nervous system disease
-
What is the nervous system?
The nervous system conducts stimuli from sensory receptors to the brain and spinal cord, and impulses back to other body parts. In humans, it consists of the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves to and from the central nervous system).
Signals containing information are electrical. Neurons communicate via synapses, transmitting action potentials either electrically through ion-conducting channels or chemically via neurotransmitters. The brain, weighing about 1,500 grams, includes the cerebrum, brainstem, and cerebellum.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What are nervous system diseases?
Nervous system diseases encompass a wide range of disorders affecting the brain, spinal cord, and nerves. These diseases can arise from various factors, including genetic inheritance, infections caused by bacteria, viruses, or fungi, and immune system reactions.
Other causes include demyelinating and degenerative processes, metabolic disorders, and exposure to toxic substances such as drugs, metals, and poisons. Deficiencies in vitamins, particularly the B group, can also lead to nervous system disorders. Neurologists diagnose and treat these complex conditions, often using advanced techniques like brain scanning.
4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What are some common symptoms of nervous system diseases?
Common symptoms of nervous system diseases include weakness, which is usually symmetrical and mainly affects the proximal or girdle muscles. This can manifest as difficulty climbing stairs or brushing hair. Facial weakness can lead to drooling, and challenges with whistling. Muscle issues may also cause swelling, tenderness, or cramps. There can be reduced muscle tone and power, as well as a reduction or loss of reflexes.
Other symptoms include pain, headache, loss of sensation, incoordination, and abnormal movements. Sensations such as tingling, burning, or itching can also occur. Memory loss, and changes in posture, gait, demeanour, expression, and speech are also indicators of nervous system diseases.
1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What are some examples of nervous system diseases?
The nervous system can be affected by many diseases, which can be caused by a variety of factors.
Examples of nervous system diseases:
* Demyelinating diseases Multiple sclerosis is a condition in which the myelin sheaths around nerve fibers are damaged, which leads to a blockage of electrical conduction.
* Degenerative diseases Alzheimer's and Parkinson's diseases are characterized by the progressive destruction of neurons.
* Deficiency states Wernicke-Korsakoff syndrome, common in alcoholics, results from a thiamine deficiency and consists of eye movement disorders, cerebellar incoordination, memory loss, and peripheral neuropathy.
* Infections Meningitis and encephalitis are inflammatory diseases caused by microorganisms that damage the blood-brain barrier.
* Autoimmune disorders Conditions characterized by inflammation of the blood vessels may reduce blood supply to parts of the nervous system, inducing neurological symptoms.4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How can nervous system diseases affect a person's daily life?
Nervous system diseases can significantly impair daily life, affecting everything from basic reflexes to thought and action. For example, Alzheimer's disease progressively and irreversibly impairs memory and cognitive functions, hindering the ability to perform simple tasks independently. Multiple sclerosis can cause numbness, muscle weakness, and visual disturbances, impacting coordination and mobility. Demyelinating neuropathies, such as Guillain-BarrƩ syndrome, lead to progressive weakness and reflex loss, potentially requiring mechanical assistance for breathing. Even minor nerve damage can result in impaired sensation and deformed joints.
5 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What treatments are available for nervous system diseases?
Systemic drug therapies can treat nervous system diseases. Alzheimer's disease, a common form of dementia, benefits from drugs that enhance cognition and memory exercises. Parkinsonism's motor function loss can be relieved with levodopa and other drugs. Migraines can be treated with ergotamine, NSAIDs, and sumatriptan.
Demyelinating diseases, like Guillain-BarrƩ syndrome, feature myelin destruction that blocks electrical impulses, while degenerative diseases involve progressive neuron destruction, as seen in Alzheimer's, Huntington, and Parkinson diseases. Genetic factors also contribute to nervous system diseases, such as muscular dystrophies and Huntington's disease.
2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
nervous system disease, any of the diseases or disorders that affect the functioning of the human nervous system. Everything that humans sense, consider, and effect and all the unlearned reflexes of the body depend on the functioning of the nervous system. The skeleton and muscles support and transport the body, and the digestive system, heart, and lungs provide nutrients; but the nervous system contains the epitome of the humanāthe mindāand commands all perception, thought, and action. Disturbance or malfunction of the functions of the nervous system causes changes felt throughout the body. Although many brain diseases cause disorders of thought or mood, this article discusses only diseases of the nervous system that have organic causes. For a discussion of psychological disorders, see mental disorders.
