Aseptic meningitis
Encyclopedia
Aseptic meningitis, or sterile meningitis, is a condition in which the layers lining the brain, meninges
, become inflamed
and a pyogenic bacteria
l source is not to blame. Meningitis
is diagnosed on a history of characteristic symptoms and certain examination findings (e.g., Kernig's sign
). Investigations should show an increase in the number of leukocytes present in the cerebrospinal fluid
(CSF), obtained via lumbar puncture
, (normal being fewer than five visible per microscopic High Power Field
).
The term aseptic is frequently a misnomer
, implying a lack of infection
. On the contrary, many cases of aseptic meningitis represent infection with viruses or mycobacteria that cannot be detected with routine methods. While the advent of polymerase chain reaction
has increased the ability of clinicians to detect viruses such as enterovirus
, cytomegalovirus
, and herpes virus
in the CSF, many viruses can still escape detection. Additionally, mycobacteria frequently require special stains and culture
methods that make their detection difficult. When CSF findings are consistent with meningitis, and microbiologic
testing is unrevealing, clinicians typically assign the diagnosis of aseptic meningitis—making it a relative diagnosis of exclusion
.
Aseptic meningitis can result from non-infectious causes; it is a relatively infrequent side effect of medications, and can be an early finding in autoimmune disease
.
There is no formal classification system. It is usually by the causative organism
if identified.
"Aseptic meningitis", like non-gonococcal urethritis
, non-Hodgkin lymphoma
and atypical pneumonia
, merely states what a condition is not, not what a condition is. Terms such as viral meningitis
, bacterial meningitis
, fungal meningitis
, neoplastic meningitis
and drug-induced aseptic meningitis
can provide more information about the condition, and without using one of these more specific terms, it is difficult to describe treatment options or prognosis.
Meninges
The meninges is the system of membranes which envelopes the central nervous system. The meninges consist of three layers: the dura mater, the arachnoid mater, and the pia mater. The primary function of the meninges and of the cerebrospinal fluid is to protect the central nervous system.-Dura...
, become inflamed
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
and a pyogenic bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
l source is not to blame. Meningitis
Meningitis
Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
is diagnosed on a history of characteristic symptoms and certain examination findings (e.g., Kernig's sign
Woldemar Kernig
Woldemar Kernig, better known as Vladimir Mikhailovich Kernig was a notable Russian and Baltic German internist and neurologist whose medical discoveries saved thousands of people with meningitis. He is best known for his pioneering work on diagnostics...
). Investigations should show an increase in the number of leukocytes present in the cerebrospinal fluid
Cerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...
(CSF), obtained via lumbar puncture
Lumbar puncture
A lumbar puncture is a diagnostic and at times therapeutic procedure that is performed in order to collect a sample of cerebrospinal fluid for biochemical, microbiological, and cytological analysis, or very rarely as a treatment to relieve increased intracranial pressure.-Indications:The...
, (normal being fewer than five visible per microscopic High Power Field
High Power Field
High Power Field when used in relation to microscopy references the area visible under the maximum magnification power of the objective being used. Often, this represents a 400x magnification level when referenced in scientific papers....
).
The term aseptic is frequently a misnomer
Misnomer
A misnomer is a term which suggests an interpretation that is known to be untrue. Such incorrect terms sometimes derive their names because of the form, action, or origin of the subject becoming named popularly or widely referenced—long before their true natures were known.- Sources of misnomers...
, implying a lack of infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
. On the contrary, many cases of aseptic meningitis represent infection with viruses or mycobacteria that cannot be detected with routine methods. While the advent of polymerase chain reaction
Polymerase chain reaction
The polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....
has increased the ability of clinicians to detect viruses such as enterovirus
Enterovirus
Enteroviruses are a genus of ssRNA viruses associated with several human and mammalian diseases. Serologic studies have distinguished 66 human enterovirus serotypes on the basis of antibody neutralization tests. Additional antigenic variants have been defined within several of the serotypes on the...
, cytomegalovirus
Cytomegalovirus
Cytomegalovirus is a viral genus of the viral group known as Herpesviridae or herpesviruses. It is typically abbreviated as CMV: The species that infects humans is commonly known as human CMV or human herpesvirus-5 , and is the most studied of all cytomegaloviruses...
