NEW YORK (Reuters Health) - About one third of adult survivors of bacterial meningitis may experience mild cognitive impairment, according to a new report.

About 4 to 6 cases of meningitis caused by bacterial infections occur among every 100,000 adults every year, Dr. Diederik van de Beek and colleagues from the University of Amsterdam note in their report in the Journal of Neurology, Neurosurgery, and Psychiatry.

"Even in patients with apparent good recovery, cognitive impairment occurs frequently," they add. Various studies, however, report differences in types of cognitive dysfunction, definition of cognitive impairment, and assessment methods.

The researchers therefore examined the cognitive outcome in 155 adult survivors of bacterial meningitis compared with 72 healthy "control" subjects.

Neuropsychological tests revealed cognitive impairment in 32 percent of the patients compared with 5.5 percent of the controls.

"We found a diffuse pattern of cognitive impairment, in which cognitive speed played the most important role," Dr. van de Beek and colleagues report. No association was observed between cognitive performance and the time that had elapsed since the meningitis episode.

After further analysis, factors associated with cognitive impairment after bacterial meningitis recovery included male gender and cranial nerve damage apparent at the time of hospital discharge; these increased the risk by three-fold and nearly five-fold, respectively.

SOURCE: Journal of Neurology, Neurosurgery, and Psychiatry, October 2007.