CNS infections (1 of 2) Ali Al Khader, MD - PowerPoint Presentation

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CNS infections(1 of 2)

Ali Al Khader, MD

Faculty of Medicine

Al-Balqa Applied University

Email: ali.alkhader@bau.edu.jo

How can microbes enter the nervous system?Hematogenous…the most common …mostly arterial …can be from facial veins (through anastomoses with venous sinuses of the skull)

Direct implantation

…penetrating (open) trauma

…lumbar puncture, surgery…etc.

…congenital problems such as myelomeningocele

Local extension

…

from

infected

sinuses (most common: mastoid, frontal), teeth, skull

, or

vertebrae

Some viruses can be transported through peripheral nervous system

…rabies

…herpes zoster

Bacterial infections

Meningitis

Localized infections

Chronic

Acute pyogenic

Abscess

…mostly bacterial

b

ut can be also

c

aused by

fungi or

parasites

Subdural

e

mpyema

…rarely can

be caused byfungi

Meningitis = inflammation of leptomeninges and subarachnoid space…mostly due to infection but may be: chemical meningitis

Meningoencephalitis = meningitis + inflammation of brain parenchyma

May be also caused by fungi

Bacterial acute pyogenic meningitis*Systemic signs of infection

*Headache, photophobia,

phonophobia

,

irritability, clouding of

consciousness

*

N

eck stiffness

*In spinal

tap (lumbar puncture):-Cloudy/purulent (too many neutrophils) CSF

-Increased pressure-As many as 90,000 neutrophils

per cubic millimeter-Increased protein concentration -

Markedly reduced glucose content-Bacteria

may be seen on a smear or may be

cultured …sometimes a few hours before

the neutrophils appear

*

Klebsiella

and anaerobes more in immunosuppressed …atypical clinical course

and CSF findings

Symptoms/signs of meningeal irritation

Bacterial acute pyogenic meningitis, cmplicationsSevere involvement of leptomeningeal veins (phlebitis) may lead to venous occlusion and hemorrhagic

infarction of the underlying

brain

Extension into brain substance…focal

cerebritis

…

sometimes formation of abscess

Extension into ventricles…

ventriculitis

Waterhouse-Friderichsen syndrome…adrenal hemorrhage due to meningococcal meningitis-associated septicemia (along with petechial rash)…also with pneumococcus

Bacterial acute pyogenic meningitis, morphology**On microscopic

examination:

*Neutrophils may

fill the entire subarachnoid space or, in

less severe cases

, may be confined to regions adjacent

to leptomeningeal blood vessels

*In untreated meningitis, Gram stain reveals varyingnumbers of the causative

organism

Elsevier. Kumar et al. Robbins and

Cotran

pathologic basis of diseases 9

th

Viral infections

Meningitis

Brainstem and spinal cord syndromes

Acute aseptic

Rhombencephalitis

Spinal poliomyelitis

Encephalitis

Encephalitis (not arthropod-borne)

Arthropod-borne encephalitis

Of viral infections, we will only discuss this in this lecture

…other viral pathologies will be discussed in the next lecture

Acute aseptic (viral) meningitis“Aseptic” is a clinical term that means: No organisms in bacterial culture are found in a patient with a picture of meningitis…also meningeal irritation, fever, and alterations of consciousness…but less fulminant than pyogenic meningitis…self-limitedViral

etiology (in about 80% of

cases enteroviruses

), but may be bacterial,

rickettsial

, or

autoimmune in

origin

Acute aseptic (viral) meningitis, cont’dCSF finding are different from pyogenic meningitis: …the pleocytosis (increased WBC count) here is lymphocytic not neutrophilic

…the

protein elevation is only

moderate

…the glucose

content is nearly always

normal

Viral aseptic

meningitides are usually self-limited and are treated symptomatically

On microscopic examination, there is either no recognizable abnormality

or a mild to moderate leptomeningeal lymphocytic infiltrate

Aseptic meningitis-like picture…due to chemical irritant or rupture of epidermoid cyst into subarachnoid space (chemical meningitis)No organisms isolated (sterile CSF)NeutrophilsMay be increased proteinNormal glucose

Chronic meningitisMainly: mycobacteria, some spirochetes, and fungi…may also involve the brain parenchyma

