A nerve is an enclosed, cable-like bundle of nerve fibers (called axons ) in the peripheral nervous system .
118-802: Peripheral neuropathy , often shortened to neuropathy , refers to damage or disease affecting the nerves . Damage to nerves may impair sensation, movement, gland function, and/or organ function depending on which nerve fibers are affected. Neuropathies affecting motor , sensory , or autonomic nerve fibers result in different symptoms. More than one type of fiber may be affected simultaneously. Peripheral neuropathy may be acute (with sudden onset, rapid progress) or chronic (symptoms begin subtly and progress slowly), and may be reversible or permanent. Common causes include systemic diseases (such as diabetes or leprosy ), hyperglycemia-induced glycation , vitamin deficiency , medication (e.g., chemotherapy , or commonly prescribed antibiotics including metronidazole and
236-445: A QWERTY computer keyboard layout to Dvorak is helpful, but meta-analyses of the available studies note limited supported evidence. There are more than 50 types of treatments for CTS with varied levels of evidence and recommendation across healthcare guidelines, with evidence most strongly supporting surgery, steroids, splinting for wrist positioning, and physical or occupational therapy interventions. When selecting treatment, it
354-495: A blood-nerve barrier similar to the blood–brain barrier . Molecules are thereby prevented from crossing the blood into the endoneurial fluid. During the development of nerve edema from nerve irritation (or injury), the amount of endoneurial fluid may increase at the site of irritation. This increase in fluid can be visualized using magnetic resonance neurography , and thus MR neurography can identify nerve irritation and/or injury. Nerves are categorized into three groups based on
472-415: A comprehensive metabolic panel screening for diabetes and pre-diabetes, and a serum immunofixation test , which tests for antibodies in the blood. The treatment of peripheral neuropathy varies based on the cause of the condition, and treating the underlying condition can aid in the management of neuropathy. When peripheral neuropathy results from diabetes mellitus or prediabetes , blood sugar management
590-691: A 10–20% response. Three of the seven authors of the review had conflicts of interest declared. In a 2019 Cochrane review of pregabalin the authors conclude that there is some evidence of efficacy in the treatment of pain deriving from post-herpetic neuralgia, diabetic neuropathy, and post-traumatic neuropathic pain only. They also warned that many patients treated will have no benefit. Two of the five authors declared receiving payments from pharmaceutical companies. A 2017 Cochrane systematic review found that oxcarbazepine had little evidence to support its use for treating diabetic neuropathy, radicular pain, and other neuropathies. The authors also call for better studies. In
708-485: A 2015 Cochrane systematic review the authors found a lack of evidence showing any effectiveness of zonisamide for the treatment of pain deriving from any peripheral neuropathy. A 2014 Cochrane review found that studies of levetiracetam showed no indication of its effectiveness at treating pain from any neuropathy. The authors also found that the evidence was possibly biased and that some patients experienced adverse events. A 2013 Cochrane systematic review concluded that there
826-411: A Mauthner cell are so powerful that a single action potential gives rise to a major behavioral response: within milliseconds the fish curves its body into a C-shape , then straightens, thereby propelling itself rapidly forward. Functionally this is a fast escape response, triggered most easily by a strong sound wave or pressure wave impinging on the lateral line organ of the fish. Mauthner cells are not
944-578: A command neuron has, however, become controversial, because of studies showing that some neurons that initially appeared to fit the description were really only capable of evoking a response in a limited set of circumstances. In organisms of radial symmetry , nerve nets serve for the nervous system. There is no brain or centralised head region, and instead there are interconnected neurons spread out in nerve nets. These are found in Cnidaria , Ctenophora and Echinodermata . Herophilos (335–280 BC) described
1062-407: A diagnosis of small-fiber peripheral neuropathy. In EMG testing, demyelinating neuropathy characteristically shows a reduction in conduction velocity and prolongation of distal and F-wave latencies, whereas axonal neuropathy shows a reduction in amplitude. Laboratory tests include blood tests for vitamin B 12 levels, a complete blood count , measurement of thyroid stimulating hormone levels,
1180-414: A gradual progression of neuropathy. Surgery to cut the transverse carpal ligament is the only known disease modifying treatment . The carpal tunnel is an anatomical compartment located at the base of the palm. Nine flexor tendons and the median nerve pass through the carpal tunnel that is surrounded on three sides by the carpal bones that form an arch. The median nerve provides feeling or sensation to
1298-413: A high probability based on characteristic symptoms and signs. It can also be measured with electrodiagnostic tests . People wake less often at night if they wear a wrist splint . Injection of corticosteroids may or may not alleviate better than simulated ( placebo ) injections. There is no evidence that corticosteroid injection sustainably alters the natural history of the disease, which seems to be
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#17328591356791416-412: A lesion in the central nervous system as a cause, a diagnosis may be made on the basis of symptoms, laboratory and additional testing, clinical history, and a detailed examination. During physical examination , specifically a neurological examination , those with generalized peripheral neuropathies most commonly have distal sensory or motor and sensory loss, although those with a pathology (problem) of
1534-507: A normal median nerve. Even more important, notable symptoms with mild disease is strongly associated with unhelpful thoughts and symptoms of worry and despair. Notable CTS should remind clinicians to always consider the whole person, including their mindset and circumstances, in strategies to help people get and stay healthy. A joint report published by the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM),
1652-582: A period of time, and are not triggered by one certain event. Many of these factors are manifestations of physiologic aging. There is no consensus reference standard for the diagnosis of carpal tunnel syndrome. A combination of characteristic symptoms (how it feels) and signs (what the clinician finds on exam) are associated with a high probability of CTS without electrophysiological testing. Electrodiagnostic testing including electromyography , and nerve conduction studies can objectively measure and verify median neuropathy. Ultrasound can image and measure
