Meningitis And Encephalitis

Introduction

Meningitis and encephalitis are two conditions which affect the central nervous system. They both have multiple causative agents including a range of microorganisms, but encephalitis may also be caused by the failure in the immune system. They are both serious conditions, which require immediate treatment. 

Meningitis

Meningitis involves the swelling of the meninges, which are protective structures surrounding the brain and spinal cord. It particularly affects children under the age of 5, immunocompromised individuals, people without a spleen and those with a cerebrospinal fluid (CSF) leak, sickle cell disease, alcohol disorder, or a head/spinal cord injury.¹

Causes

There are four main causes of meningitis: bacterial, viral, fungal and parasitic, with bacterial being the most common. 

Bacterial meningitis

Bacterial meningitis is commonly caused by Neisseria meningitidis, Haemophilus influenzae, or group B streptococcus, but other culprits are also possible. These pathogens can be found in the nose and throat and so may be transmitted through droplets when sneezing, coughing or talking. Group B streptococcus is also found in other mucosal surfaces like the gut or vagina, meaning that it may be transmitted during birth from mother to child, or through the faecal-oral route.²

Viral meningitis

Viral meningitis is most often caused by non-polio enteroviruses, which otherwise cause quite mild disease.³ These may be transmitted by contact with infected secretions including mucus, saliva, sputum, or faeces.⁴ Other causes of viral meningitis include influenza virus, mumps virus, measles virus, herpesviruses, arboviruses (viruses spread from insects, like mosquitoes or ticks, to people), and lymphocytic choriomeningitis.³

Fungal meningitis

There are three main fungi types that may lead to meningitis. The most common culprit is Cryptococcus neoformans, which is a very common environmental fungus and may be found all around us. Candida albicans, which is mostly famous for causing thrush infections, is another possible causative agent. These fungi are typically controlled in individuals with a healthy, functioning immune system but can become problematic and cause meningitis in those with immunodeficiencies as a result of HIV, inherited conditions, or cancer, or in low-weight, premature babies.⁵

Parasitic meningitis

This is a rarer type of meningitis but may occur with greater likelihood in people who have travelled to or live in Southeast Asia, the Pacific Islands, and the USA. They are more likely to cause severe complications like paralysis, loss of muscle control, coma, and permanent disability.⁶

Non-infectious meningitis

Non-infectious meningitis can result from many autoimmune conditions like rheumatoid arthritis, or lupus erythematosus. It occurs due to excess inflammation and excess white blood cells in spinal fluid.⁷

Symptoms 

The symptoms for the different types of meningitis may differ slightly but all usually exhibit the following central symptoms:

• Stiff neck
• Fever
• Confusion
• Altered mental state
• Nausea and/or vomiting
• Headache
• Tiredness

Some neurological symptoms may also present:

• Seizures
• Coma
• Neurological deficits like vision loss, and weak limbs

If the meningitis is bacterial, it is also important to look out for signs of bacterial blood infection, which may ultimately cause sepsis. These may include:

• Joint and muscle pain
• Diarrhoea
• Fast breathing
• Red/purple rash
• Cold hands and feet

Babies will also present different symptoms like:

• Being irritable or inconsolable
• Hard to awaken
• Eating less
• A stiff or floppy body
• Fontanelle (swollen soft spot on head)

Diagnosis

A doctor will usually carry out a physical examination and then perform a lumbar tap procedure to extract spinal fluid. This spinal fluid will be viewed under a microscope to determine the causative agent (bacterial, viral, fungal…). This will then be confirmed by culturing the microorganisms from blood or spinal fluid and then running a polymerase chain reaction, where the genetic material of the infectious agent will be analyzed.² Imaging like a CT or MRI may also be done. 

Treatment

Treatment depends on the causative agent. For bacterial meningitis antibiotics will be administered, whilst for fungal meningitis, antifungals will be given. If the meningitis is of viral cause, antivirals will be used and for non-infectious meningitis, corticosteroids will be given to reduce inflammation. The patient may also be given painkillers or IV fluids for hydration. 

