Mid Rabies/viral Encephalitis

Front 1

Explain olfactory spread

Back 1

-Herpes virus and coronovirus can enter the CNS through the olfactory nerves

Front 2

Explain the spectrum of neurovirulence

Back 2

-Goes from mild and asymptomatic with no changes in cellular morpholgy to subtle alterations or frank apoptosis and necrosis.

-Direct infection of oligodendroglial cells can occur. Progressive multifocal leukoencephalopathy caused by the JC virus is an example of this.

Front 3

Explain the immunopathology of viral encephalitis

Back 3

-There may be effects of the virus on immunology that result in damage to the white matter later on.

-Measles, influenza A, and varicella are all examples of this. Acute disseminated encephalomyelitis is not damage directly caused by the virus, but weeks and months later there can be demyelination and damage.

Front 4

Explain the dual effect of viral inflammation

Back 4

-Immune activation plays a protective and a pathologic role

-Perivascular inflammation, microglial activation that comes with infected neurons. They release cytokines that inhibit the virus but also result in neurodysfunction and injury at the same time.

Front 5

What is the epidemiology of viral encephalitis?

Back 5

-20k cases annually in the US
-10k deaths due to Japanese encephalitis worldwide
-60k deaths due to rabies
-Geographic and temporal niches
-The iceberg phenomenon is that the milder cases wont be picked up but the more severe cases will.
-Extremes of age and immunocompromised are at higher risk
-Epidemiology is significantly altered by routine vaccinations.

Front 6

What should be asked about in the history of a patient with possible viral encephilitis? What may be on the physical exam?

Back 6

History:
-Animal bites
-Recent travel
-Sexual exposures
-Immunizations

Physical Exam:
-Evaluate for meningitis
-Identify rashes, bites, lymph nodes
-Good neuro exam

Front 7

Describe what is needed for the diagnosis of viral encephalitis

Back 7

-History and physical
-CSF profile(helps distinguish the most treatable, serious entities, including bacterial meningitis)
-Mild-moderate lymph pleocytosis, normal or slightly elevated protein, normal glucose
-Rule out other causes
-Viral cultures, detection of viral nucleic acid, serology of CSF and serum
-MRI
-EEG

Front 8

Describe treatment of viral encephalitis

Back 8

Treatment is supportive except with HSV, then treat with acyclovir

Front 9

Describe the CSF findings in bacterial meningitis, viral meningitis/encephalitis, and TB/fungal meningitis

Back 9

Bacterial meningitis has elevated CSF pressure, extremely elevated white count full of PMNs, low glucose and high protein

Viral men/enceph has slightly elevated white count with lymphs, normal glucose and pressure, and slightly elevated protein

TB and fungal have slightly elevated pressure, white count and protein. They have lower glucose

Front 10

What is the major treatable viral encephalitis?

Back 10

HSV encephalitis

Front 11

What does neuroinvasive mean?

Back 11

The virus has the ability to enter the CNS

Front 12

What does neurovirulence mean?

Back 12

The virus has the ability to cause damage if it enters the CNS

Front 13

What does the neuroinvasiveness and neurovirulence of a virus depend on?

Back 13

Viral factors
-Inherent neuroinvasiness and neurovirulence
-Site of entry
-Size of inoculum

Host factors:
-Age
-Sex
-Immune status
-Genetic factors

Front 14

Comment on the neuroinvasiveness and neurovirulence of rabies, herpes, and mumps

Back 14

Rabies has high neuroinvasiveness and high neurovirulence

Herpes has low neuroinvasiveness but high neurovirulence

Mumps has high neuroinvasiveness, but low neurovirulence

Front 15

What are the two ways in which viruses can enter the CNS?

Back 15

-Hematogenous dissemination
-Neural dissemination

Front 16

How does hematogenous spread of viruses occur?

Back 16

It occurs despite the BBB with tight junctions
-Viruses can go through the choroid plexus
-Viruses can enter through direct infection of the cerebral capillaries
-Viruses can enter through diapedesis

Front 17

How does neural spread of viruses occur?

Back 17

-Occurs through retrograde transport

Front 18

Explain the spread of rabies virus

Back 18

-Rabies virus enters at the site of the bite
-Local replication occurs
-Enters the NMJ
-Retrograde transport to the dorsal root ganglion
-Replication in the dorsal root ganglion
-Ascends rapidly in the spinal cord
-Ends up in brain

Front 19

Explain the spread of herpes virus in the CNS

Back 19

-Retrograde transport to the dorsal root ganglion
-Gains latency
-Can undergo anterograde transport resulting in skin vesicles
-Can undergo retrograde transport resulting in encephalitis

Front 20

Explain the spread of poliomyelitis

Back 20

-Enters in the gut
-Replicates there
-May gains access to the CNS via the vagus nerve through retrograde axonal transport

Front 21

Describe the symptoms of viral Meningitis

Back 21

-Fever
-Headache
-Malaise
-Stiff neck
-Photophobia

Front 22

Describe the symptoms of viral encephalitis

Back 22

-Fever
-Headache
-Altered mental status
-Decreased consciousness
-Focal neurological findings such as confusion, cognitive impairment, personality changes, seizures, weakness and movement disorders

Focal neuro finding + Fever + Headache = think Encephalitis

Front 23

What is meningitis?

Back 23

An infection or inflammation of the meninges

Front 24

What is encephalitis?

Back 24

A direct infection of the brain parenchyma

Front 25

What is aseptic meningitis?

Back 25

Meningitis not caused by a bacteria, fungus, or parasite. The most common cause is viral meningitis.

Front 26

What is meningoencephalitis?

Back 26

A combination of meningitis and encephalitis

Front 27

What is myelitis?

Back 27

Direct infection of the spinal cord

Front 28

What viruses can cause viral meningitis?

Back 28

Enteroviruses
Herpes viruses
Arboviruses
Acute HIV

Front 29

What viruses can cause viral encephalitis?

Back 29

Herpes viruses
Arboviruses
Enteroviruses

Front 30

What does neurotrophic mean?

Back 30

That it can infect neurons

Front 31

What is the most common cause in the US of sporadic, fatal encephalitis?

Back 31

HSV encephalitis

Front 32

Describe HSV encephalitis

Back 32

-Major treatable viral encephalitis
-Most common cause in the US of sporadic, fatal encephalitis
-Usually HSV1
-Occurs year-round, kids and adults
-In kids it tends to be primary infection, in adults reactivation
-Retrograde transport to the CNS via olfactory or trigeminal nerves
-Necrotizing encephalitis and hemorrhagic necrosis, particularly in temporal lobe