Meningitis  is inflammation of the meninges, the three membranes surrounding the brain and spinal cord. Encephalitis  is inflammation of the brain. Meningoencephalitis is inflammation of both the brain and the meninges. 

Inflammation can be caused by bacteria, viruses, fungi, or parasites. Meningitis and encephalitis can be acute or chronic, and their severity can range from mild, self-limiting, or fatal. 

The accompanying inflammation and swelling can increase pressure on the brain and nerve tissue. This can interfere with the function of the organ systems that the brain and nerve tissue control, or even cause permanent damage.

Meningitis and encephalitis can disrupt the blood-brain barrier, which separates the brain from the bloodstream and regulates the distribution of substances between the blood and cerebrospinal fluid. 

The blood-brain barrier helps keep large molecules, toxins, and a large portion of blood cells out of the brain. If this barrier is disrupted, the cerebrospinal fluid can accumulate white blood cells (WBCs) and red blood cells (RBCs), immune system chemicals, and toxins, while increasing amounts of proteins and microbes that cause inflammation can accumulate.  

Cerebrospinal fluid (CSF) is a clear, water-like fluid that normally flows freely around the brain and spinal cord. Meningitis and encephalitis can slow or block the flow of CSF. This can cause the CSF to gradually increase in pressure, increasing pressure on the brain and spinal cord. Consequently, blood flow to the brain is reduced.

Meningitis

Most cases of meningitis are caused by bacterial or viral infection. The infection may be primary, originating in the meninges. Secondary infection may spread from an established infection elsewhere in the body. 

Viral meningitis is the most common form of meningitis. It is usually mild to moderate and self-limiting. Viral meningitis can be caused by enteroviruses or herpes viruses.

Bacterial meningitis is often considered a medical emergency. Acute cases can appear suddenly, with symptoms worsening over hours or even days. Rapid diagnosis and treatment are critical. 

Untreated bacterial meningitis is often fatal. While many different bacteria can cause this disease, it can also be caused by:

Pneumococcal Meningitis

Pneumococcal meningitis, also known as Streptococcus pneumoniae, is the most common form of bacterial meningitis. Infants under two years of age and those with compromised immune systems are at greatest risk.

Meningococcal Meningitis

Meningococcal meningitis, also known as Neisseria meningitidis, is most common in students, infants, children, and immunocompromised individuals. It is the leading cause of bacterial meningitis in children and young adults and is highly contagious.

Haemophilus Influenzae Type B

Group B streptococcus, Escherichia coli, and Listeria monocytogenes are the most common forms of meningitis in newborns and can be transmitted from mother to baby.

Chronic Meningitis

Chronic meningitis is a type of meningitis that lasts longer than four weeks. Mycobacterium tuberculosis (TB), Treponema pallidum (SYPH), and fungi can cause chronic meningitis. 

Cryptococcal Meningitis

Although meningitis caused by fungi is most common in people with compromised immune systems, such as those with  AIDS caused by the HIV virus, it can affect anyone.

The most common cause is exposure to the cryptococcus neoformans virus, found in dirt and bird droppings. Other agents include coccidioides immitis, histoplasma capsulatum, and candida viruses.

Encephalitis

Encephalitis is an acute brain infection characterized by fever, headache, seizures, and altered consciousness with or without symptoms. 

Most encephalitis infections are viral in origin. They can be focal (limited to a single location) or disseminated (spread throughout the brain). 

Viral encephalitis can be caused by a variety of viruses, including herpes simplex virus, enteroviruses, rabies virus, and arboviruses, which are spread primarily by diseased mosquitoes and several tick genera. 

Humans are not the preferred primary hosts of arboviruses. Most infected individuals experience mild or moderate disease. Only a small percentage of individuals develop encephalitis. The most common cause of arboviral encephalitis is West Nile virus. 

Bacteria, fungi, and parasites rarely cause encephalitis. Bacteria that cause meningitis can lead to bacterial meningoencephalitis. Lyme disease, transmitted by ticks, can cause bacterial encephalitis. 

The Toxoplasma gondii parasite, found in cats, can cause parasitic encephalitis in individuals with compromised immune systems. Other types of bacteria, fungi, and parasites can also sometimes cause encephalitis.

What are the symptoms of meningitis and encephalitis?

Meningitis and encephalitis can begin with cold-like symptoms and worsen over a few hours to a few days. These two illnesses have the following characteristic signs and symptoms: fever, severe and persistent headache, neck stiffness, sensitivity to light, mental changes, and drowsiness.

Other symptoms of the disease may include confusion, nausea, vomiting, red or purple skin rashes, and seizures.

Elderly patients may be lethargic and exhibit few other symptoms. Individuals with compromised immune systems may present with atypical symptoms.

Babies may experience symptoms such as restlessness, excessive crying, and vomiting. Because their bodies are not flexible, they may experience seizures and may not want to eat. Their fontanelles, the soft spots on the top of their heads, may bulge.

Encephalitis symptoms  may also include problems with the nervous system, such as difficulty hearing or speaking, loss of sensation, partial paralysis, seizures, hallucinations, muscle weakness, personality disorders, and coma.

