Neuropatholgy III Flashcards
What is the normal volume of CSF?
120-150ml
500ml produced per day with turnover 3-5 times a day
Where is CSF produced?
The choroid plexus in the lateral and fourth ventricles
Absorbed by arachnoid granulations
Where is the lumbar cistern located?
Between L2 and S2
What is the cytology of normal CSF?
Lymphocytes <4 cells/ml Neutrophils = 0 cells/ml No RBCs Protein <0.4 g/l Glucose > 2.2mmol/l
What is hydrocephalus?
Accumulation of excessive CSF within the ventricular system of the brain
What are the mechanisms that can cause hydrocephalus to occur?
Obstruction to CSF flow
Decrease CSF resorption
Overproduction of CSF
What is the classification of hydrocephalus?
Non-communicating = obstruction occurs within ventricular system Communicating = obstruction occurs outside of ventricular system
What happens if hydrocephalus develops before closure of the cranial sutures?
Cranial enlargement occurs
What happens if hydrocephalus develops after closure of the cranial sutures?
There is expansion of the ventricles and increase in intracranial pressure
What is hydrocephalus ex vacuo?
Dilation of ventricular system and a compensatory increase in CSF volume secondary to loss of brain parenchyma
What happens if the brain enlarges?
Some blood +/- CSF must escape from the cranial vault to avoid rise in pressure
What happens once ICP begins to rise?
Venous sinuses are flattened and there is little remaining CSF = there will be rapid rise in ICP
What are some causes of raised ICP?
Increased CSF, space occupying lesions, oedema, increased venous volume, physiological (hypoxia, hypercapnia, pain)
What effect can have raised ICP have on the brain?
Intracranial shifts and herniations, midline shift, distortion and pressure on cranial nerves/neurological centres, impaired blood flow, reduced level of consciousness
What are the types of shift that can occur in the brain?
Subfalcine, tentorial (and central), cerebellar, transcavarial
What are the clinical signs of raised ICP?
Papilloedema, headache, nausea and vomiting, neck stiffness, reduced consciousness
What are some examples of space occupying lesions?
Tumours (primary/metastases), abscess, haematoma, localised brain swelling
What are some symptoms of tumours?
Focal symptoms, headache, seizures, vomiting, visual disturbances, focal deficit, papilloedema
How common are tumours of the central nervous system?
Primary = 3% of all cancers, 20% of all childhood cancers
Metastases are more common than primary tumours
What is the difference between where tumours arise in adults and children?
70% of tumours in children arise below tentorium cerebelli, but 70% of adult tumours arise above tentorium cerebelli
What are some cancers that cause brain metastases?
Breast, bronchus, kidney, thyroid, colon carcinoma and malignant melanoma
Where are brain metastases often seen?
At the boundary between the grey and white matter
What are grade I-III astrocytomas?
Grade I = pilocytic
Grade II = well differentiated
Grade III = anaplastic
What are some features of grade I astrocytomas?
Occur in childhood, benign behaving, long hair-like processes, cystic areas
What are some features of grade II astrocytomas?
Display nuclear atypia, mean survival is 5 years
What are some features of grade III astrocytomas?
Display greater nuclear atypia and mitotic activity
What are the two kinds of grade IV astrocytomas?
Primary and secondary glioblastomas
What are some features of primary glioblastomas?
Extreme atypia, mitotic activity, necrosis or neovascularisation, survival is about 10 months
What are some features of secondary glioblastomas?
Extreme atypia, mitotic activity, necrosis and/or neovascularisation, survival is >10-12 months
What genes are implicated in grade I-III astrocytomas and secondary glioblastomas?
IDHi, P53, PDGFRA, RB and PI3KCA
What mutations are associated with primary glioblastomas?
EGFR amplification, PTEN loss, P53 mutation
What is the most common tumour of the CNS in children?
Medulloblastoma = 25% of all paediatric CNS neoplasms
What are some features of medulloblastomas?
Poorly differentiated = look like primitive undifferentiated embryonal cells
Poor prognosis if untreated, but very radiosensitive
75% 5 year survival with resection and radiotherapy
What are the most common malignant CNS tumours?
Astrocytoma (all types), oligodendroglioma, medulloblastoma
What is the most common benign CNS tumour?
Meningioma
What are some sources of infection that may cause a single abscess?
May form from local extension or direct implantation = tend to occur adjacent to source
What tends to cause multiple abscesses?
