32 - Infectious Diseases of the CNS Flashcards
Bacterial Meningitis
Most common infection of the CNS
Organisms reach the leptomeninges via hematogenous spread or direct extension
Spinal tap yields cloudy CSF with many PMNs and bacteria may be seen
Bacterial Meningitis - Neonates
Group B Strep, E Coli
Bacterial Meningitis - Infants and Children
H-Flu
Bacterial Meningitis - Adolescents and young adults
N. Meningitidis
Bacterial Meningitis - Elderly
Strep Pneumo
Path - Large Thick-walled Vessels
Landmark for the leptomeningeal space
Acute meningitis
Hella PMNs in the leptomeningeal space
Brain Abscess
Second most common CNS infection
Local contiguous spread (sinusitis, otitis, mastoiditis)
Hematogenous (septic emboli from bacterial endocarditis, pulmonary infection, etc)
Stages of Cerebral Abscess Formation
Early cerebritis (1 - 3 days)
Late cerebritis (4 - 9 days)
Early capsule formation (10 - 13 days)
Late capsule cofmation (14 days and later)
Early Cerebritis
1 - 3 days
Acute inflammation & edema
Late Cerebritis
4 - 9 days
+Necrosis
+Macrophages
Early Capsule Formation
Fibrous capsule surrounds abscess (which has degenerated to pus)
Cerebral Fungal Infection
Often opportunistic in immunocompromised patients
Hematogenous spread from other organs
May produce leptomeningitis, vasculitis, granulomas, or cerebral abscess
Cerebral Fungal Infection - Common Organisms
Asbergillus
Mucormycosis
Candida
Cryptococcus
Aspergillus
Opportunistic Septate hyphae Acute angle branches Flowery body Attacks vasculature Perivascular inflammation Massive hemorrhage
Mucormycosis
Opportunistic
Nonseptate hyphae
Candida
Opportunistic
Budding yeast
Pseudohyphae
Cryptococcus
Opportunistic or previously healthy Budding yeast Encapsulated Typically stays in leptomeninges Extends along virchow robin spaces (projections of leptomeninges cuffing perforating vessels
Polysaccharide capsule (highlighted with mucy carmen stain) Slippery brain. "Sugar coated brain" Edema/fluid restricted to leptomeninges and in virchow robin spaces.
See something all over the brain?
Hematogenous spread!!!!
Parasitic Infections - Protozoa
Toxoplasma Acanthamoeba Naegieria Plasmodium (malaria) Trypanosoma Trichinella Toxocara
Parasitic Infections - Metazoa
Cysticercosis Echinococcus Sparganum Paragonimus Schistosoma Strongyloides Angiostrongylus
Neurocysticercosis
Cysts in brain tissue containing organisms
Humans are the definitive host
Tapeworms shed ova that get ingested by pigs
We eat pigs
If we eat the ova from poop, the intermediate stage will invade muscle, eye and brain. HEMATOGENOUS spread
CNS Viral Infections - Manifestations
“Aseptic” Meningitis
Encephalitis
Meningoencephalitis
Myelitis
Stereotypical Tissue Reactions
Inflammatory Cell Infiltrates Microgliosis Neuronophagia Microglial nodules Astrocytosis Intracellular inclusion bodies Neuronal cell degeneration Cellular and tissue necrosis
Rabies - Pathology buzzword
Negri bodies
Intraneuronal cytoplasmic inclusions
Brightly eosinophilic
Inside purkinje cells
Rabies
Transmitted via bite
Virus proliferates at bite site
Transaxial migration into nervous system
Bat bites
Aggression, violence
Photophobia
Vampires come from here.
Herpes Encephalitis
Neurotropic virus
Hemorrhagic inflammatory partially necrotic legions in medial temporal lobe
Inflammatory lesion, microglial nodules, perivascular lymphocytes
Herpes Encephalitis - Path Buzzword
Cowdry bodies
intranuclear inclusions
Viral particles growing inside nucleus
HIV-1 - Primary Complications
HIV encephalitis or AIDS dementia complex
HIV-associated myelopathy (vacuolar myelopathy)
HIV-associated neuropathy (distal sensory neuropathy)
HIV-associated myopathy
HIV-1 - Secondary complications (due to immunodeficiency)
Opportunistic Infections
Cryptococcosis
Toxoplasmosis
Progressive Multifocal Leukoencephalopathy
Cytomegalovirus Infections
Primary CNS Lymphoma
HIV Encephalitis
Lymphocytic Encephalitis
Multinucleated giant cells (infected monocytes with multiple nuclei)
Toxoplasma
Large necrotic lesions
Can sit dormant for years, then flare up when immune system is compromised.
Well circumscribed mass
MRI - Ring-enhancing lesion
Differential for Ring-Enhancing Lesion on MRI
Glioblastoma
Metastatic Carcinoma
Lymphoma
Toxoplasmosis
Toxoplasma - Path Buzz Word
Tissue Cysts (bradyzoites) Cysts burst with tachyzoites (more active form)
JC Virus
Progressive Multifocal Leukoencephalopathy
JC Virus (PML) - Path Buzz Word
Oligodendrocyte infected, gets big and glassy
Astrocytes start to look like astrocytomas
Cytomegalovirus Ventriculitis
Predilection for ependymal cells
Typically CMV leads to ventriculitis
Microscopically, cells are hugesies!
Transmissible Spongiform Encephalopathies - Prion Diseases
Creutzfeldt-Jakob Disease Gerstmann-Straussier-Scheinker disease Fetal familial insomnia Kuru New Varient CJT (Mad Cow)
Animal Prion Diseases:
Scrapie
Bovine spongiform encephalopathy
Others
Creutzfeldt-Jakob Disease
Worldwide incidence of approximately 1 per million Peak incidence in seventh decade of life Sporadic (85%) Familial (15%) Iatrogenic (Rare) Rapid progressive dementia Myoclonus Ataxia Usually Fatal
Prion Hypothesis
PrP is a normal protein present EVERYWHURR
Exists in a healthy alpha helix-rich state
Exists rarely in an unhealthy beta pleated sheet state (more likely to layer like amyloid)
Sporadic cases of switchy switchy through mutation cause folks to be susceptible
Beta pleated sheet serves as a nidus for more to convert
Kuru
Rapid progressive disease myoclonus ataxia seizures death
To honor them, bitches ate the body
Women and children ate the brain
Eating the brain gives you kuru
Spongiform encephalopathy - Histo/path
Holes in the gray matter. Give spongy appearance.
Holes are INTRACELLULAR spaces.
End stage = Residual astrocytosis with dying neurons around
