7.2 Patho6 - Cns Infection 2015b

6.7.2 CNS INFECTIONS Dr. Tilbe

FORMS OF CNS INFECTIONS A. Meningitis Infection limited to subarachnoid space (leptomeningitis) Or spread into the brain (meningoencephalitis) B. Encephalitis Inflammation of brain; most often due to virus Maybe diffuse (entire brain involved) or localized to a part of the brain C. Brain Abscess Localized purulent infection of the brain Typically caused by bacteria Maybe solitary or multiple ( usually in sepsis ) 

Pathogenesis The organisms that cause bacterial Meningitis colonize the nasopharynx.

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Goes into the blood stream and enter the Subarachnoid space

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When bacteria die, lipids and oligosaccharides, including endotoxin, are released from their walls (SEPSIS) attracting circulating granulocytes and monocytes into the CSF and cause vascular injury.

MENINGITIS    

Maybe acute or chronic Maybe purulent or serous (lymphocytic or aseptic) based on CSF findings Maybe infectious or non infectious Types of infectious meningitis: meningitis : Acute pyogenic (bacterial) meningitis, o Aseptic (usually acute viral meningitis) o Chronic (usually tuberculous, spirochetal, or o cryptococcal)

Lysed granulocytes and monocytes release lysosomal enzymes and free radicals (destroy neural tissue and damage blood vessels). Polyunsaturated fatty acids released from the membranes of dying neutrophils also cause cause increased increased vascular vascular ermeabilit ermeabilit .

Increased permeability (cerebral edema) Vasculitis (ischemia) Se si s  Death from ram-ne ram-ne ative ative  shock

ACUTE BACTERIAL MENINGITIS Route of Infection Hematogenous dissemination (More Common) o Direct extension(sinusitis, mastoiditis, brain abscess, o penetrating injury, congenital defect) Cranial bone fracture due to trauma o During surgery o Etiology Neisseria meningitidis (most common in children) o Streptococcus pneumoniae (most common in adults) o Hemophilus influenzae (children) o Gram (-) bacteria ( E coli, Klebsiella, Enterobacter) in o immunosuppressed following trauma or brain surgery E coli and group B streptococcus in neonates o Age Prevalence coli  and the group B streptococci Neonates: Escherichia coli and o Newborn and Elderly: Streptococcus pneumoniae pneumoniae and o Listeria monocytogenes. Infants : S. pneumoniae o Adolescents and in young adults: Neisseria o meningitides

Diagnosis: Diagnosis: CSF EXAMINATION EXAMINATION (Cornerstone)  (Cornerstone) Cloudy or frankly purulent CSF o Abundant neutrophils ( as high as 90,000 o neutrophils/mm3) Elevated protein level o Organisms are abundant o Markedly reduced glucose content (used up by o neutrophils) Morphology Exudate is within the leptomeninges over the surface of o the brain. The location of the exudate: o  H. influenzae meningitis: meningitis : usually basal  Pneumococcal meningitis: cerebral convexities near the sagittal sinus.

Figure 1. Purulent exudate covers the cerebral h emispheres

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Mild cases: lymphocytes, plasma cells, and macrophages. Florid cases: well-formed granulomas, often with central caseous necrosis and giant cells.

Figure 2. Exudates settle along the base of the brain, around cranial nerves, and the openings of the fourth ventricle. Figure 5. Epithelioid cell granulomas with Langhans giant cells, lymphocytic infiltrates, and central caseous necrosi s. Clinical Features: Symptoms of headache, malaise, mental confusion, o and vomiting. Moderate CSF pleocytosis and elevated protein o concentration Most serious complications: o Arachnoid Fibrosis producing hydrocephalus  Obliterative Endarteritis  producing arterial  occlusion and infarction

B. FUNGAL MENINGOENCEPHALITIS  

Figure 3. Neutrophilic exudation of the subarachnoid space

CHRONIC MENINGITIS Onset: Insidious Duration: Weeks to Months Seen in: Tuberculosis o Fungal Disease o Syphilis o Sources A. TB : Ruptured tubercles into the CSF or hematogenous dissemination B. Fungal and Cryptococcal: hematogenous spread from lungs C. Syphilis: manifestation of tertiary stage of syphilis.

