Week 1 Lectures Flashcards
It is composed of two layers of dense collagenous connective tissue with large venous sinuses formed where the various leaves of the mater come together
Dura
A thin membrane containing a mixture of fibroblasts and arachnoidal cells, also known as meningothelial cells, and forms a continuous sheet subjacent to the dura and, in most places, joined to it to form one physically continuous tissue.
Arachnoid
It anchors delicate strands of the arachnoid trabeculae, which connect the arachnoid to it.
Pia
Subdural space
Normally the arachnoid matter is adherent to the dura. However, unlike the tight adherence between the inner table of the skull and the dura (only disrupted by high pressure such as arterial flow from a traumatized middle meningeal artery), this interface is more readily disrupted by minor injuries. Typically trauma results in tearing of the bridging veins that traverse this space as they pass between the cortical surface and the overlying dura resulting in the accumulation of blood in the subdural space (subdural hematoma).
Subarachnoid space
an actual (not potential) cavity between the arachnoid mater and the pia mater, which contains vascular structures and CSF.
Virchow Robin space
Since the pia mater is tightly attached to the brain and follows the vessels into the brain parenchyma, so does the subarachnoid space, creating the Virchow Robin spaces that surround vessels within the brain.
Dural sinuses
In specific locations, the dural leaflets form the draining structures named dural sinuses.
Dural sinuses are penetrated by ________ whose function is:
arachnoid villi (or arachnoid granulations); structures that conduct CSF back into the circulation
T/F Arachnoidal cells are found distributed throughout the arachnoid membrane, but are most concentrated over the arachnoid villi.
T
____________ have a distinctive histologic appearance, forming small multicellular clusters with prominent whorls and occasional ________ bodies
arachnoidal cells and psammoma bodies –> oval nuclei with fine, even dispersed chromatin and occasional pseudo-inclusions
Arachnoidal cells are thought to be the basis for a slow growing tumor seen in older adults called _______.
meningioma
T/F Normally clear, the arachnoid may become opacified with age due to thickening from the deposition of collagen in the subarachnoid space.
T –> opacification of the leptomeninges
3 components of a neuron
- dendrites – multiple elongated processes specialized in receiving stimuli
- perikaryon (soma or cell body) – trophic center, i.e. center of nutrition, support and supply, also receptive to stimuli
- axon – single process specialized in generating or conducting nerve impulses. Axons end in specialized terminal arborizations, each branch of which terminates on the next cells in dilatations called boutons, which form part of the synapse.
T/F most neurons have a prominent nucleolus.
T –> finely dispersed chromatin in nucleus too
T/F Axons have nissl and dendrites don’t.
F –> axons don’t have nissl, dendrites do.
T/F RER projects into axons.
F
Astrocytes (A) and oligodendrocytes (O) are commonly referred to as _______ cells.
glial –> common precursors but different functions in CNS
_______ are located in both gray and white matter and have long processes that are rarely visible as they merge into a feltwork of axons and dendrites called _______.
astrocytes and neuropil
Bare nuclei appearance
astrocytes
White matter vs. Gray matter astrocytes
In the gray matter astrocytes have numerous short highly branched processes (protoplasmic astrocytes). In the white matter astrocytes tend to have fewer and relatively straighter processes (fibrous astrocytes)
Protoplasmic astrocytes
Gray matter
Fibrous astrocytes
White matter
Astrocyte function
extend numerous fine foot processes towards both the pial surface, around the basement membrane of blood vessels, and the non-synaptic regions of neurons. Astrocytes thus have an important structural role, as well as functional significance as mediators of metabolic exchange between neurons and blood
Astrocytes contain an abundant amount of an intermediate filament known as __________ which can be used to highlight the presence of these fine processes, as well as to confirm the astrocytic nature of particular glial cells.
GFAP: glial fibrillary acidic protein
, these cells can only be identified histologically by their dense darkly stained nuclei and lack of conspicuous cytoplasm.
oligodendrocytes
___ are the predominant type of glial cell in the white matter
oligodendrocytes
T/F Likeastrocytes, there is no immunohistochemical stain (like GFAP) that can be used in tissue sections for ready identification of these cells.
F
In the gray matter oligodendroglial cells are often found in small groups of 2-3 cells in close proximity to neurons in a process called ______.
satellitosis
T/F A single oligodendrocyte can contribute to the myelination of up to 50 axons that may belong to the same or different fiber tracts.
