Main Difference – Meningitis vs Encephalitis
According to the National Institute of Neurological Disorders and Stroke (NINDS), Meningitis and Encephalitis are defined as two neurological conditions where the membranes surrounding the brain and the spinal cord are more or less inflamed. The main difference between Meningitis and Encephalitis is that Encephalitis is an acute inflammation of the brain parenchyma whereas Meningitis is the inflammation of the protective layers of tissue, or membranes, covering the brain. While the main cause can either be a viral or bacterial infection, the severity of both conditions could vary from mild to fatal.
It is highly important to detect how these conditions differ from each other, mainly for the purpose of treatment and follow-up, in order to prevent them from leading to irreversible and negative life-threatening consequences.
Here, we will discuss,
1. What is Meningitis? – Definitions, Causes, Signs and Symptoms, Treatment
2. What is Encephalitis? – Definitions, Causes, Signs and Symptoms, Treatment
3. What is the difference between Meningitis and Encephalitis?
What is Meningitis
Defined as an inflammation of the protective lining of the brain and spinal cord (Meninges), Meningitis is mainly caused by a bacterial or viral infection. Viral and bacterial infections are contagious and could get transmitted through sneezing, coughing or contact. Other minor causes may include tumors, radiation, chemical irritation, fungal infections and drug allergies. Other major risk factors include immune-comprised states such as HIV, AIDS, Auto-immune diseases, etc.
Viral Meningitis
The commonest cause of viral meningitis (85%) is Coxsackievirus A, Coxsackievirus B, or Echoviruses. Other possible viral infections may include Mumps, HIV, Measles, Influenza, and Herpes. Most Viral infections will resolve spontaneously, even without treatment.
Bacterial Meningitis
Streptococcus pneumonia (pneumococcal meningitis), Neisseria meningitides (Meningococcal meningitis), Haemophilus influenza, Listeria monocytogenes (food-borne) are among the main bacteria which give rise to this condition, and untreated bacterial meningitis can be life threatening.
While being able to affect anyone at any age, this condition is mostly seen in babies, young children, teenagers and young adults. Children below 5 years of age are at a high risk of contracting viral meningitis whereas infants are at high risk of contracting bacterial meningitis.
A weak and ill-looking patient brought to the hospital with signs and symptoms such as high temperature over 37.5°C, severe headache, a blotchy rash that doesn’t fade off when a glass is rolled over it (not always), neck stiffness, avoidance of bright light (photophobia), drowsiness and unresponsiveness and fits should be properly cared and immediate interventions should be taken since meningitis tops the list of differential diagnoses. More importantly, the above symptoms can manifest completely or may range in any order depending on the causative agent, fitness of the patient and severity of the condition.
A full neurological examination will help to establish a proper diagnosis up to a certain extent. A lumbar puncture will reveal inflammation (spinal tap), blood cultures will identify the causative organism and full blood count and CRP levels will detect ongoing inflammation. Chest X-ray (since pneumococcal meningitis can follow pneumonia) and CT scan (exclude brain abscess or sinusitis which can be the focus of infection) will help to exclude other causes and confirm the diagnosis.
Treatment for Meningitis mainly depends on the etiology whereas bacterial meningitis requires immediate hospitalization and treatment with intravenous antibiotics based on the type of organism; fungal meningitis is treated with antifungal agents. Viral meningitis isn’t usually treated and would resolve spontaneously, and the symptoms would disappear within about two weeks.
Patients who don’t receive timely interventions are susceptible to develop complications such as seizures, impaired hearing, brain damage, Hydrocephalus and subdural effusions (development of fluid between the brain and skull).
Additionally, vaccinations against Haemophilus influenza type B (Hib) vaccine, Pneumococcal conjugate vaccine, and Meningococcal vaccine can be given as prophylactic measures in order to prevent from Meningitis.
What is Encephalitis
Encephalitis is a rare yet serious condition defined as the acute inflammation of the brain parenchyma. Signs and symptoms of Encephalitis are so similar to those of the flu, so it is quite difficult to differentiate which is which. However, the features would last from 2-3 weeks where mild forms can recover fully whereas some types can be life-threatening. Patients will mainly complain of difficulty in speech or hearing, double vision, hallucinations, personality changes, loss of consciousness, loss of sensation (some parts of the body), weakness of muscles, partial paralysis of arms and legs, sudden severe dementia, fits and memory loss.
Mostly caused by Enteroviruses, herpes simplex virus types 1 and 2, rabies virus or Arboviruses (West Nile virus, which are transmitted from infected animals to humans via bites from infected ticks, mosquitos, or other blood-sucking insects), people with an immune-compromised state are at a high risk of getting susceptible to the primary infection, which is similar to meningitis.
Being contagious, the infection can spread through close contact with saliva, nasal discharge, feces or throat secretions.
In addition to a complete history and neurological examination, encephalitis is diagnosed by techniques similar to those done for meningitis, and CT scan or MRI will show inflammation of the brain instead of inflamed meninges. Moreover, Electroencephalography (EEG) can be carried out to reveal abnormal brain waves by monitoring electrical activity in the brain through the skull.
Management – Based on the Causative Organism
- Antiviral drugs – Acyclovir and Ganciclovir
- Anticonvulsants to stop or prevent seizures
- Corticosteroids to reduce brain swelling
- Artificial respiration
- Immunosuppressant drugs for autoimmune causes
- Screening for tumors in suspected cases
- A comprehensive rehabilitation
- Cognitive rehabilitation
- Physical, speech and occupational therapy once the acute illness is controlled
Coronal T2-weighted MR image
Difference Between Meningitis and Encephalitis
Definition:
The main difference between Meningitis and Encephalitis lies in the definition itself.
Meningitis is defined as the inflammation of the protective layers of tissue, or membranes covering the brain known as Meninges.
Encephalitis is defined as an acute inflammation of the brain parenchyma.
Causes:
Meningitis can be caused by bacteria, viruses, and fungi.
Encephalitis is commonly caused by viral agents.
Types:
Meningitis can exist only as a single form.
Encephalitis can occur as primary (infective organism directly enters the brain) or secondary types (infectious organism enters an organ before entering the brain).
Distinguishing Signs:
Both these conditions share very similar features which make it difficult to diagnosis the exact type and unfortunately there are patients who get affected by both the diseases at once, leading to a complicated situation giving rise to a need for complex modalities of treatment. However, the main distinguishing factor is the skin discoloration or rash which is only seen in Meningitis.
The other hallmark signs of Meningitis are sudden fever, severe headache, nausea, vomiting, double vision, drowsiness, photophobia and stiff neck.
Encephalitis is characterized by moderate-severe fever, seizures, behavioral changes, confusion, disorientation and related neurological signs depending on which part of the brain is affected by the encephalitic process (locally centered or global).
Diagnosis:
Meningitis is mostly diagnosed by routine blood examinations along with cultures to isolate the responsible organism.
Encephalitis might need neuroimaging techniques in addition to those.
Management:
Ampicillin is the gold standard antibiotic for meningitis (mostly bacterial) which will be given combined with aminoglycoside or cephalosporin (cefotaxime).
Encephalitis (mostly viral) will be treated with intravenous Acyclovir for 10 days while being hospitalized.
Image Courtesy:
“Symptoms of Meningitis” By Mikael Häggström (Public Domain) via Commons Wikimedia
“Hsv encephalitis” By Dr Laughlin Dawes (CC BY 3.0) via Commons Wikimedia