1770-561: A person elects to proceed directly to surgical treatment. Recommendations may differ when carpal tunnel syndrome is found in association with the following conditions: diabetes mellitus , coexistent cervical radiculopathy , hypothyroidism , polyneuropathy , pregnancy , rheumatoid arthritis , and carpal tunnel syndrome in the workplace. CTS related to another pathophysiology is addressed by treating that pathology. For instance, disease-modifying medications for rheumatoid arthritis or surgery for traumatic acute carpal tunnel syndrome. There
1888-531: A placebo. For tramadol, Cochrane found that there was only modest information about the benefits of its usage for neuropathic pain. Studies were small, had potential risks of bias and apparent benefits increased with risk of bias. Overall the evidence was of low or very low quality and the authors state that it "does not provide a reliable indication of the likely effect". For oxycodone the authors found very low-quality evidence showing its usefulness in treating diabetic neuropathy and postherpetic neuralgia only. One of
2006-925: A sensitivity greater than 85% and specificity greater than 95%. Given the key role of electrodiagnostic testing in the diagnosis of CTS, The AANEM has issued evidence-based practice guidelines, both for the diagnosis of carpal tunnel syndrome. The role of MRI or ultrasound imaging in the diagnosis of CTS is unclear. Their routine use is not recommended. Morphological MRI has high sensitivity but low specificity for CTS. High signal intensity may suggest accumulation of axonal transportation, myelin sheath degeneration or oedema. However, more recent quantitative MRI techniques which derive repeatable, reliable and objective biomarkers from nerves and skeletal muscle may have utility, including diffusion-weighted (typically diffusion tensor) MRI which has demonstrable normal values and aberrations in carpal tunnel syndrome. Cervical radiculopathy can also cause paresthesia abnormal sensibility in
2124-409: A sweat test and a tilt table test. Diagnosis of small fiber involvement in peripheral neuropathy may also involve a skin biopsy in which a 3 mm-thick section of skin is removed from the calf by a punch biopsy , and is used to measure the skin intraepidermal nerve fiber density (IENFD), the density of nerves in the outer layer of the skin. Reduced density of the small nerves in the epidermis supports
2242-460: Is a pattern of nerve damage that is quite different from mononeuropathy, often more serious and affecting more areas of the body. The term "peripheral neuropathy" sometimes is used loosely to refer to polyneuropathy. In cases of polyneuropathy, many nerve cells in various parts of the body are affected, without regard to the nerve through which they pass; not all nerve cells are affected in any particular case. In distal axonopathy , one common pattern
2360-411: Is a special type of identified neuron, defined as a neuron that is capable of driving a specific behavior all by itself. Such neurons appear most commonly in the fast escape systems of various species—the squid giant axon and squid giant synapse , used for pioneering experiments in neurophysiology because of their enormous size, both participate in the fast escape circuit of the squid. The concept of
2478-410: Is also often the case that the aforementioned medications are prescribed for neuropathic pain conditions for which they had not been explicitly tested on or for which controlled research is severely lacking; or even for which evidence suggests that these medications are not effective. The NHS for example explicitly states that amitriptyline and gabapentin can be used for treating the pain of sciatica. This
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#17328591356792596-524: Is called identified if it has properties that distinguish it from every other neuron in the same animal—properties such as location, neurotransmitter, gene expression pattern, and connectivity—and if every individual organism belonging to the same species has exactly one neuron with the same set of properties. In vertebrate nervous systems, very few neurons are "identified" in this sense. Researchers believe humans have none—but in simpler nervous systems, some or all neurons may be thus unique. In vertebrates,
2714-530: Is called "mononeuropathy", and neuropathy involving nerves in roughly the same areas on both sides of the body is called "symmetrical polyneuropathy" or simply " polyneuropathy ". When two or more (typically just a few, but sometimes many) separate nerves in disparate areas of the body are affected it is called " mononeuritis multiplex ", "multifocal mononeuropathy", or "multiple mononeuropathy". Neuropathy may cause painful cramps , fasciculations (fine muscle twitching), muscle loss, bone degeneration, and changes in
2832-494: Is caused by, or associated with, several medical conditions: Autonomic neuropathy is a form of polyneuropathy that affects the non-voluntary, non-sensory nervous system (i.e., the autonomic nervous system ), affecting mostly the internal organs such as the bladder muscles, the cardiovascular system , the digestive tract , and the genital organs. These nerves are not under a person's conscious control and function automatically. Autonomic nerve fibers form large collections in
2950-415: Is characterized by a conduction block, segmental demyelination, and intact axons. With no further compression, the nerves will remyelinate and fully recover. Severe carpal tunnel syndrome patients may have degree II/III injuries (Sunderland classification), or axonotmesis , where the axon is injured partially or fully. With axon injury there would be muscle weakness or atrophy, and with no further compression
3068-480: Is completed by the person affected by polyneuropathy. The total score and individual item scores can be followed over time, with item scoring used by the patient and care provider to estimate the clinical status of some of the more common life domains and symptoms impacted by polyneuropathy. The causes are grouped broadly as follows: Peripheral neuropathy may first be considered when an individual reports symptoms of numbness, tingling, and pain in feet. After ruling out
3186-435: Is debated. There is also little research supporting that ergonomics is related to carpal tunnel syndrome. Given that biological factors such as genetic predisposition and anthropometric features are more strongly associated with carpal tunnel syndrome than occupational/environmental factors such as hand use, CTS might not be prevented by activity modifications. Some claim that worksite modifications such as switching from
3304-412: Is despite both the lack of high-quality evidence that demonstrates the efficacy of these medications for that symptom, and also the prominence of generally moderate to high-quality evidence that reveals that antiepileptics in specific, including gabapentin, demonstrate no efficacy in treating it. In general, according to Cochrane's systematic reviews, antidepressants have shown to either be ineffective for
