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

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

Different pathogens affect people of differing ages.

0-3 months: Group B Strep, E. coli, Listeria, HSV, enteroviruses
3 months-3 years: S. pneumoniae, N. meningitidis, M. tuberculosis, HSV, enteroviruses, herpes virus 6
3 year - adults: S. pneumoniae, N. meningitidis, herpes viruses, adenovirus, enteroviruses

Risk factors include:

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

Meningitis makes people sick.

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

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:

petechial rash is associated with poor prognosis

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)