A. TUBERCULOUS MENINGOENCEPHALITIS Morphology: Macroscopic Subarachnoid space contains gelatinous or fibrinous grayish-white exudates. Often found at the base of the brain obliterating the cisterns and casing the cranial nerves. Most common pattern of involvement:   Diffuse Meningoencephalitis 

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primarily seen in immunocompromised patients most common fungi involved:  Candida albicans  Mucor  Aspergillus fumigates  Cryptococcus neoformans hematogenous dissemination composed of three main patterns of fungal infection in the CNS: chronic meningitis vasculitis parenchymal invasion   

Parenchymal Invasion: usually in the form of granulomas or abscesses  mostly encountered fungi:  Candida:  a commensal fungi which rarely causes disease in normal people  infection is caused by organisms that are already present in the intestines and other location  in neonates, it is transmitted from external sources  most disseminated infections are nosocomial and the key risk factors are catheters and antibiotics  causes meningitis, multiple microabscesses or extensive brain necrosis  at first inflammation consists of neutrophils; later stage consists of epitheloid cells and giant cells 

C. CRYPTOCOCCAL MENINGITIS   

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Figure 4: Tuberculous exudates at the base of the brain Morphology: Microscopy Caseating granuloma o

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hematogenous spread from the lungs an opportunistic infection commonly seen in immunocompromised occurs as chronic meningitis/meningoencephalitis with meningeal fibrosis   hydrocephalus (due to CSF flow obstruction) may be fulminant and fatal in as little as 2 weeks or indolent, evolving over months and years can cause dementia and focal neurologic deficits oval yeast about the size of a red cell, surrounded by a gelatinous capsule present in bird droppings, vegetables, and soil immunosuppressed host: inflammation is absent or mild

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immunocompetent host: cell mediated immune reaction with lymphocytes and epitheloid cell granulomas

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Morphology: Microscopy  Parenchymal lesions consist of aggregates of organisms within expanded perivascular ( VirchowRobin) spaces associated with minimal or absent inflammation or gliosis  Infiltrates consist of chronic inflammatory cells and fibroblasts admixed with cryptococci

Insidious but progressive loss of mental and physical functions Mood alterations (including delusions of grandeur), terminating in severe dementia

2. Paretic Neurosyphilis  Loss of neurons with proliferations of microglia, gliosis, and iron deposits (perivascularly and in the neuropil, presumably from damage to the microcirculation) 3. Tabes Dorsalis Damage to the sensory nerves in the dorsal roots  results in: Impaired joint position sense and resultant o ataxia (locomotor ataxia) Loss of pain sensation, leading to skin and o  joint damage (Charcot joints) absence of deep tendon reflexes. o

Figure 5: cryptococci present in perivascular space

Figure 6: Brain section looks like “Swiss Cheese” due to cystic dilatation (organism grows in the subarachnoid and perivascular spaces. Presents with a gelatinous material within the subarachnoid space and small cysts wi thin the parenchyma (“Soap Bubble Appearance”) 

Diagnosis  CSF analysis:  mononuclear pleocytosis  elevated protein  low glucose  mucoid encapsulated yeasts can be visualized in the CSF by India ink preparations  PAS and mucicarmine as well as silver stains (tissue sections)  antigens can be detected by latex agglutination

Histologic Findings  Obliterative endarteritis ( Heubner arteritis)  Perivascular inflammatory reaction rich in plasma cells and lymphocytes Cerebral gummas (plasma cell-rich mass lesions) may  occur in the meninges and extending into the cerebral parenchyma Symptoms of Meningitis 1. fever (more than 40C (bacterial); less than 40C (viral) 2. Onset: sudden for bacterial with prodrome for viral 3. Meningeal irritation and neurologic impairment: headache, photophobia, irritability, clouding of consciousness, neck stiffness 4. As the disease progresses, confusion, coma, and seizures develop Signs of Meningitis 1. Kernig sign (knee pain with hip flexion) 2. Brudzinski sign ( upon flexion of neck there is spontaneous similar movement of the hips and knees 3. Increased CSF with changes in biochemical composition of CSF Table 1: Cerebrospinal (CSF) Findings

D. NEUROSYPHILIS  

tertiary stage of syphilis infection 3 forms: a. Meningovascular Neurosyphilis  b. Paretic Neurosyphilis c. Tabes Dorsalis

COMPLICATIONS OF MENINGITIS 

1. Meningovascular Neurosyphilis Morphology: Involves the base of the brain and variably also the cerebral convexities and spinal leptomeninges Meningovascular Lesions  Lymphoplasmacytic infiltrates  Intimal thickening of small and medium-size leptomeningeal and parenchymal arteries (endarteritis obliterans- Heubner arteritis). Parenchymal Lesions  Tabes dorsalis  (rot of the spinal cord): Inflammation and degeneration of dorsal roots and posterior columns General paresis of the insane ( dementia paralytica)  Encephalitis due to invasion of the brain by o spirochetes

