HNNS Case 1: Japanese Encephalitis Flashcards
Describe the normal structures and physiology of meninges and brain parenchyma
See lecture
Describe the pathophysiology of acute viral meningoencephalitis
- Parenchymal infection associated with Meningeal inflammation
- Perivascular + Parenchymal Lymphocyte infiltrate / cuffing
- Microglial cell proliferation
- Neuronophagia
- Viral inclusion bodies
Clinical presentation:
- Meningoencephalitis
- Meningeal irritation
- ↑ ICP —> Headache + Vomiting
- Encephalopathic sign —> Seizures, Altered consciousness
- Focal neurological lesions —> Hemiparesis, CN palsies
- Systemic signs —> Fever - Septic shock
- Decrease in circulatory volume / perfusion
- Tachycardia
- Hypotension
- Cool clammy skin
CSF investigations
- ↑ Lymphocyte count
- Normal glucose
- ↑ Protein
- ↑ WBC
Complications
- Fibrosis —> CN palsies + Hydrocephalus
- Septic thrombosis —> Stroke
- Epilepsy
- Mental retardation
- Focal neurological lesions —> Hemiplegia
Common pathogens in acute viral meningoencephalitis
- HSV1
- HSV2
- Enterovirus
- VZV
- Japanese encephalitis virus (Arbovirus)
- EBV
- Rabies, Measles, Poliovirus
- CMV, HIV, JC virus (Immunocompromised)
Describe role of doctor in management of children with severe illnesses
- Calm children
- Explain situation to children / parents
- Psychological support —> reduce anxiety
Describe the importance of parental coping in care of paediatric patients
Parent coping mechanism:
- Vary by age, locus of control, anxiety levels, involvement of child care a activity
- Problem-focused / Emotion-focused strategies
- Intense stress —> seriously undermine functioning of family + child’s health
Recognise S/S suggestive of acute viral meningoencephalitis and method to confirm diagnosis
- Acute onset of fever
- Headache
- Confusion
- Seizures
- Stiff neck
- Drowsiness
- Irritability (Children)
- Poor appetite (Children)
Diagnosis:
- ***CSF PCR from Lumbar puncture
- Serology
- Culture (Good for meningitis / Poor for encephalitis)
- MRI brain —> determine inflammation / differentiate from other causes
- EEG —> monitor brain activity
- Urine analysis
Epidemiology and disease burden of Japanese encephalitis infection
low number of JEV in HK, rare cause of encephalitis
Mode of transmission:
- By bites of infected mosquitoes (Culex tritaeniorhynchus)
- Mosquito infected by feeding on pig / wild birds infected with virus
- common in rice field (abundant in water)
Incubation period:
- symptoms occur 4-14 days after infection
Management:
- No specific treatment
- Supportive therapy
- 90% asymptomatic
- 30% mortality with symptomatic patients
- 20-30% permanent neurological problems
How to determine whether an outbreak has occurred and how outbreaks are investigated
- Passive surveillance
- receive reports of case - Active surveillance
- **Surveillance systems to monitor disease activities in hospital / clinics
- **Confirmed reported cases
- Integrate statistics and form database
Describe communicable diseases requiring notification to the Centre for Health Protection CHP for follow-up and control
51 notifiable infectious diseases on the list:
- TB
- Chickenpox
- Small pox
- COVID-19
- SARS
- MERS
- Diphtheria
- Typhoid fever
- Food poisoning
- Cholera
- Enterovirus 71
- EHEC
- Malaria
- Measles
- Mumps
- JEV
Prevention and Control measures for Japanese encephalitis
Prevention:
- Avoid going to rural areas form dusk till dawn
- General measures to prevent mosquito bites
- loose, light coloured, long-sleeved
- DEET-containing insect repellent
- bed net with permethrin applied
Vaccination:
- safe and effective
- available in HK
- not recommended to general public
- recommended to traveller planning to stay >=1 month in endemic areas / short-term but significant outdoor/nighttime exposure during transmission season
Control:
- Prevent mosquito proliferation
- prevent accumulation of stagnant water
- store food / dispose of garbage properly
Importance of risk communication in explaining serious CNS infection and possible long-term neurological sequelae to parents
- Reduce mortality and improve prognosis
- Avoid complication
- Increase patients’ trust
GCS scale
Maximum 15
- Motor (1-6)
- Verbal (1-5)
- Eye (1-4)
Brain injury:
Mild: >=13
Moderate: 9-12
Severe: <9
Eye opening response —> Determine **Arousal level —> controlled by **Subcortical ascending reticular formation
Verbal / Motor response —> Determine **Awareness level —> controlled by **Cerebral cortex
Management while waiting for Lumbar puncture
- IV empirical broad spectrum antibiotic
- IV acyclovir
- Mannitol to lower ICP (by reducing cerebral parenchymal cell water)
