iStock 585087100 brain classification

In 1955, cerebrovascular diseases were reclassified as circulatory system diseases in the 7th edition of the International Classification of Diseases and Related Health Problems (ICD). WHO's idea then was that stroke is a condition affecting blood vessels. This decision to reclassify cerebrovascular diseases seemed contrary to the pathophysiology and symptoms leading to mortality and morbidity, which are those of brain dysfunction. Moreover, the decision deviated from the principle of ischaemia of other organs (such as the intestines, kidneys, and the eye), which were listed under their respective organs in ICD-7.

Over the past six decades, this decision has skewed statistics because the 15 million people who had a stroke each year were included under the rubric of circulatory diseases. Stroke became a Cinderella disease, attracting little attention since it was thought that treatment was not available. Treatment of stroke has been revolutionised over the past 20 years, since the advent of stroke units, thrombolysis, and thrombectomy. Hyper acute stroke units save lives if ischaemic stroke is treated within the first 4·5 h. The incorrect classification of stroke led to delay in resource allocation and training of medical, radiological, and nursing staff who know how to deal with brain diseases. The link to low allocation of resources for stroke care is clear to see.

The ICD has since been reviewed three times, with the latest revision (ICD-10) in 1990. The task to produce ICD-11 is enormous. As neurologists and neurosurgeons, we rightly manage our section of the ICD, but the WHO Department of Health Statistics and Information Systems has to deal with all of medicine, taking full consideration of the huge advances over the past 27 years.

The Neurosciences Topic Advisory Group (TAG) started reviewing ICD-10 in 2009. One of our first tasks was to rectify the stroke classification. There was agreement with the Cardiology TAG; however, the statisticians raised concerns regarding longitudinal compatibility and stability of data. An essential issue of the ICD is not only that it is a classification of disease cause, but also a scientifically sound way of informing the medical world and the public of the placement and effects of various diseases and their expression when affecting patients—ie, the clarification that stroke affects the brain and that the first symptom to alert the public of the onset of stroke is neurological means that patients will seek medical advice early and receive optimal treatment, which saves lives and reduces disability. It follows that individuals who suffer stroke symptoms immediately relate this to an impending stroke and seek urgent care.

As members of the Neurosciences TAG, we are extremely pleased that continued dialogue, including Correspondence in The Lancet,1, 2 has now led the WHO Department of Information, Evidence, and Research to reach the decision to move all cerebrovascular diseases in ICD-11 to the section of diseases of the nervous system. This reversal of a previously held position is encouraging because it exemplifies the willingness of our statistician colleagues to listen to sound scientific reasoning and interventions by health ministries and civil society, and to act appropriately. For that we are grateful. After 62 years in exile, we can say now that stroke is a brain disease.

RS is chair of the WHO ICD-11 Neurosciences Topic Advisory Group. BN is a member of the Neurosciences Topic Advisory Group.


Republished from Correspondence, Vol 389 June 17, 2017 


  1. Shakir, R, Davis, S, Norrving, B et al. Revising the ICD: stroke is a brain disease. Lancet. 2016; 388: 2475–2476
    Summary | Full Text | Full Text PDF
  2. >Boerma, T, Harrison, J, Jakob, R, Mathers, C, Schmider, A, and Weber, S. Revising the ICD: explaining the WHO approach. Lancet. 2016; 388: 2476–2477
    Summary | Full Text | Full Text PDF