Meningitis

Meningitis is the inflammation of the protective membranes (meninges) that cover the brain and spinal cord, typically resulting from bacterial or viral infections elsewhere in the body that have spread into the bloodstream and into the cerebrospinal fluid (CSF). Other causes of meningitis, such as fungal, protozoal, or specific non-infectious etiologies, are less common. Meningitis should be differentiated from encephalitis, which is the inflammation of the brain itself. Meningitis can affect individuals of any age group, from newborns to the elderly, although the specific cause may differ. Typical signs and symptoms of meningitis include fever, headache, stiff neck, photophobia, and vomiting. Although viral meningitis is the most common cause and may resolve within a few days without treatment, anyone suspected of having meningitis should be evaluated promptly, as bacterial meningitis can be severe and requires immediate treatment.

Meninges-en

Symptoms of Meningitis

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Neck stiffness

Bacterial Meningitis

Pyogenic meningitis

Meningitis-MRI

Meningitis world map

Causes

Infectious

There is a geographic variation in the incidence of the bacteria, e.g., in rural Thailand, the most common cause is S. suis. Tuberculous meningitis may also be more prevalent in developing countries.

Risk Factors

• Pneumococcal meningitis due to S. pneumoniae can be precipitated by various factors, the most significant of which is pneumococcal pneumonia. Additional risks include pneumococcal sinusitis or otitis media, alcoholism, diabetes mellitus, splenectomy, hypogammaglobulinemia, and head trauma. Mortality remains around 20% despite antibiotic therapy.
• Meningococcal meningitis caused by N. meningitidis after nasopharyngeal colonization may be either asymptomatic or become systemically invasive, progressing to death within hours of symptomatic onset. The primary host capability to eradicate N. meningitidis is through the production of antibodies and the lysis of the bacterium by both the classic and alternative complement pathway. Patients with impaired or deficient complement components, particularly the C5-9 lytic component, are highly susceptible to disseminated meningococcal infections.
• Group B streptococci meningitis due to S. agalactiae is a significant cause of neonatal meningitis, with the risk increasing if the mother has positive vaginal colonization during birth and was not given antibiotics.
• Listeria infection is mainly acquired through the consumption of contaminated foods. Reported foods at risk for Listeria contamination include milk, coleslaw, soft cheeses, and various ready-to-eat foods such as deli meat and uncooked hot dogs.
• Gram-negative bacilli infection is more common in individuals with chronic conditions such as diabetes mellitus, cirrhosis, alcoholism, or chronic urinary tract infections.
• Staphylococcus infections, such as those caused by S. aureus, are Once the specific causative organism is identified, treatment can be tailored to target that organism. In addition to antibiotics, other treatments may be administered, including:

• Corticosteroids: Dexamethasone has been shown to reduce mortality and morbidity in bacterial meningitis caused by Streptococcus pneumoniae. It is usually given before or at the same time as the first dose of antibiotics.
• Anticonvulsants: May be used to treat or prevent seizures in patients with meningitis. Commonly used anticonvulsants include phenytoin and levetiracetam.
• Analgesics and antipyretics: Pain relievers like acetaminophen or ibuprofen can help alleviate headaches, fever, and general discomfort.
• Fluid and electrolyte management: Ensuring adequate hydration and electrolyte balance is essential in the management of meningitis patients, particularly in cases of severe illness and dehydration.
• Monitoring for complications: Patients with meningitis should be closely monitored for potential complications, such as increased intracranial pressure, seizures, or other neurological issues.
• In the case of viral meningitis, there is usually no specific antiviral treatment available. Most cases of viral meningitis resolve on their own within a few days to a week. Supportive care, including pain relief, fever management, and rest, is typically recommended for these patients. However, in certain cases, such as meningitis caused by the herpes simplex virus (HSV), antiviral medications like acyclovir may be used to shorten the duration and severity of the illness.

Prevention of meningitis

Prevention of meningitis primarily involves vaccination against common causative agents. Vaccines are available for some of the leading causes of bacterial meningitis, including Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae type b. Ensuring that individuals, especially those in high-risk groups, receive the appropriate vaccinations can significantly reduce the incidence of meningitis. Additionally, maintaining good personal hygiene and avoiding close contact with individuals who are sick can help to prevent the spread of meningitis-causing pathogens.

