Overview
Meningitis is inflammation of the leptomeninges/light meninges of the central nervous system (CNS). Three layers of membranes protect and cover the brain and spinal cord. They include dura mater, arachnoid, and pia. Dura mater is the thick and durable outer layer, but the arachnoid (middle layer) and pia (inner layer) layers are very light and thin, known as leptomeninges. Hence, meningitis involves layers of arachnoid and pia mater. Meningitis occurs most commonly due to an infectious agent.
There are seven types of meningitis based on the causes, including bacterial, viral, fungal, amoebic, parasitic, non-infectious, and chronic meningitis.
Types of meningitis
There are seven types of meningitis, but viral and bacterial meningitis are the most common among them.
Viral meningitis
Viruses cause viral meningitis. This meningitis is more common than bacterial meningitis and is usually less severe. Patients with viral meningitis usually recover without medication. However, some severe symptoms should be addressed. Many viruses are responsible for viral meningitis. including
- Coxsackievirus A
- Coxsackievirus B
They are the most common viral cause of meningitis and have fecal-oral transmission.
- echoviruses
- Influenza
- Herpes viruses
- Mumps
- HIV
- Measles
- Arboviruses
- Lymphocytic choriomeningitis virus
Bacterial meningitis
This is the most severe type of meningitis and can be fatal if left untreated. However, most people recover from bacterial meningitis with the help of proper medications and treatments. Recovering from bacterial meningitis can lead to permanent disabilities such as hearing loss, brain damage, etc. The causes of bacterial meningitis include
- Streptococcus agalactiae (group B streptococcus/GBS) - in neonates
- E coli - in neonates
During childbirth, GBS and E coli infections can arise from the vaginal canal. Typically, pregnant women with GBS colonization in the third trimester are treated with antibiotics to reduce the risk of the baby being exposed during delivery.
- Listeria monocytogenes - in neonates
- Neisseria meningitidis - most common cause in children and teenagers. This enters the body through the nasopharynx and then goes to meninges membranes through the blood
- Streptococcus pneumoniae - most common cause in adults and elderly
- Haemophilus influenza - common cause in nonvaccinated infants
- Mycobacterium tuberculosis - a less common cause of meningitis, known as TB meningitis
Fungal meningitis
A fungal infection causes fungal meningitis, a rare type of meningitis. Fungal meningitis usually develops in immunocompromised people. Certain medications and medical conditions weaken the immune system, including
- Steroids
- Organ transplant medications
- Anti-TNF medications
- HIV
- Cancer
- Cryptococcus - this is discovered in contaminated soil, particularly with bird droppings. Individuals who are healthy and immunocompetent do not become ill when exposed to Cryptococcus.
- Blastomyces - found in moist soil, and decomposed leaves and woods
- Histoplasma - found in heavily contaminated soil with bat and bird droppings
- Coccidioides
- Candida - This fungus is usually found inside and outside the human body but does not cause infection. However, it can cause disease by entering the bloodstream in certain circumstances.
Fungal meningitis does not spread between individuals.
Parasitic meningitis
This type of meningitis is less common than viral and bacterial meningitis. Many parasites can infect and damage the brain or spinal cord, but three parasites cause eosinophilic meningitis (EM), a rare type of meningitis. These include
- Angiostrongylus cantonensis - infected by eating undercooked or raw snails or contaminated food
- Baylisascaris procyonis - infection is caused by accidental ingestion of parasite egg, usually found in soil contaminated with raccoon feces.
- Gnathostoma spinigerum - infected by eating undercooked or raw freshwater fish, chicken, frogs, or snakes
Usually, parasitic meningitis does not spread between people.
Amoebic meningitis
This is a rare type of meningitis that is usually fatal. Naegleria fowleri, which lives in soil and warm fresh water (not in salt water), is the most common cause of amoebic meningitis. People typically become infected by swimming in contaminated ponds, rivers, and lakes. Naegleria fowleri enters the body through the nose and damages the brain tissue. Drinking polluted water does not cause Naegleria fowleri infection.
Non-infectious meningitis
This meningitis is caused by specific medical conditions or treatments (instead of infective agents). Some causes include
- Head injury
- Lupus
- Cancer
- Brain surgery
- Certain medications
Chronic meningitis
Meningitis that lasts more than 4 weeks. Fungus, cancer, and rheumatological conditions are common causes.
Symptoms
Patients with meningitis experience the classic triad of fever, headache, and neck stiffness. Symptoms of viral and bacterial meningitis can be comparable, but bacterial meningitis is usually severe. Even though most meningitis symptoms are similar, some people experience additional symptoms.
Viral meningitis symptoms
Viral meningitis in adults may cause
- Headache
- Fever
- Neck stiffness
- Nausea
- Irritability
- Photophobia (eye discomfort in light)
- Vomiting
- Lack of energy
- Sleepiness
- Lack of appetite
- Altered mental status
Viral meningitis in infants may cause
- Fever
- Lack of appetite
- Vomiting
- Irritability
- Sleepiness
- Lack of energy
- Rash
- High-pitched cry
Bacterial meningitis symptoms
Symptoms of bacterial meningitis typically appear within a week of exposure, except for TB meningitis, which develops much later after exposure to the bacteria.