3422-436: Is further subdivided into the sympathetic and the parasympathetic nervous systems. The sympathetic nervous system is activated in cases of emergencies to mobilize energy, while the parasympathetic nervous system is activated when organisms are in a relaxed state. The enteric nervous system functions to control the gastrointestinal system. Both autonomic and enteric nervous systems function involuntarily. Nerves that exit from
3540-454: Is important to consider the severity and chronicity of the CTS pathophysiology and to distinguish treatments that can alter the natural history of the pathophysiology (disease-modifying treatments) and treatments that only alleviate symptoms (palliative treatments). The strongest evidence for disease-modifying treatment in chronic or severe CTS cases is carpal tunnel surgery to change the shape of
3658-490: Is important to distinguish it from polyneuropathy because when a single nerve is affected, it is more likely to be due to localized trauma or infection. The most common cause of mononeuropathy is physical compression of the nerve, known as compression neuropathy . Carpal tunnel syndrome and axillary nerve palsy are examples. Direct injury to a nerve, interruption of its blood supply resulting in ( ischemia ), or inflammation also may cause mononeuropathy. " Polyneuropathy "
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3776-424: Is key to treatment. In prediabetes in particular, strict blood sugar control can significantly alter the course of neuropathy. In peripheral neuropathy that stems from immune-mediated diseases, the underlying condition is treated with intravenous immunoglobulin or steroids. When peripheral neuropathy results from vitamin deficiencies or other disorders, those are treated as well. A range of medications that act on
3894-630: Is not clear whether this association is due to an alteration of pathophysiology, a variation in symptoms, or a variation in care-seeking. Hereditary neuropathy with susceptibility to pressure palsies is a genetic condition that appears to increase the probability of developing CTS. Heterozygous mutations in the gene SH3TC2 , associated with Charcot-Marie-Tooth , may confer susceptibility to neuropathy , including CTS. Association between common benign tumors such as lipomas , ganglion , and vascular malformation should be handled with care. Such tumors are very common and are more likely to cause pressure on
4012-442: Is numbness, tingling, or burning sensations in the thumb, index, middle, and radial half of the ring finger. These areas process sensation through the median nerve. Numbness or tingling is usually worse with sleep. People tend to sleep with their wrists flexed, which increases pressure on the nerve. Ache and discomfort may be reported in the forearm or even the upper arm . Symptoms that are not characteristic of CTS include pain in
4130-453: Is often stated that normal electrodiagnostic studies do not preclude the diagnosis of carpal tunnel syndrome. The rationale for this is that a threshold of neuropathy must be reached before study results become abnormal and also that threshold values for abnormality vary. Others contend that idiopathic median neuropathy at the carpal tunnel with normal electrodiagnostic tests would represent very, very mild neuropathy that would be best managed as
4248-599: Is rare, even among people with carpal tunnel syndrome (0.55% incidence within 10 years of carpal tunnel release). In the absence of other factors associated with a notable probability of amyloidosis, it is not clear that biopsy at the time of carpal tunnel release has a suitable balance between potential harms and potential benefits. Other specific pathophysiologies that can cause CTS via pressure include: Work-related factors that increase risk of CTS include vibration (5.4 odds ratio ), hand force (4.2), and repetition (2.3). Exposure to wrist extension or flexion at work increases
4366-662: Is revealed in many of the Cochrane systematic reviews listed below, studies of these medications for the treatment of neuropathic pain are often methodologically flawed and the evidence is potentially subject to major bias. In general, the evidence does not support the usage of antiepileptic and antidepressant medications for the treatment of neuropathic pain. Better-designed clinical trials and further review from non-biased third parties are necessary to gauge just how useful for patients these medications truly are. Reviews of these systematic reviews are also necessary to assess their failings. It
4484-464: Is simultaneous or sequential involvement of individual noncontiguous nerve trunks , either partially or completely, evolving over days to years and typically presenting with acute or subacute loss of sensory and motor function of individual nerves . The pattern of involvement is asymmetric. However, as the disease progresses, deficit(s) becomes more confluent and symmetrical, making it difficult to differentiate from polyneuropathy. Therefore, attention to
4602-417: Is tested with a 128-Hz tuning fork , and decreased sensation of light touch when touched by a nylon monofilament. Diagnostic tests include electromyography (EMG) and nerve conduction studies (NCSs), which assess large myelinated nerve fibers. Testing for small-fiber peripheral neuropathies often relates to the autonomic nervous system function of small thinly- and unmyelinated fibers. These tests include
4720-408: Is that the cell bodies of neurons remain intact, but the axons are affected in proportion to their length; the longest axons are the most affected. Diabetic neuropathy is the most common cause of this pattern. In demyelinating polyneuropathies, the myelin sheath around axons is damaged, which affects the ability of the axons to conduct electrical impulses. The third and least common pattern affects
4838-451: Is the double crush syndrome, where compression may interfere with axonal transport, and two separate points of compression (e.g. neck and wrist), neither enough to cause local demyelination, may together impair normal nerve function. Carpal tunnel syndrome is estimated to affect one out of ten people during their lifetime and is the most common nerve compression syndrome . There is notable variation in such estimates based on how one defines
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4956-432: Is the part of an animal that coordinates its actions by transmitting signals to and from different parts of its body. In vertebrates it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain , including the brainstem , and spinal cord . The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons , that connect
5074-403: Is unknown. Nerve Nerves have historically been considered the basic units of the peripheral nervous system. A nerve provides a common pathway for the electrochemical nerve impulses called action potentials that are transmitted along each of the axons to peripheral organs or, in the case of sensory nerves , from the periphery back to the central nervous system . Each axon, within