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Scarring and obstruction of CSF leading to hydrocephalus Organization of fibrinopurulent exudate into fibrous o tissue >>> Block the exits of the 4 th  ventricle Cranial nerve injury due to constriction may lead to neurologic deficits Destruction of brain parenchyma lead to mental deficits, sensory defects Epilepsy Abscess Formation

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Respiratory tract (Mumps, Measles) Gastrointestinal tract (Enteroviruses) By inoculation from insect bites (Arthropod-borne o viruses) From animal bites (Rabies) o Most viruses reach the CNS via the bloodstream. Some viruses travel to the CNS along nerves Herpes simplex virus(HSV) o Varicella-zoster virus (VZV) o Rabies o Some viruses have a predilection for certain groups of neurons. Poliomyelitis attacks anterior horn cells o Varicella-zoster involves sensory ganglion cells o o o

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Figure 7: Vascular narrowing after meningitis

PATHOGENESIS Viruses

Activation of T-Lymphocytes

Release of Potent Cytokines (INF-Gamma, IL-2, TNF, Lymphotoxin)

Mobilization of Macrophages

Figure 8: Postmeningitic Hydrocephalus 

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TB Meningitis: Epithelioid cell granulomas destroy the pia and invade the brain. Obliterative Endarteritis: Inflammatory infiltrates in arterial walls and marked intimal thickening >> Arterial occlusion and infarction of underlying brain. Long-Standing Cases: Dense, fibrous adhesive arachnoiditis Tuberculoma: Tumor-like mass, single or multiple well-circumscribed intraparenchymal mass. May cause significant mass effect.

Attack Virus assault the host

Causing severe vascular and tissue injury

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Parenchymal viral infection of the brain associated with meningeal inflammation = Meningoencephalitis Simultaneous involvement of the spinal cord = Encephalomyelitis.

ACUTE ASEPTIC (VIRAL) MENINGITIS 

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Generally of viral etiology 70% of cases, a pathogen can be identified, o most commonly an enterovirus Clinical Manifestations: meningeal irritation, fever, and alterations of consciousness of relatively acute onset. Less fulminant course: self-limiting o Usually associated with: encephalitis o meningoencephalitis o Source of Infection: Secondary infection in the coarse of SVI o (measles, varicella, mumps) Primary infection which maybe o Sporadic (HSV)  Epidemic (arthropod transmitted  arbovirus) Nonspecific gross findings Microscopic findings: No abnormality or o Mild to moderate infiltration of the o leptomeninges with lymphocytes. CSF: Lymphocytic pleocytosis, o Moderate protein elevation o Sugar content is nearly always normal. o

Viral encephalitis: 

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Characteristic Histologic Features: Perivascular and parenchymal mononuclear cell o infiltrates (lymphocytes, plasma cells, and macrophages) Glial cell reactions (including the formation of o microglial nodules, and neuronophagia). Viral infection of neurons and glial cells by viruses impairs neurological function and may cause seizures, focal neurologic deficits and coma. Early phase: Neutrophilic infiltration initially of lymphocytes o and macrophages. Infiltrates the arachnoid membrane and the brain o diffusely but are more concentrated around blood vessels.

REVIEW: VIRUSES Obligate intracellular organisms. Use cellular machinery for their replication and damage or kill the cells they infect. Additional brain damage is caused by the cell-mediated immune reaction that they elicit. Routes of Viral Infection

Figure 9: Perivascular Cuffing

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Microscopic: 

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Figure 10:  Activated microglial cells proliferate diffusely and form clusters around small foci of necrotic brain tissue (microglial nodules). These are histological clues of viral infection

The encephalitides caused by various arboviruses differ in epidemiology and prognosis, but the histopathologic picture is similar, except for variations in the severity and extent of the lesions within the CNS Lymphocytic meningoencephalitis Perivascular cuffing (tendency for inflammatory cells to accumulate perivascularly) Neurophagia  (single-cell neuronal necrosis with phagocytosis of the debris) Microglial nodules  (small aggregates of microglial cells around foci of necrosis)

Clinical Manifestations: Generalized neurologic deficits, such as seizures, confusion, delirium, and stupor or coma Focal signs such as reflex asymmetry and ocular palsies 

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Severe Cases: Necrotizing vasculitis hemorrhages 

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Viral Encephalitis: CSF Findings Usually colorless Slightly elevated pressure Initially there is a neutrophilic pleocytosis lymphocytic pleocytosis Protein level is elevated Sugar content is normal  

Figure 11:  Activated microglial cells encircle degenerating neurons (neuronophagia). Single-cell neuronal necrosis with phagocytosis of the debris.

