Meningitis Overview

Definition and Causes

Meningitis is a medical condition characterized by the inflammation of the protective membranes, known as meninges, surrounding the brain and spinal cord. This inflammation is primarily caused by bacterial or viral infections involving the cerebrospinal fluid. Additionally, meningitis can arise from injuries, cancer, specific medications, or various infections. The immune system’s response to infection can lead to further inflammation, manifesting in symptoms like fever, headache, seizures, and in severe cases, brain damage or death. In developed nations, the incidence of acute bacterial meningitis is approximately five cases per 100,000 adults annually, whereas it may be ten times higher in less developed regions.

Pathophysiology

Meningitis can be triggered by infections from bacteria, viruses, fungi, or parasites. Key risk factors include environmental exposures, travel history, and immunocompromised states, such as those caused by HIV, diabetes, or chemotherapy. Non-infectious causes may involve autoimmune diseases or specific medications. Bacterial meningitis is frequently associated with organisms like Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae. Viral meningitis is often due to enteroviruses, varicella zoster virus, influenza, mumps, and HIV, while fungal meningitis is mainly caused by Cryptococcus neoformans. Parasitic meningitis may result from cysticercosis, a tapeworm infection affecting the brain.

Symptoms of Meningitis

Bacterial Meningitis Symptoms

Bacterial meningitis is typically identified by a classic triad of symptoms: fever, headache, and neck stiffness. Other associated symptoms may include:
– Nausea
– Vomiting
– Photophobia (sensitivity to light)
– Sleepiness
– Confusion
– Irritability
– Delirium
– Double vision
– Coma
– Fatigue
– Muscle pain
– Anorexia

Patient history should cover exposure to similar illnesses, previous medical treatments, travel locations, seasonal factors, and any elements that may increase susceptibility.

Viral Meningitis Symptoms

Symptoms of viral meningitis can overlap with other causative agents. Enteroviral infections may present with widespread rashes, inflammation around the heart and lungs, conjunctivitis, severe muscle pain, and mouth blisters. In infants, crucial symptoms to observe include fever, lethargy, difficulty waking for feedings, vomiting, body stiffness, unusual irritability, and a bulging fontanel.

Diagnosis of Meningitis

A thorough physical examination and medical history evaluation are essential for diagnosing meningitis. Early diagnosis is critical as symptoms can escalate rapidly, leading to severe complications. Diagnostic tests may include:
– Neurological examinations to assess various functions
– Laboratory tests of blood, urine, and other body fluids
– Identification of the causative organism
– Complete blood count (CBC)
– Serum electrolytes and glucose levels
– Blood urea nitrogen (BUN) or creatinine levels

Additional tests may involve cultures from blood, respiratory secretions, or skin lesions, syphilis testing, serum prolactin levels, lumbar puncture for cerebrospinal fluid analysis, neuroimaging (CT or MRI), and electroencephalography (EEG) to monitor brain activity.

Treatment of Meningitis

Addressing complications of acute meningitis is vital, including hypotension, low oxygen levels, altered mental status, and seizures. Initial treatment often involves antibiotics capable of crossing the blood-brain barrier, tailored to the patient’s age and health status. Proper antibiotic therapy can significantly reduce mortality rates. Anticonvulsants may be prescribed to manage seizures, while corticosteroids help alleviate brain inflammation. In cases of infected sinuses, drainage may be necessary.

Viral meningitis usually resolves on its own and is rarely life-threatening, though specific antiviral treatments may be required. Fungal meningitis is typically managed with intravenous antifungal medications, and other types of meningitis are treated according to the identified causative agent.

Prevention of Meningitis

To prevent meningitis, individuals should avoid sharing food, utensils, and personal items with those potentially infected. Regular handwashing with soap and water is crucial. Vaccinations are available to protect against Haemophilus influenzae, pneumococcal, and meningococcal meningitis. Those in close contact with individuals diagnosed with bacterial meningitis may be advised to take antibiotics as a preventive measure. Additionally, limiting outdoor activities and wearing protective clothing can help reduce the risk of mosquito bites that may transmit infections.

References

Heckenberg SG, Brouwer MC, van de Beek D. Bacterial meningitis. Handb Clin Neurol. 2014;121: 1361-75.
Rodrigo Hasbun, MD. Meningitis. https://emedicine.medscape.com/article/232915-overview
Centers for Disease Control and Prevention. Meningitis. https://www.cdc.gov/meningitis/viral.html
Meningitis and Encephalitis Fact Sheet. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Meningitis-and-Encephalitis-Fact-Sheet