Meningitis Flashcards
… refers to inflammation of the meninges, which are the outer membranes covering the brain and spinal cord.
Meningitis refers to inflammation of the meninges, which are the outer membranes covering the brain and spinal cord.
Epidemiology of bacterial meningitis
The annual incidence of bacterial meningitis in developed countries is estimated at 2-5 per 100,000 population.
Meningitis has been reported to be … times more common in developing countries due to less well developed preventative programmes (e.g. vaccination).
Meningitis has been reported to be ten times more common in developing countries due to less well developed preventative programmes (e.g. vaccination).
The meninges are composed of … individual layers.
The meninges are composed of three individual layers.
The meninges form the outer membranes covering of the brain and spinal cord. These are divided into three structures.
Dura mater: tough outer membrane. Lies directly beneath the skull. Composed of two layers: outer periosteal layer and inner meningeal layer.
Arachnoid mater: avascular layer of connective tissue that sits beneath the dura mater. Beneath the arachnoid mater is the subarachnoid space that contains cerebrospinal fluid.
Pia mater: thin inner membrane. Tightly adherent to the brain and spinal cord.
The meninges are composed of three individual layers - list these
The meninges form the outer membranes covering of the brain and spinal cord. These are divided into three structures.
Dura mater: tough outer membrane. Lies directly beneath the skull. Composed of two layers: outer periosteal layer and inner meningeal layer.
Arachnoid mater: avascular layer of connective tissue that sits beneath the dura mater. Beneath the arachnoid mater is the subarachnoid space that contains cerebrospinal fluid.
Pia mater: thin inner membrane. Tightly adherent to the brain and spinal cord.
…: thin inner membrane. Tightly adherent to the brain and spinal cord.
Pia mater: thin inner membrane. Tightly adherent to the brain and spinal cord.
Arachnoid mater: … layer of connective tissue that sits beneath the dura mater. Beneath the arachnoid mater is the … space that contains cerebrospinal fluid.
Arachnoid mater: avascular layer of connective tissue that sits beneath the dura mater. Beneath the arachnoid mater is the subarachnoid space that contains cerebrospinal fluid.
Dura mater: … outer membrane. Lies directly beneath the skull. Composed of two layers: outer … layer and inner meningeal layer.
Dura mater: tough outer membrane. Lies directly beneath the skull. Composed of two layers: outer periosteal layer and inner meningeal layer.
Meningitis may be caused by a series of infectious and non-infectious aetiologies.
List some non-infectious casues
Non-infectious causes include malignancy, systemic inflammatory conditions (e.g. systemic lupus erythematous, Behçet’s disease), head injury, medications (e.g. NSAIDs, co-trimoxazole) or surgery.
Bacterial meningitis usually occurs acutely (< 1 day) and can lead to profound sepsis and subsequent complications.
Commonly implicated organisms include:
(5)
Commonly implicated organisms include:
Neisseria meningitidis Streptococcus pneumoniae Haemophilus influenzae Listeria monocytogenes Escherichia coli
Bacterial meningitis usually occurs acutely (< 1 day) and can lead to profound sepsis and subsequent complications.
The table summarises the likely organisms based on age.
Several viruses are implicated in meningitis - list them
Enteroviruses (most common): examples include echovirus and Coxsackieviruses Herpes simplex virus (HSV) Human immunodeficiency virus (HIV) West Nile virus (WNV) Varicella-zoster virus (VZV)
Several viruses are implicated in meningitis
What are the most common?
Enteroviruses (most common): examples include echovirus and Coxsackieviruses
Cryptococcus neoformans is a particularly devastating meningitis that is usually seen in patients with poorly controlled HIV. It is a …-like … that is a major cause of HIV-associated mortality worldwide.
Cryptococcus neoformans is a particularly devastating meningitis that is usually seen in patients with poorly controlled HIV. It is a yeast-like fungus that is a major cause of HIV-associated mortality worldwide.
Fungal - meningitis
Fungal infections usually occur in the setting of HIV or signifiant immunosuppression.
Cryptococcus neoformans Coccidioides immitis Candida species Histoplasma capsulatum Blastomyces dermatitidis
TB - meningitis
Mycobacterium tuberculosis (TB) should always be considered in patients who are immunosuppressed. In addition, have a low threshold for suspecting TB meningitis in patients with aseptic meningitis (initial bacterial cultures negative), chronic meningitis (> 7 days duration), or from high prevalence area.
…. meningitidis can cause a rapidly progressive, and devastating meningitis with profound bacteraemia.
N. meningitidis can cause a rapidly progressive, and devastating meningitis with profound bacteraemia.
N. meningitidis is a gram … diplococci. It is found as a commensal organism in the upper respiratory tract of 5-11% of the adult population. Around 25% of adolescents are asymptomatic carriers.