In addition to vaccinations, the following preventive measures can help lower the risk of meningitis:

• Practice good hygiene: Regular handwashing with soap and water, or using an alcohol-based hand sanitizer, is essential for reducing the spread of germs that can cause meningitis. Avoid touching your face, especially your mouth, nose, and eyes, with unwashed hands.
• Maintain a healthy lifestyle: A strong immune system can better fight off infections. To keep your immune system strong, eat a balanced diet, exercise regularly, get adequate sleep, and manage stress.
• Avoid close contact with sick individuals: Limit close contact with individuals who are showing signs of illness, especially respiratory infections, as some meningitis-causing pathogens can be transmitted through respiratory droplets.
• Cover your mouth and nose: When coughing or sneezing, use a tissue or the crook of your elbow to prevent the spread of respiratory droplets.
• Do not share personal items: Avoid sharing items such as eating utensils, drinking glasses, toothbrushes, and other personal items that can harbor germs.
• Travel precautions: If you are traveling to regions with a high prevalence of meningitis, ensure you are up-to-date on vaccinations and follow local guidelines for disease prevention. In some cases, taking prophylactic antibiotics may be recommended for travelers to certain high-risk areas.
• Be aware of outbreaks: Stay informed about meningitis outbreaks in your community, and follow public health recommendations to protect yourself and your family.

Prompt diagnosis and treatment of meningitis are crucial for minimizing the risk of complications and improving patient outcomes. If you suspect that you or someone you know may have meningitis, seek medical attention immediately. Early intervention can help prevent long-term consequences and, in some cases, save lives.

Complications

Increased Intracranial Pressure

Increased intracranial pressure is a well-known and potentially fatal complication of bacterial meningitis. The primary sign of increased ICP is altered states of consciousness, which can range from lethargy to confusion to coma. Over 90% of cases will present with CSF opening pressure > 180 mmHg, and some with > 400 mmHg. Other signs of increased ICP, besides headache and vomiting, include papilledema, sixth cranial nerve palsies, decerebrate posturing, and Cushing's reflex (bradycardia, hypotension, and Cheyne-Stokes respiration). The most fatal complication of ICP is brain herniation, occurring in 1 to 8% of cases.

Diagnosis

Although diagnosing meningitis and its specific cause is crucial, laboratory testing takes time. Due to the urgency of bacterial meningitis, treatment is often initiated before a definitive diagnosis is made.

When meningitis is suspected in a patient, a blood culture should be drawn and empiric antibiotics started immediately. Meningitis diagnosis can then be carried out with a lumbar puncture (LP) to examine the CSF. However, if the patient has had recent head trauma, is immunocompromised, has known malignant or CNS neoplasm, or has focal neurological deficits such as papilledema or altered consciousness, a CT or MRI should be performed before the LP to avoid potentially fatal brain herniation during the procedure. Otherwise, the CT or MRI should be performed after the LP, with MRI being preferred over CT due to its better ability to show areas of cerebral edema, ischemia, and meningeal enhancement. Antibiotics started within 4 hours of the lumbar puncture will not significantly affect lab results.

During the LP, the opening pressure is noted, and the CSF fluid is sent for examination of white blood cells, red blood cells, glucose, protein, Gram stain, culture, and possibly latex agglutination test, limulus lysates, or PCR for bacterial DNA.

CSF analysis in bacterial meningitis:

• Opening pressure: > 180 mmH2O
• White blood cell: 10-10,000/uL with neutrophil predominance
• Glucose: < 40 mg/dL
• CSF glucose to serum glucose ratio: < 0.4
• Protein: > 4.5 mg/dL
• Gram stain: positive in >60%
• Culture: positive in >80%
• Latex agglutination: may be positive in meningitis due to Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae, Escherichia coli, Group B Streptococci
• Limulus lysates: positive in Gram-negative meningitis

CSF cultures are usually positive in 30 to 70% of patients with viral meningitis, and those with negative cultures will typically have a positive CSF PCR test.

Treatment

Bacterial meningitis is a medical emergency with a high mortality rate if left untreated. All suspected cases, no matter how mild, require emergency medical attention. Empiric antibiotics should be started immediately, even before the results of the lumbar puncture and CSF are known. Since the most common organisms involved are Streptococcus pneumoniae and Neisseria meningitidis, therapy usually begins with a third-generation cephalosporin (such as ceftriaxone or cefotaxime) plus vancomycin. In patients who are younger than 3 years of age, older than 50 years of age, or immunocompromised, ampicillin should be added to cover Listeria monocytogenes. For hospital-acquired meningitis and cases following neurosurgical procedures, staphylococci and gram-negative bacilli are common causative agents. In these patients, ceftazidime should replace ceftriaxone or cefotaxime, as it is the only cephalosporin with activity against CNS infection with Pseudomonas aeruginosa.

