Term
| which ways does infection reach the CNS? |
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Definition
| hematogenous (common), direct extension (sinus/ear infection), penetrating trauma, ascending neural route (rabies), and opportunistic infections (AIDS/transplant pts). |
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Term
| how do meningitis pts present? dx? |
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Definition
| nuchal rigidity (neck hard to bend), fever (higher w/bacterial), photophobia, mental status changes/irritability/somnolence, and general malaise. *to dx: palpate back of neck, see if pt can raise leg up, and f/u w/spinal tap. initiate broad spectrum antibx until cx comes back. |
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Term
| what are the propensity for specific bacterial meningitis among age groups? |
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Definition
| *neonates: e. coli, group B strep. *young adults: neisseria meningitidis. *elderly: strep pneumonia, listeria monocytogenes. *immunocompromised: klebsiella. |
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Term
| what characterizes the CSF of a pt w/bacterial meningitis? |
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Definition
| increased *neutrophils, increased protein, decreased glucose, and possible visible bacterial cells (positive cx). |
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Term
| what is waterhouse fridericksen? (*know this*) |
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Definition
| a potentially life threatening syndrome associated w/meningococcal and pneumococcal infections: septicemia, meningitis, petechiae, and *adrenal hemorrhage. |
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Term
| what is the morphology of bacterial meningitis? |
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Definition
| greenish/yellow purulent exudate on the leptomeninges over the brain surface, neutrophils in the subarachnoid space, and potentially extension into the brain causing hydrocephalus. *H. influenza: basal distribution of pus. *pneumococcal: pus in cerebral convexities and chronic adhesive arachnoiditis (due to capsular polysaccharide seen in pneumococcal meningitis). |
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Term
| how does the arachnoid appear in acute meningitis? |
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Definition
| grossly: cloudy (should be clear) w/whitish-green discharge in the sulci. microscopically: neutrophil infiltrate. |
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Term
| what characterizes acute aseptic meningitis? |
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Definition
| usually viral in origin, less severe clinically, usually self-limiting, often an enterovirus, can be induced by some drugs (NSAIDs, antibx), and the CSF generally contains *lymphocytes/moderate protein increase/normal glucose. |
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Term
| what is a subdural empyema? |
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Definition
| a localized accumulation of pus/infection due to bacterial or fungal origin. it may cause a mass effect (ICP/herniation) and/or *thrombophlebitis (inflammation of bridging veins = venous occlusion/infarction). |
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Term
| what characterizes dz due to arthropod-borne viral encephalitis (arbovirus)? CSF? |
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Definition
| local manifestation: west nile virus which is transmitted via mosquitoes/ticks. CSF: slight increase in pressure, *initially neutrophils, then lymphocytes, increased protein, and normal glucose. generalized neurologic defects: seizures, confusion, delirium, stupor, and coma. |
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Term
| what characterizes poliomyelitis? gross/histologic presentation? |
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Definition
| due to a type of enterovirus, this can lead *grossly to to flaccid paralysis/muscle weakness, CN involvement, and acutely: paralysis of respiratory muscles. *histologically: mononuclear cell perivascular cuffs, neurophagia of the anterior horn motor neurons. |
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Term
| what characterizes rabies? |
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Definition
| severe encephalitis due to wild animal bites. leads to cerebral edema, vascular congestion, and inflammation of the midbrain/floor of 4th ventricle grossly. histologically: **negri bodies are seen which are cytoplasmic round to oval eosinophilic inclusions in the hippocampus and purkinje cells of the cerebellum. the virus enters the CNS along the peripheral nerves from the wound site = malaise, fever, h/a, local paresthesias around the wound site, photophobia, CNS excitability (slightest touch is painful), contraction of the pharyngeal muscles makes swallowing difficult and causes foaming from mouth + hydrophobia, also periods of mania/stupor progress to coma and death from respiratory failure. |
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Term
| what characterizes incidence of brain abscesses? |
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Definition
| 20% are unassociated w/conditions predisposing to bacterial CNS invasion and the remainder occur in pts w/pyogenic infections at extra neural sites, anatomic anomalies, penetrating trauma or neurosurgery. sources include paranasal cavities and mastoids arising from retrograde movement of bacteria through veins - usually solitary, and *only 40-50% are febrile on presentation. |
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Term
| what are the common pairings of infection site+brain location? |
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Definition
| frontoethmoid sinusitis = abscess in anterobasal frontal lobes. otitic infections = temporal lobes/cerebellar hemispheres. sphenoid sinuses = frontal/temporal regions. mixed infections are common and often involve: streptococcus intermedius bacteroides, proteus, e. coli, and klebsiella |
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Term
| what is the association between brain abscesses and dental or facial/scalp infections? |
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Definition
| odontogenetic abscesses follow tooth extraction or other dental manipulations and often consist of fusobacterium, bacteroides, and streptococcus. facial/scalp infections: staph aureus, often complicated by cavernous sinus thrombosis. mandibulofacial actinomycosis may lead to brain abscesses. |
