Brain tumours Flashcards
What are the two types of brain tumours, otherwise known as CNS neoplasms.
Primary and metastatic
What are the most frequent sources of metastatic tumours?
lung cancer, breast cancer and melanoma
What are glial cells?
Located in the CNS, they provide physical and chemical support to maintain their environment
What two types of glial cells are most likely to become cancerous? What are their roles?
Astrocytes - transport nutrients and holds neurons in place
Oligodendrocytes - provide insulation to neurons
What are the two other types of glial cells? What are their roles?
microglia - digest dead neurons and pathogens
Ependymal cells - line the ventricles and secrete cerebrospinal fluid
What are Gliomas?
An umbrella term for the tumours that originate from glial cells. They vary in aggressiveness/malignancy
What percentage of primary tumours are gliomas?
around 50%
what likely causes glial cells to be cancerous?
Their neural stem cell progenitors;
they keep regenerating themselves and this constant glycogenesis means a higher likelihood of mutation
What are the features of Grade 1 tumours
Benign, slow-growing circumscribed tumours
Cells look almost normal
Rare in adults
usually associated with long term survival
surgery alone most likely to be effective
What are the features of a grade 5 tumour?
Most malignant, fast-growing and actively producing
Spreads easily to nearby normal tissue
Cells look very abnormal under microscope
Tumour forms not blood vessels to sustain growth
Central areas of necrosis (dead tissue) are common
What is a big diagnosis contributor to the diagnosis of tumours?
Age
From what age do 50% of tumours are metastatic?
30-40 years old
What 3 ways do brain tumours produce signs and symptoms? What do the symptoms depend on?
Local brain invasion
Compression
Increased intracranial pressure
Depend on the function of the involved area?
What is the most common symptoms of tumours?
seizures; 50-80%
What might the focal signs of tumours be due to?
Local invasion, mass effect or vasogenic edema
What is vasogenic edema?
blood-brain barrier disruption causing tissue filled with water
What 4 neurocognitive symptoms can tumours cause?
Memory loss, personality/mood change, fatigue and lack of interest in everyday activities
What is evaluated in the battery for investigating low-grade gliomas?
Executive function, apraxia, language, memory and visuo-constructional abilities
What two neuroimaging techniques are used for assessing brain tumours?
CT and MR
When assessing a brain tumour, what things do we look for/think about?
Location, extension, the pattern of growth, structural categorisation, classification, grading, treatment planning and follow-up
What is a FLAIR scan in regards to MRI scanning? Why use it for brain tumours?
A type of T2 weighting where the CSF is suppressed
Allows to see the tumour better
What are the main goals of a diagnostic scan?
Detect the presence of a tumour - direct and indirect signs
Localise the tumour and define extension
Identify pattern of growth
characterise tumour’s macro- and microstructure
What are the four ways a tumour can be characterised
Extra and intra-axial (located in or out of the CNS)
Extra and intra-cerebral (originating or not from CNS cells)
What are the direct signs of brain tumour in CT and MRI scanning?
Increase water content caused by increased cellularity and increased interstitial fluids - CT hypodensity, high T2 and low T1 signal
Presence of regressive phenomena - cysts, necrosis, haemorrhages, calcifications, fatty degeneration
Vascular architecture - CT hypodensity, MR flow-void/enhancement.
What are the indirect signs in CT and MRI scanning?
mass effect (pressure on brain), edema (trapped fluid) and bone alterations
How do malignant gliomas, metastases and extra-axial tumours change the vascular architecture?
MG = formation of capillaries with fenestrated endothelium that leads to disruption of the blood-brain barrier
Metastases. = capillaries with the same properties as tissue from origin
extra-axial tumours= capillaries without tight junction
How does contrast-enhanced T1 weighted MRI works?
gadolinium contrast (paramagnetic material that reduces the relaxation times) is injected into the patient
Travels to the brain vasculature
Contrast reaches capillaries
Normal BBB = stays in capillaries and remains invisible
Disrupted BBB = the contrast leaks into the tissue and creates a hyperintensity signal typically at the BOUNDARIES of the tumour
What are the most useful contrasts for diagnosing tumours?
