Adult CNS Tumors Flashcards
How common are brain tumors?
Brain tumors are relatively less common compared to other cancers. However, brain metastases are expected to continue to increase in incidence as cancer patients are living longer, and it is estimated that 35% of cancer patients will ultimately develop brain metastases. There are approximately 13 million cancer survivors in USA.
Development of mature neurons and their supportive glial cells from pluripotent stem cells is a highly complex process controlled by cell growth promoting and suppressing genes
Overview of Neuropoiesis
Neural Stem cells give rise to Glial progenitor and neuronal progenitor cells
Glial progenitor cells form astrocytes, ependyma, and oligodedrocytes
Neuronal progenitor cells forms neurons
There is growing evidence supporting the presence of tumor stem cells in different cancers, including glial tumors.
Glial tumors are histologically differentiated into different types and may have different clinical behavior.
Mixed glial and neuronal tumors are also possible containing neoplastic neuronal and glial component (ganglioglioma). Mixed glial tumors are also possible e.g. oligo-astrocytoma
Tumors can arise from any structure present intracranially. Give some examples.
hemangioblastoma from blood vessels,
neurofibroma and schwannoma from nerves,
lymphoma from trafficking white blood cells,
germinoma from nests of germ cells,
meningioma from arachnoid cap cells,
chordoma and chondrosarcoma from bone, or an extracranial cancer may enter brain via blood stream (metastases).
Developmental cysts may mimic a brain tumor
What are the astrocytic/glial derived brain tumors?
Glioma
Ependymoma
Oligodendroglioma
What are the nerve brain tumors?
Schwannoma
Neurofibroma
What cancers commonly MET to the brain?
Breast cancer
lung
Melanoma
Renal cell carcinoma
GI cancers
Other CNS tumors
The frequency of the various primary CNS tumors ranges from 2% for meningioma and mixed oligoastrocytoma to 40% for glioblastoma multiforme (GBM) and 42% for infiltrative astrocytoma.
What are the primary cranial intraaxial tumors?
glioma
pituitary
lymphoma
What are the primary cranial extraaxial tumors?
meningioma
acoustic neuroma
What are the risk factors for CNS tumors?
Only ionizing radiation, chemotherapy/immunosuppression and certain genetic syndromes are definitely related to development of brain tumors.
What things might cause CNS tumors?
Electromagnetic Fields, including cell phone use
Diet
Occupation
Infections (HIV, EBV, HTLV)-Epstein Barr virus is linked to CNS lymphoma in immunosuppressed patients, especially after bone marrow transplant and in patients with AIDS. This represent only a small minority of brain tumors diagnosed each year
Describe Li-Fraumeni syndrome
AD syndrome with mutation of TP53 on chromosome 17p13 causing glioma and medulloblastoma
Describe Tuberous sclerosis in relation to the brain
AD syndrome caused by TSC1/2 mutation on 9q34 and 16p13 respectively resulting in subependymal giant cell astrocytomas, cortical tubers, and glioma in the brain
Describe Neurofibromatosis type I (von Recklinghausen’s disease; NF1) in relation to the brain
AD syndrome caused by mutation of NF1 on chromosome 17q11 causing glioma (optic nerve), astrocytoma, and glioblastoma
Describe Neurofibromatosis type 2 in relation to the brain
AD syndrome caused by mutation of NF2 on chromosome 22q12 causing meningioma, schwannoma (bilateral acoustic neuroma), and ependymomas
Describe MEN1 in relation to the brain
AD syndrome caused by Menin mutation on 11q13 causing pituitary tumors
What causes Retinoblastoma?
AD syndrome caused by mutation of RB1 on chromosome 13q14
Describe VHL disease in relation to the brain
AD syndrome caused by mutation of VHL on chromosome 3p25-20 causing hemangioblastoma
What must happen for a tumor to develop?
For a tumor to develop, either cell growth genes have to be over activated, or inhibitor genes have to be silenced. Many such events have now been recognized and newer targeted therapies are being developed to counter these events
What is Cerebral perfusion pressure?
The difference between mean arterial pressure and intracranial pressure (CSF and interstitial pressure).
Describe the pressure volume curve of the brain
As the intracranial volume slowly increases (graph on the left), such as with tumor growth, intracranial pressure remains fairly constant until brain compliance threshold is reached. At that stage small volume increase causes large increase in intracranial pressure.
