⁃ \- All patients have to have a clinical presentation consistent with non-bacterial meningitis (e.g. headache, neck stiffness, photo- or phonophobia, fever)

⁃ and

⁃ Cerebrospinal fluid leukocytes\>10 cells/ml

⁃ Patients with viral meningitis with undetermined pathogen have to have:

• CSF leukocytes\> 10/mL and no other more probable diagnosis assessed by the local investigator.

⁃ In case of doubt, patients are discussed with the DASGIB secretary and chair or at meetings.

⁃ and

⁃ Proven bacterial aetiology (CSF or blood culture/DNA based technology or antigen tests)

⁃ Patients with bacterial meningitis in whom the bacteria cannot not be cultured or identified by DNA-based technologies have to have:

⁃ \- CSF leukocytes\> 10/mL and no other more probable diagnosis assessed by the local investigator.

⁃ In case of doubt, patients are discussed with the DASGIB secretary and chair or at meetings.

⁃ \- All patient have a clinical presentation consistent with brain abscess (e.g. headache, focal neurological deficit, mass lesion on cranial imaging)

⁃ and

⁃ \- Proven microbiological aetiology by culture/DNA-based technology from pus from brain abscess or blood or CSF

⁃ or

⁃ \- Aspiration of pus from the brain abscess

⁃ or

⁃ \- Response to antimicrobial treatment

⁃ or

⁃ \- Tumour ruled out

⁃ or

⁃ \- Tumour thought less probable than abscess on MRI using diffusion weighted imaging (DWI) and apparent diffusion coefficient (ADC) sequences.

⁃ \- A clinical presentation consistent with neuroborreliosis (e.g. radiculopathy)

⁃ and

⁃ \- CSF pleocytosis\>10 leukocytes/mL

⁃ and

⁃ \- Positive intrathecal B.burgdorferi antibody production index.

⁃ and either

⁃ \- Positive syphilis serology in serum combined with CSF leukocytes\>10/mL

⁃ or

⁃ \- CSF syphilis antibodies.