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The classification of neurological disorders in the 11th revision of the International Classification of Diseases (ICD-11)
  1. Sanjeev Rajakulendran1,
  2. Tarun Dua2,
  3. Melissa Harper2,
  4. Raad Shakir1
  1. 1Imperial College NHS Healthcare Trust, Charing Cross Hospital, London, UK
  2. 2Department of Mental Health and Substance Abuse, World Health Organization, Geneva, Switzerland
  1. Correspondence to Dr Raad Shakir, Imperial College NHS Healthcare Trust, Charing Cross Hospital, London W8 8RP, UK; Raad.Shakir{at}

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Bringing the ICD into the 21st Century. How will ICD-11 reflect the evolution in our understanding of neurological disease over the past twenty years?

The WHO, the body responsible for the International Classification of Diseases (ICD) is currently preparing the 11th revision (ICD-11) which is scheduled for approval by the World Health Assembly in 2015. Among its many uses, the ICD is the premier tool for clinical coding and capturing morbidity and mortality statistics worldwide. As the revision process passes the halfway stage, it is timely to consider how the neurology chapter is shaping up. We outline the major changes in the classification of neurological disease expected in ICD-11, how these have been influenced by the significant progress in clinical neuroscience over the past two decades and consider the impact the changes will have on users of ICD-11.

WHO has constituted Topic Advisory Groups to assist in revision of specific chapters. The neurology Topic Advisory Group consists of an international group of neurologists, neurosurgeons and members of allied specialties and societies. Their remit is to assist and advise WHO to ensure that the latest revision reflects the progress in our understanding of neurological disease in a manner that is coherent, comprehensive and intuitive. In addition, WHO is ensuring the revision proceeds in a transparent and inclusive manner. The former has been achieved by the use of a web-based platform accessible to all by inviting all interested parties and stakeholders to provide feedback on progress to date.1 ,2

From the neurological perspective, profound changes are anticipated. ICD-11 will see a major overhaul in the organisation of the main neurological disease categories (or blocks) and a change in the approach to classification in tune with current clinical practice and understanding of neurological disease. While an increase in the number of codes is inevitable, a balance between comprehensiveness and clinical utility is the aim.

One limitation of ICD-10 is its rigid adherence to the number of blocks in the neurology chapter. Consequently, certain blocks contained a miscellany of seemingly unrelated neurological entities which bore little relation to the block headings they were contained in. For example, cerebrovascular disease was listed under the rubric of ‘Episodic and paroxysmal disorders’ along with epilepsy, headaches and sleep disorders. In ICD-11, the first three of these disease categories have their own blocks, and ‘Sleep-wake disorders’ can now be found as a chapter of its own.

In ICD-10, the ‘other disorders of the nervous system’ block was employed to capture the ‘spill over’ from other neurology blocks and those disorders which were deemed unclassifiable elsewhere. The result is an incongruent collection of diseases. In order to have a scientifically valid and clinically useful linear structure, a number of new blocks are included in ICD-11. These consist of disorders previously contained in the ‘other disorders of the nervous system’ section of ICD-10 and include ‘disorders of consciousness’, ‘disorders of cerebrospinal fluid pressure and flow’, ‘disorders of the autonomic nervous system’, ‘nutritional and toxic disorders of the nervous system’ and ‘spinal cord disorders excluding trauma’. Their promotion to block status will hopefully have a positive effect on coding practices.

Underpinned by advances in genetics, molecular biology and immunology in particular, the last two decades have seen an unprecedented expansion in the number of genes and autoantibodies associated with neurological disease. Reflecting this knowledge in a clinically meaningful way remains one of the principal challenges of ICD-11. While progress in ‘neurogenetics’ is reflected throughout the neurology chapter of ICD-11, the growth in our understanding of immune-mediated neurological disease has warranted the addition of an entirely new section in the neurology chapter—‘paraneoplastic and autoimmune disorders of the CNS’.

The genetics and molecular biology of prion disease has advanced considerably since ICD-10. In addition, the advent of bovine spongiform encephalopathy—a major public health issue in the UK in the 1990 s—has led to the recognition of new variant CJD (nvCJD) as an acquired variant of prion disease. Appropriately, these rare and enigmatic disorders are found in a self-contained block in ICD-11. Other new blocks to emerge include the dementias, which are currently classified under ‘other degenerative disorders of the nervous system’ in ICD-10.

Following completion of the linear structures (the basic classification structure in each neurology block), the next step in the development of ICD-11 is the utilisation of electronic field trials to test the accuracy, validity and reproducibility of entries and the extent of improvement from ICD-10. Members from the international neurology community and related specialties will be invited to take part in the trials and will collectively form the global neurology network. Interested participants are invited to visit the following website for registration:

ICD-10 was published in 1994. The last two decades have witnessed fundamental advances in our understanding of neurology, shifts in our perception of its classification and an information technology-induced transformation in clinical practice. An ICD-11 which assimilates, distils and reflects the essence of progress in these areas is a colossal challenge confronting those involved in the revision.


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  • Contributors SR, MH, TD and RS all contributed to the drafting of the manuscript and in critically revising it.

  • Competing interests RS is the Chair of the Topic Advisory Group (TAG) for the revision of the chapter on diseases of the nervous system for ICD-11 and SR is a member of the working group. Their input to this article represents their own views and not the official views of the TAG or the WHO. TD and MH are employed by WHO and as coauthors, they alone are responsible for the views expressed in this article and they do not necessarily represent the decisions, policy or views of the WHO.

  • Provenance and peer review Commissioned; internally peer reviewed.

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