The TOTEM study is a single-center study designed to evaluate the performance of the D-lactate assay in cerebrospinal fluid (CSF) for the diagnosis of ventriculostomy-related nosocomial meningitis. The study will be conducted in the neurosurgical intensive care unit of the Toulouse University Hospital, in patients with a suspected diagnosis of ventriculostomy-related nosocomial meningitis.

For each study participant, an additional CSF sample will be taken from the ventriculostomy during the routine sampling performed for the diagnosis of nosocomial meningitis. This sample will be stored at -80°C. Assays of D-lactate, procalcitonin (PCT), and pro-inflammatory cytokines (IL-1, IL-6, IL-8, TNFa) will be performed serially on these CSF samples.

If the CSF sample taken at inclusion does not meet the criteria for nosocomial meningitis, a second sample will be taken 48 to 96 hours later to reassess the cellularity of the CSF. Finally, the end-of-participation visit takes place after 4 weeks. Two neurosurgical reanimators will retrospectively diagnose nosocomial meningitis, or the absence of meningitis, according to the information from the patient's medical records.

Inclusion Criteria:

• Age ⩾ 18 years.
• Patient with an external ventriculostomy implanted at the Toulouse University Hospital.
• Patient suspected of nosocomial meningitis due to a febrile syndrome (in the absence of any other identified infectious site), headache, nausea, lethargy, change in neurological status, meningeal syndrome, epileptic event and cutaneous or subcutaneous inflammation at the ventriculostomy site of insertion.
• Patient having expressed oral consent, after free and informed information.
• Patient affiliated to a social security scheme.

Exclusion Criteria:

• Diagnosis of community meningitis.
• Proven or suspected meningitis and/or ventriculitis during the previous month.
• Diagnosis of nosocomial meningitis made in another medical centre prior to admission.
• Short bowel syndrome.
• Acute mesenteric ischaemia.
• End-stage renal failure (GFR < 15 ml/min/m2).
• Peritoneal dialysis.
• Patient participating in another research protocol with an exclusion period still in progress.
• Pregnant or breastfeeding woman.
• Patient under guardianship or trusteeship, persons placed under the protection of justice