Overview
Definition:
Meningitis is an inflammation of the meninges, the membranes that surround the brain and spinal cord
It can be caused by infections (bacterial, viral, fungal, parasitic) or non-infectious inflammatory conditions
Bacterial meningitis is a life-threatening medical emergency requiring prompt diagnosis and treatment.
Epidemiology:
Bacterial meningitis incidence has significantly decreased with widespread vaccination against *Streptococcus pneumoniae*, *Haemophilus influenzae* type b (Hib), and *Neisseria meningitidis*
However, it remains a major cause of morbidity and mortality, particularly in neonates and immunocompromised individuals
Viral meningitis is more common and generally less severe.
Clinical Significance:
Meningitis can lead to severe neurological sequelae such as hearing loss, developmental delay, seizures, and intellectual disability
Rapid initiation of appropriate empiric antibiotic therapy, guided by age and local resistance patterns, is critical to improve outcomes and reduce mortality and long-term complications
The role of adjunctive dexamethasone is also crucial in specific scenarios.
Clinical Presentation
Symptoms:
Fever
Headache
Nuchal rigidity (stiff neck)
Photophobia
Altered mental status (lethargy, irritability, confusion)
Vomiting
Seizures
In infants: poor feeding, hypotonia, bulging fontanelle, inconsolable crying
In neonates: irritability, poor feeding, vomiting, apnea, seizures, temperature instability.
Signs:
Nuchal rigidity
Positive Kernig's sign
Positive Brudzinski's sign
Fever
Tachycardia
Tachypnea
Altered level of consciousness
Petechial or purpuric rash (suggestive of meningococcal meningitis)
Papilledema (late sign).
Diagnostic Criteria:
Diagnosis is primarily based on clinical suspicion confirmed by cerebrospinal fluid (CSF) analysis
Typical findings in bacterial meningitis include elevated white blood cell count (predominantly neutrophils), elevated protein, and low glucose levels
CSF Gram stain and culture are essential for identifying the causative pathogen and guiding antibiotic therapy
Viral meningitis usually shows lymphocytic pleocytosis, normal or slightly elevated protein, and normal glucose.
Diagnostic Approach
History Taking:
Recent illness (e.g., otitis, sinusitis, pneumonia)
Exposure to sick contacts
Vaccination status
Travel history
Underlying medical conditions (e.g., immunocompromise, neurosurgery)
Onset and progression of symptoms
Focal neurological deficits.
Physical Examination:
Assessment of vital signs
Detailed neurological examination (mental status, cranial nerves, motor and sensory function, reflexes)
Examination for nuchal rigidity
Assessment for Kernig's and Brudzinski's signs
Skin examination for rash
Funduscopic examination.
Investigations:
Complete blood count (CBC) with differential
Blood cultures (prior to antibiotics)
CSF analysis via lumbar puncture: cell count and differential, protein, glucose (compare with serum glucose), Gram stain, bacterial culture and sensitivity, PCR for specific pathogens (e.g., *Streptococcus pneumoniae*, *Neisseria meningitidis*, *Haemophilus influenzae* type b, enteroviruses, herpes simplex virus)
Consider CSF latex agglutination tests
Imaging: CT or MRI brain may be indicated to rule out complications like abscess, hydrocephalus, or increased intracranial pressure, especially if there are focal neurological deficits or signs of herniation.
Differential Diagnosis:
Encephalitis
Brain abscess
Subarachnoid hemorrhage
Migraine
Meningismus (secondary to systemic illness)
Meningeal carcinomatosis or leukemia
Viral syndromes with headache and fever.
Management
Initial Management:
Immediate medical assessment and stabilization
Airway, breathing, circulation (ABC) management
Prompt initiation of empiric antibiotic therapy as soon as possible, ideally after lumbar puncture and blood cultures are obtained
If lumbar puncture is delayed or contraindicated (e.g., signs of markedly increased intracranial pressure, coagulopathy), begin antibiotics empirically based on clinical suspicion and imaging if available
Consider empirical acyclovir if HSV encephalitis is suspected.
