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CNS Infections

CNS Infections. 11-23-04 Chapter 235. Bacterial Meningitis. Epidemiology. 400 per 100,000 in neonates 1-2 per 100,000 in adults S pneumoniae & N meningitidis m/c HIB vaccine has been very effective Mortality 5% in children beyond infancy 25% in neonates and in adults. Pathophysiology.

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CNS Infections

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  1. CNS Infections 11-23-04 Chapter 235

  2. Bacterial Meningitis

  3. Epidemiology • 400 per 100,000 in neonates • 1-2 per 100,000 in adults • S pneumoniae & N meningitidis m/c • HIB vaccine has been very effective • Mortality • 5% in children beyond infancy • 25% in neonates and in adults

  4. Pathophysiology • S. pneumonia and N. meningitidis (and H. influenzae) are encapsulated which provides them with increased ability to invade BBB • Upper airway bloodstream subarachnoid space subcapsular constituents trigger inflammation fever, meningimus, change in MS brain/meningeal edema decreased CSF drainage hydrocephalus increased ICP ICP>CPP

  5. Clinical Features • 25% of adult cases “classic” • Rapid development of • Fever • HA • Stiff neck • Photophobia • Change in MS • Nonspecific signs/symptoms in very young/old • 25% will develop seizures

  6. Clinical Features • History • Living conditions • College dorm/barracksN meningitidis • Trauma • Recent neurosurgeryStaph/gram(-) rod • Immunocompetence • Immunization hx • NoneHiB • Antibiotic use

  7. Clinical Feratures • Physical Exam • Brudzinski • Passive neck flex hips & knees flex • Kernig • Flex hip, ext knee hamstrings contract • Skin • Purpura • Petechiae/splinter hem, pustular lesionsmicroemboli • Fundi • Neuro Exam

  8. Diagnosis • Parenchymal • CT is the imaging of choice • Brain abscess, encephalitis, toxoplasmosis • Meningeal • Lumbar puncture • Neoplasm, CNS vasculitis, SAH

  9. Diagnosis

  10. Diagnosis • An aseptic profile • Must think about… • Partially treated bacterial infection • Bacterial infections adjacent to the subarachnoid space

  11. Diagnosis • Tests to order on the CSF • Tube #1 cell count with diff • Tube #2 protein,glucose • Tube #4 cell count with diff, gram stain/culture • Tube #3 • Viral cultures • Borrelia (lyme disease) • India ink/cryptococcal antigen (immunocomp) • Acid fast stain/culture for mycobacteria (TB) • Latex agglutination for bacterial Antigens • PCR • Herpes, arbovirus

  12. Lumbar Puncture • Contraindications • Infection in overlying skin • Relative • Coagulopathy • Thrombocytopenia • If delay is anticipated obtain blood cultures and GIVE antibiotics • You have 2 hours after ATB given before sensitivity is effected

  13. Lumbar Puncture • Considerations for not obtaining CT before performing LP • Age <60 • Immunocompetent • No h/o CNS disease • No recent seizure (<1week) • Normal sensorium & cognitition • No papilledema • No focal neuro deficits

  14. Treatment • First priority • Antibiotics • Second priority in some cases • Anti-inflammatories • Third priority • Counter the adverse effects of increased ICP & vasculopathy

  15. Emperic Antibiotics

  16. Emperic Antivirals • Concern of herpes • Acyclovir 10mg/kg IV Q 8 hours

  17. Steroids • Dexamethasone • 10mg IV 15 minutes prior to antibiotics • Shown to decrease M&M in S. pneumoniae but NOT N. meningitidis • N Engl J Med 2002; 347:1549-1556, Nov 14, 2002.

