Meningitis

last authored: Oct 2009, Dave LaPierre

 

Introduction

Meningitis is an infection of the brain meninges. It occurs at a peak age of 6-12 months, and 90% of cases occur in those under 5 years of age.

 

Can follow infection, inflammation, or chemical irritation

 

 

 

The Case of...

a simple case introducing clincial presentation and calling for a differential diagnosis. To get students thinking.

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Causes and Risk Factors

Different pathogens affect people of differing ages.

Risk factors include:

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Pathophysiology

Meningitis normally follows URTI. Mucosal invasion leads to pathogen entry into the bloodstream and seeding of the meninges.

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Signs and Symptoms

Meningitis makes people sick.

  • history
  • physical exam

History

Often will be proceded by a URTI prodrome.

Common symptoms include:

  • fever, lethargy, irritability, photophobia, headache, stiff/sore neck, nausea/vomiting

Infants may show poor feeding, irritablity, lethargy

Physical Exam

Sir Charles Bell - Opisthotonos 1809 (source)

Signs include:

  • Brudzinski's sign: reflex hip/knee flexion upon active flexion of neck
  • Kernig's sign: reflex contraction and pain in hamstrings with leg extension during hip flexion
  • Opisthotonos: body-wide spasm, in which head and heels bent backward
  • Nuchal rigidity

 

Signs of increased intracranial pressure include:

  • ptosis
  • CN VI palsy
  • bradycardia and hypertension
  • apnea
  • papilledema

petechial rash is associated with poor prognosis

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Investigations

  • lab investigations
  • diagnostic imaging

Lab Investigations

Lumbar puncture is helpful for many reasons:

  • increased opening pressure
  • cloudy CSF with bacterial infection
  • exam for WBC, protein, glucose, Gram stain, C&S, latex agglutination test, Ziehl-Neilson stain for TB

Bloodwork: CBC, blood cultures, blood glucose, electrolytes (SIADH)

Diagnostic Imaging

Imaging is not normally helpful

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Differential Diagnosis

Meningitis can be caused by non-infectious causes, such as medications. Other differential diagnoses include:

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Treatments

Patients should be isolated until 24 hours after initiation of culture-sensitive antiobiotics.

Emperic bacterial therapy: vancomycin + cefotaxime, or aminoglycoside + cefotaxime if GN

Viral meningitis: supportive + acyclovir for HSV

Monitor glucose, acid-base, and hydration

Anticonvulsants as needed

 

Prophylaxis

H.influenza type b (Hib) vaccine

meningococcal vaccine - asplenism, complement deficiency, if outbreaks, routine in some places

pneumococcal vaccine: asplenism, immunocompromised, routine

 

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Consequences and Course

 

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The Case of...

Case #2 - a small story wrapping it all up and asking about esp management.

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Additional Resources

eMedicine article

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Topic Development

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editors:

reviewers:

 

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