Long Time Coming: ICD-11 Recognizes Stroke as Brain Disorder

Daniel M. Keller, PhD

November 11, 2019

DUBAI, United Arab Emirates — Major changes are coming for neurology in ICD-11, the International Statistical Classification of Diseases and Related Health Problems.

Among the 5000 entities covering neurology and neurosurgery in the latest version, a major change is the reclassification of stroke as a disorder of the brain. Since 1955, stroke has been classified as a circulatory disease in the more general category of cardiovascular disease.

Presenting the ICD changes during a presidential symposium here at the XXIV World Congress of Neurology, Raad Shakir, FRCP, of Imperial College London University, United Kingdom, and immediate past-president of the World Federation of Neurology said the reclassification of stroke is predicted to have significant ramifications.

ICD in general is a framework for health information and reporting, used by 194 countries to monitor and track morbidity and mortality, injuries, diseases, epidemics, threats to public health, and disease burden and to assess progress in meeting defined public health goals and obligations. ICD is also a basis for guidelines for care and standards of practice, as well as a means to facilitate research into better treatments and preventive strategies, Shakir said.

Among other advantages, reclassifying stroke as a disease of the brain will allow better tracking of its prevalence and trends in different countries, planning resources, and monitoring progress in achieving public health goals. With an aging population in many countries and increasing risk factors for stroke (eg, lifestyle, pollution), stroke incidence is predicted to double or triple in many regions by 2050.

According to the WHO, besides clinical entities, ICD is used by "health insurers, national health program managers, data collection specialists, and others who track progress in global health and determine the allocation of health resources."

Consistency and Interoperability of ICD-11

ICD-10 has been available in 42 languages, including the six official ones of the WHO. Advantages of ICD-11 are that it is completely electronic and is designed to work in multiple languages and function seamlessly in an electronic health records environment and at the same time be user friendly. All items in ICD-11 have accompanying definitions, which are generally not present in ICD-10.

A major goal for the ICD-11 revision was to produce a multipurpose classification of diseases that would be useful for tracking outcomes and clinical care and that would facilitate research and public health. Therefore, it was designed to have consistency and interoperability "to enhance scientific comparability and communication across different uses," Shakir said.

The WHO released ICD-11 on June 18, 2018 to allow member states and other stakeholders to prepare for its implementation on January 1, 2022. It is the culmination of the efforts of 270 institutions in 99 countries.

Work on it began in 2009, and it will replace ICD-10, which was put into place in 1992 and most recently updated in 2016. The effort to revise the neurology section of ICD-11 was led by Shakir, chair of the WHO Neurosciences Topic Advisory Group. The goal was to produce new classifications reflecting modern medicine and practice.

Shakir said there was much bureaucratic wrangling between clinicians and the WHO to reclassify stroke as a neurologic condition. ICD-11 contains 55,000 entries, of which nearly 10% fall within neurology. ICD-10 allows for 14,000 codes.

For primary care, a core version of ICD-11 contains essentials of 50 selected disorders. It will serve for disease classification and for education, covering etiology, diagnosis, and management.

Stroke Is "No Longer Hidden"

Bo Norrving, MD, PhD, of Lund University, Sweden and past president of the World Stroke Organization, presented the implications of the reclassification of stroke as a neurologic disorder.

As the second largest disorder in terms of mortality and disability, stroke has been hidden in ICD-10 under the heading of cardiovascular disease in WHO statistics and was seen as a circulatory system problem.

"This reclassification increases its visibility, potentially improving care for the patients, while providing physicians and researchers with a road map to reduce disparities in treatment," he said. Similarly, transient ischemic attacks (TIA) fell under diseases of the nervous system, and silent cerebrovascular disease was listed under "incidental imaging findings."

Since ICD-10 was issued, major advances have been made in cerebrovascular disease in terms of diagnosis, therapy, knowledge of pathophysiology, links between stroke and the dementias, and recognition of the impact of silent cerebrovascular disease.

Norrving said that at a meeting in late 2016 in Geneva, key stakeholders from professional societies, patient organizations, and ministries of health, among others, loudly made the case for bringing stroke under neurologic disease in ICD-11.

