Space Occupying Lesions of the CNS (Week 2--Yong) Flashcards
Some pathologies of mass lesions/mass effect
Solid masses
Cystic lesions
Hemorrhages
Infarct (acute/subacute)
Infection
Hydrocephalus
Cerebral edema
Brain herniation
Brain moves into place it’s not supposed to be
Major consequence of mass effect
Arteries supplying the brain
ACA to top/center
MCA to middle/lateral
PCA to bottom
What can infarct cause a few days later?
Swelling/edema
Edema greatest at 4 days after infarct
Hemorrhages and their causes
Deep gray matter hemorrhage caused by hypertension
Superficial lobar hemorrhage in older person seen with cerebral amyloid angiopathy caused by Alzheimer disease (A-beta depositions)
Multiple hemorrhages caused by coagulopathy, fungal abscesses, certain metastatic tumors
Complex vasculature hemorrhage caused by vascular malformations
Meningioma
Extra-axial mass pushing on brain
If slow-growing, brain will give way and accommodate
Leptomeningitis
AKA meningitis
Infectious and chemical
Acute purulent/PMN meningitis is bacterial
Acute lymphocytic meningitis is viral
Chronic meningitis due to various agents
Get fever, headache, stiff neck, altered mental status
Chronic meningitis
Bacteria and fungi
M Tuberculosis–lymphoplasmacytic and histiocytic, sometimes granulomatous (TB)
Cryptococcus neoformans–may elicit minimal inflammation
Can cause endarteritis obliterans followed by infarcts
Same as acute meningitis but sometimes no signs
Solid masses
Tumors
Abscesses
Tumefactive multiple sclerosis
Metastases and GBMs are usually solid or ring enhancing, can have necrotic center
Solitary in brain is often glioma (GBM)
Multiple lesions more often metastases and abscesses (hemorrhages too)
Glioblastoma (GBM)
Thick irregular wall of enhancement with gadolinium on MRI
Abscess
Smooth circumferential wall on MRI
Tumefactive multiple sclerosis
Smooth crescent of enhancement
Butterfly glioma (GBM)
Tumor that spans both hemispheres (crosses corpus callosum and is bilateral)
Brain cysts
Arachnoid cyst on surface of brain
Rathke cleft cyst, craniopharyngioma on pituitary/suprasellar
Pineal cyst
Choroid plexus cyst
Colloid cyst of 3rd ventricle
Cysticerosis, hydatid cyst in brain
Cyst with mural nodule in brain (temporal lobe, cerebellum, pliocytic astrocytoma, ganglioglioma, hemangioblastoma)
Mass with cystic change–metastasis, GBM
Hydrocephalus
Excess CSF in the brain
Noncommunicating (obstructive): obstruction of CSF flow in ventricles (tumor, infection); colloid cyst at top of 3rd ventricle gets large lateral ventricles; aqueductal stenosis gets large 3rd and lateral ventricles
Communicating (non-obstructive): no obvious blockage between ventricles and arachnoid; obstruction at leptomeninges or arachnoid granulations (post hemorrhage, meningitis); hydrocephalus ex vacuo (compensatory dilatation of ventricles from cerebral atrophy–Alzheimers)
Cerebral edema
Cerebral edema secondary to mass lesion (tumor) can amplify mass effect; metastases typically have disproportionate edema
Vasogenic edema: normal BBB disrupted, fluid in extracellular spaces (around tumor and abscesses), white matter
Cytotoxic edema: injury to cells and cells swell because of substrate and energy failure; fluid in intracellular spaces (ischemia); grey and white matter
Many lesions have combinations of above edema types
Edema commonly leads to brain herniation
Brain herniation
Uncal = transtentorial, lateral transtentorial: medial temporal lobe (uncus) compresses against tentorium cerebelli; CN III and PCA compressed
Central = diencephalic, central tentorial: downward displacement of diencephalon, may have bilateral uncal herniation
Subfalcine: cingulate gyrus under falx; ACA compressed
External = transcalvarial: brain tissue thru dural/skull defect
Tonsillar: cerebellar tonsils thru foramen magnum; brain stem/respiratory centers compressed
Duret hemorrhages: brainstem herniation causes hemorrhages; often linear and midline, secondary to tearing of blood vessles
Take home points
Butterfly glioma = GBM
Ring enhancing = GBM, metastasis, abscess
Cyst with mural nodule = pliocytic astrocytoma, ganglioma, hemangioblastoma
Pituitary cyst = Rathke cleft cyst
Multiple cysts = cysticercosis
Multiple masses = metastases, fungi/bacteria
Hemorrhagic lesions = coagulopathic, fungi, melanoma, renal cell carcinoma, choriocarcinoma
Superficial lobar hemorrhage = cerebral amyloid angiopathy (Alzheimer’s)
Deep/basal ganglia hemorrhage = hypertension
Cortical ribbon lesion = infarct; 4 day old infarct has edema/mass effect; old (months to years) there is loss of tissue
Sulcal/leptomeningeal lesion = meningitis, carcinomatosis
Hydrocephalus = communicating vs non-communicating
Edema = vasogenic vs cytotoxic
