INFECTIONS OF THE CNS Flashcards
Infections of the CNS include
meningitis, encephalitis, meningoencephalitis, cerebral abscess and myelitis.
Review of meninges
from external to internal
Bone of the skull
Epidural space
Dura mater
Subdural
Arachnoid matter
Subarachnoid space
Pia mater
Bacterial meningitis
How can bacteria reach the brain?
- Hematogenous spread
- From contiguous structures
Sinuses, middle ear or mastoid bone - Directly:
Congenital defects od cranial bones
Cranial trauma
Iatrogenic (neurosyrgery)
Bacterial Meningitis- Epidemiology
Adult population:
* Incidence: 5-10 cases / 100.000
* Predominate during cold season
* Common bacteria:
– Pneumococcus (vaccination possible for several serotypes)
– Meningococcus (vaccination possible for several serotypes)
– Haemophilus influenzae (incidence decreasing)
– Listeria monocytogenes
– Staphylococcus
– Hospital infections (staphyilococcus and gram- bacteria)
Children: the most common pathogens in children are:
1. H. Influenzae (vaccination)
2. Pneurmococco
3. Meningococco (vaccination)
Bacterial Meningitis - Risk Factors
o Age: 70% < 5 years
o Living in crowded communities: kindergarden, schools, caserme ecc
o hospitals
o Social and economical status
Bacterial Meningitis - Pathology
- Acute development of a purulent infection in the subarachnoid space; inflammation and hyperemia.
- Purulent material accumulates on the cerebral surface and sulci, Wirchow-Robin space, may also surround cranial nerves.
- Cortical edema
- Possibility of arterial and venous occlusions
- Purulent infection may recover; deposit of fibrinoid material in the subarachnoid space may follow.
- Spinal fluid circulation may then be impaired with development of hydrocephalus
Bacterial Meningitis - Clinical signs in children < 2 years of age:
o Irritability
o Weak weeping
o Vomiting
o Lethargy, stupor, coma
o Respiratory disturbances
o Rise of body temperature
o Fontanelle tension
o Skin Rash
Bacterial Meningitis - Clinical signs in older children and adults:
o Headache
o Vomiting
o Photophobia
o Rigor nucalis
o Hyperthermia
o Disturbances of vigilance
o Seizures
o Systemic manifestations: rush, arthritis, petechiae
Headache and rigor nucalis are due to activation of protective reflexes that tend to protect the spine.
BM - TYPICAL SIGNS
-Kernig sign (impossibility to extend the legs while hips are flexed
-Brudzinski sign (opposition to neck flexion).
BM NOTES
Seizures, confusion, stupor, coma, are due to the encephalopathy underlying the meningitis. Symptoms due to activation of cytokines and other toxic factors. Cerebral parenchymal lesions rare (exception: arteriolar or venous occlusion with infarcts).
Cranial nerves involvement:
* III,IV VI : diplopia, paralysis of ocular movements
* VII: peripheral facial paresis
* VIII: hypoacusia
BM DIAGNOSIS
CSF examination:
o Increase >CSF pressure (> 180 mm H2O)
o CSF non transapernt
o WBC > 1000/ml
o Proteins > 150 mg/dl
o Glucose < 30 mg/dl
CSF Sediment (Gram staining) may allow the identification of the bacteria; CSF culture RIA, latex-particle agglutination (LPA)-ELISA expensive may not be necessary.
BM IMAGING
Imaging: MRI + gadolinium cortical reaction, inflammation of the meninges. Possible demonstration of infarcts
BM THERAPY
Antibiotics treatment can be:
* Empiric
* Specific
BM PROGNOSIS
- Behavioral problems
- hypoacusia
- Language disturbances
- Mental delay
- Visual disturbances
- Motor abnormalities
- Epilepsia
- Hydrocephalus
CHRONIC MENINGITIS
- Slow - progressive course
- Symptoms lasting > 4 weeks
- Persistent inflammatory CSF
- Usually in immunodepressed patients or patients with chronic disorders (TBC)
- Variable ethiology
CM SYMPTOMS
- Headache
- Cervical pain
- Cranial nerves involvement
- Mild cognitive disturbances (attention deficit)
- Behavioral changes
- Hydrocephalus
- Radiculopathies
TBC OF THE CNS
Acute presentation is rare, while the subacute-chronic (weeks) presentation is more frequent.
Warning signs: fever, general discomfort, sub continuous headache.
Cranial nerves involvement is frequently observed (more often III, IV, V, VI, VII).
CEREBRAL ABSCESS
It can be secondary to cranial fracture (< 10% of cases); more often it can be secondary to focal infections
* 40%: paranasal sinuses infections (frontal and sphenoidal sinuses) can lead to frontal and parieto-temporal abscesses
* Middle ear infections can lead to cerebellar abscesses
* Secondary to pulmonitis, bacterial endocarditis
CEREBRAL ABSCESS SYMPTOMS
Symptoms:
* Headache
* Somnolence
* Confusion
* Seizures (focal, generalized, focal-generalized)
* Focal signs (signs depend on the site of abscess)
* > WBC, fever: not always, systemic symptoms may be absent
Viral diseases of the nervous system
HIV-1; HIV-2, HSV-1, HSV-2, VZV, EBV, CMV, poliovirus, rabies virus.Viruses may have specific tropism for specific cells:
– Poliovirus: motoneurons;
– VZV: peripheral sensitive neurons;
– Rabie: brainstem neurons.
– JC virus: oligodendrocytes (progressive multifocal leukoencephalopathy).
– Herpes simplex: may cause severe encephalitis with loss of selectivity (grey matter, white matter, arteries, meninges)
How do viruses enter the CNS?
Respiratory
Oro-fecal
Genital
Mucosae
Animals-insects bites
Transplacental
Viruses can lead to:
- Acute aseptic meningitis
- Meningoencephalitis
- Ganglionitis (herpes zoster)
- Chronic diseases (AIDS)
- Poliomyelitis
- Chronic infetions: Progressive multifocal leucoencephalopathy (PML)
VIRAL EPIDEMIOLOGY
- Incidence: 11 per 100.000
- Males>female
- Any age. More frequent in children < 1 year
- More common in hot season
VIRAL SYMTOMS
- Acute onset of fever (38 - 40°), headache, rigor nucalis (often mild)
- Photophobia, pain during ocular movements
- Rash, exanthema
The virus is identified in only 11% of cases, and the viruses are: enterovirus, virus parotite, arbovirus, HSV, HIV.
