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Path Intro - Intracranial Space Occupying Lesions
Terms in this set (102)
Intracranial space occupying lesions (SOLs) are focal lesions that take up space - what do we call this?
"Mass effect" (aside from taking up space they also add volume to the cranial cavity)
This leads to an increase in.....?
Intracranial SOLs as a term includes what?
- Abscesses (and other infective lesions)
In addition to the mass effect, SOLs are usually accompanied by what?
Brain oedema (adding further to the increase in volume)
The oedema is vasogenic, due to....?
Disruption of the blood-brain barrier and extravasation of fluid into the extracellular space
What do we see grossly in the brain if there is brain oedema (generalised)?
- Widened and flattened gyri
- Narrowed sulci
(these are accompanied by a massive rise in ICP)
In terms of clinical presentation of intracranial SOLs, what are the two categories of symptoms?
- General (non-localising) symptoms and signs
- Focal (localising) symptoms and signs depending on the size and location of the mass
What are some general (non-localising) symptoms and signs?
1) Those of increased ICP +/- brain herniation:
- Headache, nausea, vomiting, disturbed consciousness level, papilloedema
- Dilated fixed pupils, weakness
2) Seizures (lesions involving the cortex can stimulate abnormal electrical activity)
What are some focal (localising) symptoms and signs (depending on the size and location of the mass)?
- A lesion in the motor cortex can cause contralateral motor dysfunction
- Visual disturbances can be produced by a pituitary tumour that invades through the roof of of the sella turcica and impinges upon the optic chiasm
- A lesion of the frontal lobe may lead to behavioural changes
What are some effects of intracranial SOLs?
- Ventricular compression (hydrocephalus?)
- Midline shift
- Increased ICP
What are some radiological findings (found on CT/MRI) in the case of an intracranial SOL?
- Midline shift
- Ventricular compression
- Oedema around the mass
- Flattening of the gyri (brain oedema)
Brain tumours are common SOLs. Clinical presentation depends on what?
Their size, type and location
Patients with brain tumours will present in one of what following ways?
- Worsening vision -> visual cortex
- Sensory abnormality
- Limb weakness -> motor cortex
- Non-focal neurologic disturbance (such as headache and other signs and symptoms of increased ICP)
- Stroke-like fashion as a consequence of intratumoural haemorrhage
Brain tumours can be what or what?
Primary or metastatic
Arising from the brain tissue (primary brain tumours make up 2% of all cancers, and 20% of cancers in children under 15)
Haematogenous spread from a primary tumour elsewhere in the body (25-50% of brain tumours are metastatic
WHO designed a classification and grading scheme dividing primary tumours into one of four grades, ranging from....?
Grade I (benign) to grade IV (highly aggressive)
The higher the grade, the worse the....?
But even benign brain tumours could have serious consequences by virtue of their....?
space occupying nature
What are the most common group of brain tumours?
Gliomas (tumours of glial cells)
Remember from histology that glial cells are non-neuronal cells which include what three types?
- Ependymal cells
Astrocytes do what?
- Provide support for neurons and axons
- Form part of the blood-brain barrier
- Are involved in repair following injury to the CNS (so are essentially CNS fibroblasts)
Oligodendrocytes do what?
Myelinate axons in the CNS (Schwann cells of the CNS)
Ependymal cells do what?
Line the ventricles and spinal canal
Here we can see normal brain histology - contrast the white matter and the grey matter:
- Networks of axons = neuropil
If we go through some of the WHO classifications of major types of brain tumours, what are three types of gliomas?
- Astrocytomas (of astrocytes) - most common
- Oligodendrogliomas (of oligodendrocytes)
- Ependymomas (ependymal cells)
Aside from gliomas there are what other types of brain tumours?
- Neuronal and mixed neuronal-glial tumours
- Embryonal tumours (medulloblastoma)
- Meningeal tumours (meningiomas)
Astrocytomas are the most common....?
Primary brain tumour (make up 60-80% of all gliomas, and around 45-50% of all CNS tumours in adults)
What are the two major categories of astrocytomas?
- Infiltrating astrocytomas
- Non-infiltrating astrocytomas
Astrocytomas have characteristic....?
- Morphologic features
- Distribution within the brain
- Age groups typically affected
- And clinical course
What is an example of a non-infiltrating astrocytoma?
Pilocytic astrocytoma (grade I) - this is the most common astrocytoma in children
Infiltrating astrocytomas make up 80% of primary brain tumours in adults in what decades?
