W7 33 neuropathology Flashcards
How does raised intracranial pressure occur?
Relatively minor changes in the composition of the tissue can affect the pressure within the brain, and since contained by the tight skull cavity, can lead to significant pressure alterations, manifesting as diseases.
What are some causes of raised intracranial pressure?
Head injury/haemorrhage
Infection
Neoplasia
Hydrocephalus
Cerebral oedema
What is hydrocephalus?
Obstruction to the flow of CSF, leading to compression of brain and expansion of ventricles
What is cerebral oedema and how does it occur?
Accumulation of fluid in the brain, a response to either:
- vasogenic injury (causing increased vascular permeability)
- cytotoxic damage (injury to neuron/glial membranes)
What are the effects of raised intracranial pressure?
Headache, vomiting, seizures
Reduced conscious level
Papilloedema (changes in retina)
Herniation
What is herniation?
Protrusion of one part of the brain into another compartment
What are the 3 types of herniation and where are their sites of lesion? (IMG PP341)
Subfalcine (cingulate) - frontal lobe
Transtentorial (uncinate) - lateral supratentorial
Tonsillar - posterior fossa
Which herniation cause significant clinical problems?
Transtentorial and tonsillar herniations can cause significant clinical problems
Subfalcine herniation doesn’t usually cause symptoms
Why does subfalcine herniation not usually cause clinical problems and what is the exception to this?
Because the frontal lobe is involved in higher cortical functions, so damage to a small area has limited clinical consequences, so usually clinically silent
Exception if the anterior cerebral artery (ACA) becomes compressed, which can cause a stroke
What are the effects of transtentorial herniation?
Compression of third cranial nerve
Compression of posterior cerebral artery
Compression of contralateral cerebral peduncle
Tearing of vessels in upper brainstem
Transtentorial hernation can cause compression of the third cranial nerve. What can this lead to?
Ipsilateral pupillary dilatation
Ophthalmoplegia
Transtentorial hernation can cause compression of the posterior cerebral artery. What can this lead to?
Ischaemia to visual cortex, so visual disturbance
Transtentorial hernation can cause compression of the contralateral cerebral peduncle. What can this lead to?
Ipsilateral hemiparesis (false localising sign)
(normally hemiparesis occurs on the opposite side of the body to where the lesion in the brain is due to crossing fibres, but in transtentorial herniation, the contralateral cerebral peduncle might be compressed and be on the contralateral side to the lesion)
Transtentorial hernation can cause tearing of vessels in the upper brainstem. What can this lead to?
Due to mechanical effects of herniation through the small aperture
Duret haemorrhage
What are the effects of tonsillar herniation?
(where the brainstem extends through the foramen magnum)
Ataxia (due to damage to cerebellum)
Sixth nerve palsy
Brainstem compression - severe since respiratory rate and autonomic function are maintained here
What are the types of traumatic brain injury?
Parenchymal tissue damage
Vascular tissue damage
What can parenchymal tissue damage cause?
Concussion
Contusions
Diffuse axonal injury
What can vascular tissue damage cause?
Epidural haematoma
Subdural haematoma
Subarachnoid haemorrhage
Intraparenchymal haemorrhage
What is a concussion?
An abrupt transient loss of consciousness caused by massive short-lived increased intra-cranial pressure leading to temporary neuronal dysfunction; full recovery but with amnesia
What is contusion?
Contusion = bruising. Results in pathological appearance of brain.
What is coup contusion and contrecoup contusion?
Coup contusion = bruising due to striking of brain against bone at point of impact
Contrecoup contusion = bruising due to striking against bone opposite to point of impact
What is diffuse axonal injury?
Form of acceleration/deceleration injury eg in RTA, leading to widespread tearing of axons
What is epidural haematoma?
Accumulation of arterial blood between inner skull surface and dura
What is the pathogenesis of an epidural haematoma?
Usually due to skull fracture damaging artery in dura
The middle meningeal artery is particularly susceptible
What is the presentation of an epidural haematoma? (IMG PG345)
Lucid interval for several hours followed by progressive neurological impairment
What is a subdural haematoma? (IMG PG345)
Accumulation of venous blood between the dura and outer surface of the arachnoid membrane
What is the pathogenesis of subdural haematoma?
Rupture of bridging veins or sinuses in the subdural space. May be seen with only mild trauma, particularly in the elderly (with fragile vein walls)
What is the presentation of subdural haematoma?
Focal neurological signs
Personality change, confusion etc (non specific)
What is a stroke?
Rapidly developing signs of focal (at times global) disturbance of cerebral function, lasting more than 24hrs or leading to death with no apparent cause other than that of vascular origin.
What are signs of focal disturbance of cerebral function called if they last less than 24 hours?
Less than 24hrs are transient ischaemic attacks - TIAs