: Encephalitis or myelitis is defined as the inflammatory or infectious involvement of the cerebral parenchyma or spinal cord. When an infectious origin is suspected, the germ is not always identified. Next-generation sequencing could be used to correct an etiological diagnosis of these severe conditions in Guadeloupe. The rate of cases for which the infectious agent is not identified encourages continued diagnostic efforts, with the objective of identifying new pathogens or emerging pathogens, some of which may be more specific in the tropics.