Axonopathy
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Polyneuropathy () is damage or disease affecting
peripheral nerves The peripheral nervous system (PNS) is one of two components that make up the nervous system of bilateral animals, with the other part being the central nervous system (CNS). The PNS consists of nerves and ganglia, which lie outside the brain a ...
(
peripheral neuropathy 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. Neuropa ...
) in roughly the same areas on both sides of the body, featuring
weakness Weakness is a symptom of many different medical conditions. The causes are many and can be divided into conditions that have true or perceived muscle weakness. True muscle weakness is a primary symptom of a variety of skeletal muscle diseases, ...
,
numbness Hypoesthesia or numbness is a common side effect of various medical conditions that manifests as a reduced sense of touch or sensation, or a partial loss of sensitivity to Sensory receptor, sensory stimuli. In everyday speech this is generally r ...
, and burning pain. It usually begins in the hands and feet and may progress to the arms and legs and sometimes to other parts of the body where it may affect the
autonomic nervous system The autonomic nervous system (ANS), sometimes called the visceral nervous system and formerly the vegetative nervous system, is a division of the nervous system that operates viscera, internal organs, smooth muscle and glands. The autonomic nervo ...
. It may be acute or chronic. A number of different disorders may cause polyneuropathy, including
diabetes Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin, or the cells of th ...
and some types of
Guillain–Barré syndrome Guillain–Barré syndrome (GBS) is a rapid-onset Paralysis, muscle weakness caused by the immune system damaging the peripheral nervous system. Typically, both sides of the body are involved, and the initial symptoms are changes in sensation ...
.


Classification

Polyneuropathies may be classified in different ways, such as by ''cause'', by ''presentation'', or by ''classes'' of polyneuropathy, in terms of which part of the nerve cell is affected mainly: the
axon An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, -er, spelling differences) is a long, slender cellular extensions, projection of a nerve cell, or neuron, ...
, the
myelin Myelin Sheath ( ) is a lipid-rich material that in most vertebrates surrounds the axons of neurons to insulate them and increase the rate at which electrical impulses (called action potentials) pass along the axon. The myelinated axon can be lik ...
sheath, or the
cell body In cellular neuroscience, the soma (: somata or somas; ), neurocyton, or cell body is the bulbous, non-process portion of a neuron or other brain cell type, containing the cell nucleus. Although it is often used to refer to neurons, it can also ...
. * ''Distal axonopathy'', is the result of interrupted function of the peripheral nerves. It is the most common response of neurons to metabolic or toxic disturbances, and may be caused by metabolic diseases such as
diabetes Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin, or the cells of th ...
,
kidney failure Kidney failure, also known as renal failure or end-stage renal disease (ESRD), is a medical condition in which the kidneys can no longer adequately filter waste products from the blood, functioning at less than 15% of normal levels. Kidney fa ...
,
connective tissue disease Connective tissue diseases (also termed connective tissue disorders, or collagen vascular diseases), are medical conditions that affect connective tissue. Connective tissues protect, support, and provide structure for the body's other tissues a ...
, deficiency syndromes such as
malnutrition Malnutrition occurs when an organism gets too few or too many nutrients, resulting in health problems. Specifically, it is a deficiency, excess, or imbalance of energy, protein and other nutrients which adversely affects the body's tissues a ...
and
alcoholism Alcoholism is the continued drinking of alcohol despite it causing problems. Some definitions require evidence of dependence and withdrawal. Problematic use of alcohol has been mentioned in the earliest historical records. The World He ...
, or the effects of
toxin A toxin is a naturally occurring poison produced by metabolic activities of living cells or organisms. They occur especially as proteins, often conjugated. The term was first used by organic chemist Ludwig Brieger (1849–1919), derived ...
s or
drugs A drug is any chemical substance other than a nutrient or an essential dietary ingredient, which, when administered to a living organism, produces a biological effect. Consumption of drugs can be via inhalation, injection, smoking, ingestio ...
such as
chemotherapy Chemotherapy (often abbreviated chemo, sometimes CTX and CTx) is the type of cancer treatment that uses one or more anti-cancer drugs (list of chemotherapeutic agents, chemotherapeutic agents or alkylating agents) in a standard chemotherapy re ...
. They may be divided according to the type of axon affected (large-fiber, small-fiber, or both). The most distal portions of axons are usually the first to degenerate, and axonal atrophy advances slowly toward the nerve's cell body. However, if the cause is removed, then regeneration is possible, although the prognosis depends on the duration and severity of the original stimulus. People with distal axonopathies usually present with sensorimotor disturbances such as
amyotrophic lateral sclerosis Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND) or—in the United States—Lou Gehrig's disease (LGD), is a rare, Terminal illness, terminal neurodegenerative disease, neurodegenerative disorder that results i ...
* ''Myelinopathy'', is due to a loss of myelin or of the
Schwann cells Schwann cells or neurolemmocytes (named after German physiologist Theodor Schwann) are the principal glia of the peripheral nervous system (PNS). Glial cells function to support neurons and in the PNS, also include Satellite glial cell, satellite ...
. This demyelination slows down or completely blocks the conduction of
action potential An action potential (also known as a nerve impulse or "spike" when in a neuron) is a series of quick changes in voltage across a cell membrane. An action potential occurs when the membrane potential of a specific Cell (biology), cell rapidly ri ...
s through the axon of the nerve cell (
neurapraxia Neurapraxia is a disorder of the peripheral nervous system in which there is a temporary loss of motor and sensory function due to blockage of nerve conduction, usually lasting an average of six to eight weeks before full recovery. Neurapraxia is ...
). The most common cause is acute inflammatory demyelinating polyneuropathy AIDP, the most common form of
Guillain–Barré syndrome Guillain–Barré syndrome (GBS) is a rapid-onset Paralysis, muscle weakness caused by the immune system damaging the peripheral nervous system. Typically, both sides of the body are involved, and the initial symptoms are changes in sensation ...
(although other causes include
chronic inflammatory demyelinating polyneuropathy Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired autoimmune disease of the peripheral nervous system characterized by progressive weakness and impaired sensory function in the legs and arms. The disorder is sometimes calle ...
) * ''Neuronopathy'' is the result of issues in the
peripheral nervous system The peripheral nervous system (PNS) is one of two components that make up the nervous system of Bilateria, bilateral animals, with the other part being the central nervous system (CNS). The PNS consists of nerves and ganglia, which lie outside t ...
(PNS) neurons. They may be caused by
motor neurone disease Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND) or—in the United States—Lou Gehrig's disease (LGD), is a rare, terminal neurodegenerative disorder that results in the progressive loss of both upper and low ...
s, sensory neuronopathies, toxins, or autonomic dysfunction.
Neurotoxins Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature n ...
such as
chemotherapy Chemotherapy (often abbreviated chemo, sometimes CTX and CTx) is the type of cancer treatment that uses one or more anti-cancer drugs (list of chemotherapeutic agents, chemotherapeutic agents or alkylating agents) in a standard chemotherapy re ...
agents may cause neuronopathies.


