Week 2 - Diebel Flashcards
What are the key presenting clinical symptoms of encephalitis?
- Altered level of consciousness
- Focal neurological deficits
- Hemiparesis
- Aphasia
- Hemispatial neglect
- Movement disorders
- Seizures
- Coma
What do you call the condition when meningitis and encephalitis coexist in an individual?
Meningeoencephalitis
(often in TB)
What does recent research suggest is the cause of a significant proportion of encephalitis cases?
- Autoimmune disorders
- Postinfectious encephalitis
- caused by an aberrant immune response to the primary infection
What is the proposed case definition for encephalitis?
- “To be diagnosed, a patient should have evidence of ‘encephalopathy’ (altered level of consciousness persisting for more than 24 hrs)
- AND at lease 2 of the following criteria
- Fever or history of fever
- Seizures and/or focal neurological deficits
- CSF pleocytosis (elevated WBC count)
- Neuroimaging abnormalities consistent with encephalitis
- Electroencephalogram characteristics consisten with encephalitis
What is the estimated annual incidence of encephalitis?
~5 cases per 100,000 people
(higher incidence of viral encephalitis in children)
(higher prevalence of primary infections in the winter that are followed by secondary encephalitis)
What is the cause/pathogen of >50% of cases of encephalitis?
Idiopathic
In cases with a known pathogen, what is the most common cause of encephalitis?
Herpes simplex virus
(HSV-1 and HSV-2)
How prevalent is Tuberculosis as a major cause of encephalitis?
4%-8%
What are the diagnostic tests to diagnose encephalitis caused by Tuberculosis?
- PCR
- Culture
- Acid-fast staining
How prevalent are autoimmune causes of encephalitis?
4%-8%
What are the diagnostic tests for diagnosing autoimmune caused encephalitis?
- Antibodies against NMDA receptors
- Antibodies against voltage-gated K+ complexes
What is the differential for encephalitis in order of highest probability to lowest?
Skipping idiopathic causes:
- Alphaherpesviruses (i. HSV, ii. VZV)
- Postinfectious immune responses
- Tuberculosis
- Autoimmune disorders
- Enteroviruses
- Other minor/rare causes
What diagnostic tests should be considered in any patient presenting with an altered level of consciousness, especially when accompanied by otherwise unexplained fever, seizures, or new focal neurological deficits?
- CT scan
- Lumbar puncture
- Empiric antiviral therapy should be started prior to obtaining CSF results (Acyclovir)
- Additional CSF molecular diagnostic testing
- PCR for HSV-1, HSV-2, VZV, & enteroviruses
- MRI
What patients should undergo additional diagnostic testing with PCR/serology?
- Patients that recently visited areas endemic for WNV or TBEV infections
- Immunosuppressed patients
- PCR for EBV, CMV, HHV 6 & 7, and JC virus
- Patients with recent respiratory tract infectious
- test for Influenza A/B and Adenovirus
What is MRI crucial for identifying?
- ADEM
- Other postinfectious encephalitis
What type of WBCs are almost always seen on CSF differential in the case of encephalitis?
Lymphocytes
(Exceptions: Autoimmune –> low WBC,WNV –> neutrophils,
ADEM –> neutrophils)
What two pathogens causing encephalitis result in >75% abnormal MRI’s?
HSV & ADEM
What is the most common cause of encephalitis among immunocompromised patients?
VZV
What is the MOA of Acyclovir?
DNA chain polymerase inhibitor
What type of infections can result in Postinfectious Encephalitis?
- Measles virus
- Mumps virus
- Rubella virus
- Varicella-zoster virus
- Influenza virus
- ETC.
What is the most common type of Postinfectious Encephalitis?
Acute disseminated ecephalomyelitis
(a.k.a. ADEM)
What is ADEM?
An inflammatory demyelinating condition that occurs anywhere from days to 4 weeks post-viral infection.
What age group is mainly effected by ADEM?
Pediatric
How long does it take for a primary Measles virus to cause secondary Encephalitis?
10-14 days
What do you call the condition where nervous system complications arise within days of getting measles?
Primary Measles Encephalitis
a.k.a. PME
When is the typical onset of PME?
Active measles infection –> during exanthem!
When is the onset of Acute Postinfectious Measles Encephalomyelitis?
Weeks to months after measles infection or vaccination.
When is the onset of Subacute Sclerosing Panencephalitis?
3-20 years after measles infection
What is the treatment for PME?
Supportive measures
(25% experience lifelong neurological problems)
What is APME?
Measles-induced acute disseminated encephalomyelitis.
What is the clinical course for APME?
- Symptoms: motor and sensory defects, ataxia, and mental status changes
- Recent history of measles infection - within the last several weeks - months
- MRI showing disseminated white matter lesions in the brain and spinal cord due to demyelination.
What is the suggested treatment for APME?
Corticosteroids
(dampen the immune response)
What are common symptoms in Subacute Sclerosing Panencephalitis (SSPE)?
- Behavioral problems
- Decline in academic performance
- Decline in intellectual function
- Motor dysfunction
- Seizures
- Optic abnormalities
Who is most at risk of Subacute Sclerosing Panencephalitis (SSPE)?
Children who contract measles before the age of 2.
What is the prognosis of Subacute Sclerosing Panencephalitis (SSPE)?
- Most children who suffer from SSPE remain symptom free for 6-15 years post acute infection
- Survive for 1-3 years after symptoms develop
What types of Picornaviruses can cause Encephalitis?
- Poliovirus
- Coxsackie A
- Coxsackie B
- Echovirus
- Enterovirus 71
- Parechovirus
What are the typical Arboviruses that cause Encephalitis?
- West Nile Virus (WNV)
- Tick-borne encephalitis virus (TBEV)
- La Cross encephalitis virus (LCEV)
What symptoms do Arbovirus infections present?
- Most infections are asymptomatic
- Flu-like illness
- fever
- headache
- malaise
- rash
- fatigue
- Vomiting
- Hemorrhagic fever
What is the treatment for Encephalitis caused by Arboviruses?
Supportive care
(vaccination)
What symptoms are common with encephalitis caused by Rabies?
- Fever
- Excitation
- Dilation of pupils
- Excessive salivation
- Anxiety (fear of swallowing)
- Spasms of throat muscles
What eventually causes death in rabies infections?
Respiratory paralysis
What pathological findings are seen in tissue samples from rabies infected brains?
Negri bodies
What is the treatment for rabies infection?
- Tx: Rabies immune globulin (human antibodies against rabies) AND inactivated rabies virus preparation
- Prevention: human vaccination and domestic animal immunization