Adjunctive Therapy

In addition to antibiotic treatment, adjunctive therapy may be necessary to manage complications and reduce inflammation. Some possible adjunctive treatments include:

Corticosteroids: Dexamethasone is often used to reduce inflammation and can improve outcomes in some cases, particularly in patients with pneumococcal meningitis. It should be administered before or with the first dose of antibiotics. Anticonvulsants: Seizures are a common complication of bacterial meningitis, and anticonvulsant medications may be used to prevent or treat them. Analgesics and antipyretics: Pain and fever can be managed with medications such as acetaminophen or ibuprofen. Fluid management: Maintaining proper hydration and electrolyte balance is essential for patients with meningitis, but overhydration should be avoided, as it can worsen cerebral edema. Monitoring and managing increased intracranial pressure: This may involve administering medications, such as osmotic agents, or employing surgical interventions, such as ventriculostomy, if necessary.

Specific treatments

Once the results of the CSF analysis are known, along with the Gram-stain and culture, empiric therapy may be switched to therapy targeted to the specific causative organisms. Because antibiotic-resistance is a prevalent problem, information from drug susceptibility testing should also be gathered.

Neisseria meningitidis can usually be treated with a 7-day course of IV antibiotics:

Penicillin-sensitive -- penicillin G or ampicillin Penicillin-resistant -- ceftriaxone or cefotaxime Prophylaxis for close contacts (contact with oral secretions) -- rifampin 600 mg bid for 2 days (adults) or 10 mg/kg bid (children). Rifampin is not recommended in pregnancy, and as such, these patients should be treated with single doses of ciprofloxacin, azithromycin, or ceftriaxone Streptococcus pneumoniae can usually be treated with a 2-week course of IV antibiotics:

Penicillin-sensitive -- penicillin G Penicillin-intermediate -- ceftriaxone or cefotaxime Penicillin-resistant -- ceftriaxone or cefotaxime + vancomycin Listeria monocytogenes is treated with a 3-week course of IV ampicillin + gentamicin.

Gram-negative bacilli -- ceftriaxone or cefotaxime

Pseudomonas aeruginosa -- ceftazidime

Staphylococcus aureus

Methicillin-sensitive -- nafcillin Methicillin-resistant -- vancomycin Streptococcus agalactiae -- penicillin G or ampicillin

Haemophilus influenzae -- ceftriaxone or cefotaxime

Viral meningitis

Unlike bacteria, viruses cannot be killed by antibiotics. Patients with mild viral meningitis may be allowed to stay at home, while those who have a more serious infection may be hospitalized for supportive care. Patients with mild cases, which often cause only flu-like symptoms, may be treated with fluids, bed rest (preferably in a quiet, dark room), and analgesics for pain and fever. The physician may prescribe anticonvulsants such as dilantin or phenytoin to prevent seizures and corticosteroids to reduce brain inflammation. If inflammation is severe, pain medicine and sedatives may be prescribed to make the patient more comfortable.

Increased intracranial pressure

Treatment of increased intracranial pressure includes elevation of the head to 30 to 45 degrees, intubation and hyperventilation, and mannitol.

Main article: intracranial pressure

Vaccination

Vaccinations against Haemophilus influenzae (Hib) have significantly decreased early childhood meningitis.

Prognosis

The prognosis for meningitis varies depending on several factors, including the cause, the severity of the infection, the patient's age and overall health, and the timeliness of diagnosis and treatment. Generally, viral meningitis has a better prognosis than bacterial meningitis, with most cases resolving on their own within 7 to 10 days. However, severe cases of viral meningitis may require hospitalization and supportive care.

Bacterial meningitis, on the other hand, is a more severe and potentially life-threatening condition. If left untreated, the mortality rate can be as high as 70%, but with prompt diagnosis and appropriate treatment, the mortality rate can be reduced to around 15-20%. Even with appropriate treatment, some patients may experience long-term complications such as hearing loss, cognitive impairment, seizures, and motor deficits.