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Term
| what characterizes CNS abscesses from distant foci? |
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Definition
| usually this results in a multiplicity of abscesses, often near the MCA. most germinate between cortical mantle and underlying white matter and have their origin in the thorax (lung abscesses and bronchiectasis [necrotizing infection destroying the parenchyma around the bronchi]). less common: endocarditis, osteomyelitis, and infections of the deep pelvic organs/abdominal viscera. cyanotic congenital heart disease w/R->L shunts cause 2/2 polycythemia, resulting in microcirculatory sludging/regional brain hypoxia - predisposing the brain to abscess formation (osler weber rendu disease also contributes to abscesses in a similar way). instrumentation in the esophagus can also lead to iatrogenic abscess formation. |
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Term
| what pathogens are involved w/brain abscesses starting in the lungs? |
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Definition
| actinomyces, nocardia, fusobacterium, bacteroides, and streptococci |
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Term
| what pathogens are involved w/brain abscesses starting in the heart? |
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Definition
| streptococci, haemophilus (congenital heart) and s. aureus (bacterial endocarditis) |
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Term
| what pathogens are involved w/brain abscesses due to penetrating cranial trauma? |
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Definition
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Term
| what characterizes the diagnosis of brain abscesses? |
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Definition
| they are a diagnostic challenge b/c the appearance is nonspecific and the s/s are more commonly consistent w/an expanding cranial mass: h/a, mental status change, seizure, focal neurologic deficit, paresthesia, seizures, n/v, and possible death. on CT/MRI: **hypodensity w/ring enhancement, but this finding is similar to neoplasms or some demyelinating diseases. intraventricular discharge of purulent matter is one of the worst complications (b/c of access to CSF). |
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Term
| what is the morphologic progression of a brain abscess? |
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Definition
| a brain abscess begins as an ill defined zone of bacterial multiplication/PMN infiltration situated in white matter at the junction w/the subcortical ribbon. over time fibroblasts surround a central mass of fibrinopurulent debris (liquefactive necrosis - particularly if fungal). eventually a collagenous capsule forms which is surrounded by edematous chronically inflamed gliotic brain tissue. the rate at which this capsule forms varies, but if the abscess is due to hematogenous seeding of the brain from distant sites = less well formed lesions. nocardia also forms poor lesions. capsular organization is most advanced along the superficial juxtacortical perimeter and less likely to form near ventricles due to less extensive vasculature (intraventricular purulent material often results in fatal complications). |
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Term
| what are epidural abscesses? |
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Definition
| abscesses forming above the dura (not in the brain). more common in the thorax, followed by the lumbar region. 30-40% arise spontaneously and the remainder are due to 2/2 infections at distant sites, spinal trauma, or trauma. predisposing infections: vertebral osteomyelitis, psoas and perinephric abscesses, and **decubitus ulcers. |
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Term
| what are risk factors for epidural abscess? |
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Definition
| renal failure/abscess, alcoholism, DM |
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Term
| what are the clinical symptoms of epidural abscesses? |
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Definition
| h/a, fever, malaise - may progress to radiculopathy, sensorimotor, sphincter disturbances and paralysis (more peripheral signs than if in brain). |
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Term
| what is the most common pathogen which causes epidural abscesses? |
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Definition
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Term
| what characterizes mycobacterium TB in the CNS? |
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Definition
| this is more common in IVDA/immunocompromised pts. these often arise from extension of TB (low thoracic/lumbar - pott's disease) vertebral osteomyelitis or disk infection and produce caseating granulomas + tuberculomas (encapsulated granulomas w/central caseating mass) intracranially. |
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Term
| what does listeria monocytogenes cause in the CNS? |
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Definition
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Term
| what does tropheryma whippelii cause in the CNS? |
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Definition
| cerebral whipple's disease - which consists of *foamy macrophages w/granular cytoplasm w/*rod shaped baccilli and *reactive astrogliosis. |
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Term
| what kind of CNS infection bartonella henselae does cause? |
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Definition
| a space occupying inflammatory lesion associated w/immunodeficiency |
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Term
| what characterizes mycoses in the CNS? |
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Definition
| cryptococcus neoformans and candida spp are common and cause intracranial/intraspinal lesions often associated w/diffuse meningeal or systemic infection. cases of this have risen dramatically. |
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Term
| what is the most common CNS mycoses? |
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Definition
| cryptococcus neoformans, which presents as a choroid plexus based mass, often consisting of gelatinous material due to capsular mucopolysaccharides (can cause CSF flow problems). |
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Term
| what are the mold CNS pathogens? |
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Definition
