Space Occupying Lesions of the CNS (Week 2--Yong)

Question 1

Some pathologies of mass lesions/mass effect

Answer 1

Solid masses

Cystic lesions

Hemorrhages

Infarct (acute/subacute)

Infection

Hydrocephalus

Cerebral edema

Question 2

Brain herniation

Answer 2

Brain moves into place it’s not supposed to be

Major consequence of mass effect

Question 3

Arteries supplying the brain

Answer 3

ACA to top/center

MCA to middle/lateral

PCA to bottom

Question 4

What can infarct cause a few days later?

Answer 4

Swelling/edema

Edema greatest at 4 days after infarct

Question 5

Hemorrhages and their causes

Answer 5

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

Question 6

Meningioma

Answer 6

Extra-axial mass pushing on brain

If slow-growing, brain will give way and accommodate

Question 7

Leptomeningitis

Answer 7

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

Question 8

Chronic meningitis

Answer 8

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

Question 9

Solid masses

Answer 9

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)

Question 10

Glioblastoma (GBM)

Answer 10

Thick irregular wall of enhancement with gadolinium on MRI

Question 11

Abscess

Answer 11

Smooth circumferential wall on MRI

Question 12

Tumefactive multiple sclerosis

Answer 12

Smooth crescent of enhancement

Question 13

Butterfly glioma (GBM)

Answer 13

Tumor that spans both hemispheres (crosses corpus callosum and is bilateral)

Question 14

Brain cysts

Answer 14

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

Question 15

Hydrocephalus

Answer 15

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)

Question 16

Cerebral edema

Answer 16

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

Question 17

Brain herniation

Answer 17

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

Question 18

Take home points

Answer 18

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