INTERNATIONAL CLASSIFICATION OF DISEASES (ICD-11) AND NEUROLOGIC DISORDERS: THE FUTURE When the WHO’s Topic Advisory Group for Neurol-

ogy (TAG) started work on revision of the ICD-10 diag-nostic codes in June 2009, the issues were daunting. The existing classification was produced a generation ago and the need to move to the digital age was becoming imper-ative. Appreciating modern advances in genetics and immunology, and the consequent changes in under-standing of the pathophysiology of disorders of the ner-vous system,WHO’s charge to the TAG was to produce a comprehensive, up-to-date disease classification, while providing published or consensus evidence for each cod-ing change. In addition, the task would be to focus on ways to reduce the treatment gap while considering the utility of the ICD-11 when used in primary care and nonspecialist settings. The project mushroomed over the 3 years since our first meeting and continues to do so. The work was made even more difficult as the group needed to add “content models ” for the major codes for the first time (i.e., providing a definition for each disor-der, along with appropriate diagnostic tests and out-come). The ICD-11 is meant to be updated as new knowledge develops, rather than waiting some years for another whole-scale revision, but this process has yet to be defined. An unprecedented collaboration among many inter-national neurologic and neurosurgical associations is exemplified in the work of the TAG. The WHO ap-pointed 7 ad hoc members from across the world. There are also representatives from the major global neurologi