Neuroborreliosis (NBL) is diagnosed in 10-15% of patients with Lyme borreliosis. In Europe in adults, the main clinical manifestation is called "Bannwarth syndrome". This includes painful meningoradiculitis, sometimes accompanied by cranial nerve neuritis. Current European guidelines issued by the European Federation of Neurological Societies (EFNS) recommend the following triad for the diagnosis of "definite NBL": (i) Neurological symptoms suggestive of NBL without any other obvious cause; (ii) CSF pleocytosis; (iii) Intrathecal production of specific anti-Borreliella antibodies. CXCL13, C-X-C chemokine motif ligand 13, is a chemokine implicated in B cell chemotaxis. Extensive literature exists on the analysis of CXCL13i as a diagnostic marker for acute NBL. A recent meta-analysis from 2018, published by Rupprecht et al finds an overall sensitivity and specificity of 89% and 96% respectively, indicating satisfactory diagnostic value. In this study, the investigators wish to assess the place of this new marker in the diagnosis of neuroborreliosis before proposing it as a test carried out by the Borrelia CNR.

Inclusion criteria:

• Major subject (≥18 years old)
• Subject having consulted at the HUS between 01/01/2013 and 31/12/2018
• Subject not having, after being informed, expressed their opposition to the reuse of their data for the purposes of this research

Exclusion criteria:

• Subject who expressed their opposition to participating in the study
• Subject under guardianship or curatorship
• Subject under safeguard of justice

Major subject (≥18 years old) subject having consulted at the HUS between 01/01/2013 and 31/12/2018