meningitis Flashcards
what is the etiology of meningitis ?
viral is more common than bacterial
viral : Aseptic meningitis enteroviruses (echovirus, coxsackievirus) mumps, HSV - HSV2 more than HSV1 CMV EBV herpes zoster HIV, measles and influenza
bacterial :
babies over three months, children and adults the most common organisms :
Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae type b (Hib)
>50yrs Streptococcus pneumoniae (most common) Aerobic gram-negative bacilli (e.g., Escherichia coli) Listeria monocytogenes Haemophilus influenzae type b
fungi : aseptic meningitis Cryptococcus. Rare but can be life-threatening, more common in immunodeficient people coccidiosis candida asperigillus
parasitic
helminths - ecchinoccocus
protozoa
atypical :
TB, syphilis and Lyme disease
non infective secondary to cancer such as leukemias , lymphoma , autoimmune disease - sarcoidosis and drugs
secondary from direct spread of otitis media, mastoiditis, sinusitis
HOWEVER ALL CASES SHOULD BE TREATED AS BACTERIAL UNTIL PROVEN OTHERWISE because bacteria meningitis has higher mortality
what are the most significant risk factors for meningitis ?
young age :
less than 1 yr of age
Risk factors: low birth weight, prematurity, premature rupture of membranes, maternal peripartum infection
second incidence peak in teenagers and young adults
!!!!!! Sub sahara africa meningitis BELT - worlds highest incidence of meningitis cause by N meningitides !!!!!!
median age adult pop = 43
Crowded occupational or living conditions (e.g., college dormitories, military barracks, retirement homes
Basilar skull fracture -
Streptococcus pneumoniae
Haemophilus influenzae type b
immunocompromised - asplenia , heavy alcohol
Defects in humoral immunity (including splenectomy): encapsulated bacteria (N. meningitidis, S. pneumoniae, H. influenzae
Defects in cell-mediated immunity (e.g., in HIV, drug-induced immunosuppression): M. tuberculosis, L. monocytogenes
Viral: Risk is higher in individuals with cell-mediated immune deficiencies (e.g., in HIV infection).
Fungal: Risk is higher in individuals with cell-mediated immune deficiencies (e.g., HIV infection).
smoking
what is the pathophysiology of bacterial meningitis ?
via droplet spread and usually requires frequent or prolonged close contact
colonize the nasopharynx or the upper airways
Bacteria which reside in the upper respiratory tract can then travel via the bloodstream to the meninges
meningitis can occur as a result of direct spread from a local source of infection, for example, otitis media or mastoiditis
Viral meningitis: often associated with?
encephalitis (meningoencephalitis)
Meningococcal disease is a term referring to?
meningococcal meningitis
meningococcal sepsis/septicaemia (where Neisseria meningitides enters the bloodstream and can cause the classical petechial or purpuric rash- 25% of cases) or a combination of both (60% of cases)
clinical features of meningitis ?
triad of fever,
neck stiffness
and altered mental state (but only seen in 44 percent!! of ADULTS ,LESS SPEIFIC IN CHILDREN
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early symptoms non specific
fever, headache, nausea and/or vomiting, lethargy, irritability, muscle or joint pains
triad
Non-blanching rash or cutanoues petechia (meningococcal disease)
maculopapular rash - some viral meningitis - enterovirus
Photophobia
Prolonged capillary refill time
Shock (tachycardia, hypotension, respiratory distress, poor urine output)
Neurological symptoms :
Seizures
Paresis
increased ICP - seizures , papilloedema = blurred vision , bradycardia
decrease in consciousness
blurred vision
weakness in moving and talking
what are the signs of meningitis ?
Kernig’s sign (pain and resistance on passive knee extension with hips fully flexed)
Brudzinski’s sign (knees and hips flex on bending the head forward)
Signs of increased intracranial pressure: e.g., papilledema (< 5% of cases
Signs of underlying infections
Bulging and redness of tympanic membrane: acute otitis media
HSV - cold sore/genital vesicles
HIV signs (lymphadenopathy, dermatitis, candidiasis, uveitis)
parotid swelling (mumps)
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Skin manifestations
discussed
what re the specific clinical features suggestive of atypical meningitis ?
tuberculous meningitis
gradual manifestation with intermittent fever
focal neurological deficits - hemiparesis
cranial nerve deficits seen most commonly in basal meningitis predominantly the abducens nerve
crypto coccus
Meningeal symptoms are often absent
what are clinical features suggestive of meningoencephalitis ?
Focal neurological signs (e.g., paresis, extrapyramidal symptoms, aphasia)
Seizures (focal-onset or generalized)
Behavioral changes,
psychosis
Altered consciousness
initial investigations ?
Blood sugar- always required if an altered mental state is present
Biochemistry- U&Es, CRP
Haematology- FBC, clotting studies (especially if petechial rash or sepsis)
Blood culture - obtain before starting antibiotic therapy
Throat swabs (1 for bacteria, 1 for virology)
meningococcal PCR
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CT is sometimes performed if there are focal neurological deficits or if a specific underlying cause (i.e. mastoiditis) is suspected
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Lumbar puncture Cerebrospinal fluid (CSF) culture is the gold standard
performed within the hour of arriving at hospital before antibiotic treatment . However, if LP will delay antibiotic treatment longer than hour, antibiotics given and LP performed later
CSF is analysed for cell count (to count and identify the WBCs), gram stain (to identify bacteria), glucose, protein, lactate and culture. Other tests include bacterial and viral PCRs
meningococci - gram negative
listeria - gram negative
homophiles - gram negative
pneumococci - gram positive
Highly suggestive findings: pleocytosis (granulocytic or lymphocytic), low glucose, high protein >1.5g/l appearance : Cloudy, purulent fluid high opening pressure high lactate
diagnosis of viral meningitis ?
Aseptic meningitis
gram-stain is negative and no bacteria are cultured on standard media
Clear fluid Variable cell count , increased lymphocytes protein <1g/l glucose normal monocytosis
diagnosis of atypical meningitis ?
TB acid-fast bacilli on CSF Gram stain Culture is the gold standard bt takes weeks Analysis of adenosine deaminase (ADA) : ↑↑ Activity in CSF of individuals with tuberculous meningitis compared to CSF of individuals with other types of meningitis fibrin web seen mononuclear glucose low protein 1-5g/l
cryptococcus
Cryptococcal antigen testing of CSF and serum - performed via latex agglutination or enzyme immunoassay
CSF gram staining: India Ink (clear halo), mucicarmine (red inner capsule)
contra of LP?
raised intracranial pressure
reduced consciousness less than or equal to 12 on GCS
bradycardia
focal neurological signs, abnormal posturing,
abnormal pupil reflexes, papilloedema,
shock
convulsion
CT head (with or without IV contrast): before LP if increased ICP is suspected
dd of meningitis ?
Influenza or other viral illnesses
Sepsis
Encephalitis
Intracranial or spinal abscess
Malaria,
complication of meningitis ?
Waterhouse-Friderichsen syndrome -
predominantly affects small children and asplenic individuals
characterized by disseminated intravascular coagulation and hemorrhagic necrosis of the adrenal glands with resulting acute adrenal insufficiency.
= hypotension and shock
