Saturday, April 03, 2010

Neurocritical infection/ meningitis pearls

1.  Bacterial meningitis damage is half mediated by toxins, half by inflammatory response

2.  Classic triad of headache, fever, and neck stiffness is NOT sensitive for meningitis.  However, 90 + % of patients have 2 of the following four symptoms:  ha, neck stiffness, fever and mental status changes.14 % of patients are comatose on admission, and 34 % have focal deficits. Only 30 % have nuchal rigidity. Fever is often missing in elderly, immunosuppressed and the partly treated groups.  Overall fever is present in 71-77 % of cases, neck stiffness in 48 %, headache in 87-92 %, nausea and vomiting in 74 %, photophobia 57 %, seizures 5-23 %, focal signs <30 %, rash 11 %.  (see van de Beck, NEJM 2006:354:44-53; Durand NEJM 1993; 321:21-28; Thomas et al, Clin Inf Dis 2002; 35:46-52).  Latter article reveals Kernig's and Brudzinski's signs are NOT reliable and have a positive predictive value in the 20s and sensitivity of less than 10 percent.  Older patients >60 in Dutch study had less fever and neck stiffness and more encephalopathy as a presenting sign. 

In infants, signs can be subtle, bulging fontanelle and seizures is not sensitive (Klein, Pediatrics, 1986), and an LP is warranted(?controversial) in patients with first simple febrile seizure. The presentation is usually fever, lethargy, irritability, respiratory distress, jaundice, reduced food intake, vomiting and diarrhea. 

Immunocompromised patients have the triad only 21 % of time, due to less immune response and greater propensity to get atypical organisms. 

3.  Predictors of bacterial v. viral meningitis include one of the following indicators of severity:  altered consciousness, focal deficits, seizures, and shock.  Non predictors include CSF glc< 2, CSF protein > 2 (Brivet et al, Intensive Care Med 2005).

4.  Predictors of mortality include seizures (34 v. 7 %)  and decreased level of consciousness on admission (26 v. 2 %). 

5.  An unusual presentation of brainstem HSVE in an immunocompromised patient included diplopia, dysarthria, and ataxia .

6.  HSVE also causes radiculitis in immunocompromised (lumbosacral) and most cases of recurrent meningitis (previously called Mollaret's meningitis).
7.  WNV in CNS includes movement disorders with myoclonus, postural tremor and cerebellar signs in addition to polio like features.  Death can occur due to respiratory depression.

8.  Presentation of cerebral abscess includes neck stiffness only in 20 % often only shows increased ICP.  Seizures occur in up to 40 %.  Focal specific symptoms such as aphasia occur but are variable.

9. Cranial epidural abscess presents with ha, fever, nausea and usually does not lead to neurologic complications due to neurosurgery>meningitis, with organisms often Strep, Staph and polymicrobial

10.  Subdural empyema occurscausing altered level of consciousness, fever, seizures, septomthrombophlebitis, venous infarcts and more complicated course.  Sources include paranasal sinuses, hematogenous spread due to emissary veins in subdural space, and postoperative extension due to epidural abscess.

11. Peripheral lab clues:  amylase increased in mumps, cold agglutination titers in mycoplasma, CXR  abnormal could be associated with mycoplasma, legionella or lymphocytic chorionic meningitis.

12. Cancer patients much less commonly have the triad (56 % fever, 47 % headaches, 35 % altered mental status, 14 % nuchal rigidity, 14 % completely asymptomatic, and may be related to frequency of a range of neurosurgical procedures (Safdieh, Neurology 2008).

13. Novel lab tests to help diagnose bacterial meningitis include: CSF lactate> 4.2 (nonspecific and only sensitive in acute setting), CRP (normal level has high negative predictive value) and serum procalcitonin level (newest marker) (see Tunkel Clin Inf Dis 2004; Sormunen, J Ped 1999; Viallon et al, Clin Inf Dis 1999 and others).

14. Third generation cephalosporins sterilize the CSF within 2 hours in all patients; in one third by one hour. Latex agglutination and PCR techniques are useful in these situations.

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