Medical Management:
Empiric antibiotics are tailored based on age, local epidemiology, and resistance patterns
For neonates (<1 month): Ampicillin + Gentamicin (or Cefotaxime if concern for resistant Gram-negatives)
For infants and children (1 month to 12 years): Ceftriaxone (or Cefotaxime) is typically the first choice, covering *S
pneumoniae*, *N
meningitidis*, and *H
influenzae*
If *Listeria monocytogenes* is suspected (especially in neonates or immunocompromised), add Ampicillin
Vancomycin may be added if concern for penicillin-non-susceptible *S
pneumoniae* or for empirical coverage in high-risk areas
For adolescents and adults: Ceftriaxone (or Cefotaxime) + Vancomycin
Duration of therapy typically 7-21 days depending on the pathogen
Dexamethasone: Administer 0.15 mg/kg every 6 hours for 2-4 days, starting 15-20 minutes before or with the first dose of antibiotics, for suspected bacterial meningitis in children older than 6 weeks, particularly when caused by *S
pneumoniae*
Not routinely recommended for suspected meningococcal or *H
influenzae* meningitis, or in neonates.
Surgical Management:
Rarely indicated for meningitis itself, but may be required for complications such as brain abscess or hydrocephalus requiring ventriculostomy or shunting.
Supportive Care:
Fluid and electrolyte management
Pain and fever control
Seizure management (e.g., benzodiazepines, levetiracetam)
Monitoring of vital signs, neurological status, and fluid balance
Management of complications like cerebral edema or shock
Hearing screening for all survivors of bacterial meningitis.
Complications
Early Complications:
Cerebral edema
Increased intracranial pressure
Seizures
Hydrocephalus
Sepsis
Shock
Cranial nerve palsies (especially VIIIth nerve leading to hearing loss).
Late Complications:
Hearing loss (sensorineural)
Developmental delay
Intellectual disability
Learning disabilities
Behavioral problems
Epilepsy
Focal neurological deficits
Ventriculitis
Abscess formation.
Prevention Strategies:
Vaccination: Pneumococcal conjugate vaccine (PCV), meningococcal conjugate vaccines (MenACWY, MenB), Hib vaccine
Prompt diagnosis and effective antibiotic therapy
Prophylaxis for close contacts of individuals with meningococcal meningitis (e.g., rifampicin, ciprofloxacin, ceftriaxone)
Good hygiene practices.
Prognosis
Factors Affecting Prognosis:
Causative pathogen (e.g., *S
pneumoniae* and Gram-negative bacilli generally have worse prognosis than *N
meningitidis*)
Age of patient (neonates and elderly have poorer prognosis)
Delay in diagnosis and treatment
Severity of illness at presentation
Development of complications (e.g., seizures, shock, hydrocephalus).
Outcomes:
With prompt and appropriate treatment, mortality for bacterial meningitis can be reduced significantly (e.g., <5% in some series)
However, a substantial proportion of survivors experience long-term neurological sequelae
Viral meningitis usually resolves completely without sequelae.
Follow Up:
Regular follow-up visits are essential for survivors of bacterial meningitis, including developmental assessments and audiometry for hearing loss screening
Neurological and neurocognitive evaluation may be required depending on the severity of the illness and presence of deficits.
Key Points
Exam Focus:
Age-based empiric antibiotic choices for bacterial meningitis
Indications and timing of dexamethasone
CSF findings differentiating bacterial vs
viral meningitis
Key pathogens by age group and their antibiotic sensitivities
Red flags for complications and neuroimaging indications.
Clinical Pearls:
Always consider meningitis in febrile infants and children with altered mental status
Lumbar puncture is crucial but do not delay antibiotics if LP is contraindicated or delayed
Dexamethasone is most beneficial when given before or with the first antibiotic dose and primarily for pneumococcal meningitis
Watch for hearing loss and developmental issues post-bacterial meningitis.
Common Mistakes:
Delaying empiric antibiotics while waiting for diagnostic tests
Inappropriate antibiotic selection for age or suspected pathogen
Forgetting to check serum glucose when interpreting CSF glucose
Not considering dexamethasone in appropriate cases
Underestimating the risk of hearing loss and other long-term sequelae.