May be due from invasive procedures such as craniotomy, lumbar puncture, intrathecal medication infusions, placement of internal ventricular catheters, placement of external ventricular catheters, spinal anesthesia, and from complications of head trauma and in rare cases, sepsis from hospital acquired bacterial infections.
Bacterial meningitis from nosocomial causes have a varied spectrum of agents compared to meningitis acquired in the community setting.
Nosocomial bacterial meningitis results from infection from the bloodstream via the blood brain barrier or by breakdown of the external barrier formed by the skull and leptomeninges.
Occurs in 0.8 to 1.5%of patients who undergo craniotomy (McClelland S).
Approximately 1/3 of cases that occur with craniotomy, occur in the first week after craniotomy, one third in the second week and one third after the second week (Korinek AM).
Some cases may occur years after the initial craniotomy surgery (Korinek AM).
The risk is minimalized by preventing CSF leakage during craniotomy.
The risk after craniotomy is increased when the duration of surgery is more than four hours and a concomitant infection at the site of the incision is present.
Internal ventricular catheters, such as CSF shunts, used for hydrocephalus are associated with nosocomial bacterial meningitis for to 17% of cases (Conen A).
The majority of internal ventricular NBM infections occur within one month of surgery and is causally related to colonization of the catheter at the time of surgery.
Catheters used externally to monitor intracranial pressure, or the temporary diversion of CSF from an obstructed ventricle, or for the treatment of infected internal catheters are associated with a meningeal infection rate of approximately 8% (Lozier AP).
NBM infections associated with external ventricular catheters are increased with the increased duration of external drainage of greater than five days, , although this was not confirmed in a prospective randomized trial (Lozier AM, Wong GK).
NBM infections with the use of external ventricular catheters can be reduced by preventing introduction of new catheters, decreasing routine sampling of CSF, decreasing leakage of CSF at the site, preventing blockage of the drain and preventing intraventricular hemorrhage.