, and herpes virus
Herpes virus
In colloquial use, herpes virus refers to the herpes simplex virus, particularly when transmitted sexually.In scientific use, herpesvirus refers to a virus of the taxonomic family herpesviridae....
in the CSF, many viruses can still escape detection. Additionally, mycobacteria frequently require special stains and culture
Culture
Culture is a term that has many different inter-related meanings. For example, in 1952, Alfred Kroeber and Clyde Kluckhohn compiled a list of 164 definitions of "culture" in Culture: A Critical Review of Concepts and Definitions...
methods that make their detection difficult. When CSF findings are consistent with meningitis, and microbiologic
Microbiology
Microbiology is the study of microorganisms, which are defined as any microscopic organism that comprises either a single cell , cell clusters or no cell at all . This includes eukaryotes, such as fungi and protists, and prokaryotes...
testing is unrevealing, clinicians typically assign the diagnosis of aseptic meningitis—making it a relative diagnosis of exclusion
Diagnosis of exclusion
A diagnosis of exclusion is a medical condition reached by a process of elimination, which may be necessary if presence cannot be established with complete confidence from examination or testing...
.
Aseptic meningitis can result from non-infectious causes; it is a relatively infrequent side effect of medications, and can be an early finding in autoimmune disease
Autoimmune disease
Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. In other words, the body actually attacks its own cells. The immune system mistakes some part of the body as a pathogen and attacks it. This may be restricted to...
.
There is no formal classification system. It is usually by the causative organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
if identified.
"Aseptic meningitis", like non-gonococcal urethritis
Non-gonococcal urethritis
Nongonococcal urethritis is an inflammation of the urethra that is not caused by gonorrheal infection.For treatment purposes, doctors usually classify infectious urethritis in two categories: gonococcal urethritis, caused by gonorrhea, and nongonococcal urethritis .-Causes:There are many causes of...
, non-Hodgkin lymphoma
Non-Hodgkin lymphoma
The non-Hodgkin lymphomas are a diverse group of blood cancers that include any kind of lymphoma except Hodgkin's lymphomas. Types of NHL vary significantly in their severity, from indolent to very aggressive....
and atypical pneumonia
Atypical pneumonia
Atypical pneumonia aka "walking pneumonia" is a pneumonia not caused by one of the more traditional pathogens, and with a clinical presentation inconsistent with typical pneumonia. It can be caused by a variety of microorganisms...
, merely states what a condition is not, not what a condition is. Terms such as viral meningitis
Viral meningitis
Viral meningitis refers to meningitis caused by a viral infection. It is sometimes referred to as "aseptic meningitis" in contrast to meningitis caused by bacteria.An example is lymphocytic choriomeningitis....
, bacterial meningitis
Bacterial meningitis
Bacterial meningitis refers to meningitis that is caused by bacterial infection.-Signs and Symptoms:*Fever*Seizures*Meningismus*Headache*Vomiting*Photophobia*Altered mental status and coma*Anorexia...
, fungal meningitis
Fungal meningitis
Fungal meningitis refers to meningitis caused by a fungal infection.One form of fungal meningitis is cryptococcal meningitis.Many cases of fungal meningitis are associated with immune deficiencies....
, neoplastic meningitis
Neoplastic meningitis
Neoplastic or malignant meningitis, also described with the older term meningitis carcinomatosa is the development of meningitis due to the infiltration of the subarachnoid space with cancer cells...
and drug-induced aseptic meningitis
Drug-induced aseptic meningitis
Drug-induced aseptic meningitis is a form of aseptic meningitis that is caused by the administration of certain medications.Causes include:*NSAIDs*Amoxicillin*Azathioprine*Methotrexate*Intravenous immunoglobulin*Isoniazid*Allopurinol*Lamotrigine...
can provide more information about the condition, and without using one of these more specific terms, it is difficult to describe treatment options or prognosis.
Types of aseptic meningitis
- Viral meningitisViral meningitisViral meningitis refers to meningitis caused by a viral infection. It is sometimes referred to as "aseptic meningitis" in contrast to meningitis caused by bacteria.An example is lymphocytic choriomeningitis....
- Drug-induced aseptic meningitisDrug-induced aseptic meningitisDrug-induced aseptic meningitis is a form of aseptic meningitis that is caused by the administration of certain medications.Causes include:*NSAIDs*Amoxicillin*Azathioprine*Methotrexate*Intravenous immunoglobulin*Isoniazid*Allopurinol*Lamotrigine...
- Neoplastic meningitisNeoplastic meningitisNeoplastic or malignant meningitis, also described with the older term meningitis carcinomatosa is the development of meningitis due to the infiltration of the subarachnoid space with cancer cells...
- Lyme diseaseLyme diseaseLyme disease, or Lyme borreliosis, is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia. Borrelia burgdorferi sensu stricto is the main cause of Lyme disease in the United States, whereas Borrelia afzelii and Borrelia garinii cause most...
- Mumps meningoencephalitisMumpsMumps is a viral disease of the human species, caused by the mumps virus. Before the development of vaccination and the introduction of a vaccine, it was a common childhood disease worldwide...