T
The cytoplasm of the oligodendroglial cell is packed with _____, which makes sense for a cell type that makes lots of glycolipid membrane material
Golgi
The ______ lines the ventricles of the brain and the central canal of the spinal cord.
ependyma
Ependymal cell appearance
cuboidal with elongated nuclei, microvilli (thought to be involved in absorptive and secretory activity) and cilia (may be involved in propulsion of CSF through the ventricular system). Like other epithelial cells in the body, they are bound together by junctional complexes at their luminal surfaces. However, they do not rest upon a basement membrane. Instead, the base of ependymal cells breaks up into fine branches that interdigitate with an underlying layer of astrocytic processes. Specialized ependymal cells have elongated processes that extend to the subependymal vasculature, thus linking the ventricular, vascular and intraparenchymal compartments of the CSF. A similar pattern may be observed in tumors derived from ependyma (ependymoma) that often have prominent perivascular processes.
T/F Ependyma has no basement membrane.
T
Projections of vascular stroma derived from the meninges are covered with a low cuboidal epithelium that secretes _____.
CSF
_______ cells have numerous long microvilli with only a few cilia. They also have many mitochondria, large Golgi complexes and basal nuclei, which is consistent with their secretory activity.
Choroid plexus –>lateral ventricles and fourth ventricle
Cells found in layers of neocortex
- a relatively acellular outer molecular layer,
- external granular layer comprised of small round darkly staining neurons
- external pyramidal layer comprised of larger triangular shaped neurons
- internal granular layer
- internal pyramidal layer
- a polymorphous or multiform layer with a mixed populations of neurons, including large pyramidal type cells.
pyramidal cells give rise to ________ that point upwards towards the pial surface, and axons that are the efferent output of the neocortex which project downwards towards the ____________.
apical dendrites and subcortical white matter
large pyramidal cells are the efferent output of the neocortex and are located primarily in layers ______
3 and 5 –> external and internal pyramidal
. For example, the pyramidal cells of layers 3 and 5 are very large (Betz cells) in the primary __________cortex.
motor (precentral)
_______ cortex has small pyramidal cell layers but markedly expanded granular cell layers.
the primary sensory (postcentral)
Ammon’s horn
hippocampus proper
three-layered cortex that connects the hippocampus to the parahippocampal gyrus
subiculum
Sommer Sector
CA1 –> most sensitive to various insults including ischemia, seizures, and degenerative changes from Alzheimer’s
Each cerebellar _____ is comprised of a relatively hypocellular molecular layer (ML) that contains the complex dendritic processes of ______ cells
folia and purkinje
the greatest number of cerebellar neurons are actually contained in the densely packed _______.
granular layer (GL)
What cells are associated with: acute ischemic injury, chronic cell loss, and inclusions
neurons
What cells are associated with: reactive gliosis
glial cells
What cells are associated with: microglia and inflammatory infiltrates
inflammatory cells
“Red” neuron
cells that have experience irreversible ischemic injury. They are characterized by a shrunken cell body, intense cytoplasmic eosinophilia with complete loss of Nissl basophilia. They can be seen about 12-24 hours after the ischemic insult. The nucleus is frequently darkly stained without an evident nucleolus.
Red neurons can be seen about _____ hours after ischemic injury.
12-24 hours
Which regions of the brain are more vulnerable to ischemic injury?
the pyramidal neurons of the CA1 region in Ammon’s horn (hippocampus) and the Purkinje cells of the cerebellum
One of the most common subcellular alterations in neurons is the accumulation of _______, especially in large/small motorneurons of the spinal cord/brainstem/cortex.
lipofuscin in large motorneurons of the spinal cord
lipofuscin
This is a normal age-related process. Oxidized fatty acids from cell membrane breakdown accumulate as a fine light brownish retractile material, typically located along the perikaryal edge.
neuromelanin
by-product of neurotransmitter synthesis in these catecholaminergic neurons.
3 catecholaminergic areas of neurons that produce neuromelanin
These include the substantia nigra of the midbrain, locus ceruleus of the rostral pons and the dorsal motor nucleus of the vagus.