N. meningitidis is a gram negative diplococci. It is found as a commensal organism in the upper respiratory tract of 5-11% of the adult population. Around 25% of adolescents are asymptomatic carriers.
N. meningitidis is a gram negative …. It is found as a commensal organism in the upper respiratory tract of 5-11% of the adult population. Around 25% of adolescents are asymptomatic carriers.
N. meningitidis is a gram negative diplococci. It is found as a commensal organism in the upper respiratory tract of 5-11% of the adult population. Around 25% of adolescents are asymptomatic carriers.
N. meningitidis is a gram negative diplococci.
The organism typically causes meningitis in patients of all ages, except the very young (< … months). The incubation period for infection is usually ..-… days and the spectrum of disease is wide. Some patients may develop a mild self-limiting illness, whereas others may present with fulminant meningococcal disease characterised by septic shock and multi-organ failure.
The organism typically causes meningitis in patients of all ages, except the very young (< 3 months). The incubation period for infection is usually 2-7 days and the spectrum of disease is wide. Some patients may develop a mild self-limiting illness, whereas others may present with fulminant meningococcal disease characterised by septic shock and multi-organ failure.
N. meningitidis is a gram negative diplococci.
The majority of cases are caused by 6 serogroups, which are categorised according to its polysaccharide capsule. These include A, B, C, W, X and Y. More than 95% of cases of meningitis are caused by serogroups …
The majority of cases are caused by 6 serogroups, which are categorised according to its polysaccharide capsule. These include A, B, C, W, X and Y. More than 95% of cases of meningitis are caused by serogroups B, C and Y.
The UK currently offers …s vaccinations to children and young adults as part of the UK vaccination programme. This includes the MenB and MenACWY vaccines.
The UK currently offers N. meningitidis vaccinations to children and young adults as part of the UK vaccination programme. This includes the MenB and MenACWY vaccines.
… pneumoniae is commonly implicated in cases of meningitis, pneumonia, and ear infections.
Streptococcus pneumoniae is commonly implicated in cases of meningitis, pneumonia, and ear infections.
S. pneumoniae is a gram positive ….
S. pneumoniae is a gram positive diplococci.
S. … is a gram positive diplococci.
S. pneumoniae is a gram positive diplococci.
S. pneumoniae is a gram positive diplococci. It is a very common cause of … and usually transmitted by close contacts through droplet or direct contact with secretions from the respiratory tract. It colonises 5-10% of asymptomatic adults and up to 40% of children.
S. pneumoniae is a gram positive diplococci. It is a very common cause of pneumonia and usually transmitted by close contacts through droplet or direct contact with secretions from the respiratory tract. It colonises 5-10% of asymptomatic adults and up to 40% of children.
The UK currently offers S. pneumoniae vaccination to children as part of the UK vaccination programme. It also offers the vaccine to patients with significant co-morbidities (e.g. diabetes mellitus) and all adults > … years old.
The UK currently offers S. pneumoniae vaccination to children as part of the UK vaccination programme. It also offers the vaccine to patients with significant co-morbidities (e.g. diabetes mellitus) and all adults > 65 years old.
Routes of infection
Bacteria cause meningeal inflammation by two major routes:
Invasion of bloodstream: subsequent haematogenous spread to meninges (commonly seen with N. meningitidis and S. pneumoniae)
Direct contiguous spread: usually as a result of ear, nose or throat infections (e.g. sinusitis, otitis media). Alternatively trauma.
Once bacteria penetrate the blood-brain barrier (BBB), they spread quickly within the meninges and can eventually damage underlying brain tissue.
Mild vs severe cases?
Once bacteria penetrate the blood-brain barrier (BBB), they spread quickly within the meninges and can eventually damage underlying brain tissue.
Mild cases: infection usually confined to the subarachnoid space.
Severe cases: brain parenchyma underlying pia mater can be affected leading to widespread destruction.
Once bacteria penetrate the blood-brain barrier (BBB), they spread quickly within the meninges and can eventually damage underlying brain tissue.
As the immune system is activated, there is infiltration of immune cells and release of inflammatory cytokines. The combination of inflammatory cell infiltration, cytokine-mediated damage and replicating bacteria can perpetuate the infectious process. This leads to a number of complications:
Damage to cranial nerves Obstructive hydrocephalus (disruption of CSF flow, leading to fluid accumulation) Local ischaemia (local inflammatory reactions causes vessel inflammation and thrombophlebitis) Cerebral oedema: secondary to interstitial oedema (due to altered CSF and venous flow), cytotoxic oedema (due to inflammation reaction) and vasogenic oedema (due to increased BBB permeability)
If left untreated, progressive cerebral oedema leads to diffuse neuronal injury. This is usually combined with systemic complications due to bacteraemia, which include … … and …
If left untreated, progressive cerebral oedema leads to diffuse neuronal injury. This is usually combined with systemic complications due to bacteraemia, which include septic shock and multi-organ failure.