Meningitis infects what components of the brain? 

Leptomeninges (Pia matter and arachnoid matter) and CSF 

bacteria --> PMNs --> pus 

Acute Pyogenic Meningitis 

Meningoencephalitis 

Meningitis in leptomeninges and CNS parenchyma --> abscess formation

Basilar Meningitis 

Infection affecting base of brain + cranial nerves and blood vessels 

Granulomatous Meningitis 

Chronic basilar meningitis + pin head size granulomas 

Carcinomatosis of the Meninges 

Involvement of the leptomeninges by malignant cells 

Iatrogenic introduction of chemicals into subarachnoid space & irritant material spontaneously released from neoplasms 

Chemical Meningitis 

What is the most common route of infective dissemination? 

Hematogenous 

Rabies and Zoster reached the CNS via the...

Peripheral Nervous System 

What is the prototype for all forms of pyogenic or bacterial meningitis?

Meningococcus 

Neisseria Meningitidis

Group B Strep and E. Coli 

Most common in neonates 

H. Influenzae and Strep Pneumoniae 

Most common infection in Infants 

Most common infectious agent in Older adults?

S. Pneumoniae & Listeria monocytogenes 

Gross morphology of Acute Meningitis 

• surface --> milky/cloudy surface
• PMNs in CSF --> pus
• congested vessels
• cerebral edema w/ or w/out herniation

Microscopic examination of Acute Meningitis 

• PMNs in subarachnoid space & ependymal lining (ependymitis)
• Secondary vasculitis --> infarct or hemorrhage
• infection of CNS parenchyma (cerebritis)

-generalized septicemia

-fulminant septicemia

-Disseminated Intravascular Coagulopathy (DIC)

-Waterhouse-Friderichsen Syndrome

complication of Acute Meningitis 

How does hydrocephalus happen in Acute Meningitis?

irritation of meninges --> fibrosis or reactive desmoplasia --> adhesive arachnoiditis --> occlusion of foraminae of Luschka and Magendie --> hydrocephalus 

Abscess formation Mechanism 

cerebritis --> consolidation (large, round, semi-discrete mass w/ central necrosis) --> organization & repair (ingrowth of blood vessels, fibroblasts at edge) --> thick, fibrous capsule

Subdural Empyema 

Extension of preexisting, primary infection: osteomyelitis of skull, sinusitis, mastoiditis or brain abscess into subdural space w/ pus 

spread of abscess into adjacent areas of osteomyelitis/ sinusitis into epidural space of the spinal cord 

-neurosyphilis

-tuberculosis

-fungal infections

-sarcoidosis 

Basilar of GRANULOMATOUS Meningitis 

Non-necrotizing granuloma 

Sarcoid 

Granuloma w/ caseous (cheese-like) necrosis 

Tuberculoma

from Mycobacterium Tuberculosis 

Meningovascular Neurosyphilis 

-chronic infection inflammation

-subarachnoid space & leptomeninges

-vascular and cranial nerve involvement

-degeneration of the dorsal columns

-ataxia

-Charcot joints (traumatic joint injury w/ deformation)

Tabes Dorsalis 

Large granulomas w/ central core of 'rubber-like' necrosis 

Gumma granulomas 

(Neurosyphilis) 

Gross morph of Neurosyphilis 

• atrophic brain
• narrowing of gyri
• widening of the sulci
• leptomeninges are thickened
• granulomas at base of the brain/brainstem 

What kind of cells are found in basilar/granulomatous meningitis?  

reactive gliosis

lymphocytes & plasma cells 

Microglia 

Ventricles lining show areas of denudation & glial response w/ granular appearance

(in basilar/granulomatous meningitis)

Granular Ependymitis 

-Borrelia Burgdorferi

-Ixodes tick

-Mild Menigoenchephalitis

-Facial Nerve Palsies

-Neuropathies 

Lyme Disease

(Neuroborreliosis)

What is 'tropism"? 

