Chapter 2: Histology of the Nervous System Flashcards
Neurofilaments
provide structural support for the neuron, and are most numerous in the axon and the proximal parts of dendrites
Microfilaments of neurons
- form a matrix near the periphery of the neuron.
- prominent in growth cones of neuronal processes and functions to aid in motility of growth cone
- also prominent in dendrites and forms structural specializations at synaptic membranes
Where are microtubules found in the neuron?
all parts of the neuron, and are the cytoplasmic organelles used in axonal transport
What are Lewy bodies?
cytoplasmic inclusions of degenerating neurons of the substantia nigra, pars compacta, evident in Parkinson’s disease and in cortical and brain-stem neurons seen in certain forms of dementia
What are Negri bodies?
eosinophilic cytoplasmic inclusions seen in degenerating neurons in the hippocampus and cerebellar cortex in patients with rabies
Tau proteins becominng excessively phosphorylated prevents what action of the neuron?
prevents crosslinking of microtubules
Neurofibrillary tangles are prominent features of what conditions?
Alzheimer’s disease, amyotrophic lateral sclerosis, and Down syndrome
What are neurofibrillary tangles?
when tau proteins become excessively phosphorylated and prevent crosslinking of microtubules
What motor protein is important for fast anterograde transport in the neuron?
kinesin
Is slow anterograde transport dependent on microtubules or ATPase motor molecules?
neither
How does a person with diabetes manage to get polyneuropathies producing characteristic “glove and stocking” pattern?
hyperglycemia results in an alteration of proteins that form microtubules, which may disrupt axonal transport
Is retrograde transport faster or slower than anterograde transport?
slower than anterograde transport
What are the most numerous glial cells in the CNS?
astrocytes
Which glial cells have large numbers of radiating processes?
astrocytes
GFAP?
glial fibrillary acidic protein (GFAP). Large bundles of intermediate filaments that are contained within astrocytes
What are some viruses that are taken up into the neuron with retrograde axonal transport?
polio, herpes, and rabies viruses and tetanus toxins
What are radial glia?
precursors of astrocytes that guide neuroblast migration during CNS development
What are microglia cells?
smallest glial cells in the CNS
Are microglia cells derived from ecotoderm? Explain.
No, they are derived from bone marrow monocytes and enter the CNS after birth
What are oligodendrocytes?
form myelin for axons in the CNS
What are Schwann cells?
supporting cells of the peripheral nervous system
What is a collective name for groups of diseases that can affect myelin?
leukodystrophies
What are some symptoms of MS?
Multiple Sclerosis
- Symptoms separated in space and time
- vision loss (optic neuritis)
- internuclear ophthalmoplegia (MLF)
- motor and sensory deficits
- vertigo
- neuropsychiatric
- marked by hyperreflexia
What are some symptoms of GBS?
- acute symmetric ascending inflammatory neuropathy of PNS myelin
- weakness begins in lower limbs and ascends; respiratory failure can occur in severe cases
- autonomic dysfunction may be prominent
- Cranial nerve involvement is common
- sensory loss, pain, and parasthesias rarely occur
- reflexes invariably decreased or absent
Treatment for MS?
high dose steroids, interferon-beta, glatiramer
What may be a sign 1-3 weeks prior to onset of GBS?
2/3 of patients have history of respiratory or GI illness 1-3 weeks prior to onset
Describe important lab findings of those with GBS?
elevated CSF protein with normal cell count (albuminocytologic dissociation)
What are ependymal cells?
cells that line the ventricles in the adult brain. Some ependymal cells differentiate into choroid epithelial cells, forming part of the choroid plexus which produces cerebrospinal fluid (CSF)
What are tanycytes?
specialized ependymal cells that have basal cytoplasmic processes that contact with blood vessels; these processes may transport substances between a blood vessel and a ventricle
What is the BBB comprised of? What is the most important part of it?
- most important part is the cerebral capillary endothelial cells and their intercellular tight junctions
What are examples of drugs that readily diffuse across the BBB?
heroin, ethanol, and nicotine are lipid soluble compounds that readily diffuse across
What is Nissl substance?
