Table 4.

Definitions for Central Nervous System Infections Used in the DASGIB Database

	Criteria
Bacterial meningitis	A clinical presentation suggestive of bacterial meningitis (eg headache, neck stiffness, fever, altered mental status) and either of the following criteria: i)Positive culture or bacterial DNA/antigen analysis of CSF ii)Positive blood culture and CSF leukocytes >10 x 106/L iii)CSF leukocytes >10 x 106/L and seroconversion or 4-fold increase in meningococcal antibody titer within 4 weeks of admission iv)CSF leukocytes >10 x 106/L and no other diagnosis considered more likely given all available information
Viral meningitis	A clinical presentation suggestive of viral meningitis (eg headache, neck stiffness, fever, photophobia) and either of the following criteria: i)Positive viral DNA/RNA analysis of CSF ii)CSF leukocytes >10 x 106/L and positive intrathecal antibody index for HSV/VZV iii)CSF leukocytes >10 x 106/L and serology suggestive of acute infection with a known CNS pathogen, eg Tick-borne encephalitis virus, or positive PCR from other relevant samples, eg influenza in the respiratory tract iv)CSF leukocytes >10 x 106/L and no other diagnosis considered more likely given all available information
Encephalitis/myelitis	A clinical presentation suggestive of encephalitis (eg impaired consciousness >24 hours, headache, neurological deficit) and either of the following criteria: i)Positive viral DNA/RNA analysis of CSF ii)Positive intrathecal antibody index for HSV/VZV iii)CSF leukocytes >10 x 106/L and serology suggestive of acute infection with a known CNS pathogen, eg Tick-borne encephalitis virus, or positive PCR from other relevant samples, eg influenza in the respiratory tract iv)Fulfillment of the encephalitis criteria from the International Encephalitis Consortium48 v)CSF leukocytes >10 x 106/L and/or CNS imaging suggestive of encephalitis/myelitis and no other diagnosis considered more likely given all available information
Brain abscess	A clinical presentation suggestive of brain abscess (eg headache, neurological deficit, fever) and either of the following criteria: i)Aspirated or excised pus from brain abscess with or without detection of pathogen(s) by microbiological or histopathological examinations ii)Cranial imaging combined with bacteremia or identification of a relevant pathogen from a normally sterile sample site or positive serology for toxoplasmosis in a HIV positive patient iii)Cranial imaging and no other diagnosis considered more likely given all available information
Neurosyphilis	A clinical presentation suggestive of neurosyphilis (eg meningitis, headache, cranial nerve palsies, impaired vision or hearing, cerebral vasculitis, general paresis, tabes dorsalis, or dementia) combined with positive blood and/or CSF serological nontreponemal and treponemal tests. Asymptomatic neurosyphilis as well as ocular and auditory syphilis is also included.
Neuroborreliosis	A clinical presentation of Lyme neuroborreliosis (eg facial palsy or radiculitis) combined with CSF leukocytes >10 x 106/L and a positive Borrelia intrathecal antibody index. Patients without a positive Borrelia intrathecal antibody index are also included if the duration of symptoms is <3 weeks and no other diagnosis is considered more likely given all available information

Abbreviations: CSF, cerebrospinal fluid; DASGIB, Danish Study Group of Infections of the Brain; DNA, deoxyribonucleic acid; HIV, human immunodeficiency virus; HSV, herpes simplex virus; PCR, polymerase chain reaction; RNA, ribonucleic acid; VZV, varicella zoster virus.