PATHOLOGY- raised ICP Flashcards
does the brain behave like a fluid or solid?
both
what is the brain suspended in?
the CSF in the skull
what supports the brain?
the dura
What is hydrocephalus?
accumulation of excessive CSF in the brain
what types of hydrocephalus are there and describe them
NON COMMUNICATING:
-obstruction to flow of CSF occurs within ventricular system
COMMUNICATING:
-Obstruction of flow of CSF outside of ventricular system e.g. in subarach space or in the arachnoid granulations
whatwhat are the causes of hydrocephalus?
Obstruction to flow of CSF:
-inflammation
-pus
-tumours
Decrease resorption of CSF:
-post SAH
-meningitis
Overproduction of CSF:
-tumours of choroid plexus
-very rare!
how may hydrocephalus present differently before cranial sutures close?
Before cranial suture closer= cranial enlargement
how may hydrocephalus present differently after cranial sutures close?
After cranial sutures closed= expansion of ventricles and increase in ICP
presentation of increased ICP:
-N+V
-headache (worse in morning and straining)
-pupillary dysfunction +/- papilloedema
-changes in vision
-decrease level of consciousness
what is hydrocephalus ex vacuo
When the brain tissue around the ventricles shrinks due to Alzheimers, fronto temporal dementia or stroke
Not a real hydrocephalus
- the dilatation of ventricular system and compensatory increase in CSF volume secondary to loss of brain parenchyma
-ICP is normal
what conditions cause hydrocephalus ex vacuo
conditions that cause loss of brain parenchyma e.g. Alzheimers, fronto temporal dementia, infarct on one side
-Brain enlarges, some blood +/- CSF must escape to avoid rise in pressure
-a further increase in brain volume occurs and there is a rapid increase in ICP
why?
-if brain enlarges, some blood +/- CSF must escape to avoid rise in pressure
-once this process is exhausted, venous sinuses are flattened and there is little remaining CSF
-any further increase in brain volume results in rapid increase in ICP
examples of causes of raised ICP
-increase CSF (hydrocephalus)
-focal lesion in the brain (space occupying lesion)
-diffuse lesion in the brain (e.g. oedema)
-increased venous volume
-physiological (hypoxia, hypercapnia, pain)
what effects does raised ICP have on the brain?
-Intracranial shifts and herniations e.g. ‘coning’
-Midline shift
-Distortion and pressure on cranial nerves and vital neurological centres
-impaired blood flow
Cerebral perfusion pressure= MAP- ICP
give examples of brain herniations
-Subfalcine herniation
-Tentorial (and central) herniation
-Cerebellar
-Transcalvarial
Describe a Subfalcine herniation
Subfalcine herniation - unilateral/ asymmetric expansion of the cerebral hemisphere displaces the gyrus under the false cerebri
presentation of Subfalcine herniation
-can cause compression of anterior cerebral artery causing weakness in the contralateral leg
describe a Tentorial (and central) herniation
when the medial innermost aspect of the temporal lobe herniates over the tentorium cerebelli
presentation of Tentorial (and central) herniation
compression of ipsilateral CN III and can cause pupillary dilatation, impairment of ocular movements on the same side as the herniation
describe a cerebellar herniation
displacement of the cerebellar tonsils through the foramen magnum
why is a cerebella herniation life threatening?
-it compresses the brain stem and so the respiratory centres in the medulla oblangata
describe a transcalvarial herniation
-swollen brain herniates through any defect in the dura and skull
what are clinical signs of raised ICP?
-reduced level of consciousness
-papilloedema
-headache
-N+V
-neck stiffness
examples of space occupying lesions?
-Tumours
-Abscess
-Haematomas
-Localised brain swelling (e.g. swelling and oedema around cerebral infarct)
where do most brain tumours in children occur in relation to the tentorium cerebello?
70% occur below the tentorium cerebelli
where do most brain tumours in adults occur in relation to the tentorium cerebello?
70% occur above the tentorium cerebelli
where are brain tumour metastases most commonly found ?
in between grey and white matter
Most common:
-breast
-bronchus
-kidney
-thyroid
-colon
what is the most common type of primary brain tumour
astrocytoma
who does Grade I astrocytoma typically affect
children
does a Grade I astrocytoma tend to progress
no
what is the most common primary brain tumours in children?
- Medullablastoma
- Pilocytic astrocytoma
examples of malignant primary intracranial tumours?
-astrocyotoma
-oligodendroglioma
-medullablastoma
exmaples of benign primary intracranial tumours?
-meningioma
medullablastoma histologically?
-poorly differentiated/ embryonal
complications of medullablastoma?
hydrocephalus
-occurs in the midline of the cerebellum and so can readily disrupt the flow of CSF leading to hydrocephalus
What causes a single abscess?
Either local extension or direct implantation
Local extension
→ E.g. mastoiditis, chronic otitis, paranasal sinusitis, facial and dental infections
Direct implantation
E.g. skull fracture
what causes multiple abscesses?
Occur from haematogenous spread
→ In lung E.g. bronchopneumonia, bacterial endocarditis, bronchiectasis, lung abscess
→ Congenital heart disease (left to right shunt and loss of pulmonary filtration of organism)
→IV drug abuse
where do single abscesses tend to occur?
they tend to occur adjacent to the source
where do multiple abscesses tend to occur?
they tend to occur at grey and white matter boundary
how do abscesses present?
-fever
-raised ICP
-symptoms of underlying cause
how do abscesses affect the brains structure?
-oedema and midline shift
investigations for abscess?
-CT or MRI (shows ring enhancing lesion)
-Aspiration for culture and treatment
treatment for abscess
antibiotics + drainage
bacterial meningitis- what?
-inflammation of the leptomeninges and CSF within the subarachnoid space
cause of bacterial meningitis summary table
how does CSF of someone with bacterial meningitis differ than someone without
with bacterial meningitis:
-abundant polymorphs and decreased glucose in CSF
what can arachnoiditis later cause
Arachnoiditis can later cause lack of CSF absorption, hydrocephalus and raised ICP
what two classes can trauma be split into
-missile (penetrating)
-non missile (blunt)
difference between primary and secondary traumatic head injury?
PRIMARY HEAD INJURY (impact)
-injury to neurones
-irreversible
-preventative measures
SECONDARY INJURY
-haemorrhage
-oedema
-potentially treatable
what is a contra coup injury?
-injury to brain at opposite of site of impact
coup injury?
-injury to the brain at the site of impact