T/F Viral infections can lead to abnormal inclusions
T –> CMV (nuclear, cytoplasmic), herpes (nuclear), rabies (cytoplasmic)
T/F Many neurodegenerative disorders are associated with neuronal inclusions
T –> neurofibrillary tangles in AD, Lewy bodies in Parkinson’s
______ are the main effector of reaction to injury in the CNS: through both hypertrophy and hyperplasia they cause ______, a common denominator for diverse causes of injury.
astrocytes cause gliosis
_______ react to injury by hyperplasia and by developing elongated nuclei and increased elongated cytoplasmic processes
microglia
Microglial nodules are aggregates of microglial cells that are often seen in some inflammatory conditions including _______.
viral encephalitis
5 most common routes of access to the CNS (by infections)
hematogenous spread, local extension (paranasal sinuses, middle ear), retrograde PNS transport, direct implantation (trauma, surgery)
T/F Virulence and tropism of certain organisms for neural and glial elements determines “homing” to the nervous system.
T
Spread of infection into layers of the dura mater
Pachymeningitis
Inflammation of the pia and arachnoid
Meningitis/Leptomeningitis
Inflammation (usually viral) of the brain parenchyma
with mononuclear cells
Encephalitis
Inflammation (usually bacterial) of the brain parenchyma
with neutrophils
Cerebritis
Inflammation of the spinal cord
Myelitis
Inflammation of spinal gray matter
Poliomyelitis
Inflammation of the dorsal root ganglia
Ganglionitis
Inflammation of the intradural spinal nerve roots
Radiculitis
Immune response associated with: Acute (bacterial) meningitis, cerebritis, abscess
Neutrophils (acute inflammation)
Immune response associated with: Chronic (“aseptic” viral) meningitis, encephalitis
Mononuclear cells (lymphocytes and plasma cells, chronic inflammation)
Immune response associated with: Micobacteria, spirochetes, fungi, parasites
Granulomatous inflammation
Immune response associated with: Viral encephalitis
Microglial nodules
T/F Bone, dura mater, arachnoid and pia mater delineate four compartments that tend to inhibit the spread of infection from one compartment to another
T
Most common area of bacterial CNS infection
Subarachnoid space –> meningitis/leptomeningitis
Epidemics of bacterial meningitis are common/rare and almost always associated with ______.
rare and Neisseria meningitidis.
Long term complications of bacterial meningitis
hydrocephalus due to leptomeningeal scarring blocking basal cisterns and arachnoid granulations and hearing loss
3 bacteria that cause the majority of bacterial meningitis.
S. pneumoniae, N. meningiditis and H. influenzae
Which age of patients are affected by: Group B Streptococcus, Escherichia coli, Listeria monocytogenes
neonates
Which age of patients are affected by: Streptococcus pneumoniae, Listeria monocytogenes
Adults >60 years and immunosuppressed
Which age of patients are affected by: Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae
Children and Adults (6 mos to 60 years)
Macroscopic findings of bacterial meningitis
purulent exudate, opacification of leptomeninges
bacteria causing basal exudate in bacterial meningitis
H. Influenza
bacteria causing convexity exudate in bacterial meningitis
S. Pneumoniae
Microscopic findings of bacterial meningitis
neutrophils in leptomeningeal space, pia effective barrier to parenchymal spread, occasional cerebritis when infection crosses parenchyma
____are focal, destructive lesions (occasionally multifocal) of the brain parenchyma due to necrosis mediated by acute inflammation in response to bacterial infection.
Abscesses
2 sources of abscess forming CNS infections
Local (sinusitis otitis, mastoiditis) or hematogenous (septic emboli or cyanotic congenital cardiac disease-PFO)
Most common bacteria in abscess formation
S. aureus, Streptococci, often polymicrobial
T/F Bacterial endocarditis can cause
infectious emboli to travel to the brain
and cause abscesses
T
T/F Mass effect from a CNS abscess can cause herniation.
T
T/F abscesses in the CNS have surrounding fibrotic capsules.
T
4 features of early abscess formation
vascular congestion, early necrosis, edema and initiation of inflammation –> neutrophils
After approximately ______, neovascularization and collagen fibers start to create the abscess capsule that will eventually isolate the area of necrosis (eventually a cystic cavity) from the surrounding preserved parenchyma.
