Overview of Acute Meningitis

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Questions and Answers

What is the primary cause of acute pyogenic meningitis in neonates?

Escherichia coli and group B streptococci (correct)

Streptococcus pneumoniae

Listeria monocytogenes

Neisseria meningitidis

Which characteristic finding in CSF is typically associated with acute pyogenic meningitis?

Lymphocyte predominance

Decreased protein concentration

Normal glucose content

Cloudy or purulent appearance (correct)

Which age group is most commonly affected by Streptococcus pneumoniae in cases of acute pyogenic meningitis?

Infants

Adolescents and young adults

Elderly individuals (correct)

Neonates

What complication is associated with meningitis and may result from septicemia?

Waterhouse-Frederichsen syndrome Signup and view all the answers

What is the primary role of immunization against Haemophilus influenzae in the context of meningitis?

To lower the risk of infection among infants Signup and view all the answers

What symptom is commonly associated with meningeal irritation during acute pyogenic meningitis?

Clouding of consciousness Signup and view all the answers

In immunosuppressed individuals, which of the following can cause purulent meningitis?

Klebsiella or anaerobic organisms Signup and view all the answers

Which of the following symptoms is least likely to be associated with acute pyogenic meningitis?

Persistent cough Signup and view all the answers

What is a common characteristic of the exudate in pneumococcal meningitis?

It is densest over the cerebral convexities near the sagittal sinus. Signup and view all the answers

What may result from untreated pyogenic meningitis?

Hydrocephalus may develop. Signup and view all the answers

Which pathogen accounts for the majority of viral aseptic meningitis cases?

Enteroviruses Signup and view all the answers

What is a primary clinical finding in aseptic meningitis?

Moderate protein elevation in CSF Signup and view all the answers

What pathological change can occur in fulminant meningitis?

Inflammation extending to the ventricles. Signup and view all the answers

What distinguishes aseptic meningitis from bacterial meningitis?

Aseptic meningitis typically shows lymphocytic pleocytosis. Signup and view all the answers

Which condition may lead to an aseptic meningitis-like picture?

Introduction of a chemical irritant Signup and view all the answers

What is a potential complication of chronic adhesive arachnoiditis from pneumococcal meningitis?

Hemorrhagic cerebral infarction. Signup and view all the answers

Which characteristic is true regarding the choroid plexus in the context of infections?

It is often involved in blood-borne infections. Signup and view all the answers

Study Notes

Acute Meningitis Overview

Meningitis is inflammation of the meninges (membranes surrounding the brain and spinal cord) and cerebrospinal fluid (CSF) in the subarachnoid space.
Meningoencephalitis involves inflammation of both meninges and brain tissue.
Causes include infections (most common), non-bacterial irritants (chemical meningitis), and autoimmune diseases.
Types include acute pyogenic (bacterial), aseptic (viral), and chronic (tuberculous, spirochetal, or cryptococcal). Each type has distinct CSF characteristics.

Acute Pyogenic (Bacterial) Meningitis

Common causes vary by age group:
- Neonates: Escherichia coli, group B streptococci
- Elderly: Streptococcus pneumoniae, Listeria monocytogenes
- Adolescents/young adults: Neisseria meningitidis
Haemophilus influenzae infection incidence has decreased in developed countries due to immunization, especially in infants.
Symptoms include systemic infection signs plus headache, photophobia, irritability, altered consciousness, and neck stiffness.
CSF findings include cloudy/purulent CSF, high neutrophil count (up to 90,000/mm³), increased CSF pressure and protein, and decreased glucose.
Untreated can be fatal; antibiotics dramatically reduce mortality.
A serious complication is Waterhouse-Friderichsen syndrome (adrenal gland hemorrhages) often associated with meningococcal and pneumococcal meningitis.
Immunosuppressed individuals can develop purulent meningitis caused by different infectious agents (e.g., Klebsiella, anaerobic organisms); this can be harder to diagnose.

Morphology of Acute Pyogenic Meningitis

Exudate (pus) is present on the brain surface, thickening the leptomeninges.
Blood vessels in the meninges are engorged.
Exudate distribution varies depending on the causative organism (e.g., H. influenzae typically basal, S. pneumoniae often over convolutions).
Pus may follow blood vessels to other brain areas.
Fulminant meningitis can cause inflammation in the ventricles (ventriculitis).
Ventricles are potential access points for blood-borne infections due to lack of a blood-brain barrier in the choroid plexus.
Microscopic examination shows neutrophils in the subarachnoid space; often around blood vessels. Gram stain can reveal bacteria.
Inflammation might extend into brain tissue, causing vasculitis and potential hemorrhagic infarcts.
Leptomeningeal fibrosis can lead to hydrocephalus.
Chronic adhesive arachnoiditis, especially in pneumococcal meningitis, results from large capsular polysaccharide quantities producing gelatinous exudate that promotes arachnoid fibrosis.

Acute Aseptic (Viral) Meningitis

Characterized by absence of bacteria in CSF while presenting typical meningitis symptoms (meningeal irritation, fever, altered consciousness).
Primarily viral, but may have bacterial, rickettsial, or autoimmune origins.
Less severe than pyogenic meningitis.
CSF findings: lymphocytic pleocytosis (increased lymphocytes), moderate protein elevation, and usually normal glucose content.
Usually self-limiting and treated symptomatically.
Etiologic agent identified in a small percentage of cases; new detection techniques (e.g., next-generation sequencing) are being developed.
Enteroviruses are common causative agents (accounting for ~80% of cases), with seasonal and geographic variations.
Chemical meningitis can mimic aseptic meningitis (caused by substance introduced into the subarachnoid space).
CSF is sterile, neutrophil pleocytosis, increased protein, and normal glucose content.

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Description

This quiz provides an overview of acute meningitis, covering its causes, symptoms, and types, including acute pyogenic and aseptic meningitis. You'll learn about the specific pathogens responsible for infections in different age groups, as well as the implications of immunization on incidence rates. Test your understanding of this critical health issue.