Infections of the nervous systemDr,kibruyisfaw

oct, 2012Areas to be learned

Acute meningitis

Acute Bacterial MeningitisDef. bacterial infection of the subarachnoid spaceMajor presenting feature

Rapidly developing headache, fever, meningism and photophobiaPhysical exam

Nuchal rigidity, Kernig’s sign, Brudzinsk’ sign

Your immediate taskBacterial? Viral? Tuberculous?

Clinical features

Symptoms/signs Frequency (%)Headache >90%Fever >90%Meningismus >85%Altered sensorium >80%Vomiting ~35%Seizures ~30%Focal neurologic signs 10-20%

Diagnosis, CSF Examination

CSF parameter Typical finding

Opening pressure 200-500mmH2O

White blood cell count 1000-5000/mm3; %Neutrophils >80%

Protein 100-500mg/dl

Glucose <40mg/dl; CSF:serum glucose<0.4

Gram Stain Positive in 60-90%

Culture Positive in 70-85%

Detection of bacterial antigen; PCR

Acute Bacterial meningitisMicrobiology/Causes

Neonates E. coli, GBS, P. mirabilis, L. monocytogenes, Pseudomonas

Children< 5y. N. mening. S pneumoniaeH. Influenzae

Older children and adults < 50 N. mening. and S.pneumo

Adults >50 S. pneumo, G- enteric bacilli,L. mono

Viral/ Aseptic/ MeningitisEnteroviruses, Mumps, Arboviruses,

HIV,HSV-2, HZV, AdenovirusesTuberculous meningitis

Mycobacterium tuberculosis

How can you distinguish weather it is bacterial viral or tuberculosis ?

Bacterial/pyogenic/ onset---acute<2days, toxic and ill, drowsy, possible purpuric rash, CSF—turbid or opalescent, cells—500-2000, protein increased, glucose reduced, g/stain—usually pos, wbc--neutrophilia

Viral/Aseptic/ meningitisAcute<2 days, not toxic , fully conscious, CSF– clear, cells-5-1000—lymph, protein normal or modest rise, glucose normal, g/stain neg, wbc normal

Tuberculous meningitisSub acute, not toxic, alertness may be depressed, CSF—clear, may form cobweb on standing, cells—50-400, lymphocytes, protein increased, glucose reduced, g/stain neg, wbc-normal

What diagnostic tests?WBC and diffBlood culturesLP—CSF G/stain, AFB, biochemistry, CSF culture, india ink, cryptococcal antigen, fungal culture, PCR—HSV, VZV,enteroviral, cytology, viral culture,viral serologyImaging—CXR, CT, MRI

DiagnosisBacterial Typical CSF picture CSF G/stain, culture, antigen detection CSF/bloodViral Enterovirus—in faeces, CSF, throat swab Mumps---CSF, urine, serology Arbovirus—serology, PCR of CSF

Tuberculosis AFB in CSF smear, CSF PCR, CSF culture

Investigation and treatmentABM = life threatening = emergencyKey= early dx. And rx.LP in all cases unless papilloedema or neurologic deficit = b/culture and empiric abx

Indications for empiric antibioticsLP cannot be doneIll or toxicPetechial rashesLP—turbid

When to review therapy?Causative bacteria isolated

CSF guided action CSF = clear wait for lab. Results CSF = lymphocytic, normal biochemistry = probable viral meningitis – review likelihood other causes of similar CSF changes do virology tests

CSF = lymphocytic, protein raised, glucose reduced, AFB or fungal tests positive – start appropriate therapy

CSF guided therapyCSF = lymphocytic, protein raised,

glucose reduced, tests for AFB/fungal negative --- tbc still likely –antitbc + for L. mo

The only form of bact. Mening—epidemics Caused by N. meningitides G- intracellular diplococcus Pathogenic groups –A B C D X Y Z W135 Group B and C predominant in temperate areas The highest burden = Sub-Saharan Africa from Ethiopia to Senegal = meningitis belt

Both endemic and epidemicDry season – groups A C W135

Specific infectionsMeningococcal meningitis and septicemiaEpidemiology

1963--- Meningitis belt b/n latitudes 4 and 16 north w/300-1100ml annual rainfall south of Sahara Belt—high levels of endemicity w/ large superimposed epidemics ----Serogroup A = predominant

Organism in nasopharnyx, highest carriage in 15-19 years Transmission –droplet spread or direct contact w/ index case Overcrowding –Pathogenesis Colonization of nasopharyngeal mucosa—local invasion—bacteraemia—intravascular multiplication----- meningeal invasion –SAS inflammation

Or septicemic presentationRapidly progressive shockDIC---- bleeding into and dysfunctions of

many organs including adrenals =Wterhouse Friederichsen syndrome

Purpuric rashIP—1-3 days

Clinical featuresAbrupt –fever, vomiting, headache,

irritability, restlessness --signs of meningitis or

Fulminant septicemia – toxicity, drowsiness and shock

Petechial or purpuric rash = 2/3

ComplicationsWaterhouse-Friederichsen

syndrome= fulminant septicemia w/adrenal cortical failure

Ischemia –tissue damage—loss of finger and/or toes

Hydrocephalus, brain damage, subdural hemorrhage, brain abscess, deafness

DiagnosisHigh index of suspicionCSF studies

TreatmentPreferred= ceftriaxone 2 g bid q24h or

cefotaxime 2 g q4-6hx7-10 daysAlternatives= CAF 4-6 g/dx7-10 daysSteroid= dexamethasone 10 mg iv q6hx4

days

PreventionRespiratory isolation x 24hChemoprophylaxis Household or intimate contact,

med. PersonnelRif. 600 mg bid x 2 daysCipro 500mg x1 doseCeftriaxone 250mg im x1 dose

ImmunoprophylaxisConjugate vaccine

Target population= all children at 11-12 years

Anyone > 2 years w/risk = college students, military recruits, asplenia

Polysaccharide vaccine A C Y W135

For outbreaks, age>65