Viral CNS infxn Flashcards
Viral Meningitis
Usually mild and self-resolving
Bacterial Meningitis
Life threatening
Predictors of bacterial etiology regarding meningitis?
- Low CSF glucose
- High CSF protein
- High CSF white count
- High CSF neutrophil count
The presence of any one of these predicts bacterial etiology with 99% certainty
Viral meningitis appearance
- Pts don’t appear extremely ill, are NOT ENCEPHALOPATHIC
- fever and malaise
- headache
- neck stiffness
- low back pain
Usually lasts 10-14 days
Recurrent viral meningitis can result from persistent or latent infections (HSV)
Most common cause of Viral Meningitis?
Enteroviruses….80%
What are some of the enteroviruses that cause viral meningitis?
echo, coxsackie, enterovirus 71
10% of viral meningitis caused by
Mumps
How are enteroviruses spread
oral/fecal route
HSV-2 generally causes
genital herpes
Can also be a cause of RECURRENT aseptic meningitis
Mollerat cells in the CSF?
HSV-2
HIV and VZV cause?
recurrent meningitis
30% of viral encephalitis caused by
Arboviruses (arthropod born viruses) such as St. Louis, West Nile, La Crosse
Transmitted by mosquitos and ticks
Predominantly affects the children or the elderly
25% of viral encephalitis caused by
Enteroviruses (echo, coxsackie, entero 71)
25% of viral encephalitis caused by
Herpes Simplex 1
What is important to recognize about HSV-1
It is a deadly cause of encephalitis if not treated promptly with acyclovir
Clinical course of viral encephalitis
fever headache lethargy URI Confusion then.... seizures, coma, death in some cases
If you see Fever, headache, lethargy and a prodromal URTI…think encephalitis
- Looks exactly like bacterial meningitis so you MUST treat it empirically before you really even know what the diagnosis is
What is the prognosis associated with mosquito born viruses?
poor
What is the characteristic site of damage in HSV encephalitis?
Temporal lobe….MRI shows necrosis in temporal lobe
Diagnosis of HSV1?
PCR is definitive but false negatives occur
Mortality without tx for HSV1
70%
Flaviviruses
St. Louis and West Nile
Flavivirus morphology
Small, enveloped, +RNA viruses
Flavivirus replication cycle
1) Enters by receptor mediated endocytosis
2) + strand genome is translated into single polyprotein, that polyprotein is cleaved.
3) virions bud into intracellular organelles and are transported via the eocytotic pathway and released
All members of the flavivirus genus are transmitted how>
through insect vectors….They are the most important group of arboviruses
Flaviviruses that cause disease in the US
- St. Louis, West Nile, Dengue fever, Yellow Fever
SWDY
Disease course of flavivirus
Virus replicates at the site of inoculation.
Initial infection = primary viremia (mild fever, chills, aches)
Usually cleared by reticuloendothelial system (spleen, liver, etc..)
Continued replication can give rise to a secondary viremia which can invade CNS. Generally would only occur in children, elderly, or immunocompromised
SLE ( St. Louis Encephalitis) syndromes and symptoms slide
SLE found in north, central, and south america
- Onset characterized by flu-like symtpms, most do not progress. If secondary viremia occurs, it can lead to acute or subacute neurological signs and symptoms associated with CNS disease.
Primary host for west nile
birds
Vector for west nile
mosquitos
West nile disease symptoms and treatments
- Febrile, influenza like illness with abrupt onset
- moderate to high fever
- headache, sore throat, backache, myalgia, arthralgia, fatigue
- Rash, lymphadenopathy
- Acute aseptic meningitis or encephalitis
- most fatal cases occur in the elderly
Most significant cause of arbovirus encephalitis worldwide?
Japanese Encephalitis Virus
Vaccine available for JEV?
yes….people who are going to spend at least a month in a rural area should be vaccinated
Togaviridae includes what viruses
Rubella and Alphaviruses
Togaviridae morphology
small, enveloped, nonsegmented, positive stranded RNA virus…..like flavi
One genera of togaviridae is alphavirus which incldes
western, eastern, and venezuelan equine encephalitis
All transmitted by mosquitoes
Alphavirus symptoms
- ranges from asymptomatic to terrible
- Encephalitis generally seen in young and old
- Adults get mild disease with fever and drowsiness
ALphavirus vaccine?
reserved for lab workers and military.