Predilection of viral infection for specific cell tissues, such as CNS, and specific cell types: oligodendroglia

Ability of virus to hide in the nervous system followed by re-emergence and subsequent infections

Latency 

Intracytoplasmic neuronal inclusions in Purkinje cells fo the cerebellum and hippocampal formation of temporal lobes 

Rabies 

Typical histopathological features of the Rickettsial Diseases 

-inflammatory round cell infiltrate

-predilection of injury of gray matter

-glial or microglial nodules 

-children and young adults

-temporal lobes and orbital gyri of inferior frontal

-necrotic, hemorrhagic lesion

-Cowdry Type A inclusion

Herpes Simplex Type 1 (HSV 1)

-meningoencephalitis in adults

-neonates born to mother w/ active lesions

-transmitted by birth canal no placenta

Herpes Simplex Virus Type 2 (HSV 2) 

-chickenpox in childhood

-latent in NS and reactivated in adult

-painful vesicular eruption following dermatomes of sensory nerves

-Dorsal (sensory) root ganglia 

Varicella-Zoster Virus (Herpes Zoster; Shingles)

- CNS infection fetus & immunosupressed

-Periventricular necrosis --> calcification

-Microencephaly & microcephaly

-Cowdry Type A inclusion

- ++ common in AIDS pts. 

Cytomegalovirus (CMV)

-demyelinating dz

-JC Polyoma Virus

-tropism for oligodendroglia

-Cowdry Type A inclusion bodies

-bizarre astrocytes, like "tumor-cells", neoplasm?  

Progressive Multifocal Leukoencephalopathy PML

-children & young adults

-acute episode of measles

-virus latency

-widespread demyelination & gliosis

-Cowdry Type A inclusion bodies 

Subacute Sclerosing Panencephalitis 

-Poliovirus

-affects motor neurons of the anterior horn cells of the spinal cord & cranial nerve nuclei

-damage to entire motor unit 

Polyomyelitis 

-Hyperexcitable NS

-hypersensitivity to sensory input

-exaggerated motor responses and convulsions

-Hypercontraction of the pharyngeal muscles leads to inability to swally food/water (hydrophobia)

RAbies 

Inclusion bodies in Rabies?

Negri Bodies 

(eosinopholic w/in cytoplasm of neurons; esp. in Purkinje cells of the cerebellum & neurons of the hippocampal region of temporal lobe)

-AIDS-Dementia

-mild atrophy & ventricular dilation

- minimal lymphocytic infiltrate

-glial/microglial nodules 

-multinucleated giant cells 

HIV Meningoencephalitis (Subacute Encephalitis)

-cerebral palsy-like S/Os

-Calcifications of blood vessels in basal glanglia & cerebral white matter

-Delayed demyelination

-Multinucleated giant cells in parenchyma 

AIDS in children

What is a frequent CNS neoplasm seen in HIV/AIDS

Primary Malignant Lymphoma of the CNS

-multiple, ring-enhancing lesions w/ central necrosis

-rings of acute & chronic inflammation & macrophage activity

CNS Toxoplasmosis 

-Acquired by swimming

-Naegleria species

-fulminating infection & rapid death

-chronic, granulomatous meningoencephalitis 

-organisms look like macrophages 

Amebic Meningoencephalitis 

-larvae of the tapeworm Taenia solium

-multiple cysts w/in the brain

-South America 

Cysticercosis 

Transmissible Spongiform Encephalopathies 

characterized by 

prion protein in gray matter --> neuron and processes affected --> destabilization of cell body cytoplasm & dendrites --> optically empty vacuoles --> microscopic spongiform change in neurons at all levels of gray matter

Do prion proteins contain DNA or RNA? 

NO, but it is infectious and transmissible to other animals 

The abnormal prion protein has a configuration change from the normal alpha-helix to ________,

which is resistant to ____________

beta-pleated, protease digestion