Neurological disorder | |
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Neurons in person with epilepsy, 40x magnified | |
Specialty | Neurology ![]() |
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, tauopathies, and altered levels of consciousness. There are many recognized neurological disorders, some are relatively common, but many are rare.
Interventions for neurological disorders include preventive measures, lifestyle changes, physiotherapy or other therapy, neurorehabilitation, pain management, medication, operations performed by neurosurgeons or a specific diet. [1] [2] 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 their impact. [3]
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, 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.[ citation needed ]
The specific causes of neurological problems vary, but can include genetic disorders, congenital abnormalities or disorders, infections, lifestyle or environmental health problems including pollution, malnutrition, brain damage, spinal cord injury, nerve injury or gluten sensitivity (with or without intestinal damage or digestive symptoms). [2] [4] 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. [4] The neurological problem may start in another body system that interacts with the nervous system. For example, cerebrovascular disease involves 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 Institute for Health and Care Excellence recommends considering the evaluation of an underlying coeliac disease in people with unexplained neurological symptoms, particularly peripheral neuropathy or ataxia. [5]
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.[ citation needed ] Generally speaking, a substantial number of neurological disorders may have originated from a previous clinically not recognized viral infection. For example, it is thought that infection with the Hepatitis E virus, which is often initially asymptomatic may provoke neurological disorders, [6] but there are many other examples as well.
Numerous examples have been described of neurological disorders that are associated with mutated DNA repair genes (for reviews see [7] ). Inadequate repair of DNA damages can lead directly to cell death and neuron depletion as well as disruptions in the pattern of epigenetic alterations required for normal neuronal function.[ citation needed ]
Neurons are highly oxygenated cells and as a consequence DNA damage caused by chronic exposure to endogenous reactive oxygen species is a substantial challenge for neurons. [8] Germline mutations deficient in the repair of DNA damages cause neuronal disfunction and are etiologically linked to many neurological disorders. [8] For example, the neurological disorders, amyotrophic lateral sclerosis (ALS) and frontotemporal dementia are linked to DNA damage accumulation and DNA repair deficiency. [9]
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: [10]
Nervous system | |
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![]() Human nervous system | |
Identifiers | |
MeSH | D009422 |
Anatomical terminology |
Many of the diseases and disorders listed above have neurosurgical treatments available, such as Tourette's syndrome, Parkinson's disease, essential tremor and obsessive compulsive disorder.
Neurological disorders in non-human animals are treated by veterinarians. [11] [12]
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.[ citation needed ]
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. [13] Neuropsychiatry deals with mental disorders arising from specific identified diseases of the nervous system.[ citation needed ]
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. [14]
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 derealization 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.[ citation needed ]
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. [15] 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 to 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.[ citation needed ]
Moreover, 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.[ citation needed ]
Motor neuron diseases or motor neurone diseases (MNDs) are a group of rare neurodegenerative disorders that selectively affect motor neurons, the cells which control voluntary muscles of the body. They include amyotrophic lateral sclerosis (ALS), progressive bulbar palsy (PBP), pseudobulbar palsy, progressive muscular atrophy (PMA), primary lateral sclerosis (PLS), spinal muscular atrophy (SMA) and monomelic amyotrophy (MMA), as well as some rarer variants resembling ALS.
A nerve is an enclosed, cable-like bundle of nerve fibers in the peripheral nervous system.
Transverse myelitis (TM) is a rare neurological condition wherein the spinal cord is inflamed. The adjective transverse implies that the spinal inflammation (myelitis) extends horizontally throughout the cross section of the spinal cord; the terms partial transverse myelitis and partial myelitis are sometimes used to specify inflammation that affects only part of the width of the spinal cord. TM is characterized by weakness and numbness of the limbs, deficits in sensation and motor skills, dysfunctional urethral and anal sphincter activities, and dysfunction of the autonomic nervous system that can lead to episodes of high blood pressure. Signs and symptoms vary according to the affected level of the spinal cord. The underlying cause of TM is unknown. The spinal cord inflammation seen in TM has been associated with various infections, immune system disorders, or damage to nerve fibers, by loss of myelin. As opposed to leukomyelitis which affects only the white matter, it affects the entire cross-section of the spinal cord. Decreased electrical conductivity in the nervous system can result.
Myelitis is inflammation of the spinal cord which can disrupt the normal responses from the brain to the rest of the body, and from the rest of the body to the brain. Inflammation in the spinal cord can cause the myelin and axon to be damaged resulting in symptoms such as paralysis and sensory loss. Myelitis is classified to several categories depending on the area or the cause of the lesion; however, any inflammatory attack on the spinal cord is often referred to as transverse myelitis.
The somatic nervous system (SNS) is made up of nerves that link the brain and spinal cord to voluntary or skeletal muscles that are under conscious control as well as to skin sensory receptors. Specialized nerve fiber ends called sensory receptors are responsible for detecting information within and outside of the body.
Paresthesia is an abnormal sensation of the skin with no apparent physical cause. Paresthesia may be transient or chronic, and may have many possible underlying causes. Paresthesias are usually painless and can occur anywhere on the body, but most commonly occur in the arms and legs.