What are the three types of infiltrating astrocytomas?
- Diffuse astrocytoma (grade II)
- Anaplastic astrocytoma (grade III)
- Glioblastoma (grade IV)
Here we can see the difference between non-infiltrating vs infiltrating astrocytomas:
Here we see a gross view of an infiltrating astrocytoma:
If we look at the gross morphology of an infiltrating astrocytoma, these are poorly defined infiltrative tumours that do what?
Expand and distort the invaded brain without forming a discrete mass
The cut surface of the tumours is either....?
Firm or soft and gelatinous
Here we again see the gross morphology of an infiltrating astrocytoma:
Glioblastomas (grade IV astrocytomas) show what?
Areas of haemorrhage and necrosis (tissue breakdown)
On CT/MRI, after IV injection of contrast, glioblastomas give what?
A characteristic ring-like contrast enhancement - this is due to abnormal, abundant tumour vascularisation (microvascular proliferation) (periphery) against central tumour necrosis
Histological (microscopic) diagnosis of astrocytomas is based on what?
- Presence of abnormal appearing astrocytes with variation in their size and shape (pleomorphism)
- Cellularity of the tumour (density of tumour cells within a give volume of tissue) compared to normal brain tissue
- Extension of tumour cells into surrounding brain tissue without a discrete of sharp interface (this is infiltration)
Increases in cellularity, pleomorphism and what else lead to increases in tumour grade?
Glioblastomas (grade IV astrocytomas) show, in addition to the above, what else?
Foci of necrosis and vascular proliferation (this is considered a hallmark of the tumour)
Here we see the microscopic morphology of a glioblastoma (grade IV) vs normal white matter - what are the significant changes seen in the case of the grade IV glioblastoma?
- High cellularity
- Marked pleomorphism
What are the two microscopic hallmarks of glioblastomas?
- Microvascular proliferation
Necrosis in a glioblastoma is characteristically surrounded by what?
Viable tumour cell nuclei in a parallel arrangement called "palisaded" necrosis
Microvascular proliferation refers to proliferation of endothelial cells and capillaries within the tumour under the effect of what?
VEGF produced by the tumour cells
What is the second most common tumour of the CNS (following astrocytomas)?
Meningiomas are derived from the meningothelial cells of the....?
Arachnoid granulations (these are "extra-axial" = outside the brain)
Meningiomas are more common in women, and most are....?
"benign", non-infiltrating, slowly growing, low grade (grade I) tumours
Grade I meningiomas become adherent to the dura (dura based) and do what to the underlying brain?
Impinge upon, but don't invade underlying brain
Symptoms are related to what?
Compression of the area of the brain affected by the tumour
Here we see the gross morphology of a meningioma, what are three things we can see?
- The tumour is adherent to the dura (dura-based)
- It has rounded, well circumscribed margins
- It presses against, but doesn't invade, the underlying brain
Here in imaging studies and grossly we again see a....?
Dura-based, well circumscribed mass
If we now look at the microscopic morphology of meningiomas, we can see clusters of what?
Meningothelial cells (some of which have a "whorled" appearance), with indistinct clel membrane
The nuclei show what?
Calcific spherules called what are seen (arrows)?
When dealing with a brain tumour, the possibility of what should always be considered?
What are the five most common primary sites of brain metastases?
1) The lung (both adenocarcinoma and small cell)
2) Breast carcinoma
3) The skin (melanoma)
4) The kidney (renal cell carcinoma)
5) The GIT (adenocarcinoma)
Metastatic brain tumours are often....?
Multiple, well-demarcated, and may be surrounded by gliosis
Metastatic brain tumours may be the....?
First presentation of the primary cancer
Metastatic brain tumours tend to arise where?
At the interface between the grey matter and white matter
Why is this?
This region contains a dense capillary network (remember this is haematogenous spread of the primary tumour)
Metastases may also involve the....?
spinal cord or meninges
Here we see a metastatic melanoma in the brain - note what found in these tumours?
Dark brown melanin pigment
Pituitary tumours may also present as space occupying lesions. The most common are what type?
Benign adenomas arising in the anterior pituitary (adenohypophysis)
These adenomas arising in the anterior pituitary represent roughly what % of intracranial tumours?
Pituitary adenomas may present in what two ways?
1) Signs and symptoms of endocrine disturbances
2) Localised "mass effect"
The normal pituitary gland (hypophysis) is formed of what two parts?
- The anterior pituitary (adenohypophysis)
- The posterior pituitary (neurohypophysis)
The anterior pituitary constitutes how much of the pituitary gland?