In 1955, cerebrovascular disease was moved out of the ICD chapter on diseases of the nervous system. Sixty-two years later, in March 2017, Robert Jakob of the WHO emailed Shakir and Norrving to inform them that their efforts paid off: stroke was coming back home to neurology: "The grouping 'cerebrovascular diseases' has moved into 'Diseases of the nervous system.' "

Cerebrovascular diseases will constitute a single block in ICD-11 within Diseases of the Nervous System, and that block will include TIA, stroke, and cerebrovascular diseases not causing acute neurologic dysfunction (silent cerebral infarcts and cerebral microbleeds). The final global definition of stroke is a cerebral ischemic stroke, intracerebral hemorrhage, subarachnoidal hemorrhage, and stroke not known as ischemic or hemorrhagic.

Not considered strokes are TIA, silent cerebral infarct of microbleed, and nontraumatic subdural or epidural events. The definition of TIA will be tissue-based and not time-based.

The Bottom Line on Stroke: It's a Brain Disease

Norrving listed what the reclassification means for stroke in medical practice, planning, policy, and more:

  • Correctly signals that when stroke happens, it happens in the brain

  • Stroke no longer is in the shadow of other cardiovascular/circulatory diseases

  • Stroke is a single entity on its own

  • Facilitates recognition of stroke as one of the core noncommunicable diseases, with the possibility to prevent and treat it

  • The categorization of stroke is now settled — in all different circumstances

William Carroll, MD, president of the World Federation of Neurology and clinical professor at the University of Western Australia in Perth, sat down with Medscape Medical News to discuss the impact of the new ICD-11 and the reclassification of stroke as a brain disorder.

It has been a long struggle to get the WHO to carve out a significant section in ICD-11 for neurological disease, Carroll said.

"It's been hidden away in mental disease and substance abuse...so it doesn't exist as far as the WHO is concerned, so to get stroke back into neurological disease, and then they have to bring neurological disease out of the cupboard. That's the real benefit," he said.

"It's all about brain health...so we've argued for a long time to try and get this changed. They [the WHO] are bureaucrats that don't want to change. So we've decided, made a conscious decision virtually, that we're going to go outside them, [and] we're going to make public opinion make them change."

Regarding neurology in ICD-11, Carroll said, "We are fairly sure it will have a profound impact in terms of planning for provisions for the management and the costing of the care of stroke in different medical jurisdictions. As you saw, the ICD-11 is used worldwide."

Carroll foresees that the new system will be used both for reimbursement to healthcare providers who operate within an activity-based funding system and for institutions.

"If central governments are allocating funds, they can look at what the stroke rates have been and duration of inpatient stay, and use [ICD-11] to calculate and be more accurate in their budgeting," he said. These data may improve upon the accuracy of the current rates of stroke that the Global Burden of Disease Institute for Health Metrics and Evaluation has stated.

"We may see that the actual stroke rate is higher," he said, "and therefore that should affect the provision of services."

Included in these services would be the number of stroke doctors needed, interventional radiologists to do thrombectomies, and transport systems to get patients to centers with these services.

Even with the classification of stroke as a brain disorder, its etiology is still circulatory, whether an ischemic or hemorrhagic event.

"But the disease is and its implication and its long term rehabilitation and costs are all due to brain injury...so I think you have to go with the organ-based classification, and that is that it's a brain disease," he said.

Furthermore, stroke is a risk factor for dementia. There is increasing evidence that pericytes, the small cells around blood vessels, are related to the vascular impact on the development of dementia, he said. "So [if] you can reduce that, then you may reduce the incidence or at least the severity of dementia."

With advances in understanding, and often treating, many other neurologic diseases — for example, Parkinson's, Alzheimer's, epilepsy, multiple sclerosis, motor neuron diseases, immune-mediated brain diseases, and diseases of ion channels — Carroll said the time has certainly come for neurology no longer to be hidden away under other categories of disease in the ICD system.

There was no commercial funding regarding ICD-11. Shakir and Norrving have disclosed no relevant financial relationships. Carroll has received travel assistance and honoraria for participation in industry-sponsored meetings from and has provided advice to Bayer Schering Pharma, Biogen-Idec, Novartis, Genzyme, sanofi-aventis, CSL, Teva, Merck, and Cellgene.

XXIV World Congress of Neurology (WCN): Presented October 28, 2019.

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