Meningitis

Introduction
o Inflammation of the meninges.
o Incidence rates in adults is 1.05 cases per 100,000 population (2004-2011)
• Highest rates between the 45-64 age group.
o Usually caused by an infection, however rare non-infective causes of meningitis can occur.
o Viral meningitis is commonly benign and self-limiting.
o If untreated bacterial meningitis is fatal.
• Average mortality rate of community acquired bacterial meningitis is 20%
o The most common causes of bacterial meningitis in adults include:
• Streptococcus pneumonia, Haemophilus influenza type b (if unvaccinated) and Neisseria meningitides.
• Listeria monocytogenes is common in the elderly and immunocompromised population.
o Fungal and atypical bacterial infections can occur in immunocompromised patients or following acute head trauma.
o Meningitis can lead to meningococcal septicaemia, however sepsis can occur without meningitis.
• This is associated with worse prognosis.
Presentation
o Meningitis
• Triad: Headache, neck stiffness and fever.
• Photophobia
• Vomiting
• Fever
• Seizures
• Altered mental state
o Meningococcal septicaemia
• Fever
• Non-blanching rash (purpuric or petechial), however any rash should raise suspicion.
• Shock
History
o If the patient is unstable then measures to stabilise the patient must be taken initially before a history (including collateral) is taken.
o Source of entry → otitis media
o Onset of symptoms
• Acute onset suggests bacterial infection.
o Previous history of head trauma → skull fractures.
• Risk for recurrent meningitis.
• Likely to be pneumococcal cause.
o HIV status or any history suggestive of immunocompromise.
• Atypical infections
o Recent travel
• Toscana virus (Mediterranean).
• Tick Borne Encephalitis Virus (Central and Eastern Europe).
• Other meningococcal (meningitis belt in Africa).
• West Nile Virus (USA).
• Lyme disease (Europe or USA).
• Parasitic meningitis (South America or parts of Africa).
Vital signs
o National Early Warning Score
• 5/6 (or a score of 3 in any parameter) – urgent clinician review.
• 7 or more – urgent assessment by critical care team.
• Low scores can be falsely reassuring → meningitis or meningococcal septicaemia can rapidly deteriorate.
o Glasgow coma scale – recorded for prognostic information and monitoring
• GCS ≤8 – poor outcome
Examination findings
o Presence or absence of rash
o Full neurological examination
• Focal signs suggestive of complications such as, venous sinus thrombosis, cerebral oedema e.t.c.
o Kernig’s sign – pain leading to resistance on extension of the knee when both the hip and knee are flexed at 90 degrees
o Brudzinski’s sign – any positive of the following three medical sign’s
• Cheek sign – pressure on the cheek leads to a reflex rise and flexion of the forearm.
• Symphyseal sign – pressure on the pubic symphysis leads to a reflex abduction of the leg and flexion of the hip and knee.
• Neck sign – forced flexion of the neck leads to reflex flexion of the hips.
Bedside tests
o (see vital signs)
Laboratory investigations
o Suspected meningitis (with no signs of shock or severe sepsis)
• Bloods
• Blood cultures (taken within 1 hour of hospital arrival)
• Full blood count
• Urea & Electrolytes
• LFTs
• Procalcitonin (CRP if unavailable)
• Meningococcal and pneumococcal PCR
• Serology sample
• Glucose
• Throat swab
• Bacterial culture
o Suspected meningococcal sepsis
• Same as meningitis
Radiological investigations
o Suspected meningitis (with no signs of shock or severe sepsis)
o Suspected meningococcal sepsis
Special investigations
o Suspected meningitis (with no signs of shock or severe sepsis)
• Lumbar puncture (LP)
• Opening pressure
• Microscopy, culture and sensitivity
• Meningococcal and pneumococcal PCR
• Protein
• Glucose
• Lactate
o Suspected meningococcal sepsis
• Contraindicated
o LP is contraindicated in:
• Sepsis
• Respiratory or cardiac compromise
• Anticoagulant therapy/ coagulopathy
• Infection at site of LP
• Focal neurological signs
• Papilloedema
• Continuous or uncontrolled seizures
• GCS ≤12
o If safe LP should be taken within 1 hour of arrival or as soon as safely possible.
Management
o Initial:
• Stabilisation of the patient’s airway, breathing and circulation.
• Decision to admit to intensive care should be made in the first hour.
• Rapidly evolving rash.
• GCS or 12 or less.
• Evidence of severe sepsis.
• Initial investigations (as above).
• If sepsis present:
• Antibiotics should be immediately given after blood cultures.
• Fluid rescuscitation commenced (initial bolus of 500ml crystalloid over 5-10 mins).
• If sepsis not present or suspected then a LP should be carried out prior to the use of antibiotics.
• If this is not possible then a LP should be performed within 4 hours or starting antibiotics.
• All patients (meningitis or meningococcal septicaemia) should be given 2g ceftriaxone intravenously (IV) every 12 hours or 2g cefotaxime IV every 6 hours.
• If allergic (history of anaphylaxis) to penicillins or cephalosporins → IV chloramphenicol 25mg/kg every 6 hours.
• Recent travel (within 6 months) to a country with high rates of penincillin resistant pneumococci → IV vancomycin 15-20mg/kg should be added 12-hourly (or 600mg rifampicin 12-hourly IV or orally)
• Over 60 or Immunocoompromised patients → 2g IV ampicillin/amoxicillin 4-hourly in addition to a cephalosporin.
• Input from Infectious diseases team needed.
o Once the causative organism and antimicrobial sensitivities have been found then definitive antibiotic treatment can commence.
• Definitive treatment can last between 4-21 days depending on the organism.
Complications
o Acute:
• Meningitis
• Subdural empyema
• Seizures
• Cerebral venous sinus thrombosis
• Hydrocephalus
• Meningococcal sepsis
• Purpura fulminans
• Septic shock
o Long-term sequelae:
• Hearing loss
• Problems with balance
• Dizziness
• Tinnitus
• Cognitive deficits/learning impairments
• Epilepsy
• Movement disorders
• Visual disturbances
• Amputations (sepsis complication only)
• Psychiatric/Psychosocial problems
• Renal impairment

Reference:
The UK joint specialist societies guideline on the diagnosis and management of acute meningitis and meningococcal sepsis in immunocompetent adults.

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