5192-468: The National Institute for Occupational Safety and Health (NIOSH) indicated that job tasks that involve highly repetitive manual acts or specific wrist postures were associated with symptoms of CTS, but there was not a clear distinction of paresthesia (appropriate) from pain (inappropriate) and causation was not established. The distinction from work-related arm pains that are not carpal tunnel syndrome
5310-660: The cell bodies of neurons directly. This affects the sensory neurons (known as sensory neuronopathy or dorsal root ganglionopathy ). The effect of this is to cause symptoms in more than one part of the body, often symmetrically on the left and right sides. As for any neuropathy, the chief symptoms include motor symptoms such as weakness or clumsiness of movement; and sensory symptoms such as unusual or unpleasant sensations such as tingling or burning ; reduced ability to feel sensations such as texture or temperature, and impaired balance when standing or walking. In many polyneuropathies, these symptoms occur first and most severely in
5428-567: The fluoroquinolone class of antibiotics (such as ciprofloxacin , levofloxacin , moxifloxacin )), traumatic injury , ischemia , radiation therapy , excessive alcohol consumption, immune system disease , celiac disease , non-celiac gluten sensitivity , or viral infection. It can also be genetic (present from birth) or idiopathic (no known cause). In conventional medical usage , the word neuropathy ( neuro- , "nervous system" and -pathy , "disease of") without modifier usually means peripheral neuropathy . Neuropathy affecting just one nerve
5546-428: The glycocalyx and an outer, delicate, meshwork of collagen fibres. Nerves are bundled and often travel along with blood vessels , since the neurons of a nerve have fairly high energy requirements. Within the endoneurium, the individual nerve fibres are surrounded by a low-protein liquid called endoneurial fluid . This acts in a similar way to the cerebrospinal fluid in the central nervous system and constitutes
5664-434: The perineurium , which forms a complete sleeve around a bundle of axons. Perineurial septae extend into the nerve and subdivide it into several bundles of fibres. Surrounding each such fibre is the endoneurium . This forms an unbroken tube from the surface of the spinal cord to the level where the axon synapses with its muscle fibres, or ends in sensory receptors . The endoneurium consists of an inner sleeve of material called
5782-401: The peripheral nervous system . Symptoms depend on the nerves involved, but may include pain , paresthesia (pins-and-needles), paresis (weakness), hypoesthesia (numbness), anesthesia , paralysis , wasting, and disappearance of the reflexes . Causes of neuritis include: Types of neuritis include: Those with diseases or dysfunctions of their nerves may present with problems in any of
5900-468: The 5 million carpal tunnel diagnosed in the US that year were related to work. Women are more likely to be diagnosed with work-related carpal tunnel syndrome than men. Many if not most patients described in published series of carpal tunnel release are older and often not working. Normal pressure of the carpal tunnel has been defined as a range of 2–10 mm (0.079–0.394 in). Wrist flexion increases
6018-480: The American Academy of Physical Medicine and Rehabilitation (AAPM&R), and the American Academy of Neurology defines practice parameters, standards, and guidelines for EDX studies of CTS based on an extensive critical literature review. This joint review concluded median and sensory nerve conduction studies are valid and reproducible in a clinical laboratory setting and a clinical diagnosis of CTS can be made with
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#17328591356796136-529: The CNS to all remaining body parts. Nerves that transmit signals from the CNS are called motor or efferent nerves, while those nerves that transmit information from the body to the CNS are called sensory or afferent . Spinal nerves serve both functions and are called mixed nerves. The PNS is divided into three separate subsystems, the somatic , autonomic , and enteric nervous systems. Somatic nerves mediate voluntary movement. The autonomic nervous system
6254-518: The actual site of damage, a phenomenon called referred pain . Referred pain can happen when the damage causes altered signalling to other areas. Neurologists usually diagnose disorders of nerves by a physical examination , including the testing of reflexes , walking and other directed movements, muscle weakness , proprioception , and the sense of touch . This initial exam can be followed with tests such as nerve conduction study , electromyography (EMG), and computed tomography (CT). A neuron
6372-399: The affected glands and organs, but common symptoms are poor bladder control, abnormal blood pressure or heart rate, and reduced ability to sweat normally. Peripheral neuropathy may be classified according to the number and distribution of nerves affected (mononeuropathy, mononeuritis multiplex, or polyneuropathy), the type of nerve fiber predominantly affected (motor, sensory, autonomic), or
6490-410: The autonomic nervous system, but not the only one; some conditions affecting the brain or spinal cord also may cause autonomic dysfunction , such as multiple system atrophy , and therefore, may cause similar symptoms to autonomic neuropathy. The signs and symptoms of autonomic neuropathy include the following: Neuritis is a general term for inflammation of a nerve or the general inflammation of
6608-428: The base of the thumb, and the hamate hook that can be palpated along the axis of the ring finger. From the anatomical position, the carpal tunnel is bordered on the anterior surface by the transverse carpal ligament, also known as the flexor retinaculum . The flexor retinaculum is a strong, fibrous band that attaches to the pisiform and the hamulus of the hamate. The proximal boundary is the distal wrist skin crease, and
6726-455: The benefit of antidepressant medications for several types of chronic non-cancer pains (including neuropathic pain) in children and adolescents and the authors found the evidence inconclusive. A 2017 Cochrane systematic review found that daily dosages between 1800–3600 mg of gabapentin could provide good pain relief for pain associated with diabetic neuropathy only. This relief occurred for roughly 30–40% of treated patients, while placebo had
6844-428: The best known identified neurons are the gigantic Mauthner cells of fish. Every fish has two Mauthner cells, located in the bottom part of the brainstem, one on the left side and one on the right. Each Mauthner cell has an axon that crosses over, innervating (stimulating) neurons at the same brain level and then travelling down through the spinal cord, making numerous connections as it goes. The synapses generated by
6962-538: The blood vessels surrounding the nerve all cause nerve damage , which can vary in severity. Multiple sclerosis is a disease associated with extensive nerve damage. It occurs when the macrophages of an individual's own immune system damage the myelin sheaths that insulate the axon of the nerve. A pinched nerve occurs when pressure is placed on a nerve, usually from swelling due to an injury, or pregnancy and can result in pain , weakness, numbness or paralysis, an example being CTS. Symptoms can be felt in areas far from