Complications and Disease Process

The prognosis for those with meningitis and encephalitis depends on the specific cause and severity of the disease, the patient's health and immune status, and how quickly the disease is identified and treated.

While people with mild cases may recover within a few weeks, they may also develop persistent or permanent complications.

Even with appropriate and prompt treatment, 15% to 25% of newborns with bacterial meningitis, and up to 15% of other patients, will die. Of those who survive, up to 15% to 25% may develop neurological sequelae, including hydrocephalus, deafness, blindness, intermittent seizures, and mental retardation (sequelae). While these complications can occur at any age, newborns are at greater risk.

Diagnostic Methods for Meningitis and Encephalitis

Doctors begin with a physical exam and medical history. This exam may begin in the emergency room because symptoms can appear suddenly and worsen rapidly over a few hours to a few days.

Providing information about recent illnesses, exposure to animals, mosquitoes, ticks, and other diseases is vital.

Doctors will note the presence or absence of signs and symptoms associated with meningitis and encephalitis. A nervous system examination may be performed to assess the patient's nervous system, sensory and motor functions, coordination, vision, hearing, strength, and mental status.

Laboratory Tests

Laboratory tests are performed to detect, diagnose, evaluate, and monitor meningitis and encephalitis. These tests may be performed on patients for the following purposes:

• To distinguish it from other diseases with similar symptoms to infectious diseases,
• To determine as quickly as possible whether there is a bacterial, viral, fungal, parasitic or other cause for the purpose of initiating and guiding treatment,
• To guide the elimination of disease symptoms by evaluating the patient's general health status, immune system status, current symptoms, findings and complications,
• Minimize inflammation and nerve or brain damage,
• Identify the source of infection whenever possible.

Identifying the source of infection is particularly important when the causative agent is a public health problem.

Cerebrospinal Fluid (CSF) Analysis

It is the primary diagnostic tool used for encephalitis and meningitis. CSF analysis involves various tests ordered and performed on a CSF sample. A cerebrospinal fluid sample is obtained through a procedure called a lumbar puncture or spinal tap.

Initial CSF tests

When central nervous system infections are suspected, basic CSF tests are frequently performed. These tests evaluate the following factors:

• Physical Properties:  Normal CSF appears clear and colorless. The appearance of a CSF sample is often compared to that of water. In cases of infection, CSF pressure may be elevated during sample collection. The sample may be cloudy due to the presence of white blood cells (WBCs) or microbes.
• CSF Protein:  Because proteins are large molecules and cannot easily cross the blood/brain barrier, the CSF normally contains small amounts of protein. Increased protein levels may be observed in meningitis, brain abscess, and neurosyphilis.
• CSF Glucose:  Normally, CSF glucose is present in a blood sample at approximately two-thirds of the blood glucose level. Glucose levels can drop when cells that should not normally be detected consume, or metabolize, glucose. These cells can be bacterial cells or white blood cells (leukocytes) produced by inflammation.
• CSF Total Cell Counts  An increase in the number of white blood cells may be observed in central nervous system infections.
• CSF Formula Leukocytes  : A CSF sample normally contains low numbers of lymphocytes, monocytes, and, in neonates, neutrophils. However, neutrophils may be increased in bacterial, viral, and sometimes parasitic infections.
• CSF Gram Staining  is a method used to directly observe microbes.
• CSF Bacteria, Fungi, Viruses, Culture and Sensitivity Tests

CSF Tests Used for Additional Follow-up

If any initial tests are abnormal, additional tests for infection may be ordered. These tests may include one or more of the following:

• PCR Virus Detection Test:  These are tests used to determine the genetic content (DNA, RNA) of herpes and enteroviruses.
• CSF Cryptococcal Antigen Test:  This test is performed to detect the presence of a specific fungal infection.
• Other CSF Antigen Tests:  These are the tests to be performed according to the suspected microbe(s).
• Specific CSF Antibody Tests:  These are tests to be performed according to the suspected microbe(s).
• CSF Infectious Disease Tests:  CSF infectious disease tests, ordered less frequently and performed when tuberculosis is suspected, are performed by obtaining a CSF AFB swab and culture. If infection is present, mycobacteria tests will yield positive results.
• CSF Molecular Tests  are tests to detect Mycobacteria tuberculosis bacteria.
• CSF Syphilis Test (VDRL)  is positive for neurosyphilis. A negative result does not exclude syphilis.

 To definitively distinguish between viral and bacterial meningitis , other CSF tests may sometimes be ordered.

• CSF Lactic Acidity  : This is often used to distinguish between viral and bacterial meningitis. Lactic acid levels are generally high in bacterial and fungal meningitis, while lactic acid levels will be normal or slightly elevated in viral meningitis.
• CSF Lactate Dehydrogenase (LDH)  is the test used to distinguish bacterial and viral meningitis.
• CSF C -Reactive Protein ( CRP )  is an acute-phase reactant and will increase in inflammatory states. A significant increase is observed in bacterial meningitis. Because it is so sensitive, it can be used to distinguish bacterial from viral meningitis , even in the early stages of bacterial meningitis.