10 days
Features of late abscess formation
neutrophil debris and fibroblastic collagenous capsule
Typically, tuberculous meningitis involves the ____ aspect of the brain and presents with cranial nerve involvement
basal
CSF findings of TB meningitis
lymphocytosis, hypoglycemia, increase in protein
Acid fast stain
identify filamentous mycobacteria like TB
Which condition? chronic basal meningitis with associated obliterative endarteritis. Perivascular inflammatory infiltrate, rich in plasma cells and lymphocytes. Cerebral gummas (mass lesions) may also occur.
Meningovascular neurosyphilis
Which condition?invasion of the brain byTreponema pallidum.Inflammatory lesions associated with parenchymal damage in the cerebral cortex with loss of neurons, proliferations of microglia (rod cells), gliosis, and iron deposits. The spirochetes can, at times, be demonstrated in tissue sections.
Paretic neurosyphilis
Which condition? damage by the spirochetes to the sensory nerves in the dorsal roots and posterior columns. Organisms are not demonstrable in the cord lesions.
Tabes dorsalis
T/F In neurosyphilis, CNS is affected in the primary stage
F –> tertiary stage
Stage at which chancres form
primary syphilis
Stage of neurosyphilis with hematogenous spread, generalized lymphadenopathy, maculopapular rash, condyloma lata, mucous patches
secondary syphilis
Which organism causes lymphocytic meningitis, cranial nerve palsies, and polyradiculitis, and occurs several months after a skin rash known as erythema chronicum migrans?
Borrellia burgdorferi –> Lyme
Viral Inflammation restricted to the meninges
aseptic meningitis
Viral disease restricted to the grey matter
polioencephalitis, poliomyelitis
Viral disease of both grey and white matter
panencephalitis, panmyelitis
Viral disease of white matter
leukoencephalitis
What kind of viral meningitis? enterovirus
aseptic meningitis
What kind of viral meningitis? poliovirus, coxsackie, arbovirus, echovirus, tick-borne, rabies
polioenceph/myelitis
What kind of viral meningitis? HSV, HIV
panenceph/myelitis
What kind of viral meningitis? JC, PML, HIV
leukoencephalitis
T/F Viral meningitis is generally less severe than bacterial meningitis.
T
One form of recurrent aseptic meningitis ______ that was previously regarded as non-infective has been linked to infection with herpes simplex virus (HSV), especially HSV-2.
Mollaret’s
What kind of viral meningitis? acute infection of meninges + lymphocytes in CSF,
aseptic meningitis
T/F Survivors of viral CNS infections involving the parenchyma can subsequently develop permanent neurological disease.
T
Which of the following are seasonal in nature? Arbovirus, HSV
Arbovirus Acute Viral Encephalitis
Most common cause of epidemic encephalitis.
Arbovirus (arthropod borne) –> birds, horses, small mammals, arthropods –> incidental/terminal hosts in humans
T/F The majority of human arbovirus infections are asymptomatic or may result in a nonspecific flu-like syndrome.
T
Site of arbovirus replication in humans
The virus replicates at the site of host inoculation and then spreads to regional lymph nodes and other lymphoreticular tissues (primary viremia) where it proliferates before disseminating hematogenously (secondary viremia) to systemic tissues, including, in some cases, the CNS.
General pathologic features of acute viral encephalitis
perivascular lymphocytic infiltrate, microglial nodules (gray or white matter + rod cells, macrophages, lymphocytes), neuronophagia, intranuclear cytoplasmic inclusions, gliosis
Bilateral, asymmetrical, hemorrhagic necrosis of temporal lobes is classical in _____ encephalitis.
HSV (but diff dx includes infarction and contusion) –> temporal involvement = seizure
_____ is the most common cause of acute necrotizing encephalitis in immunocompetent individuals.
HSV1 (sometimes CMV or VZV)
The initial HSV1 infection involves the _____
oropharyngeal mucosa
The putative routes of HSV1 CNS infection are
Centripetal spread of virus along olfactory nerve fibers and tracts, and reactivation of latent virus in the trigeminal ganglia
_____ virus replicates within skeletal muscle at the site of inoculation before being taken up by axons and transported centripetally to the CNS.
