Each center has a coordinator team that includes a neurologist, a physician - neurology or internal medicine resident -, and a research coordinator. The team is constantly screening the patients admitted to the center. The patients that fulfill the criteria for cases or controls are approached by the research coordinator who is in charge to inform the participant about the study and complete the informed consent. Then, the medical team perform the neurological evaluation, including the history and the physical exam according to the NEAS forms. Samples of blood and urine are collected in all participants. If a lumbar puncture is done as part of the standard of care, spinal fluid is also collected. Based on resources availability, the participants are followed every week for a 4-week period and in each visit a clinical assessment and sample collection are completed.