Neurological conditions national action plan 2019-2024: draft for consultation

Annex B: Definition of neurological conditions

The most simple definition of neurological conditions might be any condition which leads to neurological symptoms. Such a broad definition is problematic, as neurological symptoms are so common, and many entirely compatible with normal health. Restricting the definition to specific conditions is too narrow, as many patients with disorders of the nervous system remain undiagnosed with a specific entity. In addition there are many developmental disorders (e.g. dyslexia, dyspraxia) which result in neurological symptoms, but are not traditionally thought of as neurological disorders. There are significant areas of crossover with mental health disorders (unsurprising given both areas share the same organ, the brain), and many neurological conditions commonly lead to mental health symptoms (e.g. anxiety in Parkinson’s disease). Neurological symptoms are commonly encountered in other diseases and disorders primarily arising from other systems (e.g. sleepiness/fatigue due to obstructive sleep apnoea).

The World Health Organisation (WHO) defined neurological conditions as follows (2016): Neurological disorders are diseases of the central and peripheral nervous system. In other words, the brain, spinal cord, cranial nerves, peripheral nerves, nerve roots, autonomic nervous system, neuromuscular junction, and muscles. These disorders include epilepsy, Alzheimer disease and other dementias, cerebrovascular diseases including stroke, migraine and other headache disorders, multiple sclerosis, Parkinson's disease, neuroinfections, brain tumours, traumatic disorders of the nervous system due to head trauma, and neurological disorders as a result of malnutrition. Many bacterial (i.e. Mycobacterial tuberculosis, Neisseria meningitides), viral (i.e. Human Immunodeficiency Virus (HIV), Enteroviruses, West Nile Virus, Zika), fungal (i.e. Cryptococcus, Aspergillus), and parasitic (i.e. malaria, Chagas) infections can affect the nervous system. Neurological symptoms may occur due to the infection itself, or due to an immune response. Hundreds of millions of people worldwide are affected by neurological disorders. More than 6 million people die because of stroke each year; over 80% of these deaths take place in low- and middle-income countries. More than 50 million people have epilepsy worldwide. It is estimated that there are globally 47.5 million people with dementia with 7.7 million new cases every year - Alzheimer's disease is the most common cause of dementia and may contribute to 60–70% of cases. The prevalence of migraine is more than 10% worldwide.

Thus defining what constitutes a neurological condition is less straightforward than it might at first appear, and may explain why many different specialties overlap in the care of people with such conditions.

Table: Examples of common neurological conditions and prevalence in Scotland based on Scottish Burden of Disease project

*This list is not exhaustive and reflects limitations of current data.

**Scottish Burden of Disease study, 2015. NHS Health Scotland and NHS Information Services Division http://www.scotpho.org.uk/media/1474/sbod2015-overview-report-july17.pdf