Haematogenous spread = occur at grey and white matter boundary
What are some features of abscesses?
Central necrosis with oedema fibrous capsule
May cause midline shift
Symptoms = fever, raised ICP, underlying cause
How are abscesses diagnosed?
CT or MRI, plus do aspiration for culture
What organisms may cause abscesses?
Often polymicrobial = staph aureus and strep, fungi and protozoa in immunocompromised
What is meningitis?
Inflammation of leptomeninges and CSF within the subarachnoid space
What are some features of bacterial meningitis?
Causes severe oedema and raised ICP
Abundant polymorphs on CSF and decreased glucose
Arachnoiditis can cause lack of CSF absorption = hydrocephalus and raised ICP
What are some organisms that cause bacterial meningitis?
Ecoli = neonates
H. infulenzae = infants and children
N. meningitidis = adolescents and young adults
S. pneumoniae = older adults and children
L. monocytogenes = older adults (>65)
What can head injuries cause?
Skull fractures, parenchymal injury and vascular injury
What damage can a penetrating injuries cause?
Focal injury, lacerations, haemorrhage
How can blunt trauma cause head injury?
Sudden acceleration/deceleration of head = brain moves within the cranial cavity and makes contact with inner table of cranium and bony protrusions
What effect does contact time have on force in blunt trauma?
The smaller the contact time of the object, the greater the force generated
What are some causes of blunt trauma?
RTCs, falls, assaults, alcohol
What are primary and secondary head injuries?
Primary = damage to neurons, irreversible Secondary = haemorrhage and oedema, potentially treatable
What are some examples of primary head injuries?
Scalp lesions, skull fracture, surface contusions or lacerations, diffuse axonal and vascular injuries, petechial haemorrhages
What are some examples of scalp lesions?
Bruising, laceration, bleeding = route for infection
What are the types of skull fractures?
Linear = straight and sharp, may cross sutures
Compound and depressed
What are compound fractures associated with?
Full thickness scalp lacerations
Base of skull fractures
What are skull fractures associated with a higher incidence of?
Intracranial bleeding and haematomas
Where do surface head injuries tend to occur?
Lateral surface of hemispheres
Under surface of temporal and frontal lobes
What is one cause of surface head injuries?
Coup and contracoup injuries
What are contracoup injuries?
Injury to non-impact side = may occur at same time as coup, may occur due to rebound, tend to be worse
What are coup injuries?
Injury to brain on the side of impact
When do diffuse axonal injuries occur?
At the moment of the insult to the head = occurs due to shearing forces
What areas are affected by diffuse axonal injury?
Central areas = brainstem (immediate death occurs), corpus callosum, parasagittal areas, interventricular septum, hippocampal formation
What symptoms do patients with diffuse axonal injuries tend to have?
Reduced consciousness and coma = may lead to vegetative state
What are some examples of secondary brain injuries?
Intracranial haematoma, reduced cerebral blood flow, hypoxia, excitotoxicity, oedema, raised ICP, infection
What are the types of traumatic intracranial haematoma?
20% are extradural/epidural
80% are intradural = subdural, intracerebral, subarachnoid
What are some features of a “burst lobe” traumatic intracranial haematoma?
Subdural in continuity with the intracerebral haematoma particularly in the frontal and temporal lobes
What is a common cause of traumatic extradural haematomas?
Usually a complication of a fracture in the tempero-parietal region involving the middle meningeal artery
What are some features of traumatic extradural haematomas?
Immediate brain damage often minimal = may cause midline shift if untreated (compression and herniation)
Mortality of 10-20%
What is a subdural haemorrhage?
Collection of blood between the internal surface of the dura mater and arachnoid mater
What causes subdural haemorrhage?
Disruption to bridging veins that extend from the surface of the brain into the subdural space
What are some features of acute subdural haemorrhages?
Clear history of trauma = more common in head injury of elderly
Mortality of >60%
What effect do acute subdural haemorrhages have on the brain?
May be unilateral or bilateral = sulci preserved, swelling of cerebrum on the affected side
What happens to untreated non-fatal acute subdural haematomas?
Become liquefied = form yellowish neomembrane
What are some features of chronic subdural haematomas?
Less frequently associated with a well-defined traumatic insult
Often associated with brain atrophy
What are chronic subdural haemorrhages composed of?
Liquefied blood/yellow-tinged fluid separated from inner surface of dura mater and underlying brain by neomembrane
