CNS Tumours Flashcards
What is the Monro-Kellie hypothesis?
The sum of volunes of CSF, intracranial blood and brain remains constant. An increase in one should result in a decrease in the other two.
However, blood, brain and CSF are largely incompressible, thus CSF containing spaces and skull foramina are the only places where volumes can accomodate chage.
Thus, compensation by reducing cerebral CSF and blood volume are the only ways the body can regulate ICP.
What is the Monro-Kellie hypothesis?
The sum of volunes of CSF, intracranial blood and brain remains constant. An increase in one should result in a decrease in the other two.
However, blood, brain and CSF are largely incompressible, thus CSF containing spaces and skull foramina are the only places where volumes can accomodate chage.
Thus, compensation by reducing cerebral CSF and blood volume are the only ways the body can regulate ICP.
How can herniation occur?
Increased ICP can lead to displacement of soft tissue through whatever anatomical openings are available
WHat are the three levels of herniation?
- Subfalcine - Herniation of cingulate gyrus
- Transforaminal - Cerebellar tonsils herniate
- Transtentorial - Brain stem herniation (central transtentorial) and temporal lobe herniation (uncus transtentorial)
How can we measure ICP?
Difficult to do, but can measure CSF pressure as a proxy.
- Normal = 7-15mmHg in SUPINE adult
- >15mmHg = abnormal
- >20mmHg = pathological
Causes of raised ICP?
- Space occupying lesion e.g. tumour, haemorrhage
- CSF flow obstruction
- Cerebral oedema e.g. stroke, traumatic injury
Symptosm and signs of iCP
- Headache
- Seizures
- Vomiting
- Hypertension and bradycardia
- Focal neurological signs
What can occur in compensation of raised ICP?
- Decreased CSF and blood volume
- Parenchymal displcement - midline shift, compressed gyri, effacement of ventricles
- Herniation of brain
What is the most important first step for classifying CNS tumours?
Determining if primary or metastatic.
What are the most commonly identified neoplastic lesions of the brain?
Common sites from which they came?
Metastases from other sites.
Can be any tumour that spread haematogenously, but most common primary sites are the most common cancers:
- Lung
- Breast
- Renal
- Colorectal + GIT carcinomas
- Melanoma
Three common radiographic features of metastatic brain lesions
- Multiple well encapsulated mass lesions
- Mass effect
- Surrounding vasogenic oedema
What does multiple metastases indicate in teh brain?
Multiple sites = very likely to be metastatic, but a single site may also be metastatic.
Describe the incidence of primary brain tumours in teh adult and paediatric population?
Priamry CNS neoplasms are very rare in adults - 2 in 1 million. Most are sporadic mutations.
However, brain tumours account for 20% of paediatric malignancies.
(astrocytic and embryonal tumours)
What is the role of staging in primary brain tumours?
Not so important, as primary brain tumours tend not to spread. More important to type based on pathological features.
What is the difficulty in grading brain tumours as benign or malignant?
Usually, malignant = metastatic spread and ability to cause death.
However, in the brain, even benign tumours in the wrong place can have lethal effects.
Which type of glioma has the worst prognosis?
What would you expect in radiological findings?
High grade astrocytoma / glioblastoma
Radiology - central necrosis and peripheral vascularity - shows a bright ring around the brain.