At this stage intermittent increase in intracranial pressure (graph on the right) may exceed cerebral perfusion pressure (plateau waves) and cause multiple symptoms from focal weakness, numbness, mental status change to seizure like activity. This is called plateau wave phenomenon and is an important concept to remember.
What are the general signs/symptoms of CNS tumors?
HA due to raised intracrnaila pressure or local irritation; often non-specific but may have migraine features; may show laterality
Vomiting
Mental status changes (depression, irritability, aparthy)
When shoudl you suspect a tumor as the source of a HA
worse on awakening with improvement within 1 hour
new onset at any age
change in character or severity of headaches in a chronic headache patient
Describe the vomiting associated with CNS tumors
may or may not be associated with nausea
occurs more often on awakening
more common in children
suggests tumor if vomiting immediately follows an acute onset headache suggesting increased ICP
Signs and symptoms of brain tumors result from what?
increased intracranial volume. This may stretch basal blood vessels or dura causing pain. Increased intracranial pressure may reduce cerebral perfusion (mean arterial pressure –intracranial pressure = perfusion pressure) and result in ischemic symptoms. Finally involvement of eloquent brain structures may produce deficits
What are some other signs of CN tumors (possible)?
- papilledemia (often asymptomatic but may cause visual changes; more common in children)
- Seizures (partial or generalized; Episodic alterations in smell, taste, personality, memory, motor or sensory function depending on the origin of neural discharge)
Focal neurologic deficits
What Focal neurologic deficits may be seen with CNS tumors?
Will vary depending on location
Includes but not limited to:
weakness (i.e. pre-central gyrus)
paresthesias (i.e.. post-central gyrus)
visual impairment (i.e.. optic pathway/occipital lobe)
personality changes (i.e.. frontal lobe)
May or may not be reversible depending on the cause (tumor invasion vs. edema vs. compression) and time since onset of deficit
Focal signs with CNS tumors result from direct involvement of eloquent brain structures. What is the pathogenesis of the seizures?
unclear and may arise from entrapped neurons in the tumor, or pressure from infiltrating tumor edge
What are common common etiologies of the signs and symptoms of CNS tumors?
Invasion of neural or vascular structures
Compression of adjacent neural or vascular structures
Obstruction of CSF pathways <–> Hydrocephalus <-> Inc ICP
Herniation from mass effect
Cerebral hypoperfusion because of increased intracranial pressure
Describe what is occurring in #1 below
1 – Subfalcine herniation of cingulate gyrus. May compress anterior cerebral artery and CVA.
Describe what is occurring in #2 below
2 – Diencephalic downward herniation. Compression of upper brainstem causes drowsiness, impaired vertical gaze and uni- or bilateral small pupils because of involvement of sympathetic fibers (Horner syndrome).
Describe what is occurring in #3 below
3- Classical uncal herniation. Causes ipsilateral oculomotor nerve palsy and contra or ipsilateral hemiparesis
Describe what is occurring in #4 and #5 below
- Upward herniation through tentorium. May cause ipsilateral oculomotor, Horner (mid position unreactive pupil) and contralateral hemiparesis.
5, Tonsillar herniation causing BP changes, weakness, respiratory disturbance, weakness and Horner syndrome.
What are some diagnostic tools for diagnosing CNS tumors
Definitive diagnosis of a CNS tumor can only be achieved through what?
tissue biopsy,
One exception is primary CNS lymphoma (PCNSL)…malignant cells may be found in the CSF via lumbar puncture
Describe T1 weighted MRI scan
–Water (i.e.. CSF, tumor, edema) is hypointense (dark): decreased signal or darker than surrounding brain
–Injected contrast that leaks across disrupted BBB within tumors appears hyperintense (bright): increased signal or brighter than surrounding brain
Describe T2 weighted MRI scan
–CSF/edema/tumor appears hyperintense (bright)
–Differentiating edema from infiltrating tumor on T2: Edema spares the cortex but Tumor does
There is a large ring enhancing tumor in the left frontal lobe. There is a mass effect with midline shift. Tumor has grown rapidly outstripping its blood supply resulting in central necrosis (darker area). All these are indicative of a highly malignant tumor, most likely a grade IV astrocytoma (GBM)
Left T2 images also show edema in the brain tissue. On T2 images stationary and moving water both appear bright or white
What is the most common brain tumor in adults?
Gliomas