CNS infections and intoxications Flashcards
What is the difference between meningitis and encephalitis?
Meningitis is inflammation of the leptomeninges whereas encephalitis is inflammation of the brain parenchyma (usually accompanied by meningitis: meningoencephalitis)
What is a localized CNS infection called?
Brain abscess
What are the different types of meningitis?
Bacterial, fungal, amebic/tuberculous, viral, and non-infectious
What are the common causative pathogens of bacterial meningitis in a newborn?
E. coli
Group B streptococci
What are the common causative pathogens of bacterial meningitis in a patient between 1-12 months old?
Strep pneumoniae
Haemophilus influenzae
What are the common causative pathogens of bacterial meningitis in a patient between 1 yr and 16 y/o?
Neisseria meningitidis
Haemophilus influenzae
Strep pneumoniae
What are the common causative pathogens of bacterial meningitis in a patient between 16 y/o and 50 y/o?
Strep pneumoniae
Neisseria meningitidis
What are the common causative pathogens of bacterial meningitis in patients at age extremes?
Listeria
Pseudomonas
Describe the gross appearance of bacterial meningitis
The suparachnoid space is full of pus, which gives the meninges a yellow/cloudy appearance compared to the normal transparent appearance. Edema is also visible as flattened gyri and sulci.
A CSF tap reveals cloudy fluid full of PMNs with high protein and low glucose. What type of meningitis is this?
Bacterial
A CSF tap reveals clear fluid full of lymphocytes with slightly high protein and normal glucose. What type of meningitis is this?
Viral
A CSF tap reveals lymphocytes, moderately high protein and mildly low glucose. What type of meningitis is this?
TB
List the causative agents of chronic meningitis
Tuberculosis Fungal Parasitic Syphilis Borreliosis Neurosarcoid
What meningitis types can cause granuloma formation?
TB and fungal
What are the parasitic CNS infections?
Cysticercosis
Toxoplasmosis
Amoebiasis (Naegleria fowleri, Entamoeba histolytica)
What are the common causes of viral meningitis?
Eneterovirus (75% of all cases)
Arboviruses (West Nile)
HSV 2
WNV
What viruses target the meninges?
Mumps
Enterovirus
Coxsackie
HIV
What viruses target motor neurons?
Polio
Enterovirus
What viruses target neurons and glial cells?
Herpes
Rabies
Measles
What viruses target neurons, glial cells and endothelium?
CMV (in immunocompromised)
What viruses target oligodendroglia?
Papovirus (in immunocomprimised)
What viruses target microglia?
HIV
What viruses target dorsal root ganglia?
HSV
VZV
What viruses target the fetal nervous system?
Rubella
CMV
What are the microscopic findings associated with viral encephalitis?
Perivascular inflammation
Leptomeningeal inflammation
Microglial clusters/nodules
Neuronophagia
*T-lymphocytes predominate
What is the pathogenesis of polio encephalitis?
Fecal-oral transmission, replicates in oropharynx and small intestine
Causes destruction of anterior horn cells
What is the pathogenesis of rabies?
Caused by exposure to rabid animals (dog, bat, raccoon, skunk)
Prodrome of flu-like symptoms
Negri bodies are seen in neurons of brainstem, hippocampus and cerebellum
What is the pathogenesis of herpes encephalitis?
Transmitted via saliva
Causes latent infection of trigeminal ganglion. Can cause focal encephalitis: medial temporal lobe edema, hemorrhage and necrosis
What is the characteristic appearance of a cell infected with HSV-1?
Intranuclear inclusions look like Owl’s eyes
What are the infectious agents that can cross the placenta?
ToRCHeS: Toxoplasmosis Rubella CMV Herpes Syphilis (And now Zika virus)
What is the presentation of congenital CMV encephalitis?
Moderately dilated ventricles with several foci of periventricular calcifications
What is the pathogenesis of progressive multifocal leukoencephalopathy?
Caused by JC virus (papovirus) Usually affects immunocompromised Disease of white matter Causes loss of myelin with axonal sparing, bizarre appearing astrocytes and oligodendroglial inclusions Untreatable
What is the characteristic finding of HIV encephalitis?
Multinucleated giant cells with predilection to gray matter
What is HIV leukoencephalopathy?
Subacute onset cognitive impairment and apathy related to diffuse white matter myelin degeneration. Etiology poorly understood.
What predisposes patients to brain abscesses?
Direct introduction of organisms via trauma or surgery
Infection elsewhere (brain or distant site)
Diabetes
EtOH
What are the stages in evolution of an abscess?
Day 1-3: Early cerebritis
Day 2-7: Confluent necrosis
Day 5-14: Early encapsulation
Days 14+: Late encapsulation
How does tetanus affect the CNS?
C. tetani exotoxin binds to interneurons of the brain, brainstem, and spinal cord preventing the release of inhibitory glycine and GABA resulting in motor disinhibition, painful muscle spasms and generalized convulsive seizures
How does botulism affect the CNS?
C. botulinum exotoxin binds to presynaptic nerve terminals preventing ACh release leading to paralysis presenting as ptosis, diplopia, dysphagia, facial/limb/respiratory weakness
What is the affect of lead poisoning on adults? What about children?
Adults get peripheral neuropathy
Children get encephalopathy, abdominal pain
What drugs are commonly associated with drug-related stroke syndromes?
Cocaine, amphetamines, PCP and LSD
What are the stages of alcohol withdrawal syndrome?
Early hypersympathetic stage for up to 3 days
Delirium tremens 3-4 days after cessation of drinking
What is Wernicke-Korsakoff syndrome?
Often associated with chronic alcoholism
Thiamine deficiency leads to encephalopathy (nystagmus, ophthalmoplegia, gait ataxia and confusion) and Korsakoff psychosis (amnesia, confabulation)
Which is more severe: acute bacterial meningitis or viral meningitis?
Bacterial is more severe than viral. Can be fatal if not treated early and aggressively.
What are the complications of bacterial meningitis?
Hydrocephalus due to pus obstructing the CSF pathway
Secondary edema of the cortex
Infarction from inflamed vessels
Deafness
What is the presentation of Herpes simplex encephalitis?
Frontal and temporal lobe degeneration can cause aphasia, behavioral changes and memory impairment
What is shingles?
Reactivation of latent varicella-zoster virus in the dorsal root ganglia causes vesicular rash with severe pain within a dermatomal distribution
What are prion diseases?
Infectious proteins (no nucleic acid) that cause transmissible spongiform encephalopathies in humans and animals. Misfolded prions trigger conformational changes in normal proteins which trigger neuronal death without inflammation.
What is Creutzfeldt-Jakob disease?
Prion disease that is rapidly progressive, untreatable and fatal within months. Presents as dementia with myoclonus. Can have corticospinal, extrapyramidal, cerebellar or lower motor neuron signs.
