Tumor of The Central Nervous System Flashcards
Brain Tumor Epidemiology
-7.6/100,000 males, 5.4/100,000 females
-100,000 death/year from brain metastases
Prevalence: 122, 000
Lifetime Risk: 0.6%
-35% of patients will get brain metastases
Neuropoiesis
-development of mature neurons & their supportive glial cells from pluripotent stem cells is highly complex process controlled by cell growth promoting & suppressing genes
Primary Brain Tumors
- presence of tumor stem cells (including glial tumors)
- Glioma progenitor cells (astrocytoma, ependymoma, oligodendroglioma)
- Neuronal progenitor cells (neuronal tumors)
- can arise from any structure present intracranially (hemangioblastoma from blood vessels, neurofibroma & schwannoma from nerves, lymphoma from trafficking white blood cells, germinoma from nests of germ cells, meningioma from arachnoid cap cells, chordoma & chondrosarcoma from bone, or an extracranial cancer may enter brain via blood stream (metastases)
- developmental cysts may mimic a brain tumor
Primary Brain Neoplasia Frequency
- meningioma & mixed oligoastrocytoma 2%
- glioblastoma multiforme 40%
- infiltrative astrocytoma 42%
Risk Factors for CNS Tumors
Definitive:
- ionizing radiation
- immunosuppression (latrogenic, chemo, acquired AIDS)
- genetic syndromes
Possible:
- electromagnetic fields (cell phone)
- diet, occupation, infections (HIV, EBV, HTLV)
Pathogenesis of Brain Tumor
-cell growth genes must be over activated or inhibitor genes have to be silenced
Pressure Volume Curve & Intracranial Pressure Waves
- cerebral perfusion pressure is difference b/w mean arterial pressure intracranial pressure (CSF & interstitial pressure)
- as intracranial volume slowly inc. pressure remains constant until brain compliance threshold is reached, then small inc. in volume causes large inc. in pressure
- may exceed cerebral perfusion pressure and cause focal weakness, numbness, mental status change to seizure like activity
- Plateau wave phenomenon*
Signs of CNS Tumors: Headache
- due to raised intracranial pressure or local irritation
- often non-specific but may have migraine features
- suspect tumor if: worsen on awakening with improvement in 1 hr, new onset at any age, change in character or severity of headaches in a chronic headache patient
Signs of CNS Tumors: Vomiting
- may or may not be associated with nausea
- occurs more often on awakening
- more common in children
- suggests tumor if immediately follows an acute onset headache suggesting inc. ICP
Signs of CNS Tumors: Mental Status Changes
-depression, irritability, apathy
Signs of CNS Tumors: Papilledema
-often asymptomatic (may have visual changes)
-more common in children & young adults when compared to elderly
-
Signs of CNS Tumors: Seizures
- partial (focal) or generalized seizures
- episodic alterations in smell, taste, personality, memory, motor or sensory function depending on the origin of neural discharge
Signs of CNS Tumors: Focal Neurologic Deficits
- vary depending on location
- includes: weakness (pre-central gyrus), paresthesias (post-central), visual impairment (optic pathway/occipital lobe), personality changes (frontal lobe)
- may be reversible depending: cause (tumor invasion vs. edema vs. compression
- time since onset of deficit
Etiology of Signs & Symptoms of CNS tumors
- invasion of neuronal or vascular structures
- compression of adjacent neural or vascular structures
- obstruction of CSF pathways - hydorcephalus - inc. ICP
- Herniation from mass effect
- cerebral hypoperfusion b/c of inc. intracranial pressure
Brain Herniation
- Subfalcine herniation of cingulate gyrus, may compress ant. cerebral artery & CVA
- diencephalic downward herniation, compression of upper brainstem causes drowsiness, impaired vertical gaze and uni or bilateral small pupils b/c of sympathetic fiber involvement (horner)
- Classical uncal herniation (ipsilateral oculomotor nerve palsy & contra or ipsilateral hemiparesis)
- Upward herniation through tentorium (ipsilateral oculomotor, Horner, and contralateral hemiparesis)
- Tonsillar herniation (BP changes, weakness, respiratory disturbance, weakness & Horner syndrome)
CNS Tumor Diagnostics
- H&P
- MRI (contrast enhancement optional), study of choice for suspected tumor
- MRI superior to CT differentiation tumors from vascular malformations & other lesions but CT better identifying calcifications & pathology
- diagnosis by biopsy except primary CNS lymphomas (found in CSF by lumbar puncture)
TI weighted MRI Scan
- water is hypointense (dark), dec. signal or darker than surrounding brain
- injected contrast that leaks across disrupted BBB within tumors appears hyperintense (bright), inc. signal or brighter than surrounding brain
T2 weighted MRI Scan
-CSF/edema/tumor appears hyperintense (bright)
-Differentiating edema from infiltrating tumor on T2
edema spares the cortex
tumor does not spare the cortex