| aspergillus and mucoraceae, which are fungi existing in pure hyphal form at both room temp and 37 degrees C. these opportunistic infections rarely infect otherwise healthy pts, instead alcoholic, IVDA, and pts on corticosteroids are susceptible. usually these infections are intraparenchymal (vs meningeal). orbital or paranasal sinus infections spreading to the meninges is a common route of transmission. molds may occlude, invade, and trigger thrombosis - leading to multifocal strokes. fungi can migrate through damaged blood vessels and lesions are usually seen in the cerebral hemispheres, cerebellum and brainstem. |
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Term
| what characterizes candida infection of the CNS? |
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Definition
| this is one of the most common CNS mycoses in immunocompromised pts. many are found at autopsy, resulting from fungemia. often suppurative lesions and macroabscesses are formed which may only involve the meninges. |
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Term
| what generally characterizes parasitosis of the CNS? which is the most common? |
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Definition
| this includes protozoal and helminthic infections. *neurocysticercosis is the most common parasitic cerebral infection, caused by the larvae of the pork tapeworm. |
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Term
| how is parasitosis of the CNS usually acquired? |
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Definition
| ingestion of food or water contaminated by feces containing the cestodes ova. seizures are common b/c the infection involves the cerebral cortex as well as hydrocephalus/ICP due to involvement of the ventricular system. appearance of cysticerci is almost pathognomonic: small diameter, fibrous pseudocapsule, single larval scolex |
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Term
| what is toxoplasmosis? (*know this*) |
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Definition
| toxoplasma gondii, an *intracellular protozoan can infect the CNS (favors neuron rich areas such as the cerebral cortex, basal ganglia, and brainstem). toxoplasmosis is often seen as a space occupying lesion in AIDs pts. some present w/seizures, hemiparesis, cranial nerve defects - but some pts present only with h/a, fever, and lethargy. growth takes months. |
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Term
| how does toxoplasmosis appear morphologically? |
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Definition
| grossly: central necrotic mass surrounded by edema and inflammation. histologically: perivascular, intramural lymphoid infiltrates, endothelial swelling, thrombosis, fibrinoid necrosis, and fibrous obliteration. |
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Term
| what are the 2 forms of toxoplasma gondii? |
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Definition
| tachyzoite: causes tissue injury. bradyzoite: fills cysts/pseudocysts which collect around neurons and perivascular macrophages. |
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Term
| what are the CNS-infecting spirochetes? |
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Definition
| treponema pallidum: neurosyphilis, borrelia burgdorferi: lyme disease, and gummas: necrosis/fibrosis seen in syphilis. |
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Term
| what does herpes simplex encephalitis cause? |
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Definition
| focal, necrotizing **hemorrhagic encephalitis** featuring fever, disordered affect, seizures, and deterioration of consciousness. often localized to one or both frontotemporal regions (insulae+cingulate gyrus). CSF will have HSV specific antigens. |
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Term
| what is the microscopic manifestation of HSV encephalitis? |
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Definition
| neuronal shrinkage, eosinophilia, vascular congestion, pallor, eosinophilic intranuclear inclusion bodies, *lymphocytes/plasma cells (which colonize the meninges, cuff blood vessels, and migrate to the cortex), and monocytes which converge on infected neurons to form *neuronophagic nodules. |
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Term
| what is progressive multifocal leukoencephalopathy (PML)? |
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Definition
| an opportunistic demyelinating disease of the CNS caused by some DNA viruses such as JC and HIV-1 - almost always associated w/defective cell mediated immunity. |
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Term
| what is the clinical presentation of PML? |
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Definition
| motor deficits, cognitive decline, visual loss |
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Term
| what is the clinical morphology of PML? |
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Definition
| PML usually occurs in the cerebral hemispheric white matter, involving oligodendrolions, causing enlargement of the nuclei, dissolution of the chromatin and replacement by basophilic "ground glass" material. an expanding zone of oligodendroglial loss and infiltration of macrophages ingesting myelin develops. this appears as yellowish gray discoloration of white matter, which may progress to cavitation. florid astrogliosis (scarring) w/bizarre nuclei is seen histologically. |
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Term
| what characterizes invasion of the brain by VZV? |
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Definition
| similar to PML, seen in immunocompromised pts - affecting cerebral hemispheric white matter via multifocal expanding lesions w/demyelination and variable axonal loss. there may be small infarcts from vascular involvement. the astrocytes have *cowdry A type intranuclear inclusions, the oligodendrocytes have a ground glass appearance, but cells do not enlarge (vs PML). VZV may cause cerebral vasculitis, leading to stroke and aneurysm. |
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Term
| what characterizes HIV encephalitis? |
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Definition
| HIV replicates in (mononucleated/multinucleated) macrophages and microglia which harbor and release virions. this appears as vasocentric inflammatory infiltrate in cerebral hemispheric white matter, basal ganglia, and rostral brainstem. HIV encephalitis thus appears as diffuse astrogliosis/microglial activation w/pallor of the cerebral white matter and atrophy of the brain. |
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