Neuropsychological sequelae of bacterial and viral meningitis

Survivors of meningitis often complain about neurological and neuropsychological consequences. In this study, the extent of these sequelae was quantified and correlated to MRI findings. Neurological, neuropsychological and neuroradiological examinations were performed with adult patients younger than 70 years, 1-12 years after recovery from bacterial meningitis (BM; n = 59), or from viral meningitis (VM; n = 59). Patients with other potential causes for neuropsychological deficits (e.g. alcoholism) were carefully excluded. Patients were compared to 30 healthy subjects adjusted for age, gender and length of school education. With the exception of attention functions, both patient groups showed more frequently pathological results than the control group for all domains examined. Applying an overall cognitive sum score, patients after BM did not differ significantly in their performance from patients after VM. Separate analyses of various cognitive domains, however, revealed a higher rate of persistent disturbances in short-term and working memory after BM than after VM. Moreover, patients after BM exhibited greater impairment of executive functions. Associative learning of verbal material was also reduced. These deficits could not be ascribed to impaired alertness functions or decreased motivation in BM patients. Applying a logistic regression model, the neuropsychological outcome was related to the neurological outcome. Patients with a Glasgow Outcome Scale (GOS) of < 5 had more frequently impaired test results for non-verbal learning and memory. GOS was also correlated with performance in executive functions. Brain volume was lower and ventricular volume was higher in the bacterial than in the VM group, and cerebral volume and the amount of white matter lesions of patients after BM were negatively correlated with short-term and working memory. In conclusion, patients after both BM and VM with favourable outcome showed affected learning and memory functions. More patients after BM than after VM displayed pathological short-term and working memory. BM resulted in poorer performance in executive functions, language, short-term memory and verbal learning/memory tests. As a result of neurological and neuropsychological sequelae, BM with a GOS >= 4 led to decreased activities of daily living but only a minority of patients were disabled in a way that social functions were affected. The extent of neuropsychological sequelae of BM might have been overestimated in earlier studies which often had not been controlled for comorbidity factors such as alcoholism.