The prognosis for fungal, protozoal, and non-infectious meningitis varies depending on the specific cause, the patient's immune status, and the effectiveness of treatment. In general, these types of meningitis are less common and may require more specialized treatment approaches.

Follow-up and Rehabilitation

Following recovery from meningitis, patients may require ongoing follow-up care and rehabilitation to address any long-term complications or residual effects of the infection. Depending on the severity of the illness and the presence of any complications, patients may need:

• Physical therapy: To help regain strength, mobility, and coordination, especially if motor deficits are present.
• Occupational therapy: To help patients relearn everyday tasks and adapt to any changes in their physical or cognitive abilities.
• Speech therapy: To address any speech or language difficulties that may have arisen as a result of the infection.
• Audiology services: For patients who experience hearing loss or other auditory complications, ongoing audiological care and possible hearing aids or cochlear implants may be necessary.
• Cognitive rehabilitation: In cases where cognitive impairment is present, patients may benefit from cognitive rehabilitation programs to help improve memory, attention, and problem-solving skills.
• Psychological support: The experience of a serious illness like meningitis can be emotionally challenging for patients and their families. Mental health support services, such as counseling or therapy, can be beneficial in coping with the emotional impact of the illness and adjusting to any long-term complications.

Regular follow-up visits with healthcare providers are essential to monitor the patient's progress and adjust treatments as needed. With appropriate care and support, many patients can make a full or near-full recovery from meningitis and lead healthy, productive lives.

Glossary

Types of Meningitis

• African meningitis belt - A region in sub-Saharan Africa known for its high incidence of epidemic meningitis, primarily caused by Neisseria meningitidis.
• Aseptic meningitis - A form of meningitis not caused by bacterial infection and therefore does not grow bacteria in cultures; often caused by viruses, fungi, or other non-bacterial agents.
• Austrian syndrome - A rare combination of meningitis, pneumonia, and infective endocarditis, typically associated with infection by Streptococcus pneumoniae.
• Chronic meningitis - Meningitis characterized by symptoms that last for more than four weeks, caused by a variety of infectious and non-infectious agents.
• Drug-induced aseptic meningitis - A form of aseptic meningitis caused by a reaction to medications or illicit drugs.
• Fungal meningitis - A rare form of meningitis caused by a fungal infection, often affecting individuals with weakened immune systems.
• Haemophilus meningitis - Meningitis caused by Haemophilus influenzae type b bacteria, now less common due to effective vaccination.
• Herpes meningitis - A type of viral meningitis caused by herpes simplex viruses.
• Lymphocytic choriomeningitis - A form of viral meningitis caused by the lymphocytic choriomeningitis virus (LCMV), typically transmitted through rodent droppings.
• Meningoencephalitis - An inflammation of both the brain and the meninges, often caused by infections.
• Mollaret's meningitis - A rare form of recurrent viral meningitis, characterized by sudden and severe episodes.
• Neonatal meningitis - Meningitis occurring in newborns, often caused by bacteria that are transmitted from the mother during birth.
• Neoplastic meningitis - Also known as leptomeningeal carcinomatosis, it's caused by the spread of cancer to the meninges.
• Tuberculous meningitis - A form of meningitis caused by Mycobacterium tuberculosis, part of the wider spectrum of tuberculosis infections.
• Viral meningitis - The most common and typically the least severe form of meningitis, caused by various viruses.

Vaccines and Initiatives

• MenAfriVac - A vaccine developed specifically to provide protection against Neisseria meningitidis serogroup A, which is prevalent in the African meningitis belt.
• Meningitis Vaccine Project - A partnership between the World Health Organization (WHO) and PATH that aimed to eliminate epidemic meningitis as a public health concern in sub-Saharan Africa through the development and introduction of MenAfriVac.

Organizations

• Meningitis Now - A UK-based charity focused on providing support for people affected by meningitis and campaigning for greater awareness and research into the disease.

See Also

• Infectious disease
• Neisseria meningitidis
• Streptococcus pneumoniae
• Brain inflammation

References

• Kasper DL, Braunwald E, Fauci AS, et al, Harrison's Principles of Internal Medicine, 16th Ed, McGraw-Hill 2005

External links

• Merck Manual: Central nervous system infections
• WHO: Meningococcal meningitis
• CDC: Meningococcal disease
• Meningitis Research Foundation (UK and Ireland)

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