Infection-VIRAL MENINGOENCEPHALITIS Flashcards
VIRAL MENINGOENCEPHALITIS
- Arthropod-Borne Viral Encephalitis
- Herpes Simplex Virus Type 1
- Herpes Simplex Virus Type 2
- Varicella-Zoster Virus (Herpes Zoster)
- Cytomegalovirus
- Poliomyelitis
- Rabies
- Human Immunodeficiency Virus
- Progressive Multifocal Leukoencephalopathy
- Subacute Sclerosing Panencephalitis
What is Viral encephalitis?
It is a parenchymal infection of the brain almost invariably associated with
meningeal inflammation (meningoencephalitis) and sometimes with simultaneous involvement of
the spinal cord (encephalomyelitis).
Some viruses tend to infect the nervous system.
Such neural tropism takes several forms:
- some viruses infect specific cell types (such as oligodendrocytes),
- while others** preferentially involve particular areas** of the brain (such as** medial temporal lobes** or the** limbic system).**
What __________y is an
important facet of several viral infections of the CNS (e.g., herpes zoster, progressive multifocal
leukoencephalopathy).
Latency
What viruses exhibit latency?
Systemic viral infections in the absence of direct evidence of viral penetration into the CNS may be followed by an __________ (see “Acute Disseminated Encephalomyelitis and _______________.
immune-mediated disease, such as perivenous
demyelination
and Acute Necrotizing Hemorrhagic
Encephalomyelitis”)
Intrauterine viral infection may cause congenital malformations, as occurs
with__________.
rubella
A slowly progressive degenerative disease syndrome may follow many years after
a viral illness; an example is____________ after the 1918 viral influenza pandemic.
** post-encephalitic parkinsonism**
____________ are an important cause of epidemic encephalitis, especially in tropical regions of
the world,and they arecapable of causing serious morbidity and high mortality.
Arboviruses
In the Western
hemispherethe most important types are :
- Eastern and Western equine,
- West Nile,
- Venezuelan,
- St. Louis, and La Crosse;
- elsewhere in the world, pathogenic arboviruses include Japanese B (Far East),
- Murray Valley (Australia and New Guinea),
- and tick-borne (Russia and Eastern Europe).
All have animal hosts and mosquito vectors, except for the ________________
tick-borne type
What is the clinical manifestation of viral neurological diseases?
- affected individuals develop generalized neurologic deficits, such as:
- seizures,
- confusion,
- delirium,
- and stupor or coma
- , and often focal signs,
- such as reflex asymmetry and
- ocular palsies.
Involvement of the spinal cord in ____________ can lead to a polio-like syndrome with paralysis.
West Nile encephalitis
What is the appearance of arthropod-borne Viral Encephalitis?
The CSF is usually :
- colorless
- but with a slightly elevated pressure and,
- initially, a neutrophilic pleocytosis that rapidly converts to lymphocytes;
- the protein concentration is elevated,
- but glucose content is normal.
The encephalitides caused by various arboviruses differ in ____________but the histopathologic picture is similar, except for variations in the severity and
extent of the lesions within the CNS.
epidemiology and
prognosis,
What is the characteristic of encephalitis caused by arbovirus? ,
- there is a lymphocytic meningoencephalitis (sometimes with neutrophils),
- and a tendency for inflammatory cells to
- accumulate perivascularly ( Fig. 28-23A ).
- Multiple foci of necrosis of gray and white matter
- are found;
- in particular, there is evidence of single-cell neuronal necrosis with phagocytosis of
- the debris (neuronophagia).
- **Microglial cells form small aggregates around foci of necrosis, **called microglial nodules ( Fig. 28-23B ).
In severe cases in encephalitis caused by arbovirus there may be a ________________
- necrotizing vasculitis with associated focal hemorrhages.
- While some viruses reveal their presence by inclusion bodies
the identification of viral pathogens is most often by a combination of
- ultrastructural,
- immunohistochemical,
- and molecular methods.
______________) encephalitis is most common in children and young adults.
Herpes simplex virus type 1 (HSV-1
Only about ____________ of the affected individuals have a history of prior herpes.
10%
The most commonly
observed clinical presenting symptoms in herpes encephalitis are___________
- alterations in mood,
- memory,
- and behavior.
_____________ for virus detection in CSF
samples have increased the ease of diagnosis and the recognition of a subset of patients with
less severe disease.
Polymerase chain reaction (PCR)–based methods
Antiviral agents now provide effective treatment in many cases, with a
significant reduction in the mortality rate.
In some individuals, HSV-1 encephalitis follows a
_______________
subacute course with clinical manifestations (weakness, lethargy, ataxia, seizures) that evolve
during a more protracted period (4 to 6 weeks).
What is the characteristic of HSV encephalitis?
This encephalitis starts in, and most severely involves, the inferior and medial
regions of the temporal lobesand theorbital gyri of the frontal lobes ( Fig. 28-24 ).
The
infection is necrotizing and often hemorrhagic in the most severely affected regions.
What is the inclusion body seen in HSV-1?
Perivascular inflammatory infiltrates are usually present, and Cowdry type A intranuclear viral
inclusion bodies may be found in both neurons and glia.
In individuals with slowly evolving
HSV-1 encephalitis, there is more diffuse involvement of the brain.
____________also infects the nervous system;
in adults it causes
meningitis,but asmany as 50% of neonates born by vaginal delivery to women with active
primary HSV genital infections acquire the infection during passage through the birth canal and
develop severe encephalitis.
Herpes simplex virus type 2 (HSV-2)
In the face of active HIV infection, HSV-2 may cause an____________-
- acute,
- hemorrhagic,
- necrotizing encephalitis
Primary varicella infection presents as one of the childhood _____________, ordinarily
without any evidence of neurologic involvement.
exanthems (chickenpox)
What is the pathophysio of Varicella Zoster Virus?
Following the cutaneous infection, the virus
enters a latent phase within** sensory neurons of the dorsal root or trigeminal ganglia.**
Reactivation of infection in adults (“shingles”) usually manifests as a painful, vesicular skin
eruption in a single or limited dermatomal distribution.
Herpes zoster reactivation is usually a** self-limited process,** but there may be a persistent postherpetic neuralgia syndrome particularly
after age 60, including both persistent pain as well as painful sensation following nonpainful
stimuli.
Overt CNS involvement with herpes zoster is much rarer but can be severe.
Herpes zoster has
been associated with a g___________; immunocytochemical and electron microscopic
evidence of viral involvement has been obtained in a few of these cases.
ranulomatous arteritis
In immunosuppressed
individuals, herpes zoster may cause acute encephalitis with ____________
numerous sharply circumscribed
lesions characterized by demyelination followed by necrosis.
CMV infection of the nervous system occurs in____________individuals.
fetuses and immunosuppressed individuals
What is the
outcome of CMV infection in utero is ____________
- *periventricular necrosis** that produces severe brain destruction
- *followed later by microcephaly** and **periventricular calcification. **
The diagnostic histologic finding in Rabies is the eosinophilic Negri body, as
seen here in a Purkinje cell
HIV encephalitis. Note the microglial nodule and multinucleated giant cells.
Progressive multifocal leukoencephalopathy.
Section stained for myelin
showing irregular, poorly defined areas of demyelination, which become confluent in
places.
Inset, Enlarged oligodendrocyte nucleus represents the effect of viral infection.