7080-410: The carpal tunnel. The American Academy of Orthopedic Surgeons recommends proceeding conservatively with a course of nonsurgical therapies tried before release surgery is considered. A different treatment should be tried if the current treatment fails to resolve the symptoms within 2 to 7 weeks. Early surgery with carpal tunnel release is indicated where there is evidence of median nerve denervation or
7198-519: The carpal tunnel. Severe CTS is also associated with weakness and atrophy of the muscles at the base of the thumb. The ability to palmarly abduct the thumb may be lost. CTS can be detected on examination using one of several maneuvers to provoke paresthesia (a sensation of tingling or "pins and needles" in the median nerve distribution). These so-called provocative signs include: Diagnostic performance characteristics such as sensitivity and specificity are reported, but difficult to interpret because of
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#17328591356797316-749: The central nervous system have been used to symptomatically treat neuropathic pain. Commonly used medications include tricyclic antidepressants (such as nortriptyline , amitriptyline . imapramine , and desipramine ,) serotonin-norepinephrine reuptake inhibitor (SNRI) medications ( duloxetine , venlafaxine , and milnacipran ) and antiepileptic medications ( gabapentin , pregabalin , oxcarbazepine zonisamide levetiracetam , lamotrigine , topiramate , clonazepam , phenytoin , lacosamide , sodium valproate and carbamazepine ). Opioid and opiate medications (such as buprenorphine , morphine , methadone , fentanyl , hydromorphone , tramadol and oxycodone ) are also often used to treat neuropathic pain. As
7434-447: The common traditional phrases "my poor nerves", " high-strung ", and " nervous breakdown ". Carpal tunnel syndrome Carpal tunnel syndrome ( CTS ) is a nerve compression syndrome associated with the collected signs and symptoms of compression of the median nerve at the carpal tunnel in the wrist . Carpal tunnel syndrome is an idiopathic syndrome but there are environmental, and medical risk factors associated with
7552-410: The condition. CTS can affect both wrists. Other conditions can cause CTS such as wrist fracture or rheumatoid arthritis . After fracture, swelling, bleeding, and deformity compress the median nerve. With rheumatoid arthritis, the enlarged synovial lining of the tendons causes compression. The main symptoms are pain in the hand, numbness , and tingling in the thumb, index finger, middle finger and
7670-553: The cranium are called cranial nerves while those exiting from the spinal cord are called spinal nerves . Cancer can spread by invading the spaces around nerves. This is particularly common in head and neck cancer , prostate cancer and colorectal cancer . Nerves can be damaged by physical injury as well as conditions like carpal tunnel syndrome (CTS) and repetitive strain injury . Autoimmune diseases such as Guillain–Barré syndrome , neurodegenerative diseases , polyneuropathy , infection, neuritis , diabetes , or failure of
7788-407: The cross sectional diameter of the median nerve, which has some correlation with CTS. The role of ultrasound in diagnosis—just as for electrodiagnostic testing—is a matter of debate. EDX cannot fully exclude the diagnosis of CTS due to the lack of sensitivity. The role of confirmatory electrodiagnostic testing is debated. The goal of electrodiagnostic testing is to compare the speed of conduction in
7906-403: The direction that signals are conducted: Nerves can be categorized into two groups based on where they connect to the central nervous system: Specific terms are used to describe nerves and their actions. A nerve that supplies information to the brain from an area of the body, or controls an action of the body is said to innervate that section of the body or organ. Other terms relate to whether
8024-535: The disease, including several loci previously known to be associated with human height. Some other factors that contribute to carpal tunnel syndrome are conditions such as diabetes, alcoholism, vitamin deficiency or toxicity as well as exposure to toxins. Conditions such as these don't necessarily increase the interstitial pressure of the carpal tunnel. One case-control study noted that individuals classified as obese ( BMI >29) are 2.5 times more likely than slender individuals (BMI <20) to be diagnosed with CTS. It
8142-449: The distal boundary is approximated by a line known as Kaplan's cardinal line . This line uses surface landmarks, and is drawn between the apex of the skin fold between the thumb and index finger to the palpated hamate hook. The carpal tunnel is formed by the carpal bones and the transverse carpal ligament. The median nerve passes through this space along with the flexor tendons . Increased compartmental pressure for any reason can squeeze
8260-415: The drug is ineffective for treating neuropathic pain. The authors caution against positive interpretations of the evidence. For sodium valproate the authors of a 2011 Cochrane review found that "three studies no more than hint that sodium valproate may reduce pain in diabetic neuropathy". They discuss how there is a probable overestimate of the effect due to the inherent problems with the data and conclude that
8378-412: The entire nerve is wrapped in a layer of connective tissue called the epineurium . Nerve cells (often called neurons) are further classified as sensory , motor , or mixed nerves . In the central nervous system , the analogous structures are known as nerve tracts . Each nerve is covered on the outside by a dense sheath of connective tissue , the epineurium . Beneath this is a layer of fat cells,
8496-498: The evidence does not support its usage. In a 2014 systematic review of carbamazepine the authors believe the drug to be of benefit to some people. No trials were considered greater than level III evidence; none were longer than 4 weeks in length or were deemed as having good reporting quality. A 2017 Cochrane systematic review aiming to assess the benefit of antiepileptic medications for several types of chronic non-cancer pains (including neuropathic pain) in children and adolescents found
8614-642: The evidence inconclusive. Two of the ten authors of this study declared receiving payments from pharmaceutical companies. A Cochrane review of buprenorphine, fentanyl, hydromorphone, and morphine, all dated between 2015 and 2017, and all for the treatment of neuropathic pain, found that there was insufficient evidence to comment on their efficacy. Conflicts of interest were declared by the authors in this review. A 2017 Cochrane review of methadone found very low-quality evidence, three studies of limited quality, of its efficacy and safety. They could not formulate any conclusions about its relative efficacy and safety compared to
