Meningitis (Meningitides)

Meninges-en[1]

Meningitis is an inflammation of the meninges. The most common causes in adults are bacterial infections with Streptococcus pneumoniae, Neisseria meningitidis or Haemophilus influenzae. Aseptic meningitis may be caused by drugs (eg. NSAIDs, metronidazole and IV immunoglobulin), neoplasms or viruses. Typical signs and symptoms include severe headache, nuchal rigidity, fever, altered mental status, photophobia, phonophobia or vomiting.


Presentation

Most patients present with multiple symptoms. The most common symptoms of meningitis are fever, headache, neck stiffness and altered mental status. Other symptoms include nausea, vomiting, photophobia, confusion and irritability (exhibited by uncontrolled cry in children).

Signs elicited include bulging anterior fontanelle in children less than 18 months. Signs of meningeal irritation, focal neurological signs and some systemic findings are also present.

Workup

Laboratory tests

  • Blood studies like serum electrolytes, serum glucose and blood urea nitrogen.
  • Cultures like blood and urine culture.
  • Lumbar puncture for CSF analysis [5] – Intracranial pressure should be checked before this procedure to avoid cerebral herniation. Focal neurological signs might suggest herniation.
  • Syphilis testing
  • HIV screening

Imaging

CT scan is not routinely done but may be required when then are signs of focal neurological deficit.

Treatment

This involves treating the active infection and managing complications. The medication used is dependent on the type of meningitis. Severe life threatening situations should be managed first by rehydrating patients who are in shock and are hypovolemic, managing seizures and securing the airway if unconscious. Medications that are used are dependent on a wide range of variable like causative organism, age of patient and complications. Such medication may include:

  • Antibiotics: Sulfonamides, tetracyclines, carbapenems, fluoroquinolones, penicilins, cephalosporins.
  • Antivirals
  • Antifungals
  • Antituberculosis agents
  • Corticosteroids [6]
  • Diuretics like osmotic and loop diuretics
  • Anticonvulsants like hydantoins and barbiturates

Prognosis

Meningitis is a medical emergency and if treated early, some patients can attain full remission. Some factors have however been identified that could worsen the prognosis and they include:

  • Advanced age
  • Low Glasgow Coma Scale
  • Tachycardia
  • Reduced CSF leucocyte count
  • Presence of gram-positive cocci on gram staining

Late intervention in bacterial meningitis could lead to permanent brain damage or death. 50% of survivors develop complications like deafness [3], blindness, cranial nerve palsy and hydrocephalus amongst others.

Etiology

Meningitis is caused by a number of agents including:

  • Bacteria: This is the commonest cause and agents include H. influenza, S. pneumonia and N. meningitidis.
  • Viruses: Some viruses that can cause meningitis are enterovirus and West Nile virus.
  • Parasites: This is a very rare cause of meningitis and is fatal in most cases [4].
  • Fungi: This is usually as a result of background immunosuppression and some of the organisms implicated are C. neoformans
  • Drugs: NSAIDs, IV immunoglobulin and metronidazole.

There are some risk factors that make an individual more susceptible to some particular pathogens, like age and immune status.

Epidemiology

The incidence of meningitis is higher in developing countries because of the poor health sectors which is highlighted by the limited availability of preventive measures like vaccination. The incidence is also dependent on the type of meningitis.

Most meningitis forms affects the extremes of age. Children are particular susceptible to many forms of meningitis [2]. Neonates have the highest risk. Individuals older than 60 years are also at increased risk for meningitis infection.

Sex distribution is equal for most forms of meningitis, although overall, it is slightly more common in males. Meningitis is more common in blacks than in Caucasians and Asians. A particular form, meningococcal meningitis, is endemic in tropical regions alike sub-Saharan Africa and India, and there have been recorded periodic outbreak of epidemics.

Sex distribution
Age distribution

Pathophysiology

Pathogens that cause meningitis can get to the meninges in three major ways:

  • Through the blood stream which is the most common route of spread for most pathogens.
  • Through a retrograde neuronal pathway.
  • Through local contiguous spread.

