A neurological disorder is any disorder of the nervous system.
Structural, biochemical or electrical abnormalities in the brain, spinal cord or other nerves
can result in a range of symptoms.
Examples of symptoms 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.
Interventions for neurological disorders include preventative measures, lifestyle changes,
physiotherapy or other therapy, neurorehabilitation, pain management, medication, operations performed
by neurosurgeons or a specific diet.
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.
== Causes == 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 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 circuits 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 extents, but 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, nerve injury and gluten sensitivity
(with or without intestinal damage or digestive symptoms).
Metal poisoning, where metals accumulate in the human body and disrupt biological processes,
has been reported to induce neurological problems, at least in the case of lead.
The neurological 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; autoimmune disorders involve damage
caused by the body's own immune system; lysosomal storage diseases such as Niemann-Pick disease
can lead to neurological deterioration.
The National Institutes of Health recommend considering the evaluation of an underlying
celiac disease in people with unexplained neurological symptoms, particularly peripheral
neuropathy or ataxia.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.
== Classification ==
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 disorders and peripheral nervous system
disorders.
The Merck Manual lists brain, spinal cord and nerve disorders in the following overlapping
categories: Brain:
Brain damage according to cerebral lobe (see also 'lower' brain areas such as basal ganglia,
cerebellum, brainstem): Frontal lobe damage
Parietal lobe damage Temporal lobe damage
Occipital lobe damage Brain dysfunction according to type:
Aphasia (language) Dysgraphia (writing)
Dysarthria (speech) Apraxia (patterns or sequences of movements)
Agnosia (identifying things or people) Amnesia (memory)
Spinal cord disorders (see spinal pathology, injury, inflammation)
Peripheral neuropathy and other Peripheral nervous system disorders
Cranial nerve disorder such as Trigeminal neuralgia
Autonomic nervous system disorders such as dysautonomia, Multiple System Atrophy
Seizure disorders such as epilepsy Movement disorders of the central and peripheral
nervous system such as Parkinson's disease, Essential tremor, Amyotrophic lateral sclerosis,
Tourette's Syndrome, Multiple Sclerosis and various types of Peripheral Neuropathy
Sleep disorders such as Narcolepsy Migraines and other types of Headache such
as Cluster Headache and Tension Headache Lower back and neck pain (see Back pain)
Central neuropathy (see Neuropathic pain) Neuropsychiatric illnesses (diseases and/or
disorders with psychiatric features associated with known nervous system injury, underdevelopment,
biochemical, anatomical, or electrical malfunction, and/or disease pathology e.g. Attention deficit
hyperactivity disorder, Autism, Tourette's syndrome and some cases of obsessive compulsive
disorder as well as the neurobehavioral associated symptoms of degeneratives of the nervous system
such as Parkinson's disease, essential tremor, Huntington's disease, Alzheimer's disease,
multiple sclerosis and organic psychosis.)Many of the diseases and disorders listed above
have neurosurgical treatments available (e.g. Tourette's Syndrome, Parkinson's disease,
Essential tremor and Obsessive compulsive disorder).
Delirium and dementia such as Alzheimer's disease
Dizziness and vertigo Stupor and coma
Head injury Stroke (CVA, cerebrovascular attack)
Tumors of the nervous system (e.g. cancer) Multiple sclerosis and other demyelinating
diseases Infections of the brain or spinal cord (including
meningitis) Prion diseases (a type of infectious agent)
Complex regional pain syndrome (a chronic pain condition)Neurological disorders in non-human
animals are treated by veterinarians.
== Mental functioning == A neurological examination can, to some extent,
assess the impact of neurological damage and disease on brain function in terms of behavior,
memory or cognition.
Behavioral neurology specializes in this area.
In addition, clinical neuropsychology uses neuropsychological assessment to precisely
identify and track problems in mental functioning, usually after some sort of brain injury or
neurological impairment.
Alternatively, a condition might first be detected through the presence of abnormalities
in mental functioning, and further assessment may indicate an underlying neurological disorder.
There are sometimes unclear boundaries in the distinction between disorders treated
within neurology, and mental disorders treated within the other medical specialty of psychiatry,
or other mental health professions such as clinical psychology.
In practice, cases may present as one type but be assessed as more appropriate to the
other.
Neuropsychiatry deals with mental disorders arising from specific identified diseases
of the nervous system.
One area that can be contested is in cases of idiopathic neurological symptoms - conditions
where the cause cannot be established.
It can be decided in some cases, perhaps by exclusion of any accepted diagnosis, that
higher-level brain/mental activity is causing symptoms, rather than the symptoms originating
in the area of the nervous system from which they may appear to originate.
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 refers 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, free will, moral responsibility and social
stigma can play a part in this, whether from the perspective of the clinician or the patient.
Conditions that are classed as mental disorders, or learning disabilities and forms of intellectual
disability, are not themselves usually dealt with as neurological disorders.
Biological psychiatry seeks to understand mental disorders in terms of their basis in
the nervous system, however.
In clinical practice, mental disorders are usually indicated by a mental state examination,
or other type of structured interview or questionnaire process.
At the present time, neuroimaging (brain scans) 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.
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.
In general, numerous fields intersect to try and understand the basic processes involved
in mental functioning, many of which are brought together in cognitive science.
The distinction between neurological and mental disorders 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.
Moveover, the definition of disorder in medicine or psychology is sometimes contested in terms
of what is considered abnormal, dysfunctional, harmful or unnatural in neurological, evolutionary,
psychometric or social terms.
== See also