Raised intracranial pressure, SOL and trauma Flashcards
The brain behaves mechanically like a ____ filled _____ solid; ______. It lies within the skull (_____/_____ volume). Suspended in ________ ____ which supports the brain (_____ buoyancy). It is supported by the ____.
The brain behaves mechanically like a fluid filled porous solid; viscoelastic. It lies within the skull (rigid/fixed volume). Suspended in cerebrospinal fluid which supports the brain (neutral buoyancy). It is supported by the dura.
What happens when the process of CSF escaping from cranial vault to avoid rise in pressure is exhausted?
Venous sinuses are flattened and there is little or no CSF. Any further increase results in rapid increase in ICP.
What are the causes of raised ICP?
- Increased CSF
- Focal lesion in brain
- Diffuse lesion in brain
- Increased venous volume
- Physiological (hypoxia, hypercapnia, pain)
Define hydrocephalus
Accumulation of excessive CSF within the ventricular system of the brain
What is the normal volume of CSF
120-150ml
500ml (turnover of 3-5 times per day)
Where is CSF produced?
By the chorioid plexus in the lateral and fourth ventricles of the brain
Where is CSF absorbed?
Absorbed by arachnoid granulations
CSF is a clear fluid containing;
________ <4 cells/ml
Neutrophils _ cells/ml
Protein <___g/l
_______ >2.2mmol/l
No ___.
CSF is a clear fluid containing;
lymphocytes <4 cells/ml
Neutrophils 0 cells/ml
Protein <0.4g/l
Glucose >2.2mmol/l
No RBCs
What are the causes of hydrocephalus?
Obstruction to flow of CSF (e.g. inflammation, pus and tumours)
Decreased resorption of CSF (post SAH, or meningitis)
Overproduction of CSF (v. rare: tumours of choroid plexus)
What are the two main types of hydrocephalus?
Non-communicating
Commiunicating
What is non-communicating hydrocephalus?
Obstruction to flow of CSF occurs within ventricular system
What is communicating hydrocephalus?
Obstruction to flow of CSF outside of the ventricualr system e.g. in subarachnoid space or at the arachnoid granulations
Why is the timing of hydrocephalus important?
If hydrocephalus occurs before closure of cranial sutures then cranial enlargement occurs
If hydrocephalus develops after the closure of the cranial sutues, then there is expansion of ventricles and increase in intracranial pressure
What is hydrocephalus ex vacuo
Dilatation of the ventricular system and a compensatory increase in CSF volume secondary to a loss of brain parenchyma (e.g. in alzheimers disease)
What are the effects of raised intracranial pressure?
- intracranial shifts and herniations- coning
- midline shift
- distortion and pressure on cranial nerves and vital neurological centres
- impaired blood floow
- reduced level of consciousness
What are the types of herniations?
- subfalcine
- tentorial
- cerebellar
- transcalvarial
What are the clinical signs of raised ICP?
Papilloedema
Headache
Nausea and vomiting
Neck stiffness
What are SOL?
- tumours- primary brain tumours, metastases
- abscess- single/multiple
- haematomas
- localised brain swelling- e.g. swelling and oedema around cerebral infarct
70% of brain cancers in children occur where?
Below the tentorium cerebelli
70% of brain cancers in adults occur where?
Above the tentorium cerebelli
What are the commonest metastasic brain cancers?
- breast
- bronchus
- kidney
- thyroid
- colon carcinomas
- malignant melanomas
Where are brain mets usually seen?
Boundaries between grey and white matter
How are brain tumours graded?
- mitoses
- neovascularisation
- necrosis
- also atypia, cellularity etc
What are the commonest malignant brain tumours in adults
- Astrocytoma 45%
- oligodendroglioma 6%
- ependymoma 5%
- medulloblasotma 2%
- haemangioblastoma 2%
- lymphoma 1%
- pineal (germ cell) <1%
What ar the commonest malignant brain tumours in children?
- Astrocytoma 50%
- Medulloblastoma 25%
- Ependymoma 6%
- Oligogendroglioma 1%
- haemangioblastoma <1%
- lymphoma <1%
- pineal (germ cell) <1%
What are the commonest benign brain tumours in adults?
Meningioma 18%
Pituitary adenoma 10%
Schannoma 8%
Craniopharyngioma 2%
What are the commonest benign brain tumours in adults?
Craniopharyngioma 9%
Meninigoma 3%
Schwannoma 1%
Pituitary adenoma <1%
What are the WHO astrocytoma gradings
Grade I: Pilocytic
Grade II: well differentiated
Grade III: Anaplastic
Grade IV: Glioblastoma
Describe grade I pilocytic astrocytoma
- childhood
- benign behaving
- long, hair like processes
- cystic areas
What is seen in Grade II Astrocytoma?
Nuclear atypia
What is seen in Grade III Astrocytoma?
Greater nuclear atypic
Mitotic activity
What is seen in Grade IV Astrocytoma?
Extreme nuclear atypia
Mitotic activity
Necrosis and/or neovascularisation
Medulloblastomas are poorly _________/______ (look like primitive undifferentiated embryonal cells)
Medulloblastomas are poorly differentiated/embryonal (look like primitive undifferentiated embryonal cells)
Where do medullloblastomas occur?
Midline of cerebellum
What is the prognosis for medulloblastoma?
Untreated has dismal prognosis, but is exquisitely radiosensitive
75% 5 year survival with resection and radiotherapy
how do single abscesses occur?
Through local extension e.g. mastoiditis
Direct implantation e.g. skull fracture
Where do single abscesses tend to occur?
Adjacent to source
How to multiple abscesses occur?
Via haematogenous spread e.g. bronchipneumonia, bacterial endocarditis
Tend to occur at grey and white matter boundary
Describe the appearance of an abscess
Central necrosis, oedema and fibrous capsule
How may an abscess present?
