Histo: Cerebrovascular disease and Trauma Flashcards
What are the two types of cerebral oedema?
- Vasogenic - due to disruption of blood-brain barrier
- Cytotoxic - secondary to cellular injury (e.g. hypoxia, ischaemia). This is usually due to damage to astrocyte end feet
Which water transporting molecule is found in the brain?
Aquaporin 4
What radiological appearance is characteristic of cerebral oedema?
Loss of gyri
Describe the passage of CSF through the brain.
- The choroid plexus (mainly found in the lateral ventricles) pumps out CSF
- It passes from the lateral ventricles, through the interventricular foramina and into the 3rd ventricle
- It then goes down the cerebral aqueduct into the 4th ventricle
- It then flows down into the medulla and down the spinal cord in the central canal of the spinal cord
- Most of the CSF will leave the 4th ventricle and enter the subarachnoid space
- CSF will circulate around the subarachnoid space and will drain via arachnoid granulations into the superior sagittal sinus (and hence back into the systemic circulation)
What constitutes the floor and the roof of the 4th ventricle?
Floor = pons
Roof = cerebellum
Name and describe the two types of hydrocephalus.
- Non-communicating - caused by obstruction of CSF flow (usually in the cerebral aqueduct)
- Communicating - caused by reduced reabsorption of CSF into the venous sinuses (this could be caused by infection (e.g. meningitis))
What is the normal range for ICP?
7 - 15 mmHg
Name and describe the three sites of brain herniation.
- Subfalcine - the cortex is pushed under the falx cerebri
- Transtentorial (uncal) - the posterior cranial fossa is covered by the tentorium cerebelli which has a rigid opening for the brainstem. Supratentorial pressure can result in herniation of the medial temporal love over the rigid end of the opening of the tentorium cerebelli
- Tonsillar - herniation of the cerebellar tonsils through the foramen magnum (this can put pressure on the medulla and kill)
Define stroke.
A clinical syndrome characterised by rapidly developing clinical symptoms and/or signs of focal or global loss of cerebral function with symptoms lasting > 24 hours or leading to death with no apparent cause other than that of vascular origin
Which diseases are encompassed by the term ‘stroke’?
- Cerebral infarction
- Primary intracerebral haemorrhage
- Intraventricular haemorrhage
- Subarachnoid haemorrhage (most of the time)
Which diseases are excluded by this definition of ‘stroke’?
- Subdural and epidural haemorrhage
- Infarction due to infection or tumour
What is a TIA?
Same definition as stroke but resolving within 24 hours
NOTE: TIA is an important predictor of future infarct (1/3 people with TIA will have a significant infarct within 5 years)
What is non-traumatic intraparenchymal haemorrhage?
Haemorrhage into the substance of the brain (parenchyma) due to rupture of small intraparenchymal vessels
Where do non-traumatic intraparenchymal haermorrhages tend to occur most frequently?
Basal ganglia
NOTE: hypertension is implicated in > 50% of bleeds
What is an arteriovenous malformation?
- A malformation where blood bypasses quickly from artery to vein without going through a normal capillary network
- They can occur anywhere in the CNS and they can rupture
- As they occur under high pressure, they tend to cause massive bleeds
How are arteriovenous malformations treated?
- Surgery
- Embolisation
- Radiosurgery
Define cavernous angioma.
- Well-defined malformative lesion composed of closely-packed vessels with no parenchyma interposed between vascular spaces
- NOTE: it is similar to an arteriovenous malformation but there is no brain substance wrapped up amongst the vessels
- NOTE: these tend to bleed at lower pressure causing recurrent small bleeds
Describe the appearance of cavernous angiomas on MRI.
Shows target sign
What causes subarachnoid haemorrhages?
Rupture of a berry aneurysm
NOTE: berry aneurysms are congenital
Where are berry aneurysms typically found?
- 80% at the internal carotid bifurcation
- 20% within the vertebro-basillar circulation
- NOTE: highest risk of rupture if diameter of 6-10 mm
What is the most common cause of cerebral infarctions?
Cerebral atherosclerosis
Where is atherosclerosis most commonly found within the cerebral vasculature?
- Carotid bifurcation
- Basilar artery
Which part of the cerebral vascular tends to be affected by infarcts resulting from emboli?
Middle cerebral artery branches
List some differences between infarctions and haemorrhagic strokes.
Infarction
- Tissue necrosis
- Rarely haemorrhagic
- Permanent damage in the affected area
- No recovery
Haemorrhage
- Dissection of parenchyma
- Fewer macrophages
- Limited tissue damage
- Partial recovery
What is the biggest cause of death in people < 45 years?
Traumatic brain injury
Describe how traumatic brain injury can be classified.
- Non-missile and missile (e.g. shrapnel)
- Acceleration and deceleration (e.g. RTA, includes rotational)
- Focal or diffuse
What are the consequences of base of skull fractures?
- The fracture may pass through the middle ear or anterior cranial fossa
- It can cause otorrhoea or rhinorrhoea
- Increased risk of infection
NOTE: battle sign and raccoon eyes are manifestations of basal skull fractures
With regards to brain injury, what is a laceration?
Bruising of the brain that causes rupture of the pia mater
What is the term used to describe reboud injury to the opposite side of the brain?
Contrecoup injury
What is diffuse axonal injury?
- Occurs at the moment of injury
- Shear and tensile forces causes damage to the axons
- This is the most common non-bleed related cause of coma
- Midline structure are particularly affect (e.g. corpus callosum)
- Some people suffer cognitive and behavioural changes further down the line