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Certain viruses cause intranuclear and cytoplasmic inclusions. These inclusions consist of packed viral particles and products of their replication. Viruses that cause inclusions are Herpes simplex o Cytomegalovirus o Varicella-zoster o Papovaviruses o Measles o Intranuclear inclusions, e.g. herpetic infection (Cowdry  body) Cytoplasmic inclusions, e.g. rabies (Negri body) Nuclear and cytoplasmic inclusions e.g. (cytomegalovirus)

II. HERPES SIMPLEX VIRUS TYPE 1 (HSV-1) ENCEPHALITIS   

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Most common in children and young adults 10% of the patients have a history of prior herpes Alterations in mood, memory, and behavior (most commonly observed clinical presenting symptoms) Location: inferior and medial regions of the temporal lobes and the orbital gyri of the frontal lobes (initial and most severely affected. Most common year-round viral encephalitis Most people become primarily infected with HSV in their teens or twenties HSV type 1 is transmitted by the  saliva

MORPHOLOGY: Gross: Necrotizing and often hemorrhagic Microscopic: Cowdry type A  intranuclear viral inclusion  bodies in both neurons and glia

Figure 12: Viral inclusion bodies 

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Direct indications of viral infection: Viral inclusion bodies o Identification of viral pathogens by o ultrastructural, immunocytochemical, and molecular methods. Presumptive indirect evidence: An immune-mediated disease, such as o perivenous demyelination following systemic viral infections

I. ARTHROPOD-BORNE VIRAL ENCEPHALITIS 

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Arboviruses are an important cause of epidemic encephalitis They are capable of causing serious morbidity and high mortality All have animals hosts and mosquito vectors except for tick-borne type

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PATHOGENESIS: Initial HSV infection  stomatitis  virus remains latent in the trigeminal ganglion  reactivated virus can spread in the: Skin (along the branches of the trigeminal nerve)  sores on the lips (herpes labialis) Brain   infecting the meninges of the anterior and middle cranial fossae From the meninges, HSV extends to the adjacent brain  affects the temporal and inferior frontal lobes (first and more severely) then spreads to the rest of the brain 

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ADULT HSV ENCEPHALITIS Limited to the brain Symptoms: fever, confusion, coma and seizures Involvement of the frontal and temporal lobes –  bizarre  behavior, personality changes, anosmia and gustatory hallucinations Survivors may have Korsakoff’s amnesia, dementia and seizures   

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IV. CYTOMEGALOVIRUS (CMV) Infected pregnant mother may transmit the virus to the fetus, causing a generalized fetal CMV infection CMV infection may develop at any stage during pregnancy and may continue after delivery CNS infection occurs in fetuses and immunosuppressed individuals In utero infection: periventricular necrosis  severe brain destruction   microcephaly with periventricular calcification Infected neurons and glial cells enlarge and develop cytoplasmic and intranuclear inclusions

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Figure 13:  Adult HSV encephalitis (gross) - diffuse softening and edema, hemorrhagic necrosis of the inferior frontal and temporal lobes

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Microscopic findings: (1) Acute phase: Meningeal and perivascular mononuclear cells Increased microglia Focal necrotizing vasculitis Eosinophilic intranuclear inclusions in glial cells and neurons    

Figure 16: Cytomegaly and intranuclear inclusions

Figure 14: Intranuclear eosinophilic amorphous or droplet-like  bodies surrounded by a clear halo (pointed structures) (2) End stage: Brain atrophy and gliosis Brain destruction is more severe than any other viral encephalitis  

CSF Findings: Pleocytosis (early neutrophils, late lymphocytes) Elevated protein (depends on the degree of brain necrosis) Glucose is normal  

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Figure 17: (Gross: Congenital CMV, cortical atrophy and calcifications) heavily infected areas become necrotic and calcify. Lesions have a predilection for the walls of the ventricles. Infection before mid-gestation may derange the process of neuronal migration, causing microcephaly and cortical dysplasia. Cytomegalovirus Encephalitis Rare in adults and usually occurs as part of a generalized CMV infection in i mmunocompromised patients Most common opportunistic viral pathogen in patients with AIDS, affecting the CNS in 15-20% of cases 

