CNS Flashcards
The dominant variable in diagnoses of CNS tumours
Age
Three possible factors:
- increase in life expectancy
- increasing availability of CT and MRI scans
- An increased interest in geriatrics and overall importance of elderly health care
Age of incidence of CNS cancer
A bimodal peak in incidence by age.
First peak: during childhood between 3-12
Second peak: between 50-80 years, most diagnosed between 55-64 years with a median age of 57 at diagnoses.
Brain metastasis
20-40% of cancer patients will develop brain metastases.
The most common primary site of disease in the lung.
Most metastatic lesions occur in the cerebral hemispheres.
Risk factors of primary brain tumours
Largely unknown.
Occupational and environmental exposures
- chemicals
- synthetic rubber
- pesticides/herbicides
- ionizing radiation
- electromagnetic fields
Lifestyle and dietary factors
- cell phones
- nitrates
- hair dyes
- smoking
Medical conditions
- drugs
- viral infections
- AIDS
Genetic factors
- two to three times increased incidence when close relative diagnosed with glioma
- von Recklinghausen’s disease
- autosomal dominant disorder (NF1 and Nf2 genes)
Most important prognostic factors of primary CNS cancer
3 most important factors:
Age
Performance status
Tumour type
Other contributing factors:
Location: a natural prognostic indicator for survival time and neurological defects
Tumour grade: grouped into benign (low-grade) and malignant (high grade)
Necrosis: the presence or absence of necrosis has prognostic significance.
KPS
Karnifsky performance scale: measures the neurological and functional status of the patient.
Ranges from 0 to 100.
80-100 range: patients who can work and whose lifestyle is not affected by the disease.
50-70 range: patients who are unable to work, but can still care for themselves with varying amounts of assistance.
0-40 range: unable to care for self, required hospital care, disease progressing rapidly.
CNS tumour grading
Because primary tumours rarely spread to other parts of the body a traditional staging system is not needed.
grade I: the tissue is benign. The cell looks nearly like healthy brain cells and they grow very slowly.
grade II: the tissue is malignant. The cells look less like healthy cells than do the cells in grade I
grade III: The malignant tissue has cells that look very different from healthy cells. The abnormal cells are actively growing (anaplastic)
grade IV: The malignant tissue has cells that look abnormal and tend to grow quickly.
Ventricles
Cavities that form a communication network with each other, the central canal of the spinal cord and subarachnoid space.
The ventricles, canals and subarachnoid space are filled with cerebrospinal fluid.
Tentorium
A fold of the dura mater (outermost layer of the brain) separates the supratentorial region and infratentorial region.
The supratentorial region consists of the cerebral hemispheres.
The Infratentorial region consists of the cerebellum, medulla, pons, upper spinal cord and brainstem.
Composition of brain
40% grey matter which contains the supportive nerve cells, forms the cortex or outer part of the cerebrum and surrounds the white matter.
60% white matter composed of bundles of nerve fibres, axons that carry impulses away from the cell body and dendrites that carry impulses towards the cell body.
Blood supply of the brain
Comes from the internal carotid arteries and vertebral arteries via the circle of Willis.
BBB
The blood-brain barrier hinders the penetration of some substances into the brain and CSF. Exists between the vascular system and the brain. The purpose is to protect the brain from potentially toxic compounds. Substances must be lipid-soluble.
Spread of gliomas
Spread invasively because they do not form natural capsules that inhibit growth.
They do not metastasize by the lymph system and rarely metastasize outside the CNS.
Tumour cells may break off and circulate through the CSF spreading to other parts of the CNS.
The lumbosacral area is the most common area of seeding although it can occur anywhere.
Clinical presentation of spinal cord tumours
Pain: may be an early sign
Weakness: usually occurs in the distal extremities then works its way proximally.
Loss of sensation
Loss of bowel and bladder control
Immediate treatment is necessary for patients who have a sudden onset of symptoms to avoid permanent paralysis.
Frontal lobe tumour symptoms
Often asymptomatic until late
Symptoms of increased intracranial pressure (headaches that are made worse by exertion or most severe at night or early morning)
Personality changes
Defective memory
Seizures
Weakness
Loss of smell
Speech disorder
Urinary incontenince
Parietal lobe tumour symptoms
Symptomatic earlier then frontal lobes
Loss of vision
Spatial disorientation
Tingling sensation
Loss of memory
Weakness
Temporal lobe tumours symptoms
Speech disorder
Loss of smell
Disturbance of hearing
Seizures
Hallucinations/dreams
Space-preception disturbances
Occipital lobe tumour symptoms
Seizures
Loss of vision
Tingling
Weakness
ICP symptoms
Intracranial pressure symptoms include:
- headache
- nausea
- vomiting
- blurred vision
- trouble with balance
- personality or behaviour changes
- seizures
- drowsiness
- rare occasions coma
Astrocytoma
Tumour arises from star-shaped astrocytes
Often arise in the cerebrum
In children the occur in the brainstem, cerebrum and cerebellum
Grade III astrocytomas are usually called anaplastic astrocytoma
Grade IV astrocytoma is usually called glioblastoma multiforme
Brain stem glioma
Found in glioma cells (star-shaped) commonly found between neurons and blood vessels to provide support.
Tumour occurs in the lowest part of the brain
Most often diagnosed in young children and middle-aged adults
Ependymoma
Tumour arises from cells that line the ventricles or the central canal or spinal cord.
Most commonly found in children and young adults.
Oligodendroglioma
Arises in cells that make the fatty substances that cover and protect nerves.
Usually form in the cerebrum
Grow slowly and do not spread to surrounding brain tissue
Most common in middle-aged adults.
Medulloblastoma
Small blue round mass cells. Do not usually remain after birth.
Typically arises in the cerebellum
Most common brain tumour in children
Meningioma
Tumour arises in the meninges that protect the brain and spinal cord
Usually grows slowly (benign)
Schwannoma
A tumour that grows around the Schwann cells that line nerves that control balance and hearing
Also called acoustic neuroma
Crainopharyngioma
The tumour grows at the base of the brain near the pituitary gland
Occurs most often in children
Germ cell tumours
Very rare
Arise in germ cells
Most occur in people younger than 30
The most common type of germinoma is very radiosensitive.
Pineal region tumours
Rare tumours arise in or near the pineal gland.
Located between the cerebrum and the cerebellum
Borders for whole-brain irradiation
Inf border: superior orbital ridge to external auditory meatus
Ant, sup, and post: 1-2cm clearance
SSD should be set to mid-sep
Hair loss doses
2000-4000cGy: temporary hair loss
>4000cGy: permanent hair loss
