Neuropathology Flashcards
How do microorganisms gain entry into the CNS?
Direct spread
- Middle ear infection
- Base of skull fracture
Blood-borne
- Sepsis
- Infective endocarditis
Latrogenic
- V-P shunt
- Surgery
- Lumbar puncture
What is meningitis?
Inflammation of the leptomeninges (the inner two meninges)
Variously classified:
- Acute vs chronic
- Bacterial vs non-bacterial
With or without septicaemia
Prompt diagnosis and treatment is life saving
What are the causative organisms of meningitis?
Different depending on age
Neonates:
- E. Coli
- L. monocytogenes
2-5 years
- H. influenzae type B (HiB)
5-30 years
- N. Meningitides (types)
Over 30 years
- S. pneumonia
Varies in immunocompromised
Tell me what happens in chronic meningitis.
Chronic clinical course
M. tuberculosis
- Granulomatous inflammation
- Fibrosis of meninges
- Nerve entrapment
What are the complications of meningitis?
Local: Death (swelling>RICP) Cerebral infarction > neurological deficit Cerebral abscess Subdural empyema Epilepsy
Systemic (if associated with septicaemia)
What is encephalitis?
Classically viral not bacterial
Infection of parenchyma not meninges
Neuronal cell death by virus
- Inclusion bodies
Temporal lobe
- Herpes virus
Spinal cord motor neurons
- Polio
Brain stem
- Rabies
Lymphocytic inflammatory reaction
- Perivascular cuffing with lymphocytes
What are prions?
They are prion proteins (PrP), a normal constituent of synapse
But they can be mutated
These then interact with normal PrP to undergo a post translational conformational change
These proteins then form extremely stable aggregates
What is prion disease?
PrP aggregates > neuronal death and “holes” in grey matter
Results in: Spongiform encephalopathy's: - Scrapie in sheep - BSE in cows - Kuru in tribes of New Guinea - Varient Creutzfeld-Jacob disease
What is dementia?
Acquired global impairment of intellect, reason and personality without impairment of consciousness
What happens in Alzheimer’s Disease?
Exaggerated aging process
Loss of cortical neurones
- \/ brain weight
- Cortical atrophy
Due to /\ neuronal damage:
- Neurofibrillary
- Senile plaques
What are neurofibrillary tangles?
Intracellular twisted filaments of Tau protein
Tau normally binds and stabilises microtubules
Tau becomes hyperphosphorylated in AD
Tauopathy
What are senile plaques?
Foci of enlarged axons, synaptic terminals and dendrites
Amyloid deposition in vessels in centre of plaque
What different types of brain herniation’s are there?
Subfalcine
Tentorial
Tonsilar
What is a subfalcine herniation?
Same side as mass
Cingulate gyrus pushed under the free edge of the falx cerebri
Ischaemia of medial parts of the frontal and parietal lobe and corpus callosum due to compression of anterior cerebral artery > infarction
What is a tentorial herniation?
Uncus/medial part of parahippocampal gyrus through the tentorial notch
- Damage to the occulomotor nerve on the same side
- Occlusion of blood flow in posterior cerebral and superior cerebellar arteries
Frequently fatal because of secondary haemorrhage into the brainstem > Duret haemorrhage
Common mode of death in those with large brain tumours and intracranial haemorrhage
What is a cerebella herniation?
Cerebellar tonsils pushed into the foramen magnum compressing the brainstem
What are the clinical consequences of RICP and herniation?
Prodromal phase
- Headache
- Vomiting
- Papilloedema
Acute phase
- Occulomotor nerve compression = dilation of pupil
- Compression of the brain stem = coma
Compression of the cerebral peduncles
- Hemiparesis
Further herniation produces apnoea and cardiac arrest due to compression of vital brainstem structures
Tell me a little about tumours of the CNS.
RARE!!!!!!!!!!!
Benign
- Meningeal origin > meningioma
Malignant
- Astrocyte origin > astrocytoma
- Spread along nerve tracts and through sub arachnoid space often presents with a spinal secondary
Others
- Neurofibroma
- Ependymoma
- Neuronal e.g. medulloblastoma
Tumours from non-CNS tissues
- Lymphoma
- Metastasis (the most common)
What are the two phases of head injury?
Primary damage
- Due to force causing the injury
- Secondary damage
- Reaction to the primary damage itself worsening the injury
What are the two categories of primary damage of head trauma?
Focal damage
- Bruising and laceration of the brain as it hits the inner surface of the skull
- Tearing of blood vessels and nerves as the brain moves > haemorrhage
Diffuse
- Direct tearing to axons
- Diffuse axonal injury (DAI)
Tell me about diffuse axonal injury.
Micro-tears to axons at sites of differing densities of brain substance
- e.g. junction of white and grey matter
Tearing of nerves and small vessels
Tearing of the pituitary stalk
Severity proportional to the degree of force (especially rotational), often persistent vegetative state
Heals by gliotic scarring
What is a subdural haemotoma?
Bridging veins from surface of cerebral hemispheres connect with vessels in the dura
Vessels susceptible to tearing as they pass through the subdural space
Brain floats freely within CSF but vessels are fixed
Sudden brain movement will tear the bridging veins
Elderly and alcohol-related