T2, FLAIR and contrast-enhanced T1
What does advanced MRI add to the diagnosis of tumours?
adds important structural, hemodynamic and physiological information
What are the 3 advanced MRI techniques?
Diffusion MRI, Perfusion MRI, MR spectroscopy
What is Diffusion-Weighted MRI?
probes tissue water molecular diffusion over distances comparable to the size and spacing between the cells
What is ADC?
Apparent Diffusion Coefficient - quantifies the water molecular mobility within tissues
What is the relationship between ADC and cellularity
Reduced ADC = Increased cellularity = Decreased mobility of water to move around
What does an increase in ADC mean?
vasogenic edema or widening of the extra-cellular structure due to matric degeneration
What does a reduction in ADC mean?
Increased cellularity OR cytotoxic cell swelling
What is tumour angiogenesis
When the tumour starts creating blood vessels into the tumour by sending out angiogenic factors (signals). This is so the tumour can be given fresh oxygen to survive
What does perfusion-weighted imaging allow us to see? what two techniques do you use to do this?
neoangiogenesis
1. Dynamic Susceptibility Contrast-Enhanced (DSC)
2. Dynamic contrast-enhanced (DCE)
What does DSC-MRI allow us to measure?
the intratumoral relative cerebral blood volume (rCBV)
rCBV proved to accurately predict the grading and outcome of patients with brain gliomas
What is the relationship between the rCBV and grading?
Low grade = low rCBV
High grade = high rCBV
What T weighting is DSC-MRI?
T2*
What T weighting is DCE-MRI?
T1
What can DCE-MRI quantify?
The tumour microvessel permeability and proliferation
What the DCE-MRI allow us to measure?
Contrast Transfer constant (Ktrans) - vascular permeability
intra-vascular compartment volume - microvessel density
What 3 ways can you treat brain tumours?
Microsurgical maximal safe resection
Chemotherapy
Radiation therapy
What are the goals of surgery?
To obtain representative tissue samples for an integrated diagnosis
to delay (avoid) malignant transformation
to increase the progression-free survival (PFS)
to impact on overall survival (OS)
to contain symptoms (seizures/mass effect)
to maintain function integrity
What is intraoperative stimulation brain mapping?
A group of techniques which allow to safely and effectively remove tumours and at the same time preserve functional integrity
apply electrical stimulation at cortical and subcortical level during resection and look for evoked responses either during rest or doing a task
What impact has been shown from Intraoperative stimulation mapping?
Glioma resections using ISM have been associated with fewer late severe neurological deficits and more extensive resection (will remove more of the tumour knowing where not to touch more confidently)
Why type of neurological functions do we want to preserve?
Motor-sensory, speech, vision
Language, memory, attention, exec functions, emotions, praxis and visuo-constructional abilities
What are the two main pre-operative techniques? What do they help with?
fMRI = identification of eloquent cortical areas
MR tractography = identification of subcortical connections
What relationship was found between pre-operative mapping with fMRI and intraoperative mapping with DES in Bizzi et al’s (2008) study?
There was a high concordance between them
High sensitivity and specificity of motor areas by fMRI
What affects the diagnostic performance of fMRI validation?
the grade of the tumour
What is language mapping?
aims to detect language functional sites at cortical and subcortical level during brain surgery
What are 3 examples of language mapping paradigms?
Auditory Verb Generation, Verbal Fluency and Picture Naming
Where in the brain was language localised for right-handed people?
The left hemisphere
What test can we do to confirm the lateralisation of language?
WADA test - sends on side of the brain to sleep
What is the problem with language mapping?
theres a great amount of interindividual variability
What are the two streams of language?
Ventral and Dorsal?
What does the ventral stream do?
maps acoustic speech inputs onto conceptual and semantic representations
supports the perception and recognition of auditory objects
bilateral
What does the dorsal language stream do?
Supports sensory-motor integration
The stimulation causes speech arrest and phenomical paraphasia