Complications

If left untreated meningitis may progress and cause:

• Vision/hearing loss
• Sepsis (if bacterial)
• Arthritis
• Memory and concentration issues
• Epilepsy
• Organ damage
• Behavioural issues or learning difficulties in children¹

Encephalitis

Encephalitis involves swelling of the brain, which can lead to brain damage and long-term effects. Although it can affect anyone at any stage of life, it tends to be more common in the elderly or very young.⁸

Causes

Viral encephalitis

Viral encephalitis is commonly caused by arboviruses (viruses transmitted by ticks, fleas, or mosquitoes like Dengue, or West Nile Virus, therefore you may be more likely to contract this disease if living in or travelling to regions with higher levels of the aforementioned insect prevalence. Other viral causes may also be measles, chickenpox, HIV. 

Autoimmune encephalitis

Autoimmune encephalitis is caused by the body’s immune system attacking the brain, leading to swelling. Therefore, those suffering from an autoimmune condition may be more prone to developing encephalitis.⁹

Bacterial, fungal, or parasite encephalitis 

These types of encephalitis are very rare. Causative bacteria may include Mycoplasma, Listeria and pneumococcal bacteria. Causative fungi may be Cryptococcus or Candida, while parasites may include malaria.¹⁰

Symptoms

Encephalitis symptoms may be divided into two categories: warning signs and life-threatening signs. Symptoms, which count as warning signs are:

• Mild/moderate neck stiffness
• Fever
• Fatigue
• Headache

Symptoms considered life-threatening signs that should urge immediate medical treatment are:

• Nausea and/or vomiting
• Confusion
• Drowsiness
• Problems with memory
• Unusual personality changes
• Loss of consciousness
• Seizure
• Speech issues
• Loss of movement in certain body parts

Diagnosis 

To diagnose encephalitis, a doctor would often carry out a blood test and/or lumbar puncture. Imaging technology like an MRI or CT scan may be used to look for brain inflammation. The doctor may also perform a neurological exam.

Treatment

To treat viral encephalitis, antivirals will often be prescribed. There are a few options for treating autoimmune encephalitis including corticosteroids, immune globulin, and plasmapheresis, aiming to dampen the immune response to decrease swelling. Certain symptoms may be treated, e.g. anti-seizure medication will be administered in the case of seizures.

Depending on the state of the patient they may receive breathing assistance, enteral nutrition, as well as IV fluids to keep the patient oxygenated, fed, and hydrated. Since encephalitis may cause longer lasting issues with speech or movement, speech therapy or physical therapy may be provided. 

Complications 

If encephalitis is not treated as soon as possible it can lead to further, severe issues like:

• Hearing loss
• Memory loss
• Issues with balance
• Speech and language issues
• Personality changes⁹

Comparing Meningitis and Encephalitis

Site of infection

The two conditions have different infection sites. Meningitis affects the meninges, whilst encephalitis affects the whole brain. They both, however, cause swelling of the affected areas and are caused by similar causative agents with the only difference being frequency. This is to say that bacterial meningitis is very common whilst bacterial encephalitis is not, or on the other hand, viral encephalitis is very common whilst viral meningitis is less encountered. 

Symptoms

The symptoms for both conditions are overall very similar. However, it may be possible to tell the two apart as meningitis is less likely than encephalitis to cause neurological issues like change in behaviour, speech or hearing disruption, disorientation, and seizures.¹¹

Diagnosis

They are both diagnosed by taking blood or spinal samples, culturing any pathogens and screening their genetic material. However, sometimes depending on the case, imaging using MRIs or CTs is performed.

Meningitis and Encephalitis prevention

Both conditions may be prevented by appropriate bacterial or viral vaccinations as well as maintaining good hygiene practices like washing hands with soap and warm water, coughing and sneezing into tissues, disinfecting contaminated surfaces, reducing contact with people who are ill and practising food safety by eating/drinking from safe sources and preparing food properly. For encephalitis, protection from insects is a key preventative measure.

This may be done by wearing protective clothing, using insect repellants, and using mosquito nets/screens.⁹ For meningitis, high-risk individuals would be recommended to take antibiotics prophylactically (to prevent disease).¹

Summary

Overall, both diseases affect the central nervous system by causing inflammation and can lead to serious complications if not treated promptly. There are multiple causes for each condition including bacterial, viral, fungal, parasitic, and non-infectious, which is usually related to suffering from an autoimmune condition. Both illnesses may be prevented by vaccination as well as protective measures against insects, good hygiene measures, and proper food safety.