Fever, raised ICP
How are abscesses diagnosed?
CT or MRI
What happens after an abscess has been diagnosed?
Aspiration for culture and treatment
What is the definition of bacterial meningitis?
Inflammation of the leptomeninges and CSF within the subarachnoid space
What does bacterial meningitis cause?
Severe oedema and raised ICP
What is seen on CSF in bacterial meningitis?
Abundant polymorphs on CSF, decreased glucose
Arachnoiditis can later cause lack of CSF ______, ______ and raised ___
Arachnoiditis can later cause lack of CSF absorption, hydrocephalus and raised ICP
In bacterial meningitis
_____ is at peak incidence in neonates; it is a gram ___ rod
In bacterial meningitis
E.coli is at peak incidence in neonates; it is a gram -ve rod
In bacterial meningitis
_____ is at peak incidence in infants and adolescents ; it is a gram ___ ____ ______
In bacterial meningitis
H. influenzae is at peak incidence in infants and adolescents ; it is a gram -ve cocco bacilli
In bacterial meningitis
N. meningitidis is at peak incidence in ________ and ____ _____ ; it is a gram ___ ________
In bacterial meningitis
N. meningitidis is at peak incidence in adolescents and young adults ; it is a gram -ve diplococci
In bacterial meningitis
_. _______ is at peak incidence in older adults and children ; it is a gram ___ ______ in _____
In bacterial meningitis
S. pneumoniae is at peak incidence in older adults and children ; it is a gram +ve cocci in chains
In bacterial meningitis
_. _______ is at peak incidence in older adults ; it is a gram ___ ____
In bacterial meningitis
L. Monocytogenes is at peak incidence in older adults ; it is a gram +ve rod
What are the different types of head injury?
Missile or Non-missile
Penetrating or blunt
What is a missile injury?
Penetrating injury
What does a missile injury result in?
Lacerations in region of brain damage
Haemorrhage
What is non-missile (blunt injury) caused by?
Sudden acceleration/decelleration of head
Describe blunt injury to the head
Brain moves within cranial cavity and makes contact with the inner table of the cranium and bony protrusions
What causes blunt injury?
RTCs
Falls
Assaults
Alcohol
The ______ the contact time the ______ the force
F= mv-mu
t
The smaller the contact time the larger the force
F= mv-mu
t
Describe the primary injury of trauma to head?
Injury to neurones
Irreversible
Preventative measures
Describe the secondary injury of trauma to head?
Haemorrhage
Oedema
Potentially treatable
Give examples of primary injuries
Scalp lesions
Skull fractures
Surface contusions
Surface lacerations
DIffuse axonal injury
Diffuse vascular injury
Petechial haemorrhages
Why are scalp lesions so dangerous
Bleed profusely
Route for infection
What are the different types of skull fracture?
Linear
Compound
Depressed
Describe linear skull fracture
straight sharp fracture line, that may cross sutures (diastatic fracture)
Describe compound skull fracture
Associated with full thickness scalp lacerations
Where are contusions and lacerations common?
Lateral surface of hemispheres
Under surface of temporal and frontal lobes
What are coup and contra-coup injuries?
Coup: primary impact of the skull
Contra-coup: rebound against cranium
Why are contra-coup injuries worse than coup injuries?
theory 1; Denser CSF moves to impact (coup) side first, forcing brain to contra-coup side 1st.
theory 2; Cavitation- low pressure in brain moving away from zone opposite the impact side. low pressure created cavitation bubbles, which damages brain parenchyma
When does DAI occur?
At moment of injury
Where does DAI affect?
Central areas
What does DAI cause?
Reduced consciousness and coma
Can lead to vegetative state
Grades of increasing severity- correlate with patients clinical state
Describe the pathophysiology of secondary brain injury?
- Intracranial haematoma
- Reduced cerebral blood flow
- Hypoxic brain damage
- Excitotoxicity
- Oedema
- Raised ICP
- Infection
What does calcium influx result in?
Protease activation
Mitochondrial dysfunction
Oxidative stress
What causes cytotoxic oedema?
Intoxication, reye’s and severe hypothermia
What causes ionic oedema?
Also called osmotic oedema, occurs in hyponatraemia and excess water intake e.g. in SIADH
What causes vasogenic oedema?
Most important occuring in:
trauma, tumours, inflammation and infection and hypertensive encephalopathy
What is haemorrhagic conversion?
conversion of a bland infarction into an area of hemorrhage
__% of traumatic intracranial haematomas are extra dural
20% of traumatic intracranial haematomas are extra dural
80% of traumatic intracranial haematomas are intradural;
__% are subdural
__% are intracerebral haematomas
_% are subarachnoid
80% of traumatic intracranial haematomas are intradural;
13% are subdural
15% are intracerebral haematomas
3% are subarachnoid
What is a burst lobe?
Subdural in continuity with intracerebral haematoma particularly in frontal and temporal lobe
What are traumatic extradural haematomas usually a result of?
Complication of fracture in tempero-parietal region that involves middle meningeal artery
Describe the pathophysiology of extradural haematomas?
Immediate brain damage is often minimal but if left untreated- midline shift, compression and herniation
What are subdural haematomas?
Collections of blood between the internal surface of dura mater and arachnoid mater
Caused by disruption of bridging veins that extend from the surface of the brain into subdural space
Why are gyral contours preserved in subdural haemorrhages?
pressure is evenly distrubuted
Non-treated, non fatal haematomas become _______ and form a _______ neomembrane
Non-treated, non fatal haematomas become liquiefied and form a yellowish neomembrane
What are chronic subdural haemorrhages associated with?
Brain atrophy