Laboratory Tests Performed with Samples Other Than Cerebrospinal Fluid

The following tests may also be ordered along with CSF tests or after CSF tests are completed but no abnormalities are observed:

• Blood Sugar, Protein, Complete Blood Count  are requested to evaluate and compare with CSF levels.
• Tests to Determine Antibodies Formed in the Blood Against Various Viruses, Such as West Nile Virus:  If a fourfold increase is observed between the antibody titers of two samples collected approximately one month apart, it is concluded that the person has recently had an infection due to this virus.
• Blood Culture Test:  It is a culture test required to detect and identify bacteria in the blood.
• Other Culture Tests  Culture evaluations of samples from other parts of the body may also be performed to determine the source of the infection causing meningitis or encephalitis.
• Comprehensive Metabolic Panel:  These are tests that evaluate the patient's organ functions.

Examinations Other Than Laboratory Tests

While imaging studies may be performed to look for signs of brain inflammation or disorders, they may not yield noticeable results in encephalitis. They can detect brain damage, tumors, bleeding, and abscesses. These tests may include:

• CT (Computed Tomography),
• MRI (Magnetic Resonance Imaging),
• Ultrasound ,
• EEG (Electro Encephalography) to detect abnormal brain waves .

Ways to Prevent Meningitis and Encephalitis

Vaccines are available to protect against Haemophilus Influenzae Type B, Streptococcus Pneumoniae, and Neisseria Meningitidis.

People who have had close enough contact with a patient with meningococcal meningitis to be able to contract the virus through breathing may be advised to take antibiotics for a few days to reduce the risk of developing a severe infection.

The risk of arbovirus can be minimized by reducing exposure to mosquitoes, wearing long-sleeved and long-legged clothing, using insect repellents, and removing unattended puddles around the home.

Meningitis and Encephalitis Treatment Methods

The aim of treatment for encephalitis, meningitis and meningoencephalitis is to target the cause of inflammation, minimize tissue damage and complications, and relieve the patient's complaints.

Rest in a dark, quiet room, fluid intake, pain relievers for headaches and body aches, anti-inflammatory and anti-seizure medications, sedatives, and anti-nausea medications may be recommended. In some cases, corticosteroids may also be prescribed to prevent tissue and brain swelling.

Treatment of Bacterial Meningitis and Encephalitis

Acute meningitis and encephalitis caused by fungi and bacteria are considered medical emergencies.

Bacterial infections can generally be treated with broad-spectrum antibiotics. Culture results can identify specific bacteria and their antibiotic susceptibility, and treatment planning can be tailored accordingly.

The selected antibiotics must be able to cross the blood-brain barrier and reach sufficient levels in the cerebrospinal fluid. These antibiotics can be administered intravenously to achieve high blood levels.

Patients are monitored for drug toxicity and organ function. Depending on the type of bacteria and the patient's immune system, treatment may need to continue for weeks, months, or even years. Medical procedures may also be necessary to drain infected abscesses or sinuses.

Treatment of Viral Causes

Many  cases of viral encephalitis and meningitis  are mild to moderate, self-limited, and require only monitoring, rest, and symptom relief. Patients with more severe cases may require hospitalization.

Antiviral medications may be recommended for viral encephalitis due to herpes or varicella-zoster viruses. Highly active antiretroviral therapy may be required for HIV.

Treatment of Meningitis and Encephalitis Due to Fungal Infections

Fungal infections are usually treated with antifungal medications administered intravenously. Treatment may last for a long time, depending on the patient's response to treatment.

People with compromised immune systems may need to continue oral therapy for life to prevent recurrence of infection.

Frequently Asked Questions

1. Is meningitis and encephalitis always caused by infection?

Although very rare, meningitis and encephalitis can occur due to non-infectious causes. These can include an autoimmune disorder that triggers components of the nervous system, a reaction to medication, and some types of cancer.

2. Can other diseases have the same symptoms as meningitis and encephalitis?

Different diseases, despite their different causes and treatment modalities, can cause symptoms similar to those of meningitis and encephalitis. These conditions include brain abscesses, brain lesions, medications, trauma, or inflammation between the dura mater and arachnoid layers of the meninges (subdural empyema).

3. Do meningitis and encephalitis begin in the brain?

A blood infection or an infection near the brain that allows germs to enter the CSF (ear infection) or a head injury that allows bacteria to cross the blood-brain barrier and enter the sinuses can cause meningitis.

Infections originating from the respiratory, gastrointestinal tract or blood and spreading to the central nervous system can cause encephalitis.

4. Is meningitis contagious?

The contagiousness of meningitis depends on the microbe that causes it. People who come into contact with someone with meningococcal meningitis may be given antibiotics for several days to minimize the risk of developing meningitis.

Vaccines are available for Streptococcus pneumoniae, Haemophilus influenzae type b, and Neisseria meningitidis, which are the most common causes of bacterial meningitis and can be transmitted to others through respiratory secretions.

5. Can a person who has had meningitis or encephalitis once get the disease again?

Depending on the type of infection, it's possible for someone who has had meningitis or encephalitis to contract the disease again. Some people with compromised immune systems may need to continue antimicrobial therapy to prevent recurrence.