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Central Nervous System Pathology > CNS Malformations & Tumors > Flashcards

CNS Malformations & Tumors Flashcards

1
Q

Neurulation

A
  • Days 17-27 after fertilization
  • NOTOCHORD induces overlying ectoderm to differentiate into NERUOECTODERM –> forms NEURAL PLATE

NEURAL PLATE –> NEURAL GROOVE –> NEURAL TUBE + NEURAL CREST CELLS

Neuropore = site of tube closure

  • Anterior Neuropore: site of cephalic closure
  • Posterior Neuropore: site of caudal closure
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2
Q

Anencephaly
vs.
Encephalocele

A

Anencephaly: occurs before 24 days gestation

  • Rostral closure defect, with absence of Brain and skull
  • frog-like appearance of fetus
  • Maternal polyhydramnios due to impairment of fetal swallowing of amniotic fluid
  • Clinical finding: increased AFP

Encephalocele: occurs before 26 days

  • defective closure of rostral tube
  • outpouching of brain tissue, mostly OCCIPITAL
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3
Q

Spina Bifida Occulta

A
  • Occurs before 26 days of gestation
  • Failure of bony spinal canal to close, but no structural hernation (Dura is intact)
  • presents as a dimple or patch of hair overlying vertebral defect
  • Clinical finding: increased AFP
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4
Q

Spina Bifida

  • Meningocele
  • Meningomyelocele
A

Meningocele: meninges, but not the spinal cord, herniate through the spinal canal defect

Meningomyelocele: Meninges AND spinal cord herniate through the spinal canal defect

  • Clinical finding: increased AFP
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5
Q

Arnold-Chiari Malformation (Type II)

A
  • Significant cerebellar tonsillar and vermian herniation through the foramen magnum
  • midbrain roof deformed
  • results in aqueductal stenosis and hydrocephalus due to blockage of the 4th ventricle
  • often occurs with meningomyelocele & syringomyelia (syrinx expansion into anterior white commissure)
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6
Q

Dandy-Walker Malformation

A
  • Agenesis of CEREBELLAR VERMIS (failed hindbrain development)
  • presents as cystic enlargement of 4th ventricle with absent cerebellum
  • associated with hydrocephalus and spina bifida
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7
Q

The Types of Glial Cells

A
  1. Astrocytes: Physical support, maintaining BBB
  2. Oligodendroglia: Myelinate CNS neurons
  3. Ependyma: Embryologic inner lining of the neural tube
  4. Choroid Plexus Epithelium: produces CSF
  5. Microglia (by convention, but are mesodermal in origin): CNS phagocytes
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8
Q

Components of Meninges

A

Pachymenix: Dura Mater

Leptomeninges:

  • Arachnoid
  • Pia mater
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9
Q

CNS Tumor Principles

A

Most common in incidence:

  1. Gliomas
  2. Meningioma
  3. Metastases
  4. Pituitary Adenoma
  5. Schwannoma
  • Adult primary tumors: usually supratentorial
  • Pediatric primary tumors: usually infratentorial
  • Morbidity/Mortality: Correlates best with surgical respectability
  • Primary CNS tumors rarely metastasize beyond CNS
  • CNS tumors act as space-occupying masses: results in increased intracranial pressure & brain herniations
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10
Q

Pediatric Primary CNS Tumors

A

- 70 percent located bellow tentorium cerebelli (infratentorial)
- 60-70 percent derived from primitive CNS
precursor celllls or glia

Common Pediatric Tumors:
- Medulloblastoma: Cerebellar vermis
– Diffuse astrocytoma: Brainstem astrocytoma: Low-grade astrocytoma (Astrocytoma, Grade II); Glioblastoma multiforme (Astrocytoma, Grade IV)
– Circumscribed astrocytoma: Pilocytic astrocytoma (Astrocytoma, Grade I)
- Ependymoma: IV ventricle
- Craniopharyngioma: Region above sella turcica (suprasellar)
- Germ cell tumors: Region of pineal gland (posterior III ventricle)

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11
Q

Subfalcine/Cingulate Herniation

A
  • Cingulate gyrus pushed under falx cerebri by expanding frontal/parietal mass
  • May compress branches of anterior cerebral
    artery (ACA) with infarction in ACA distribution
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12
Q

Transtentorial/Uncal/Hippocampal Herniation

A
  • Medial-most part of temporal lobe (uncus) pushed out over edge of tentorium and wedged into cleft between tentorium and cerebral peduncle of midbrain
  • Compresses ocullomotor nerve (CN III), resulting in fixed dilated pupil
    - May push midbrain against contralateral tentorium, resulting in IPSILATERAL hemiparesis from peduncular compression
  • Compresses posterior cerebral artery (PCA) with infarction in PCA distribution
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13
Q