Tuberculous meningitis

Spirochetal infection

Fungal meningitis

…see next slide

*General symptoms: headache

,

malaise

,

mental confusion

, and

vomiting

*Moderate increase in WBCs

(mononuclear or mononuclear +

polymorphonuclear

)

*Protein is markedly high*Glucose is moderately reduced or normal*May cause a well-defined mass (=

tuberculoma)*May cause arachnoid fibrosis…hydrocephalus

*Neurosyphilis…tertiary (occurs in 10% of the untreated)…more and more severe in AIDS…3 patterns (isolated or in combination)

Meningovascular

n

eurosyphilis

…

obliterative

endarteritis

…base of brain

Paretic

n

eurosyphilis

…progressive parenchymal

l

oss and increased microglial

c

ells…loss

of

mental and

physical functions

…psychiatric problems

…eventually severe

d

ementia

Tabes

dorsalis

…damage

to the sensory nerves

in

the dorsal

roots

…impaired joint position sense and

ataxia

…loss of pain sense…skin & joint

damage (Charcot joints)

…lightning pains

…absence of deep tendon reflexes

*

Neuroberreliosis

Remember:

-sensory ataxia

…positive Romberg test

…Stamping gait

Fungal meningitisCryptococcus neoformansHistoplasma capsulatumCoccidioides immitis

Especially in immunocompromised

…can be associated with high fatality

Parenchymal infectionsBrain abscessViral encephalitis…will be discussed in the next lectureFungal encephalitisParasitic encephalitis

Brain abscessMostly bacterialOf the predisposing conditions:-Acute bacterial endocarditis, from which septic emboli are released …multiple abscesses

-

cyanotic

congenital heart

disease

…right-to-left

shunt and loss of

pulmonary filtration of

organisms -chronic pulmonary infections, as in bronchiectasisDiscrete destructive lesion with liquefactive necrosis surrounded by granulation tissue/fibrosis…outside: gliosis

Elsevier. Kumar et al. Robbins basic pathology 10th

Check

http

://

www.radiologyassistant.nl/en/p47f86aa182b3a/brain-tumor-systematic-approach.html for references

Brain abscess, clinical manifestationsLike a tumor: focal neurological deficit and increased intracranial pressureCSF white blood cell count and protein may

be elevated

…However, lumbar

puncture has little role in the

diagnosis of

brain

abscess since organisms are more reliably cultured by draining the

abscess directlyA systemic or local source of infection may

or may not be apparentAbscess rupture can lead to ventriculitis, meningitis, and venous sinus thrombosis

If untreated, progressive and can result in fatal herniation

Fungal encephalitisUsually granulomas or abscesses, often with meningitisCandida albicans…multiple microabscesses, with or without granulomasMucormycosis

…infection of nose/sinuses in diabetics with ketoacidosis is a risk

Aspergillus

fumigatus

…

widespread septic hemorrhagic infarctions because

of its

marked

predilection

for blood vessel wall invasion with subsequent thrombosis

Parasitic parenchymal infectionsCerebral toxoplasmosis (by Toxoplasma gondii):-immunosuppressed adults

or

neonates (

transplacentally

)

…triad of

chorioretinitis, hydrocephalus, and intracranial calcifications

-inflammation and breakdown of the blood-brain barrier at sites of

infection…imaging studies often show edema associated with ring- enhancing lesions

-abscesses, frequently multiple, most often involving the cerebral cortex (near the gray-white junction) and

deep gray nuclei-both free tachyzoites

and encysted bradyzoites may be found at the periphery of the necrotic foci

Giemsa

Check

https://emedicine.medscape.com/article/229969-overview for references...modified

Check

https://www.cdc.gov/dpdx/toxoplasmosis/index.html for references...modified

Tachyzoites

Bradyzoites in cyst

Parasitic parenchymal infections, cont’dCysticercosis:-It is the consequence of an end-stage infection by the tapeworm Tenia solium

-

Cysticercosis

typically manifests as a mass lesion and

can cause

seizures. Symptoms can intensify when the

encysted organism

dies, as occurs after therapyAmebiasis

-Naegleria species…rapidly fatal necrotizing encephalitis

-Acanthamoeba…chronic granulomatous meningoencephalitis

Thank You