In adults, it may cause
- Headache
- Fever
- Neck stiffness
- Vomiting
- Irritability
- Nausea
- Photophobia (sensitivity to light)
- Confusion
In children, it may or may not cause the symptoms listed above. In addition, children with bacterial meningitis may present with
- Lack of appetite
- Irritability
- Vomiting
- Inactive
Anyone who suspects they have meningitis should seek immediate medical attention because bacterial and viral meningitis can be fatal.
Fungal meningitis symptoms
- Headache
- Fever
- Neck stiffness
- Vomiting
- Nausea
- Confusion
- Eye sensitivity to bright light (photophobia)
- Disorientation
Parasitic meningitis symptoms
- Headache
- Neck stiffness
- Vomiting
- Nausea
- Sensitivity to light
- Confusion
- Tingling on the skin - in patients with eosinophilic meningitis (EM) caused by Angiostrongylus cantonensis
- Low-grade fever
Amoebic meningitis symptoms
Early symptoms of amoebic meningitis are similar to those of bacterial meningitis. Symptoms typically appear 1 to 12 days after infection. Within 1 to 18 days of the onset of symptoms, this can progress quickly and even result in death.
Early symptoms include
- Fever
- Headache
- Vomiting
- Nausea
Late symptoms include
- Neck stiffness
- Seizure
- Hallucination
- Confusion
- Disorientation
- Coma
Non-infectious meningitis symptoms
- Headache
- Fever
- Neck stiffness
- Vomiting
- Nausea
- Confusion
- Sensitivity to bright light
Chronic meningitis symptoms
Meningitis symptoms that last more than 4 weeks indicate the presence of chronic meningitis.
Diagnosis
Any sign of meningitis requires immediate medical attention, especially bacterial meningitis, which can be fatal. Meningitis can be diagnosed using a variety of methods. Including
- Lumbar puncture (sampling of CSF) - The goal is to collect and analyze the fluid from the subarachnoid space. The needle is inserted between L4 and L5 (level of the iliac crest). The reason is the spinal cord ends at L2, but the subarachnoid space of the cauda equina continues to S2. As a result, if the needle is inserted between L4 and L5, CSF can be obtained from the subarachnoid space without damaging the spinal cord. After the cerebrospinal fluid (CSF) is collected, it is analyzed to determine the cause of meningitis.
Neutrophils with low glucose levels - This indicates bacterial meningitis. Neutrophils are visible because they fight bacterial infections. Bacteria consume the glucose in the CSF, resulting in Low glucose levels.
Lymphocytes with normal glucose levels - This indicates viral meningitis. Lymphocytes are visible because they fight the viral infection. Viruses do not use glucose, so normal glucose levels are seen in CSF.
Lymphocytes with low glucose levels - This indicates fungal meningitis. Because fungus consumes glucose.
- Blood test - Blood is analyzed to identify any infections
- Computed tomography (CT) scans - make images of the body using X-rays and computers. CT scans provide detailed images of body parts, including tissues, organs, bones, etc. CT scan monitors and analyzes the head to identify abnormal findings due to meningitis.
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| CT scan |
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| Lumbar puncture |
Complications
Complications of meningitis are classically seen with bacterial meningitis. including
- Hearing loss
- Vision abnormality
- Memory problems
- Migraine headaches
- learning disabilities
- Seizures
- Subdural empyema
- Hydrocephalus - the build-up of fluid in the brain ventricles
These are all based on the healing process during the recovery. Bacterial meningitis causes extensive tissue damage, resulting in fibrosis. This fibrosis can destroy the normal CSF pathways, resulting in hydrocephalus and nerve damage as it exits the brain (e.g., hearing loss). Furthermore, it has the potential to scar the brain's surface, increasing the risk of seizures.
- Death - Bacterial meningitis produces puss, inflammation, and inflammatory exudate, creating pressure on the brain and causing brain herniation. Brain herniation can be fatal.
Treatments
Treatments can vary based on the cause. Treatments include
- Viral meningitis - Treatment is usually not required as people with viral meningitis recover in 7 to 10 days without treatment. In some cases, it is treated with antiviral medications.
- Bacterial meningitis - requires immediate medication and treatment because it is more severe than other meningitis. It is usually treated with intravenous (IV) antibiotics. Early treatment and recovery prevent serious complications, including nerve damage and death. A type of steroid called dexamethasone is used to reduce the inflammatory response caused by bacteria.
- Fungal meningitis - is treated with intravenous (IV) and oral antifungal medications.
- Parasitic meningitis - There is no specific treatment. Medications can be used for the headache and the body's reaction to the parasite.
- Amoebic meningitis - Treated with a combination of medications that have activity against Naegleria fowleri.