Cerebellar Tonsillar Herniation

A
  • Inferior-most parts of cerebellar hemispheres (tonsils) pushed into foramen magnum, compressing respiratory centers of medulla
    - may result from spinal tap in patient with intracranial pressure (ICP); Check for papilledema, obtain CT and/or MRI
    before tapping patient with suspected ICP
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14
Q

Pilocytic Astrocytoma

A
  • Well Circumscribed Astrocytoma
  • MOST COMMON CNS TUMOR IN CHILDREN, usually in cerebellum (infratentorial)
  • Cystic lesion (empty space) with MURAL NODULE (solid tumor nidus in cyst wall)
  • Biphasic microscopic pattern:
    • Piloid cells: dense, fascicles of elongated spindle cells
    • microcystic zones: loose
  • ROSENTHAL FIBERS: eosinophilic, corkscrew processes of astrocytes
  • GFAP POSITIVE
  • amenable to resection
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15
Q

Diffuse Astrocytoma: Grade II

A

– Poor demarcation from surrounding brain with deep extension into neighboring tissue
– Complete surgical resection often not possible; late recurrence common
– Progression of Grade II lesions to Grades III/IV
- CT/MRI: Hypodense lesion without contrast enhancement; minimal/absent edema
- Gross: Gray-white poorly demarcated mass expanding or effacing normal architecture; NO HEMORRHAGE OR NECROSIS
- Micro: Hypercellularity (increased astrocytes) with nuclear pleomorphism; NO MITOSES, VASCULAR PROLIFERATION OR NECROSIS

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16
Q

Anaplastic Astrocytoma

A
  • Grade III astrocytoma
    – Cerebral hemispheric white matter in adult 40-50
  • CT/MRI: Low density lesion with irregular contrast enhancement, ± edema (greater contrast than grade II)
  • Microscopic: Hypercellularity, pleomorphism, MITOSES
    – Recurrence after surgery in 12-24 months
17
Q

Gioblastoma Multiforme (Grade IV Astrocytoma)

A
  • Most common primary brain tumor in adults
  • Malignant, high grade tumor of astrocytes, with < 1 year life expectancy
  • found in cerebral hemispheres, usually crossing the corpus callosum (BUTTERFLY LESION)
  • CT/MRI: Heterogeneous, hyperdense lesion, with Peripheral rim of contrast enhancement (“ringenhancing”); Significant peritumoral edema and “mass effect”
  • Gross: Hemorrhage, necrosis; can cause FUNGUS CEREBRI appearance
  • Microscopic: Hypercellularity, pleomorphism, mitoses,
    GLOMERULOID vascular proliferation, necrosis surrounded by PSEUDOPALISADING viable tumor cells
  • GFAP STAIN POSITIVE
18
Q

Ependymoma

A
  • Malignant pediatric tumor of ependymal cells
  • Children: most common in 4th ventricle (presents with hydrocephalus)
  • Adults: most common in spinal cord
    Gross: Solid/papillary intraventricular tumor; Relatively circumscribed
  • Microscopic: Glial tumor with PERIVASCULAR PSEUDOROSSETTES, ±
    ependymal canals
19
Q

Perivascular Pseudorosette

A
  • characteristic histological finding in ependymoma
  • Characteristic 3 ring target:
    1. blood vessel
    2. cytoplasmic processes: attach themselves to blood vessels
    3. nuclei: congregate in a stripe outside the pink processes
20
Q

Medulloblastoma

A
  • highly malignant, pediatric cerebellar tumor (primitive neuroectoderm), which can compress 4th ventricle (hydrocephalus)
  • “Drop metastasis”: spread to spinal cord
  • CT/MRI: Hyperdense contrast enhancing lesion
  • Gross: Variable circumscription, gray-white to hemorrhagic
  • Microscopic: “Small round blue-cell tumor”
    Cells with very high nuclear:cyttoplasmic ratio
    – HOMER WRIGHT ROSETTES: small round blue cells wrap around neuritic processes
    – High mitotic activity, apoptosis, pleomorphism
  • TX: Surgery plus radiation/chemo
21
Q

Oligodendroglioma

A
  • malignant tumor of oligodendrocytes, found in cerebral hemispheric white matter, commonly involving FRONTAL LOBE, of adults
  • clinical: presents with seizures
  • CT: calcified tumor
  • Gross: Gray-pink mass with cysts, calcification, hemorrhage
  • Miicroscopic: Uniform cells with clear cytoplasm and central nuclei (“fried eggs”); follows acutely branching capillary stroma (“chicken wire vasculature”)
  • Variable survival, but somewhat better than
    astrocytomas (5-10 years)
22
Q

