13) Neuropathology Flashcards
How can micro-organisms gain entry to the CNS?
Direct spread - middle ear infection, base of skull fracture
Blood borne - sepsis, endocarditis
Iatrogenic - V-P shunt, surgery, LP
What is meningitis?
Inflammation of the leptomeninges (pia and arachnoid)
What are some symptoms of meningitis?
Headache, photophobia, neck stiffness
Why is a prompt diagnosis of meningitis needed?
Risk of sepsis and swelling of the brain
What are the likely causative organisms of meningitis in neonates?
E. coli
L. monocytogenes
Group B strep
What are the likely causative organisms of meningitis in 2-5 year olds?
H. influenzae type B (vaccine against this now)
What is the likely causative organism of meningitis in 5-30 year olds?
N. meningitidis
What is the likely causative organism of meningitis in >30 year olds?
S. pneumoniae
What is ‘chronic meningitis’?
Caused by M. tuberculosis, granulomatous inflammation causing fibrosis of meninges leading to cranial nerve entrapment
What are some complications of meningitis?
Death - RICP Cerebral infarction Cerebral abscess Subdural empyema Epilepsy
What is encephalitis?
Usually a viral infection affecting brain parenchyma
List some viruses that can infect the brain:
Herpes virus
Polio
Cytomegalovirus
Rabies
What are prions?
Infectious agents composed entirely of protein material that can fold in multiple ways that are transmissible to other prion proteins
What are the normal and mutated forms of prions?
Normal is PrPc
Mutated or diseased is PrPsc
How do mutated prions cause neuronal death?
Interact with normal prions to undergo post translational conformational changes. Build up of protein causes death of the neurone
What is the name given to prion diseases in the brain? Give some examples.
Spongiform encephalopathies
Scrapie, Kuru, variant Creutzfeld-Jacob disease
What is dementia?
Acquired global impairment of intellect, reason and personality without impairment of consciousness
Name some types of dementia:
Alzheimer’s, vascular, Lewy body, Pick’s disease
What is the mechanism behind Alzheimer’s disease?
Exaggerated ageing process causing loss of cortical neurones due to neuronal damage by neurofibrillary tangels and senile plaques
What are neurofibrillary tangles?
Intracelullar twisted filaments of Tau proteins which can’t be metabolised
What are senile plaques?
Foci of enlarged axons, synaptic terminals and dendrites. Amyloid deposition in vessels at centre of the plaque
What condition is linked to early onset Alzheimer’s disease?
Down’s syndrome
What mutations on chromosome 21 predispose to Alzheimer’s?
Amyloid pre-cursor protein gene
Presenilin genes 1+2
What is normal intracranial pressure?
0-10mmHg
What are some compensation mechanisms against raised ICP?
Reduced blood pressure
Reduced CSF volume
Brain atrophy
What is Cushing’s reflex?
Increased systolic pressure, decreased HR and irregular respiration
What is a subfalcine herniation?
Cingulate gyrus pushed under free edge of falx cerebri on same side as mass
What are the complications of a subfalcine herniation?
Causes compression of ACA so can lead to ischemia in medial frontal and parietal lobes and corpus callosum
What is a tentorial herniation?
Uncus herniates through the tentorial notch
What are the complications of a tentorial herniation?
Damages oculomotor nerve on same side and occlusion of blood flow in posterior cerebral and superior cerebellar arteries
What is Duret’s haemorrhage?
Secondary haemorrhage into brainstem after downward displacement of brainstem
What is a tonsillar herniation?
Cerebellar tonsils pushed into foramen magnum, compressing brainstem
What are some benign tumours of the brain?
Meningioma, schwannoma, pituitary adenoma
What are some malignant tumours of the brain?
Astrocytoma Neurofibromas Ependymoma Medulloblastoma Lymphoma Metastasis
How does an astrocytoma spread, and therefore often present?
Spread along nerve tracts and through sub-arachnoid space
Often presents with spinal secondary
What is a stroke?
Sudden event producing a disturbance of CNS function due to vascular disease
What are the types of stroke?
Cerebral infarction (85%) Cerebral haemorrhage (15%)
What are some risk factors for stroke?
Hyperlipidemia
Hypertension
Diabetes
What is the pathogenesis of a cerebral infarction?
Usually from embolism: heart (AF), carotid atheroma, aneurysm or from thrombus
What is the pathogenesis of a cerebral haemorrhage?
Spontaneous: abnormal or friable vessels
Associated with hypertensive vessel disease
What is the cause of a sub-arachnoid haemorrhage?
Rupture of berry aneurysm
What are the risk factors for a subarachnoid haemorrhage?
Male, hypertensive, atheroma
What are the symptoms of a subarachnoid haemorrhage?
Sudden severe headaches, sentinel headache (builds up), loss of consciousness