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III. HERPES SIMPLEX VIRUS TYPE 2 (HSV-2) 

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HSV-2 infection of the brain is usually manifested in adults as meningitis Severe encephalitis develops in as many as 50% of neonates born by vaginal delivery to women with active primary HSV genital infections HSV-2 may cause an acute, hemorrhagic, necrotizing encephalitis in AIDS patients

NEONATAL HSV INFECTION 70% are caused by HSV type II (herpes genitalis) Acquired during vaginal delivery HSV transmitted across the placenta Acquired by babies in the NB nursery or at home    

Figure 15:  Neonatal HSV encephalitis. (Gross) Diffuse necrotizing encephalitis. In time, the lesions evolve into cystic encephalomalacia with microcephaly.

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V. POLIOMYELITIS  

Poliovirus infection causes a subclinical or mild gastroenteritis. Secondarily invades the nervous system in vulnerable persons

Morphology  Acute cases   Mononuclear cell perivascular cuffing  neuronophagia of the anterior horn motor neurons of  the spinal cord.  Postmortem examination in long-term survivors of symptomatic poliomyelitis shows loss of neurons and gliosis in the affected anterior horns of the spinal cord, some residual inflammation, atrophy of the anterior (motor) spinal roots, and neurogenic atrophy of denervated muscle. Clinical Features.  Initial manifestation: meningeal irritation and a CSF picture of aseptic meningitis  May progress to involve the spinal cord where it causes loss of motor neurons producing flaccid paralysis with muscle wasting and hyporeflexia in the corresponding region of the body—the permanent neurologic residue

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In acute disease, death can occur from paralysis of the respiratory muscles, and a myocarditis sometimes complicates the clinical course. sis or paralysis follows (when it involves the innervation of the compromise may occur and cause long-term morbidity)

Post-polio syndrome  25 to 35 years after the resolution of the initial illness.  Progressive weakness associated with decreased muscle mass and pain

VII. HUMAN IMMUNODEFICIENCY VIRUS   

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VI. RABIES 

Severe encephalitis  Transmitted to humans by the bite of a rabid animal, a dog or various wild animals Morphology Gross: Brain shows intense edema and vascular congestion Microscopic:  Widespread neuronal degeneration  Inflammatory reaction; most severe in the brainstem (basal ganglia, spinal cord, dorsal root ganglia may also be infected)  Regions most severely affected: midbrain, floor of fourth ventricle (part in the medulla)

Figure 18: Negri bodies = Pathognomonic microscopic finding for Rabies  Cytoplasmic, round to oval, eosinophilic inclusions in pyramidal neurons of the hippocampus and Purkinje cells of the cerebellum (sites usually devoid of inflammation) Contains rabies virus  Clinical Features:  Virus enters the CNS by ascending along the peripheral nerves from the wound site  Incubation period (bet 1 and 3 months) depends on the distance between the wound and the brain  The disease begins with nonspecific symptoms (malaise, headache, fever) but the conjunction of these symptoms with local paresthesias around the wound is diagnostic.  As the infection advances, the affected individual exhibits extraordinary CNS excitability; the slightest touch is painful, with violent motor responses progressing to convulsions. Contracture of the pharyngeal musculature on swallowing produces foaming at the mouth, which may create an aversion to swallowing  even water (hydrophobia).  There is meningismus , and as the disease progresses, flaccid paralysis.  Periods of alternating mania and stupor progress to coma and death from respiratory center failure.

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60% of patients with AIDS develop neurologic dysfunction during the course of their illness Infects and destroys CD4 lymphocytes, causing immune deficiency Neurologic Dysfunction due to: Direct or indirect effects of HIV  Opportunistic infection  Primary CNS lymphoma  If there is CNS lymphoma you should rule out the  possibility of immunodeficiency of whatever cause AIDS patients are susceptible to opportunistic infections  CNS toxoplasmosis  Cryptococosis and other mycoses  CMV encephalitis  Papovavirus infections (PML) AIDS patients develop cerebral and other extranodal Bcell lymphomas Directly cause aseptic meningitis, encephalitis, leukoencephalopathy, myelopathy, neuropathy, and myopathy

