Diagnosis and characterization of viral infections of the central nervous system

Viral infections of the central nervous system (CNS) are underdiagnosed and their etiology often unknown. To increase case finding and etiologic diagnosis, patients with at least two symptoms among which fever, headache, impaired consciousness, focal signs and neck stiffness entered a diagnostic algorithm, including risk factors, epidemiological, clinical, laboratoristic and radiological criteria. A check list of serologic and molecular virology tests to be performed on blood and cerebrospinal fluid was developed. Tests were performed following a priority algorithm. The study was conducted in the 2012-2014 period and data were compared with what was found in the 2009-2011 period. In the 2012-2014 period, 34 cases of suspected viral infection of the CNS were identified. Viral etiology was confirmed in 21/34 (61.7%). In the 2009-2011 period, 27 cases of suspected viral infection of the CNS were identified. Viral etiology was confirmed in 10/27 (37.0%). Overall, in the 2009-2014 period, 61 cases have been diagnosed. Males were 34/61 (55.7%), mean age was 50.2 (range 18-85). Etiology was established in 31/61 (50.8%) as follows: VZV 9 cases, Toscana Virus 6, HSV 1 6, HSV 2 and Enterovirus 3, West Nile 2, HHV 7 and parvovirus B19 one. When lumbar puncture was performed within 72h from the onset of symptoms, an etiologic diagnosis was made in 15/27 cases (55.5%); when lumbar puncture was performed after 72h from the onset of symptoms, an etiologic diagnosis was made in 10/28 cases (35.7%). At CSF examination, leukocytes count was increased (>5x109/L) in 59/60 (98.3%) and lymphocytes were prevalent in 57/60 (95.0%); glucose was reduced (<50 mg/dl) in 12/60 (20.0%), but CSF/blood glucose ratio was less than 40% only in 2/60 (3.3%); proteins were increased (>60 mg/dl) in 40/60 (66.6%). Overall mean CSF leukocytes count was 280x109/L while mean leukocytes count of Enterovirus infections was 151x109/L and that of VZV infections was 625x109/L. Mean protein concentration was 110 mg/dl while that of VZV infections was 237.9 mg/dl. Additionally, a seroprevalence survey for Toscana Virus was conducted on consecutive patients admitted in the Infectious Diseases Unit, regardless the symptoms: IgG or IgM were positive in 34/100 cases (34%), with a clear trend to increase with age.