of the falx cerebri due to raised intracranial pressure
- MOST COMMON
Describe cerebellar/tonsillar herniations.
Transforaminal herniation, or “coning”, the cerebellar tonsils move downward through the foramen magnum possibly causing compression of the lower brainstem and upper cervical spinal cord as they pass through the foramen magnum
What are the 4 main symptoms or raised ICP?
- Papilloedema
- N+V
- Neck stiffness
- Headache
What causes papilloedema?
Pressure on the optic disc
Describe the headache in raised ICP.
Worse when lying down, coughing, straining and sneezing
How does raised ICP cause N+V?
Pressure on vom centre in pons and medulla
How does raised ICP cause neck stiffness?
Pressure on the dura around the brainstem and cerebellum
Give examples of SOL’s.
- Tumour (primary or mets)
- Abscess
- Haematoma
What are the common signs when a patient has a brain tumour?
- Focal deficit
* Papilloedema
What are the common symptoms when a patient has a brain tumour?
- Focal sx (68%).
- Headache (54%)
- Vomiting.
- Seizures (26%).
- Visual disturbances.
Why are headaches in relation to brain tumours worse in the morning?
We tend to become slightly hypercapneic, retaining CO2 while we sleep
This leads to increased blood flow, and a commensurate increases the size of the brain.
And as a result the headache can improve slightly as we blow off CO2
Where do 70% of brain tumours in children occur?
Below the tentorium cerebelli
Where do 70% of brain tumours in adults occur?
Above the tentorium cerebella
Where do 70% of brain tumours in adults occur?
Above the tentorium cerebelli
What are the commonest cancers to metastasise to the brain?
Breast, bronchus, kidney, thyroid and colon carcinomas
Malignant melanomas
Where are brain mets most often seen?
At the boundaries between grey and white matter
What is the most common brain tumour in adults?
Astrocytoma
What is the most common benign brain tumours in adults?
Meningioma
What can some high grade tumours secrete? What does this lead to?
VEGF
Increased vascularity
What is the most common brain tumour in children?
Pilocytic astrocytomas
What is the 2nd most common brain tumour in children?
Medulloblastoma