Patterns of inflammation: Aseptic meningitis  Encephalitis  Meningoencephalitis  1. ASEPTIC HIV 1 MENINGITIS occurs 1-2 weeks of seroconversion in about 10% of o patients; antibodies to HIV can be demonstrated and the virus can be isolated from the CSF mild lymphocytic meningitis, perivascular o lymphocytic inflammation, and some myelin loss in the hemispheres. Among the cell types of the CNS, only microglia have o the appropriate combination of CD4 and a chemokine receptor (CCR5 or CXCR4) to allow for the efficient infection by HIV. During the chronic phase, an HIV encephalitis is o commonly found when symptomatic individuals o come to autopsy. 2. HIV 1 MENINOENCEPHALITIS (SUBACUTE ENCEPHALITIS) Presents with AIDS-dementia complex o Cognitive changes, both mild and florid enough to be o termed, HIV associated dementia, appear to have persisted into the era of effective anti-HIV treatment regimens. HIV Encephalitis  Causes AIDS-dementia complex: progressive memory loss, intellectual deterioration, behavioral changes, and motor deficits  Damage to neurons and oligodendrocytes occurs indirectly through the release of toxic cytokines and alterations of the blood-brain barrier Morphology: Gross  Meninges are clear  Ventricular dilation with sulcal widening  Normal cortical thickness Microscopic:  Diffuse myeline damage (spongy myelinopathy, gliosis)  Neuronal loss  Vascular damage  Microglial nodules  Lymphocytic infiltrates

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BRAIN ABSCESS 

Figure 19: chronic inflammatory reaction with widely distributed infiltrates of microglial nodules,  sometimes with associated foci of tissue necrosis and reactive gliosis

Figure 20: HIV envelope glycoproteins cause the membranes of HIV-infected macrophages to fuse >>> form multinucleated giant cells (Black Arrow)= hallmark of HIV encephalitis. ) Microglial nodules are also found in the vicinity of small blood vessels.  

Arise by: 1. Direct extension  from infection in neighborhood, e.g., middle ear-mastoid, paranasal sinuses, open wounds 2. Hematogenous , particularly from endocarditis and  bronchial-pulmonary infections  Predisposing conditions:  Acute bacterial endocarditis >> multiple abscesses Cyanotic CHD: right-to-left shunt >> pulmonary  filtration of organisms is lost Chronic pulmonary sepsis (bronchiectasis).  **Streptococci and staphylococci: most common organisms in non-immunosuppressed CSF findings:   increased pressure;  white cell count and protein level are elevated  Sugar content is normal. Pathogenesis: Destruction of brain tissue   progressive loss of neurological function Pus and edema of surrounding tissue causes ICP to elevate   Increased ICP and progressive herniation can be fatal. Morphology:

An important component of the microglial nodules the macrophage-derived multinucleated giant cell. In some cases there is also a disorder of white matter characterized by multifocal or diffuse areas of myelin pallor, axonal swelling, and gliosis.

Congenital HIV infection Caused when an HIV infected mother transmits the infection to the fetus  More severe than the adult form may result in microcephaly  Distinctive feature of congenital AIDS: basal ganglia calcification 

Figure 21: (Gross) Discrete lesions with central liquefactive necrosis, a surrounding fibrous granulation tissue capsule, and edema.

I. CEREBRAL TOXOPLASMOSIS  

Pathogenesis  Virus is carried into the brain by infected CD4 lymphocytes and perivascular monocytes  Microglial cells pick up free viral particles  The only cells that harbour HIV in the brain are perivascular monocytes and microglia  Brain damage is caused mainly by activated monocytes and microglial cells producing: Cytokines (such as TNF)  Neurotoxins (such as glutamate and NO  produced by activated monocytes and microglial cells)

VIII. SUBACUTE SCLEROSING PANENCEPHALITIS (SSPE)    

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Etiology: Toxoplasma gondii One of the most common causes of neurologic symptoms and morbidity in patients with AIDS. Clinical symptoms are subacute, evolving during a 1- or 2week period, and may be both focal and diffuse. Primary maternal infection with toxoplasmosis ( early in the pregnancy)  cerebritis in the fetus production of multifocal cerebral necrotizing lesions  calcify  producing severe damage

Morphology: Gross: Brain shows abscesses most involving the  cerebral cortex (near the gray-white junction) and deep gray nuclei  Microscopy: Acute lesions consist of central foci of necrosis with variable petechiae surrounded by acute and chronic inflammation, macrophage infiltration, and vascular proliferation

Rare Progressive clinical syndrome characterized by cognitive decline, spasticity of limbs, and seizures. It occurs in children or young adults, months or years after an initial, early-age acute infection with measles. Probably due to persistent infection of the CNS by an altered measles virus

Microscopic Findings:  

Widespread gliosis and myelin degeneration Viral inclusions, largely within the nuclei of oligodendrocytes and neurons

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