  18. Complications • Seizures • Hyponatremia • SIADH • CVA • Coagulopathies • Cognitive deficits, epilepsy, hydrocephalus, hearing loss affect 25% of survivors

  19. Chemoprophylaxis • Household/school/daycare contacts last 7 days • Direct exposure to secretions • Kissing, sharing utensils/toothbrushes, mouth to mouth, intubation without a mask • First line: rifampin 10mg/kg (max dose 600mg) Q12h x 4 doses • Alternative: ceftriaxone, cipro, sulfisoxazole

  20. Viral Meningitis

  21. Viral Menigitis • 85% secondary to • Echo- • Coxsackie • Entero- • Also consider HSV, and EBV • Neutrophils may predominate in the CSF in the first 24 hours • Consider starting ATB’s until cultures come back (-)

  22. Viral Encephalitis

  23. Viral Encephalitis • Infection of brain parenchyma • Presents of neurological abnormalities distinguish it from meningitis

  24. Epidemiology • Incidence is 1/10 of bacterial meningitis • HSV-1, zoster, EBV,CMV, rabies, arbo • Arbo • LAC (La Crosse)-diagnosed most frequently • SEE(St Louis)-20% mortality in elderly • WEE(Western)- causes seizures in 90% of infected infants, permanent neuro deficits in 50% • EEE(Eastern)- most devastating, mortality 70% • WNV(West Nile)

  25. Pathophysiology • Portals of entry • Arbo-transmitted by mosquitoes, ticks • Rabies-bite by infected animal • Hematogenous dissemination v. travel backwards on axons (HSV,HZV,rabies) • Dysfunction & damage caused by disruption of neural cell function & inflammation

  26. Pathophysiology cont. • Gray matter predominately affected • Cognitive/psychiatric signs, lethargy, seizures • White matter affected in post-infectious encephalomyelitis

  27. Clinical features • New psych symptoms • Cognitive deficit (aphasia, amnesia, confusion) • Seizure • Movement d/o

  28. Diagnosis • MRI-more sensitive than CT • CT • EEG • LP-findings consistent with aseptic meningitis

  29. Differential • Exclude the killers • Bacterial meningitis & SAH • More meningeal symptoms • Lyme, TB, fungal, bacterial, viral, neoplastic • More parenchymal symptoms • Abscess, bacterial endocarditis, post-infectious encephalomyelitis, toxic or metabolic encephalopathy

  30. Treatment • HSV: acyclovir 10mg/kg IV • CMV: ganciclovir • Rabies/EEE/HSVdevastating & usually fatal or residual deficits

  31. Brain Abscess

  32. Brain Abscess • Focal pyogenic infection • Pus-filled cavity ringed by granulation tissue & outer fibrous capsule surrounded by edematous brain tissue

  33. Epidemiology • Paranasal sinus focus • 10-30 y/o • Otic • Bimodal: <20 y/o & >40 y/o

  34. Pathophysiology • Hematogenous spread • 1/3 of cases • Contiguous (middle ear, sinus, teeth) • 1/3 of cases • Otogenic (Bacteroides)temporal lobe/cerebellum • Sinogenic & odontogenic(anaerobic & microaerophilic streptococci)frontal lobe

  35. Clinical Features • Classic triad • HA, fever, focal deficit • <1/3 of cases • Toxic appearance is rare • Seizures, vomiting, confusion, obtundation possible • Frontal lobe-hemiparesis • Temporal lobe- homonymous superior quadrant visual field deficit or aphasia • Cerebellum-limb incoordination or nystagmus

  36. Diagnosis • CT with contrast • LP contraindicated • Biopsy or aspiration for confirmation

  37. Treatment

  38. Questions • 1. CSF analysis returns with the following values: glucose 20 WBC 1200 Protein 300. This profile is consistent with • A. Bacterial meningitis • B. viral meningitis • C. Fungal meningitis • 2. Which of the following is an absolute contraindication to performing an LP • A. Coagulopathy • B. Infection of the overlying skin • C. thrombocytopenia

  39. Questions • 3. T/F Steroids have been shown to decrease morbidity & mortality in meningitis caused by Strep pneumo • 4. T/F Brain abscesses are confirmed by LP. • 5. Which antibiotic regimen should be initiated in an immunocompromised patient suspected of having bacterial meningitis without any allergies • A. Pen G • B. Ceftriaxone & vanco • C. Vanco, gent, & ceftazidime • Answers: 1. A 2. B 3. T 4. F 5. C

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