Meningioma

A
  • 2nd most common primary brain tumor (F>M; tumor expresses estrogen receptor)
  • benign tumor of arachnoid cells, with dural tail, located over cerebral convexity
  • extra-axial (external to brain parenchyma); well circumscribed
  • my present with seizures and focal signs (compresses, but does not invade cortex)
  • Histo: Whorled pattern; psammoma bodies (calcified whorled spindle cells) present; minimal pleomorphism and mitotic activity
  • prognosis: easy to resect
23
Q

Schwannoma

A
  • 3rd most common primary brain tumor
  • Benign tumor of Schwann cells (extra-axial)
  • Locations: Vestibular Schwannoma: at Cerebellopontine angle with
    hearing loss (CN VIII)
  • Gross: Well circumscribed, encapsulated, attached to nerve root; May show degenerative changes (cysts,
    hemorrhage)
  • Microscopic: Biphasic with dense (Antoni A) and loose (Antoni B) zones; Spindle Cells (long, flat nuclei); Alignment of nuclei in palisades/zebra-stripe pattern (VEROCAY BODIES); Parent nerve pushed to one side
  • surgically curable
24
Q

Neurofibromatosis type 2

A
  • bilateral acoustic schwannoma, especially at cerebellopointine angle
25
Q

Neurofibroma

A

– Tumor in Spinal canal, attached to nerve root (usually dorsal) with nerve root compression

  • Gross: Unencapsulated, diffuse fusiform expansion of nerve; Soft with shiny gelatinous cut surface
  • Microscopic: Loose myxoid background with small wavy or comma shaped schwann cell nuclei; Axons of parent nerve embedded in, and separated by, tumor
26
Q

Neurofibromatosis type 1 (NF1) (von Recklinghousen’s Disease)

A
  • Multiple neurofibromas
  • Autosomal dominant, with 100% penetrance, variable expression
  • cafe-au-lait spots
  • Lisch nodules (pigmented iris hamartomas)
27
Q

Metastatic Tumors

A
  • characteristically present as multiple, well-circumscribed lesions at the watershed gray-white junction
  • Primary tumors include: Lung carcinoma; Breast carcinoma; Malignant melanoma; Renal cell carcinoma; Gastrointestinal tract carcinomas
  • CT/MRI: Multiple heterogeneous masses with contrast enhancement and surrounding edema (ring-enhanced lesion)
  • Gross: Circumscribed tumors with necrosis, hemorrhage
  • Microscopic: Histology matches primary neoplasm
28
Q

Craniopharyngioma

A
  • Pediatric supratentorial brain tumor, involving cerebrum
  • benign Rathke’s pouch tumor with cholesterol crystals & calcification
  • May compress optic chiasm –> bitemporal hemianopsia
29
Q

Holoprosencephaly

A
  • Occurs at 5-6 weeks (disorder of ventral induction)
  • Failure of segmentation and cleavage into paired brain hemispheres
  • Usually sporadic, but can be associated with Patau Syndrome (Trisomy 13), Edward Syndrome (Trisomy 18), and Sonic Hedgehog gene mutation
30
Q

Microcephaly Vera

A
  • Autosomal recessive disorder of nerve cell proliferation; brain doesn’t grow
  • Occurs around 2-4 months
  • causes severe mental retardation

E.g., Down Syndrome: too few neurons in certain areas of the brain

31
Q

Marcocephaly

A
  • autosomal dominant or recessive disorder in nerve proliferation, where you have too much nerve proliferation
  • occurs ~2-4 months of gestation
  • frequently associated with HETEROTOPIAS (misplaced gray matter)
32
Q

Disorders of Nerve Cell Migration

A

Occur during 3-5 months

  1. Agenesis of Corpus Collosum
  2. Lissencephaly: smooth cortex; POLYHYDRAMNIOS IN PREGNANCY
  3. Pachygyria: Thick wide gyri; heterotopic neurons
  4. Polymicrogyria: small, multiple gyri, with cobblestone appearance; assoc w/ Zellwegger syndrome
  5. Schizencephaly: a congenital split or cleft in the brain; usually early in brain development
  6. Fetal Alcohol Syndrome: Microcephaly, motor disorders, MR, dysmorphisms
33
Q

Myelination

A
  • Final process in brain development, occuring at 5 months gestation
  • Usually completed at 18 months of age
  • Direction:
    • Inferior to superior
    • Posterior to anterior
34
Q

Hydraencephaly

A
  • Destructive prenatal lesion
  • Almost complete absence of the hemispheres
  • Damage is along distribution of internal carotid arteries
  • Clinically normal until 3-4 months
35
Q

Porencephaly

A
  • Destrutive prenatal lesion
  • Cavitary defect in the brain, often extending from the surface of hemisphere to the ventricle
  • Predilection for parietoccipal region

Central Nervous System Pathology (15 decks)

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