Myoclonus is a brief, involuntary, irregular twitching of a muscle, a joint, or a group of muscles, different from clonus, which is rhythmic or regular. Myoclonus describes a medical sign and, generally, is not a diagnosis of a disease. It belongs to the hyperkinetic movement disorders, among tremor and chorea for example. These myoclonic twitches, jerks, or seizures are usually caused by sudden muscle contractions or brief lapses of contraction. The most common circumstance under which they occur is while falling asleep. Myoclonic jerks occur in healthy people and are experienced occasionally by everyone. However, when they appear with more persistence and become more widespread they can be a sign of various neurological disorders. Hiccups are a kind of myoclonic jerk specifically affecting the diaphragm. When a spasm is caused by another person it is known as a provoked spasm. Shuddering attacks in babies fall in this category.
Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness.
A demyelinating disease refers to any disease affecting the nervous system where the myelin sheath surrounding neurons is damaged. This damage disrupts the transmission of signals through the affected nerves, resulting in a decrease in their conduction ability. Consequently, this reduction in conduction can lead to deficiencies in sensation, movement, cognition, or other functions depending on the nerves affected.
Foot drop is a gait abnormality in which the dropping of the forefoot happens due to weakness, irritation or damage to the deep fibular nerve, including the sciatic nerve, or paralysis of the muscles in the anterior portion of the lower leg. It is usually a symptom of a greater problem, not a disease in itself. Foot drop is characterized by inability or impaired ability to raise the toes or raise the foot from the ankle (dorsiflexion). Foot drop may be temporary or permanent, depending on the extent of muscle weakness or paralysis and it can occur in one or both feet. In walking, the raised leg is slightly bent at the knee to prevent the foot from dragging along the ground.
Progressive bulbar palsy (PBP) is a medical condition. It belongs to a group of disorders known as motor neuron diseases. PBP is a disease that attacks the nerves supplying the bulbar muscles. These disorders are characterized by the degeneration of motor neurons in the cerebral cortex, spinal cord, brain stem, and pyramidal tracts. This specifically involves the glossopharyngeal nerve (IX), vagus nerve (X), and hypoglossal nerve (XII).
Dysesthesia is an unpleasant, abnormal sense of touch. Its etymology comes from the Greek word "dys," meaning "bad," and "aesthesis," which means "sensation". It often presents as pain but may also present as an inappropriate, but not discomforting, sensation. It is caused by lesions of the nervous system, peripheral or central, and it involves sensations, whether spontaneous or evoked, such as burning, wetness, itching, electric shock, and pins and needles. Dysesthesia can include sensations in any bodily tissue, including most often the mouth, scalp, skin, or legs.
Pallesthesia, or vibratory sensation, is the ability to perceive vibration. This sensation, often conducted through skin and bone, is usually generated by mechanoreceptors such as Pacinian corpuscles, Merkel disk receptors, and tactile corpuscles. All of these receptors stimulate an action potential in afferent nerves found in various layers of the skin and body. The afferent neuron travels to the spinal column and then to the brain where the information is processed. Damage to the peripheral nervous system or central nervous system can result in a decline or loss of pallesthesia.
Central nervous system diseases or central nervous system disorders are a group of neurological disorders that affect the structure or function of the brain or spinal cord, which collectively form the central nervous system (CNS). These disorders may be caused by such things as infection, injury, blood clots, age related degeneration, cancer, autoimmune disfunction, and birth defects. The symptoms vary widely, as do the treatments.
Nervous system diseases, also known as nervous system or neurological disorders, refers to a small class of medical conditions affecting the nervous system. This category encompasses over 600 different conditions, including genetic disorders, infections, cancer, seizure disorders, conditions with a cardiovascular origin, congenital and developmental disorders, and degenerative disorders.
Myelomalacia is a pathological term referring to the softening of the spinal cord. Possible causes of myelomalacia include cervical myelopathy, hemorrhagic infarction, or acute injury, such as that caused by intervertebral disc extrusion.
The following outline is provided as an overview of and topical guide to the human brain:
Cervicocranial syndrome or is a neurological illness. It is a combination of symptoms that are caused by an abnormality in the neck. The bones of the neck that are affected are cervical vertebrae (C1-C7). This syndrome can be identified by confirming cervical bone shifts, collapsed cervical bones or misalignment of the cervical bone leading to improper functioning of cervical spinal nerves. Cervicocranial syndrome is either congenital or acquired. Some examples of diseases that could result in cervicocranial syndrome are Chiari disease, Klippel-Feil malformation osteoarthritis, and trauma. Treatment options include neck braces, pain medication and surgery. The quality of life for individuals suffering from CCJ syndrome can improve through surgery.
Neurogenic bowel dysfunction (NBD) is the inability to control defecation due to a deterioration of or injury to the nervous system, resulting in faecal incontinence or constipation. It is common in people with spinal cord injury (SCI), multiple sclerosis (MS) or spina bifida.
Peripheral mononeuropathy is a nerve related disease where a single nerve, that is used to transport messages from the brain to the peripheral body, is diseased or damaged. Peripheral neuropathy is a general term that indicates any disorder of the peripheral nervous system. The name of the disorder itself can be broken down in order to understand this better; peripheral: in regard to peripheral neuropathy, refers to outside of the brain and spinal cord; neuro: means nerve related; -pathy; means disease. Peripheral mononeuropathy is a disorder that links to Peripheral Neuropathy, as it only effects a single peripheral nerve rather than several damaged or diseased nerves throughout the body. Healthy peripheral nerves are able to “carry messages from the brain and spinal cord to muscles, organs, and other body tissues”.