Meningitis Flashcards
Definition
Inflammation of the leptomeninges (dura mater and Pia mater)
Brain inflammation is known as encephalitis
Brain inflammation and meningitis together is meningoencephalitis
Aetiology
It can be caused by virus, bacteria and fungi
Viral meningitis is the most common form of meningitis
Bacterial being less common but more serious and presents as a medical emergency
Bacteria abd viruses–> acute meningitis
Fungi –> chronic meningitis
Viral meningitis
Inflammation of the sub arachnoid space that has been caused by a virus:
Most common:
– herpes simplex
– enterovirus
– coxackie
– HIV
Less common:
– Epstein-Barr virus
– polymyositis
– varicella zoster
– mumps
Viral meningitis epidemiology
Usually self limiting and benign with the symptoms lasting 4-10 days
Tends to go away without treatment
Most common form of meningitis
Viral meningitis pathophysiology
The viruses can reach the meninges in a number of ways
Haematogenous spread:
– both meningococcus and pneumococcus have capsules which render them resistant to phagocytosis
– the bacteria will reach the sub arachnoid space, where the blood brain barrier is weak
– weak areas of the blood brain barrier where a pathogen can enter:
—- they can bind to the surface receptors
—- areas of damage within the endothelial cells
—- choroid plexus (an area of vulnerability within the blood-brain barrier)
—– then they can multiply rapidly in the CSF causing an inflammatory response inside the meninges
—- white blood cells will release cytokines, triggering the immune response
Direct spread:
– where the pathogen penetrates straight through the brain into the sub arachnoid space
—- can be due to:
—— congenital spina bifida
—— skull fracture
There is predominantly lymphocytic inflammatory CSF reaction without pus formation, polymorphs or adhesions.
There is little or no cerebral oedema unless encephalitis develops
Viral meningitis clinical presentation
Classic triad:
– headaches
– fever
– nuchal rigidity
– usually benign and self limiting that lasts for about 4-10 days
Bacterial meningitis
Medical emergency, inflammation of the leptomeninges that is caused by bacteria
It requires immediate treatment or else the person who is suffering with it could die
Aetiology Bacterial meningitis
Caused by bacteria
Most common ages are under 5 and 15-19
Most common form of bacterial meningitis:
– meningococcal disease (caused by neisseria meningitidis)
Newborns:
– step group B
– e coli
– listeria monocytogenes
15-19:
– neiserria meningitidis
– streptococcus pneumoniae
Bacterial meningitis epidemiology
Most serious but rarer than viral meningitis
1 in 20 can die, with 1 in 5 having prolonged damaging effects from it
Bacterial meningitis pathophysiology
Pachymeningitis:
– inflammation of the dura mater
– most commonly due to direct spread following:
—- mastoiditis
—- otitis media
Leptomeninges:
– frequently a consequence of blood borne infection (haematogenous spread) or direct spread from skull bones
The Pia-arachnoid is congested with polymorphs.
There is a layer of pus that forms
This may organise to form adhesions, causing cranial nerve palsies and hydrocephalus
Cerebral oedema occurs in any bacterial meningitis
Bacterial meningitis clinical presentation
Headaches
fever
nuchal rigidity
photophobia
phonophobia
vomiting
positive kernels sign for both
papilledema may occur
rash
confusion
seizures can occur
feeling fatigued
Investigations
lumbar puncture to analyse the CSF
L’Hermittes sign, brudzinskis sign and Kernigs sign
Gram staining can narrow it down the cause of bacterial meningitis
Treatment
Viral is less serious and will most likely run its course as its self limiting and will require no treatment
Bacterial is a medical emergency and is potentially life threatening and should be treated imminently with appropriate antibiotics