Vaccines for horses used extensively
Bunyavirus morphology
enveloped, single stranded negative sense RNA
Two kinds of bunyavirus we need to know
california encephalitis virus
La Crosse virus
MOst common cause of arboviral induced pediatric encephalitis in US
LaCrosse
Pretty low mortality rate though
Rabies Virus (Rhabdoviridae) morphology
enveloped, nonsegmented, - RNA
Bullet shaped morphology
Rhabdoviruses have a single membrane glycoprotein called G which is both the attachment protein and the fusion orotein
ok…Low pH induces membrane fusion
DO NOT INDUCE SYNCYTIA
Rabies the disease
Slow progressive disease that characteristically involves the CNS. Why? Because the rabiesvirus glycoprotein has a neurotropism
- Rabies initially replicates only in the neuronal cells but then disseminates to other organs
- found in high concentrations in the salivary glands during the final stages of the disease
incubation period of rabies
anywhere from 1 week to 2 months depending on bite site (how close it is to the CNS)
Rabies replicates in muscles and then travels through nervous system to brain
3 phases of rabies disease development
1) prodromal period: 2-10 days following exposure includes malaise fever and headache
2) Acute neurologic phase: can occur months to years after initial exposure, nervous system dysfunction,
Know LCMV
Enveloped, segmented, ambisense RNA viruses. Virions contain two RNA segments
- Enter by pH dependent pathways
Transmission occurs by inhalation of aerosolized rodent excreta and saliva.
The disease is characterized by two phases. The initial phase shows a prodrome of fever, headache, nausea, and vomitting
Aseptic meningitis appears two days later. ….rarely fatal
Epidural abscess signs and symptoms
- Point tenderness
- Elevated ESR which is a non-specific index of an inflammatory process.
- Elevated white count
Tumor destroys bone but spares disc,
infection involves the disc but spares the bone
A key feature of the back pain associated with spinal epidural abscess?
Worsening pain on recumbency, because the venous plexus that drains teh lower thoracic and lumbar vertebrae has no valves when you are lying down
Bowel and bladder dysfunction mean?
There is a 24-48 hour window in which treatment can save the spinal cord
Failing to recognize spinal epidural abscess is one of the top 10 reasons that doctors are sued for malpractive
so is bacterial meningitis and subarachnoid hemorrhage
Most common pathogen for spinal epidural abscess
Staph
Rocky Mountain Spotted Fever causative organism
Rickettsia
Describe Rickettsia
Gram negative intracellular anaerobe
- attack vascular endothelial cells
- cause systemic vasculitis
- transmitted by ticks
RMSF signs and symptoms
Fever, headache, flu-like symptoms 3-14 days after a tick bite
Early petechial rash in distal extremities, rash moves proximally
Lyme disease
Neuroborreliosis
- spirochete transmitted by ticks
- Rare in memphis
- Target skin rash at the bite site (erythema migrans)…gradually expands over the next few days
- Within weeks pts experience flu-like symptoms, acute arthritis, heart block, headache, stiff neck,
3 stages of syphillis
Primary- painles genital chancre 3 weeks after infection
Secondary- 2-3 weeks after chancre, macular-papular rash on PALMS, SOLES and body, adenopathy, iridocyclitis, arthritis, meningitis or meningo-vascular stroke
Tertiary: If untreated, skin, cardio, and neuro complications arise after 15-20 years.
Who is at high risk for meningitis and stroke due to secondary syphillis
immunocompromised
What is the CSF profile for an HIV pt with neurosyphillis
Positive serum FTA (fluorescent treponemal antibody)
Positive CSF VDRL
If FTA is positive but the CSF VDRL is negative, one diagnosis probably neurosyphillis as long as their is CSF pleocytosis (inc white cell count) and elevated CSF protein
If untreated, TB can produce
Granulomatous meningitis that is especially severe at the base of the brain. Can entrap multiple cranial nerves and block CSF flow, causing hydrocephalus and raised ICP
Chronic meningitis clinical symptoms
- fever
- headache
- lethargy
- poor appetite/wt loss
- cranial neuropathy
- personality change
- cognitive impairment
In addition to meningitis, TB can cause
vasculitis with vessel thrombosis and brain infarcts
Early clinical features of TB Meningits
confusion
lethargy
low grade fever
headache vomitting
How do you confirm the diagnosis of TB
- one option is a new RNA PCR test
- you also want to isolate the org from the CSF though
CNS TB treatment
BIG THREE plus one (IRP + strep or eth)
Isoniazid, Rifampin, Pyrazinamide
Plus streptomycin or ethambutol
main risk for zoster
Ulceration of the cornea
HSV-1 encephalitis responds to
acyclovir
CMV encephalitis responds to
ganciclovir