The first part of this article describes the neurological examinationāthe medical history, the physical examination of the patient, and the diagnostic tests and procedures that can be employed to provide a physician with information about a possible neurological disorder. Next the principles used in localizing a disease within the nervous system are explained. The third part of this article provides an overview of pathological processes. Finally, an account is presented of the diseases of the nervous system, using a general classification based upon the primary or major site of the disease.
The neurological examination
Medical history
An old saying in medicine, āListen to the patient; he is telling you the diagnosis,ā is especially true in neurology. A patientās description of symptoms is a valuable tool that allows the physician to learn about the nature and location of a possible neurological disease. While taking a patientās medical history, the neurologist notes the patientās level of awareness, memory loss, posture and gait, demeanour and expression, speech, and, to some extent, personality. The neurologist also notes symptoms such as pain, headache, loss of sensation, weakness, incoordination, wasting of certain muscle groups, and abnormal movements.
" height="20" alt="HEW Logo">
Altered consciousness
The ability to notice and react to oneās environment is not an on-off phenomenon but a continuum. From full alertness a person can descend through drowsiness to stupor, a condition in which awareness is greatly reduced and the best motor response to stimulation is a groan or other vocal (but not verbal) reaction. Deeper levels of unconsciousness pass through light coma, in which strong stimulation produces only a clumsy motor response, to deep coma, in which there is only a reflex movement or no response at all. Such depression of consciousness occurs when there is impairment of the functions of the brainstem or of the cerebral cortex. Brainstem disorders can cause coma if the brainstem is compressed by other parts of the brain swollen because of disease or if it is afflicted by local disease such as encephalitis, stroke, or concussion. Diseases of the cerebral cortex causing coma include poisoning by sedative drugs, lack of glucose or oxygen in the blood, brain hemorrhage, and certain rare infiltrative disorders in which descent through the levels of consciousness occurs over weeks or months. Brief periods of unconsciousness, of which the patient may not be aware, occur in many forms of epilepsy, narcolepsy, repeated attacks of low blood sugar, and reduction in the blood supply to the braināparticularly the brainstem.
Headache
When pressure inside the cranium is increased, pain-sensitive structures in and around the brain are distorted and cause pain in an ill-localized area but often identifiably in the front or back of the head called a traction headache. Traction headaches may be caused by brain swelling, infection, bleeding, tumour, stress, or obstructed flow of cerebrospinal fluid. Also, pain may be felt in the head region although the disorder causing the pain is situated elsewhere; an example is the facial pain sometimes felt with lack of blood to the heart. Local disease of such cranial structures as the jaw joints, the paranasal sinuses and teeth, the middle ear, and the skull bones themselves may also generate pain.
Tension headaches are caused by prolonged excessive contraction of the muscles that run front-to-back over the skull; these headaches are often caused by stress. A persistent pressing or pulling pain, often with a throbbing component, is usually described. Migraine headaches may occur simultaneously with tension headaches and are characterized by throbbing pain with scalp tenderness, nausea, vomiting, and sensitivity to noise and light.
Cognitive changes
Poor concentration resulting from preoccupation, fatigue, or depression is the most common cause of memory loss, but widespread brain disease, vitamin deficiency, epilepsy, and dementia (loss of intellectual power) are also causes. When the period of memory loss is well defined, prominent causes are trauma to the head, seizures, poisoning (e.g., alcohol), and brief episodes of inadequate blood supply to the brain. Impaired comprehension, reasoning, logical thinking, and ability to plan ahead may also be symptoms of a neurological disorder.
The trusted destination for professionals, college students, and lifelong learners.
SUBSCRIBE
Language and speech deficits
Patients with aphasia may know exactly what they want to say, but they are unable to express their thoughts in spoken (and often written) words. They may also be unable to comprehend the meaning of spoken or written language, so that normal speech sounds like a foreign tongue. Strokes are the most common cause of aphasia, but any focal brain disease may be responsible.
Similar problems of language and speech comprehension are apraxia and agnosia. Apraxia is the inability to perform useful or skilled actions; apraxic patients may be able to name an object such as a comb or key, but they may not know how to use it. Agnosia is the failure to comprehend the significance of a nonlanguage stimulus; an agnosic patient may be unable to recognize the origin of a sound from a musical instrument.
Dysarthria, or difficulty in articulation, usually is caused by an abnormality in the nerves and muscles in and around the mouth or in their connections. Problems in the production of speech sounds, called dysphonia, often indicate a problem affecting the larynx or the nerves and muscles of that structure. Since the cranial nerves supplying these areas originate in the brainstem, neurological disease of this region may also be a cause.