W1 - Intracranial Space Occupying Lesions (ISOLs) Flashcards
Define the term “space-occupying lesion”
SOL - A body of tissue or fluid that resides within a body structure and compresses or displaces normal tissue structures, commonly cause local signs and symptoms (but may be asymptomatic).
ISOL - SOLs found in the cranial cavity. These are commonly neoplastic, but may include haematomas, granulomas and vascular aneurysms.
Define the term “malignant” with respect to brain tumours
Malignancy generally refers to an aggressive tumour that commonly metastasises, as well as rate of growth.
Brain tumours (and more generally, CNS neoplasms) malignancy is normally defined solely by rate of growth. Faster rate of growth --> Increased rate of normal CNS tissue replacement --> Loss of function --> death.
Discuss the mechanisms by which intracranial tumours produce clinical symptoms and signs
Rapid growth rate - Key indicator of malignancy, causes:
- Invasion and replacement of normal CNS tissue - Neoplastic tissue has different properties, resulting in loss of function and focal ssx
- Local compression & shifting of CNS structures - Due to tumour growth, degeneration (outgrows blood supply), necrosis, inflammation & haemorrhage.
- Angiogenesis - Absence of Blood-Brain Barrier (not regulated by glial cells, specifically astrocytes) means there is free passage of ions, resulting in oedema –> increased ICP. Oedema slow to drain due to lack of lymphatics in brain. Furthermore, new blood vessels more fragile –> higher chance of leakage or rupture.
- Obstruction of CSF flow -Especially if tumour present in 3rd or 4th ventricle –> Hydrocephalus (esp in children) –> Increased ICP
- CNS herniation - Local (the tumour) or generalised (raised ICP) increases in pressure cause bulging of normal brain tissue through susceptible areas (eg. subfalcial, uncal, downward, external, tonsillar
Discuss the headache which is characteristic of raised ICP caused by neoplasms
- Early stage - Usually diffuse (may be focal) mild headache, worse in morning or after long periods in horizontal postures and relieved by vertical postures (ICP elevated by horizontal postures due to gravity) and deep breathing. (decreases ICP due to increased venous return to heart, away from head)
- Intermediate stage - As tumour grows HA becomes more severe and constant. Aggravated by coughing, bending & sudden head movements
Late stage - Pain caused by HA may wake patient
Discuss the general classification of the clinical manifestations produced by intracranial tumours. In each case, discuss the underlying mechanism(s) responsible for the production of signs & symptoms.
Generalised Ssx - Due to raised ICP
Focal Ssx - Local to area affected by tumour, caused by compression and/or ischaemia of normal CNS tissue.
False-localising Ssx - Present distant from tumour site, normally due to shifting of structures resulting from tumour growth.
List and discuss the major generalised symptoms and signs which accompany intracranial tumours
Headache - Starts as a diffuse, mild headache and progresses in severity and constancy as tumour grows. May wake patient due to pain in late stages.
Papilloedema - Swelling and bulging of optic disc, leading to visual disturbances. Mainly caused by CSF pathway obstruction but may also be due to thrombosis of central retinal vein (backflow of blood –> bulging of optic disc)
Vomiting - Common in children. Usually occurs in morning, usually accompanied by HA, +/- preceding nausea)
Mental changes - May include irritability, apathy, sleep changes (early to bed, later to rise), forgetfulness, psychological depression
Plateau waves - Acute failure of normal cerebral vascular auto-regulation –> abrupt increase in cerebral blood volume –> Rapid increase in ICP. May be brought on by sitting up suddenly, sneezing, coughing. May be asymptomatic or symptomatic. Ssx may include: HA, visual changes, altered consciousness, +/- weakness of extremities
Generalised seizures (no notes, have not learned, explanation not assessable yet?)
List and discuss the major focal symptoms which accompany intracranial tumours of:
a) Frontal lobe
b) Parietal lobe
c) Temporal lobe
d) Occipital lobe
e) Brain stem
f) Cerebellum
g) Cranial nerves
a) Frontal lobe
- Often asymptomatic until tumour is very large, parts of frontal lobe functionally “silent” (thus general ssx usually occur before focal)
- Personality changes (irritability and facetiousness, depression and apathy, or a combination)
- Abnormal gait
- Urinary frequency
- Post frontal lobe may affect motor function –> mild mono/hemiparesis, Broca’s aphasia (if dominant hemisphere affected)
b) Parietal lobe
- Cortical senory abnormalities (contralateral half of body)
- Contralateral impairment of all sensory modalities (if thalamus involved)
- If dominant side affected: Apraxia (loss of ability to follow out purposeful movements in absence of paralysis or peripheral/motor impairment)
- If non-dominant side affected: Anosognosia (loss of ability to recognise/acknowledge bodily deficit), difficulty with visual-spatial orientation
c) temporal lobe
- Seizures (often early manifestation)
- Hallucinations (common) - olfaction, hearing, “déjà vu” phenomenon
- Superior quadrantanopia (commonly occurs during seizures) - visual deficit to the left or right superior field of vision
- Wernicke’s aphasia - Loss of speech interpretation
d) Occipital lobe
- Contralateral visual field defects
- Contralateral visual seizures
e) Brain stem
- UMN or LMN Ssx that may affect any of the CNs (depends on location and size of SOL)
f) Cerebellum
- Early Ssx of raised ICP (often tumour compresses 4th ventricle), common in children
- Gait ataxia (midline tumours/spinocerebellum)
- Ipsilateral extremity ataxia (lateral tumours/cerebrocerebellum)
g) Revise CN lesion Ssx. Any CN may be affected.
Discuss endocrine conditions which are typically produced by tumours in the region of the:
a) Sella turcica
b) Pineal gland
a) Sella turcica
- Most commonly from a pituitary adenoma (benign growth that often secretes excessive amounts of hormones made by parent cell). Usually very small, rarely observe raised ICP Ssx
- Amenorrhoea-galactorrhoea syndrome (hyperprolactinaemia)
- Acromegaly (excess growth hormone)
- Cushing’s disease (excessive ACTH)
Other adenomas may become large and compress the: Diaphragm sella, optic chiasm, oculomotor nerve (causing ocular palsies)
b) Pineal gland
- Usually embryonic growths (eg teratomas, germinomas), common in children
- Hydrocephalus (Cerebral aqueduct compression)
- Loss of upward gaze or pupillary fixation gaze (upper brain stem compression)
- Deafness (compression of inferior colliculus)
List the intracranial tumours which commonly produce endocrine abnormalities
Lesions of the:
- Pituitary fossa
- Suprasellar cistern
- Pineal area
Define the term “leptomeninges”
The two inner meningeal layers (arachnoid and pia), between which circulates the CSF (subarachnoid space)
List the tumours which most commonly affect the leptomeninges
- Meningioma
- Lymphomas
- Leukaemia
- Breast cancer
- Lung cancer
- Malignant melanoma
What is a false localising symptom/sign? Discuss
A symptom/sign caused by compression/displacement of normal CNS tissue distant from tumour site, resulting from the displacement of CNS structures due to tumour growth (eg. Right-sided HA due to compression of right cerebral hemisphere, but resulting from a left-sided tumour)
Less of an issue nowadays due to modern imaging technologies (CT/MRI)