8732-430: The feet. Autonomic symptoms also may occur, such as dizziness on standing up, erectile dysfunction , and difficulty controlling urination. Polyneuropathies usually are caused by processes that affect the body as a whole. Diabetes and impaired glucose tolerance are the most common causes. Hyperglycemia-induced formation of advanced glycation end products (AGEs) is related to diabetic neuropathy. Other causes relate to
8850-452: The flexor tendons such as with rheumatoid arthritis. Prolonged pressure can lead to a cascade of physiological changes in neural tissue. First, the blood-nerve barrier breaks down (increased permeability of perineureum and endothelial cells of endoneural blood vessels). If the pressure continues, the nerves will start the process of demyelination under the area of compression . This will result in abnormal nerve conduction even when
8968-427: The four authors declared receiving payments from pharmaceutical companies. More generally, a large-scale 2013 review found opioids to be more effective for intermediate-term use than short-term use, but couldn't properly assess effectiveness for chronic use because of insufficient data. Most recent guidelines on the pharmacotherapy of neuropathic pain however are in agreement with the results of this review and recommend
9086-518: The functions of the optic nerve in sight and the oculomotor nerve in eye movement. Analysis of the nerves in the cranium enabled him to differentiate between blood vessels and nerves ( Ancient Greek : νεῦρον (neûron) "string, plant fiber, nerve"). Modern research has not confirmed William Cullen 's 1785 hypothesis associating mental states with physical nerves, although popular or lay medicine may still invoke "nerves" in diagnosing or blaming any sort of psychological worry or hesitancy, as in
9204-487: The growth processes finds the regeneration tube, it begins to grow rapidly towards its original destination guided the entire time by the regeneration tube. Nerve regeneration is very slow and can take up to several months to complete. While this process does repair some nerves, there will still be some functional deficit as the repairs are not perfect. A nerve conveys information in the form of electrochemical impulses (as nerve impulses known as action potentials ) carried by
9322-412: The hands and wrist. The distribution usually follows the nerve root, and the paresthesia may be provoked by neck movement. Electromyography and imaging of the cervical spine can help to differentiate cervical radiculopathy from carpal tunnel syndrome if the diagnosis is unclear. Carpal tunnel syndrome is sometimes applied as a label to anyone with pain, numbness, swelling, or burning in the radial side of
9440-457: The hands or wrists. When pain is the primary symptom, carpal tunnel syndrome is unlikely to be the source of the symptoms. When the symptoms and signs point to atrophy and muscle weakness more than numbness, consider neurodegenerative disorders such as Amyotrophic Lateral Sclerosis or Charcot-Marie Tooth . There is little or no data to support the concept that activity adjustment prevents carpal tunnel syndrome. The evidence for wrist rest
9558-404: The individual neurons that make up the nerve. These impulses are extremely fast, with some myelinated neurons conducting at speeds up to 120 m/s. The impulses travel from one neuron to another by crossing a synapse , where the message is converted from electrical to chemical and then back to electrical. Nerves can be categorized into two groups based on function: The nervous system
9676-687: The lack of a consensus reference standard for CTS. Most presentations of CTS have no known disease cause ( idiopathic ). The association of other factors with CTS is a source of notable debate. It is important to distinguish factors that provoke symptoms, and factors that are associated with seeking care, from factors that make the neuropathy worse. Genetic factors are believed to be the most important determinants of who develops carpal tunnel syndrome due. In other words, one's wrist structure seems programmed at birth to develop CTS later in life. A genome-wide association study ( GWAS ) of carpal tunnel syndrome identified 50 genomic loci significantly associated with
9794-457: The median nerve with conduction in other nerves supplying the hand. When the median nerve is compressed, it will conduct more slowly than normal and more slowly than other nerves. Nerve compression results in damage to the myelin sheath and manifests as delayed latencies and slowed conduction velocities. Electrodiagnosis rests upon demonstrating impaired median nerve conduction across the carpal tunnel in context of normal conduction elsewhere. It
9912-462: The median nerve. Similarly, the degree to which transthyretin amyloidosis -associated polyneuropathy and carpal tunnel syndrome is under investigation. Prior carpal tunnel release is often noted in individuals who later present with transthyretin amyloid-associated cardiomyopathy . There is consideration that bilateral carpal tunnel syndrome could be a reason to consider amyloidosis, timely diagnosis of which could improve heart health. Amyloidosis
10030-417: The median nerve. Theoretically, increased pressure can interfere with normal intraneural blood flow, eventually causing a cascade of physiological changes in the nerve itself. There is a dose-respondent curve such that greater and longer periods of pressure are associated with greater nerve dysfunction. The symptoms and signs of carpal tunnel syndrome causes are hypertrophy of the synovial tissue surrounding
10148-441: The most common form, length-dependent peripheral neuropathy, pain and parasthesia appear symmetrically and generally at the terminals of the longest nerves, which are in the lower legs and feet. Sensory symptoms generally develop before motor symptoms such as weakness. Length-dependent peripheral neuropathy symptoms make a slow ascent of the lower limbs, while symptoms may never appear in the upper limbs; if they do, it will be around
10266-401: The nerve affects the same side ("ipsilateral") or opposite side ("contralateral") of the body, to the part of the brain that supplies it. Nerve growth normally ends in adolescence, but can be re-stimulated with a molecular mechanism known as " Notch signaling ". If the axons of a neuron are damaged, as long as the cell body of the neuron is not damaged, the axons can regenerate and remake
10384-479: The nerve to disrupt its microvascular environment. The critical pressure necessary to disrupt the blood supply of a nerve is approximately 30 mm Hg below diastolic blood pressure or 45mm Hg below mean arterial pressure . For normohypertensive (normal blood pressure) adults, the average values for systolic blood pressure is 116mm Hg diastolic blood pressure is 69mm Hg. Using this data, the average person would become symptomatic with approximately 39mm Hg of pressure in
10502-408: The nerve, is an extension of an individual neuron , along with other supportive cells such as some Schwann cells that coat the axons in myelin . Within a nerve, each axon is surrounded by a layer of connective tissue called the endoneurium . The axons are bundled together into groups called fascicles , and each fascicle is wrapped in a layer of connective tissue called the perineurium . Finally,