80% of the gland
The anterior pituitary is composed of many types of cells that produce what?
The different hormones released by the gland
The posterior pituitary is formed of axons and their terminals - derived from neurons....?
Located in the hypothalamus
These terminals in the posterior pituitary release what hormones?
- Vasopressin (ADH/anti-diuretic hormone)
By means of its different cell types, the anterior pituitary releases what six hormones?
- ACTH = adrenocorticotrophic hormone
- FSH = follicle-stimulating hormone
- GH = growth hormone
- LH = luteinising hormone
- PRL = prolactin
- TSH = thyroid-stimulating hormone
These hormones are under the control of stimulatory and inhibitory hypothalamic factors - which ones?
- CRH = corticotropin-releasing hormone
- GHRH = growth hormone-releasing hormone
- GnRH = gonadotropin-releasing hormone
- TRH = thyrotropin-releasing hormone
- GIH = growth hormone inhibitory hormone (somatostatin)
- PIF = prolactin inhibitory factor (dopamine)
The pituitary gland lies within the what in the sphenoid bone?
The pituitary gland is bound laterally by what, and superiorly by what?
- Laterally by the cavernous sinuses
- Superiorly by the sella diaphragma (a dural fold)
What lies above the sella diaphragma?
The optic chiasm
Here we see some of the different structures + the normal pituitary gland in a T1 weighted MRI:
What type of pituitary tumour can arise from any of the cell types in the anterior pituitary?
About 85% are what?
"Functioning adenomas" - that is, they autonomously (irrespective of the hypothalamic releasing hormones) produce hormones
Even small functioning adenomas (microadenomas of less than 1cm) can become clinically evidence because they present with....?
Here we see a small discrete microadnoma. It's hyperintense due to what?
The haemorrhage into the lesion
Non-functioning adenomas tend to present as what?
Space-occupying lesions - because they can grow to a larger size (macroadenoma of more than 1cm) before becoming symptomatic
As such, non-functioning pituitary adenomas can cause what symptoms?
Symptoms of increased ICP (headache, nausea, vomiting etc)
However, given their location, pituitary tumours may also produce more specific....?
Here we see an MRI of a macroadenoma:
Here we see the microscopic morphology of a pituitary adenoma - what can we see?
- Sheets of monotonous/monomorphic cells with eosinophilic cytoplasms and round-oval nuclei
- There are no features of malignancy seen
What are some localising effects/findings of pituitary adenomas?
Pituitary adenomas can extend laterally into the cavernous sinus and impinge on what, leading to what?
- CN III
- CN IV
- CN VI
- CN V(1) (opthalmic nerve)
- CN V(2) (maxillary nerve)
This leads to:
- Dilated pupils
- Partial facial sensory dysfunction
Larger lesions could produce what?
Brainstem compression or hydrochephalus
Acute haemorrhage into an adenoma is called what here?
This can lead to what symptoms?
- Severe headache
- Visual disturbances
Brain abscesse can also present as SOLs. What are some sources of infection that lead to this?
- Direct implantation due to trauma
- Extension from paranasal sinusitis or mastoiditis
- Blood-born spread from a distant infection (e.g. IE) - in this case abscesses are multiple, located at the grey/white matter interface (where the rich capillary network is)
In immunocompetent patients, what are the most common organisms identified?
In immunocompromised patients, a broader range of organsims are encountered, including....?
Fungal and protozoal infections
Brain abscesses are destructive processes that present as what?
Rapidly expanding mass lesions, with increasing ICP and focal deficits depending on the location of the abscess
What are some present symptoms and signs?
- Changes in mental state (drowsiness, confusion)
- Focal neurological deficits
- Nausea and vomiting
- Neck stiffness
Here we see the gross morphology of a brain abscess - what does it look like?
Well-circumscribed cavities filled with pus and surrounded by oedema and fibrosis (in older lesions)
If we now look at the microscopic morphology of brain abscesses, the early abscess cavity is filled with what?
Neutrophils and necrotic debris (suppurative necrosis), without sharp separation from adjacent brain tissue (adjacent brain tissue shows scattered neutrophils)
Brain abscesses are serious infections that require rapid treatment. A potentially fatal complication is what?
Rupture of the abscess into the ventricular system causing ventriculitis
Treatment of abscesses involves what?
Surgical drainage (to decrease ICP and provide materal for culture) + antibiotic therapy + elimination of the primary site of infection
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