ER of the neuron; none are found in the axon
Schwannomas typically affect which cranial nerve fibers?
Vestibulocochlear nerve (CN VIII)
Name the primary tumors of the brain.
- glioblastoma multiforme ( grade IV astrocytoma)
- astrocytoma (pilocytic)
- oligodendroglioma
- ependymoma
- medulloblastoma
- meningioma
- Schwannoma
- Retinoblastoma
- craniopharyngioma
What are some feature of glioblastoma multiforme ( grade IV astrocytoma)?
- most common primary malignant brain tumor
- usually lethal in 8-12 months
- can cross the midline via the corpus callosum (“butterly glioma”)
What are some features of astrocytoma (pilocytic)?
- benign tumor of children and young adults
- usually in posterior fossa in children
What are some histological features of glioblastoma multiforme?
areas of necrosis surrounded by rows of neoplastic cells (pseudopalisading necrosis)
Histopath and other lab features of astrocytoma (piloyctic)?
- rosenthal fibers - eosinophilc corkscrew fibers
- immunostaining with GFAP
What are some features of oligodendrogliomas?
- slow growing
- long survival (avg 5-10 years)
- typically seen in frontal lobe
What are some histopathologic features of oligodendriomas?
- “fried-egg” appearance - perinuclear halo
- finely branched capillaries resembling chicken wire
What are some featues of ependymoma?
- ependymal origin
- can arise in IV ventricle and lead to hydrocephalus
- adult presentation in cauda equina
- common presentation in neurofibromatosis Type II
Histopathology of ependymoma?
- rosettes and pseuduorosettes
- rod shaped blephoroplasts (basal ciliary bodies)
What mutation is related to medulloblastomas?
SHH mutation
What are some features of medulloblastoma?
- highly malignant cerebellar tumor
- can compress the 4th ventricle or arise from 4th ventricle
- A type of primitive neuroectodermal tumor (PNET)
- locomotion difficulties, truncal ataxia, wide gait
- common in children
- highly radiosensitive
What is the histopathology of medullblastoma?
blue, small, round cells with pseudorosettes
Homer Wright rosettes
lots of mitotic figures
What are some features of meningiomas?
- second most common primary brain tumor
- most common non malignant-non glial primary tumor
- can be benign or malignant
- arises from arachnoid villi which are involved with reabsorption of CSF
- increased bone density in surrounding area
- seizures, hearing loss, unilateral vision loss, contralteral weakness depending on where brain compressing
- dural convexities; parasagittal region
- attaches to dura, (dural mass with calcifications compresses underlying brain without invasion
- common in neurofibromatosis Type II
Histo of meningiomas?
psammoma bodies
What are the features of Schwannoma?
- third most common primary brain tumor
- other names: acoustic Schwannoma, vestibular Schwannoma, acoustic neuroma
- most frequent location CN VIII at cerebellopontine angle hearing loss, tinnitus
- CN V+ VII signs corneal reflex loss
- Bilateral acoustic schwannomas - pathognomonic for neurofibromatosis type 2
- good prognosis after surgical resection
Schwannoma histology.
- Antoni A (hypercellular) and B (hypocellular) areas
- S100 +
What are some features of retinoblastoma?
- sporadic - unilateral
- familial - bilateral; associated with osteosarcoma
- Rb gene on chromosome 13
- can present with leukocoria, strabismus, and vision loss
Dx: genetic testing
Rx: cryotherapy, photocoagulation, chemotherapy: carboplatin, vincristine, etoposide radiation
Surgery: (enucleation) surgical removal of the eye
What is the histopathology of retinoblastoma?
small, round, blue cells; may have rosettes
Craniopharyngioma features.
- derived from oral epithelium (remnants of Rathke pouch)
- forms in suprasellar region of brain and can cause hypopituitarism because of compression of pituuitary
- usually children and young adults
- often calcified
- symptoms due to encroachment on pituitary stalk or oral cavity
- benign but may recur
- cyst surrounded by enamel like calcification (cyst filled with cholesterol crystals and yellow viscous fluid
Histology of craniopharyngioma.
- histology resembles adamantinoma (most common tumor of tooth)