10620-515: The nerves may be perfectly normal; may show proximal weakness, as in some inflammatory neuropathies, such as Guillain–Barré syndrome ; or may show focal sensory disturbance or weakness, such as in mononeuropathies. Classically, ankle jerk reflex is absent in peripheral neuropathy. A physical examination will involve testing the deep ankle reflex as well as examining the feet for any ulceration . For large fiber neuropathy, an exam will usually show an abnormally decreased sensation to vibration, which
10738-493: The nerves may only partially recover. While there is evidence that chronic compression is a major cause of carpal tunnel syndrome, it may not be the only cause. Several alternative, potentially speculative, theories exist which describe alternative forms of nerve entrapment. One is the theory of nerve scarring (specifically adherence between the mesoneurium and epineureum ) preventing the nerve from gliding during wrist/finger movements, causing repetitive traction injuries. Another
10856-606: The normal nerve functions. Symptoms vary depending on the types of nerve fiber involved. In terms of sensory function, symptoms commonly include loss of function ("negative") symptoms, including numbness , tremor , impairment of balance, and gait abnormality . Gain of function (positive) symptoms include tingling , pain , itching , crawling, and pins-and-needles . Motor symptoms include loss of function ("negative") symptoms of weakness, tiredness , muscle atrophy , and gait abnormalities ; and gain of function ("positive") symptoms of cramps , and muscle twitch ( fasciculations ). In
10974-422: The number of millimeters two points of contact need to be separated before you can distinguish them. A person with idiopathic carpal tunnel syndrome will not have any sensory loss over the thenar eminence (bulge of muscles in the palm of hand and at the base of the thumb). This is because the palmar branch of the median nerve, which innervates that area of the palm, separates from the median nerve and passes over
11092-441: The only identified neurons in fish—there are about 20 more types, including pairs of "Mauthner cell analogs" in each spinal segmental nucleus. Although a Mauthner cell is capable of bringing about an escape response all by itself, in the context of ordinary behavior other types of cells usually contribute to shaping the amplitude and direction of the response. Mauthner cells have been described as command neurons . A command neuron
11210-723: The palm remains normal because the superficial sensory branch of the median nerve branches proximal to the TCL and travels superficial to it. Median nerve symptoms may arise from nerve compression at the level of the thoracic outlet or the area where the median nerve passes between the two heads of the pronator teres in the forearm, although this is debated. Severe CTS is associated with measurable loss of sensibility. Diminished threshold sensibility (the ability to distinguish different amounts of pressure) can be measured using Semmes-Weinstein monofilament testing. Diminished discriminant sensibility can be measured by testing two-point discrimination:
11328-422: The particular type of polyneuropathy, and there are many different causes of each type, including inflammatory diseases such as Lyme disease , vitamin deficiencies, blood disorders, and toxins (including alcohol and certain prescribed drugs). Most types of polyneuropathy progress fairly slowly, over months or years, but rapidly progressive polyneuropathy also occurs. It is important to recognize that at one time it
11446-477: The pattern of early symptoms is important. Mononeuritis multiplex is sometimes associated with a deep, aching pain that is worse at night and frequently in the lower back, hip, or leg. In people with diabetes mellitus , mononeuritis multiplex typically is encountered as acute, unilateral, and severe thigh pain followed by anterior muscle weakness and loss of knee reflex. Electrodiagnostic medicine studies will show multifocal sensory motor axonal neuropathy. It
11564-417: The prediabetes group", and stated that "A search for alternate neuropathy causes is needed in patients with prediabetes." The treatment of polyneuropathies is aimed firstly at eliminating or controlling the cause, secondly at maintaining muscle strength and physical function, and thirdly at controlling symptoms such as neuropathic pain . Mononeuritis multiplex , occasionally termed polyneuritis multiplex ,
11682-428: The pressure eight-fold and extension increases it ten-fold. There is speculation that repetitive flexion and extension in the wrist can cause thickening of the synovial tissue that lines the tendons within the carpal tunnel. A variety of patient factors can lead to CTS, including heredity, size of the carpal tunnel, associated local and systematic diseases, and certain habits. Non-traumatic causes generally happen over
11800-522: The pressure is relieved leading to persistent sensory symptoms until remyelination can occur. If the compression continues and is severe enough, axons may be injured and Wallerian degeneration will occur. At this point there may be weakness and muscle atrophy , depending on the extent of axon damage. The critical pressure above which the microcirculatory environment of a nerve becomes compromised depends on diastolic/systolic blood pressure . Higher blood pressure will require higher external pressure on
11918-432: The problem, in particular whether one studies people presenting with symptoms vs. measurable median neuropathy whether or not people are seeking care. Idiopathic neuropathy accounts for about 90% of all nerve compression syndromes. The best data regarding CTS comes from population-based studies, which demonstrate no relationship to gender, and increasing prevalence (accumulation) with age. The characteristic symptom of CTS
12036-423: The process affecting the nerves; e.g., inflammation ( neuritis ), compression ( compression neuropathy ), chemotherapy ( chemotherapy-induced peripheral neuropathy ). The affected nerves are found in an EMG (electromyography) / NCS (nerve conduction study) test and the classification is applied upon completion of the exam. Mononeuropathy is a type of neuropathy that only affects a single nerve . Diagnostically, it
12154-666: The risk of CTS by two times. Current evidence is insufficient to demonstrate that keyboard and computer use causes CTS as of 2014 . As of 2008 , a definitive study on the relationship between CTS and computer use had not been completed. The international debate regarding the relationship between CTS and repetitive hand use (at work in particular) is ongoing. The Occupational Safety and Health Administration (OSHA) has adopted rules and regulations regarding so-called "cumulative trauma disorders" based concerns regarding potential harm from exposure to repetitive tasks, force, posture, and vibration . A review of available scientific data by