Rabies
Negri bodies are the hallmark of _____
rabies —>sharply delineated round to oval eosinophilic inclusions in neuronal cytoplasm
3 sites for negri bodies
Purkinje cells, hyppocampal pyramidal neurons, cortical neurons and brain stem nuclei
Which polio vaccine can revert to wildtype through back mutation?
live attenuated oral vaccine can revert and cause paralytic disease
Features of acute poliomyelitis
intense chronic perivascular inflammation of parenchyma and meninges, microglial nodules and neuronophagia, blood vessel congestion and possible hemorrhage
Diffuse encephalitis with space occupying lesions, septic infarcts, leptomeningitis, and hemorrhage are associated with _____
fungal infection
____ fungus often affects ACA, MCA territories causing early hemorrhagic infarcts and late abscesses
aspergillosis –> feature of chronic infection (from direct spread vs. hematogenous)
Grocott silver stain demonstrates thin filamentous fungal forms with branching in _____
aspergillosis
_____ usually starts with nasal or unilateral facial swelling and hyperemia.
Rhinocerebral mucormycosis with focal ulceration and necrosis of skin/mucosa –> The infection extends rapidly into the orbit, producing unilateral ophthalmoplegia, proptosis, edema of the lids, corneal edema, and blindness in some cases
2 classical presentations of mucormycosis
diabetic ketoacidosis, rhinocerebral disease
Hyphae are nonseptate in _____
mucor
Hyphae are wider in aspergillus/mucor
mucor
_____, has been isolated from fresh water, soil, sewage, heating, ventilation and air conditioning units, dental units, gastrointestinal washings, and dust and is a cause of meningoencephalitis.
Naegleria fowleri –> infection from swimming in fresh water at high temperature –> nasal cavity–> CNS
Which organism causes Fulminant, acute meningoencephalitis with cerebral swelling and hemorrhagic necrosis frontal lobes and olfactory bulbs ?
Naegleria fowleri
Most common helminthic CNS disease
cysticercosis
Cysticercosis is caused by _______
Taenia solium
______ cause of CNS infection is associated with epilepsy.
cysticercosis
Clinical features of cysticercosis
Manifestations can include focal and generalized seizures, papilledema, headache, vomiting and ataxia (which may be intermittent), vertigo produced by abrupt movements of the head, focal motor and sensory deficits, dementia, acute hydrocephalus due to obstruction of the ventricular system, and occasionally, sudden death.
T/F cysts formed in cysticercosis result in robust inflammatory responses.
F –> almost non response –> Shortly after the cysticerci die, the cysts are surrounded by neutrophils, lymphocytes, macrophages, foreign body giant cells, and eosinophils and then enclosed by a zone of granulation tissue, which eventually produces a dense collagenous capsule and eventually some of the cysts become calcified.
Most common cause of fungal meningitis
Cryptococcus neoformans
T/F Cryptococcomas (Cryptococcal abscesses) are much less common than cryptococcal meningitis and usually occur in patients who are not immunocompromised.
T
T/F in cryptococcus is usually pulmonary with subsequent hematogenous spread to the CNS.
T –> The pulmonary lesions have often resolved before the neurologic disease manifests.
Which organism is visible in India Ink?
Cryptococcus
Collections of _______ produce gelatinous pseudocystic dilations of Virchow – Robin spaces (“bubbles”) with little surrounding inflammation or gliosis
Cryptococcus
_______ is an opportunistic infection common in the setting of HIV caused by the protozoan, an obligate intracellular parasite with a propensity to infect the nervous system. The definitive hosts for this parasite are domestic cats and other feline species.
Toxoplasmosis
T/F In toxoplasmosis, symptomatic neurologic disease is unless associated with depression of cell-mediated immunity, particularly in AIDS, and is probably due to reactivation of dormant infection.
T
Which organism? Most common pattern is brain abscesses, presenting as multiple ring-enhancing lesions
Toxoplasma gondii
Which organism? Free tachyzoites and encysted bradyzoites may be found at the periphery of centrally necrotic lesions.
Toxoplasma gondii
3 areas affected by HIV encephalitis
Involves subcortical white matter, basal ganglia and brainstem
Which condition? Widespread low-grade inflammation with perivascular and parenchymal lymphocytes and microglial nodules, multinucleated giant cells, and leukoencephalopathy
HIV encephalitis
T/F In the CNS, HIV infects mainly microglial cells or macrophages.
T
Which organism has a tropism for oligodendroglia?
JC virus/polyoma
Which organism? Ill-defined demyelinating lesions, lipid-laden macrophages, intranuclear viral inclusions, bizarre atypic astrocytes.
JC virus/polyoma
glass nuclei are associated with _____
JC virus/polyoma