The first event is invasion of the meninges by the pathogens. The exact method of how they cross the blood-brain barrier is poorly documented but it is usually preceded by an overwhelming sepsis. This triggers an inflammatory response and inflammatory cells cross the now porous blood-brain barrier to enter the brain. There is then predominance of lymphocytes or neutrophils based on the pathogen responsible. This process further worsens the condition as it leads to brain swelling and then ischemia of parts of the brain [1]. The inflammatory cells increased the membrane permeability and alter normal chemical contents of the cerebrospinal fluid like glucose and protein.

Prevention

The mainstay of prevention of meningitis is vaccination [7]. Vaccination should be given to individuals who are susceptible to H. influenza and S. pneumonia. Also, individuals who live in and those who travel to endemic areas should be vaccinated against N. meningitidis. Researchers who work with the bacteria should also be vaccinated against it.

Chemoprophylaxis is a second form of prevention and is usually reserved for individuals who have had prior exposure to H. influenza, S. pneumonia and N. meningitidis. Rifampin is the drug of choice. Ceftriaxone can also be used.

Summary

Meningitis is defined as inflammation of the meninges. The meninges are the three layers of membrane that enclose the brain and spinal cord. Meningitis is a disease of the membranes covering the brain. It is often an infectious disease with bacteria being the commonest cause. It manifests via a myriad of CNS symptoms and could result in permanent disability or death. Meningitis is a medical emergency.

Patient Information

Definition

Meningitis is an infection of the layers covering the brain.

Cause

The cause of meningitis are mainly microorganisms although some people at higher risk of meningitis, like very young children and people who are old. People who have an infection is areas close to the brain, like the ear and throat are also at increased risk of getting this disease.

Signs and symptoms

The common symptoms are fever, headache and neck stiffness. Other symptoms are nausea, vomiting, inability to look bright lights, confusion, irritability and confusion. In babies, there will be a characteristic high-pitched cry. Meningitis is an emergency and if any of this symptoms are noted, the individual should be taken to the hospital immediately.

Diagnosis

Diagnosis involves a series of blood tests to check the level of sugar and protein and also to check for infection of the blood. Part of the fluid surrounding the brain, the cerebrospinal fluid is also checked to know the cause of the meningitis. CT scan may also be required.

Treatment

Treatment of meningitis involves mainly, to treating the underlying cause of the disease. Other supportive therapies are instituted as well as treatment of complications that may arise.

Self-assessment

Ask Question


5000 Characters left Format the text using: # Heading, **bold**, _italic_. HTML code is not allowed.

References

  1. Berkhout B. Infectious diseases of the nervous system: pathogenesis and worldwide impact. IDrugs. Nov 2008;11(11):791-5.
  2. Thigpen, M, Rosenstein, NE, Whitney, CG. Bacterial meningitis in the United States--1998-2003. Presented at the 43rd Annual Meeting of the Infectious Diseases Society of America, San Francisco, CA. October 2005;65.
  3. Worsøe L, Cayé-Thomasen P, Brandt CT, Thomsen J, Østergaard C. Factors associated with the occurrence of hearing loss after pneumococcal meningitis. Clin Infect Dis. Oct 15 2010;51(8):917-24.
  4. Ramirez-Avila L, Slome S, Schuster FL, Gavali S, Schantz PM, Sejvar J, et al. Eosinophilic meningitis due to Angiostrongylus and Gnathostoma species. Clin Infect Dis. Feb 1 2009;48(3):322-7.
  5. Seupaul RA. Evidence-based emergency medicine/rational clinical examination abstract. How do I perform a lumbar puncture and analyze the results to diagnose bacterial meningitis?. Ann Emerg Med. Jul 2007;50(1):85-7.
  6. Brouwer MC, Heckenberg SG, de Gans J, Spanjaard L, Reitsma JB, van de Beek D. Nationwide implementation of adjunctive dexamethasone therapy for pneumococcal meningitis. Neurology. Oct 26 2010;75(17):1533-9.
  7. Advisory Committee on Immunization Practices (ACIP). Updated recommendations for use of meningococcal conjugate vaccines. MMWR Morb Mortal Wkly Rep. Jan 28 2011;60(3):72-6.

Media References

  1. Meninges-en, Public Domain

Languages