12272-508: The skin, hair, and nails. Additionally, motor neuropathy may cause impaired balance and coordination or, most commonly, muscle weakness; sensory neuropathy may cause numbness to touch and vibration, reduced position sense causing poorer coordination and balance, reduced sensitivity to temperature change and pain, spontaneous tingling or burning pain, or allodynia (pain from normally nonpainful stimuli, such as light touch); and autonomic neuropathy may produce diverse symptoms, depending on
12390-404: The synaptic connections with neurons with the help of guidepost cells . This is also referred to as neuroregeneration . The nerve begins the process by destroying the nerve distal to the site of injury allowing Schwann cells, basal lamina, and the neurilemma near the injury to begin producing a regeneration tube. Nerve growth factors are produced causing many nerve sprouts to bud. When one of
12508-417: The thorax, abdomen, and pelvis outside the spinal cord . They have connections with the spinal cord and ultimately the brain, however. Most commonly autonomic neuropathy is seen in persons with long-standing diabetes mellitus type 1 and 2. In most—but not all—cases, autonomic neuropathy occurs alongside other forms of neuropathy, such as sensory neuropathy. Autonomic neuropathy is one cause of malfunction of
12626-676: The thumb side of the ring finger. Symptoms are typically most troublesome at night. Many people sleep with their wrists bent, and the ensuing symptoms may lead to awakening. Untreated, and over years to decades, CTS causes loss of sensibility, weakness, and shrinkage ( atrophy ) of the thenar muscles at the base of the thumb. Work-related factors such as vibration, wrist extension or flexion, hand force, and repetition are risk factors for CTS. Other than work related causes there are many known risk factors for CTS including being overweight, female, diabetes mellitus, rheumatoid arthritis and thyroid disease, and genetics. Diagnosis can be made with
12744-413: The thumb, index finger, long finger, and half of the ring finger. At the level of the wrist, the median nerve supplies the muscles at the base of the thumb that allow it to abduct, move away from the other four fingers, as well as move out of the plane of the palm. The carpal tunnel is located at the middle third of the base of the palm, bounded by the bony prominence of the scaphoid tubercle and trapezium at
12862-541: The time that leg symptoms reach the knee. When the nerves of the autonomic nervous system are affected, symptoms may include constipation, dry mouth, difficulty urinating, and dizziness when standing . A user-friendly, disease-specific, quality-of-life scale can be used to monitor how someone is doing living with the burden of chronic, sensorimotor polyneuropathy. This scale, called the Chronic, Acquired Polyneuropathy - Patient-reported Index (CAP-PRI), contains only 15 items and
12980-498: The treatment of neuropathic pain or the evidence available is inconclusive. Evidence also tends to be tainted by bias or issues with the methodology. Cochrane systematically reviewed the evidence for the antidepressants nortriptyline, desipramine, venlafaxine, and milnacipran and in all these cases found scant evidence to support their use for the treatment of neuropathic pain. All reviews were done between 2014 and 2015. A 2015 Cochrane systematic review of amitriptyline found that there
13098-463: The tunnel pressure as high as 111mm Hg. Many of the activities associated with carpal tunnel such symptoms as driving, holding a phone, etc. involve flexing the wrist and it is likely due to an increase in carpal tunnel pressure during these activities. Nerve compression can result in various stages of nerve injury. The majority of carpal tunnel syndrome patients have a degree I nerve injury (Sunderland classification), also called neuropraxia . This
13216-492: The use of opioids. A 2017 Cochrane review examining mainly propoxyphene therapy as a treatment for many non-cancer pain syndromes (including neuropathic pain) concluded, "There was no evidence from randomised controlled trials to support or refute the use of opioids to treat chronic non-cancer pain in children and adolescents." A 2016 Cochrane review of paracetamol for the treatment of neuropathic pain concluded that its benefit alone or in combination with codeine or dihydrocodeine
13334-474: The wrist (69 - 30 = 39 and 69 + (116 - 69)/3 - 45 ~ 40). Carpal tunnel syndrome patients tend to have elevated carpal tunnel pressures (12-31mm Hg) compared to controls (2.5 - 13mm Hg). Applying pressure to the carpal tunnel of normal subjects in a lab can produce mild neurophysiological changes at 30mm Hg with a rapid, complete sensory block at 60mm Hg. Carpal tunnel pressure may be affected by wrist movement/position, with flexion and extension capable of raising
13452-445: The wrists or hands, loss of grip strength, minor loss of sleep, and loss of manual dexterity. As the median neuropathy gets worse, there is loss of sensibility in the thumb, index, middle, and thumb side of the ring finger. As the neuropathy progresses, there may be first weakness, then to atrophy of the muscles of thenar eminence (the flexor pollicis brevis , opponens pollicis , and abductor pollicis brevis ). The sensibility of
13570-649: Was high-quality evidence to suggest that lamotrigine is not effective for treating neuropathic pain, even at high dosages 200–400 mg. A 2013 Cochrane systematic review of topirimate found that the included data had a strong likelihood of major bias; despite this, it found no effectiveness for the drug in treating the pain associated with diabetic neuropathy. It had not been tested for any other type of neuropathy. Cochrane reviews from 2012 of clonazepam and phenytoin uncovered no evidence of sufficient quality to support their use in chronic neuropathic pain." A 2012 Cochrane systematic review of lacosamide found it very likely that
13688-403: Was no evidence supporting the use of amitriptyline that did not possess inherent bias. The authors believe amitriptyline may have an effect in some patients but that the effect is overestimated. A 2014 Cochrane systematic review of imipramine notes that the evidence suggesting benefit were "methodologically flawed and potentially subject to major bias." A 2017 Cochrane systematic review assessed
13806-623: Was thought that many of the cases of small fiber peripheral neuropathy with typical symptoms of tingling, pain, and loss of sensation in the feet and hands were due to glucose intolerance before a diagnosis of diabetes or pre-diabetes. However, in August 2015, the Mayo Clinic published a scientific study in the Journal of the Neurological Sciences showing "no significant increase in...symptoms...in
13924-502: Was unclear. It is proposed that repetitive use of the arm can affect the biomechanics of the upper limb or cause damage to tissues. It is proposed that postural and spinal assessment along with ergonomic assessments should be considered, based on observation that addressing these factors has been found to improve comfort in some studies although experimental data are lacking and the perceived benefits may not be specific to those interventions. A 2010 survey by NIOSH showed that two-thirds of
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