A neurological disorder is a disorder of the body's nervous system. Structural, biochemical or electrical abnormalities in the brain, spinal cord or nerves leading to or from them, can result in a range of symptoms. Examples include paralysis, muscle weakness, poor coordination, loss of sensation, seizures, confusion, pain and altered levels of consciousness.There are many recognized neurological disorders, some relatively common, but many rare. They may be assessed by neurological examination, and studied and treated within the specialities of neurology and clinical neuropsychology. Examples of symptoms include
Interventions for neurological disorders include preventative measures, lifestyle changes, physiotherapy or other therapy, neurorehabilitation, pain management, medication, or operations performed by neurosurgeons. The World Health Organization estimated in 2006 that neurological disorders and their sequelae (direct consequences) affect as many as one billion people worldwide, and identified health inequalities and social stigma/discrimination as major factors contributing to the associated disability and suffering.[1]
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Although the brain and spinal cord are surrounded by tough membranes, enclosed in the bones of the skull and spinal vertebrae, and chemically isolated by the so-called blood-brain barrier, they are very susceptible if compromised. Nerves tend to lie deep under the skin but can still become exposed to damage. Individual neurons, and the neural networks and nerves into which they form, are susceptible to electrochemical and structural disruption. Neuroregeneration may occur in the peripheral nervous system and thus overcome or work around injuries to some extent, it is thought to be rare in the brain and spinal cord.
The specific causes of neurological problems vary, but can include genetic disorders; congenital abnormalities or disorders; infections; lifestyle or environmental health problems including malnutrition; and brain injury, spinal cord injury or nerve injury. The problem may start in another body system that interacts with the nervous system; for example cerebrovascular disorders involve brain injury due to problems with the blood vessels (cardiovascular system) supplying the brain, and autoimmune disorders involve damage caused by the body's own immune system.
In a substantial minority of cases of neurological symptoms, no neural cause can be identified using current testing procedures, and such "idiopathic" conditions can invite different theories about what is occurring.
| Nervous system | |
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| The Human Nervous System. |
Neurological disorders can be categorized according to the primary location affected, the primary type of dysfunction involved, or the primary type of cause. The broadest division is between central nervous system (CNS) disorders and peripheral nervous system (PNS) disorders. The Merck Manual lists brain, spinal cord and nerve disorders in the following overlapping categories:[2]
Neurological disorders in non-human animals are treated by veterinarians.[3][4]
The brain is the most complex part of the nervous system, with many different functions. Behavioral neurology is the subspeciality of neurology that uses neurological examination to address the impact of neurological damage and disease upon behavior, memory and cognition. In addition, clinical neuropsychology is a subspeciality of psychology that uses neuropsychological assessment to precisely identify and track problems in mental functioning, usually after some sort of brain injury or neurological impairment.
Neuropsychiatry is the subspeciality of psychiatry, in turn a subspeciality of medicine, which deals with mental disorders attributable to diseases of the nervous system. Biological psychiatry is the more general term for the approach in psychiatry that seeks to explain all mental disorders primarily in terms of the biological functioning of the nervous system. In either case, a mental state examination, or a more specific structured interview or questionnaire process, is used to assess signs and symptoms in order to make a diagnosis of a mental disorder. At the present time at least, neuroimaging alone cannot accurately diagnose a mental disorder or tell the risk of developing one; however, it can be used to rule out other medical conditions such as a brain tumor.[5] In research, neuroimaging and other neurological tests can show correlations between reported and observed mental difficulties and certain aspects of neural function or differences in brain structure.
One area that can be contested is the issue of idiopathic neurological symptoms - conditions where the cause cannot be established. In some cases it may be decided, perhaps by exclusion of any accepted diagnosis, that higher brain/mental activity is causing symptoms, rather than the symptoms originating in those areas of the nervous system. Classic examples are "functional" seizures, sensory numbness, "functional" limb weakness and functional neurological deficit ("functional" in this context is usually contrasted with the old term "organic disease"). Such cases may be contentiously interpreted as being "psychological" rather than "neurological". Some cases may be classified as mental disorders, for example as conversion disorder, if the symptoms appear to be causally linked to emotional states or responses to social stress or social contexts.
On the other hand, dissociation refer to partial or complete disruption of the integration of a person’s conscious functioning, such that a person may feel detached from one's emotions, body and/or immediate surroundings. At one extreme this may be diagnosed as Depersonalization disorder. There are also conditions viewed as neurological where a person appears to consciously register neurological stimuli that cannot possibly be coming from the part of the nervous system to which they would normally be attributed, such as phantom pain or synesthesia, or where limbs act without conscious direction, as in alien hand syndrome. Theories and assumptions about consciousness, willpower and personal responsibility can play a part, either from the perspective of the clinician or of the patient.
In terms of higher-level brain functioning, or what may be referred as the mind, numerous fields intersect to try and understand the basic processes. Cognitive science brings many of these together. There are subspecialities of psychology and neuroscience, such as neuropsychology, cognitive neuropsychology or cognitive neuroscience (thinking processes), affective neuroscience (emotional/mood processes), behavior neuroscience (also known as biopsychology), social neuroscience, and neurophenomenology (subjective experiences in consciousness). This research may employ neuroimaging (brain scanning) tests as well as verbal and behavioral assessments.
Mental disorders, learning disabilities and mental retardation are not usually classified as primarily neurological. However the distinction can be a matter of some debate, either in regard to specific facts about the cause of a condition or in regard to the general understanding of brain and mind. The definition of disorder in medicine or psychology can be contested in terms of what is considered abnormal, dysfunctional, harmful or unnatural in neurological, evolutionary, psychometric or social terms.
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