Signs and symptoms

Among the signs and symptoms of polyneuropathy, which can be divided (into sensory and hereditary) and are consistent with the following, are: * ''Sensory polyneuropathy'' –
ataxia Ataxia (from Greek α- negative prefix+ -τάξις rder= "lack of order") is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in e ...
, numbness,
muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...
wasting and paraesthesiae. * ''Hereditary polyneuropathy'' –
scoliosis Scoliosis (: scolioses) is a condition in which a person's Vertebral column, spine has an irregular curve in the coronal plane. The curve is usually S- or C-shaped over three dimensions. In some, the degree of curve is stable, while in others ...
and hammer toes


Causes

The causes of polyneuropathy can be divided into hereditary and acquired and are therefore as follows: * ''Inherited'' – hereditary motor neuropathies,
Charcot–Marie–Tooth disease Charcot-Marie-Tooth disease (CMT) is an inherited neurological disorder that affects the peripheral nerves responsible for transmitting signals between the brain, spinal cord, and the rest of the body. This is the most common inherited neuropath ...
, and
hereditary neuropathy with liability to pressure palsy Hereditary neuropathy with liability to pressure palsy (HNPP) is a peripheral neuropathy, a condition that affects the nerves.update 2014 Pressure on the nerves can cause tingling sensations, numbness, pain, weakness, muscle atrophy and even paraly ...
* ''Acquired'' –
diabetes mellitus Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained hyperglycemia, high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin, or th ...
,
vascular Vascular can refer to: * blood vessels, the vascular system in animals * vascular tissue Vascular tissue is a complex transporting tissue, formed of more than one cell type, found in vascular plants. The primary components of vascular tissue ...
neuropathy,
alcohol use disorder Alcoholism is the continued drinking of alcohol despite it causing problems. Some definitions require evidence of dependence and withdrawal. Problematic use of alcohol has been mentioned in the earliest historical records. The World Hea ...
,
vitamin E deficiency Vitamin E deficiency is a rare condition caused by low levels of vitamin E that may result from malabsorption disorders (such as abetalipoproteinemia, cystic fibrosis, or Crohn's disease), or impaired lipid transport. As a potent antioxidant, vit ...
, and
vitamin B12 deficiency Vitamin B12 deficiency, also known as cobalamin deficiency, is the medical condition in which the blood and tissue have a lower than normal level of Vitamin B12, vitamin B12. Symptoms can vary from none to severe. Mild deficiency may have fe ...


Pathophysiology

The pathophysiology of polyneuropathy depends on the ''type''.
Chronic inflammatory demyelinating polyneuropathy Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired autoimmune disease of the peripheral nervous system characterized by progressive weakness and impaired sensory function in the legs and arms. The disorder is sometimes calle ...
, for instance, is an
autoimmune In immunology, autoimmunity is the system of immune responses of an organism against its own healthy cells, tissues and other normal body constituents. Any disease resulting from this type of immune response is termed an " autoimmune disease" ...
disease:
T cells T cells (also known as T lymphocytes) are an important part of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor (TCR) on their ce ...
involvement has been demonstrated, antibodies alone are not capable of
demyelination 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 con ...
.


Diagnosis

The diagnosis of polyneuropathy begins with a history (anamnesis) and
physical examination In a physical examination, medical examination, clinical examination, or medical checkup, a medical practitioner examines a patient for any possible medical signs or symptoms of a Disease, medical condition. It generally consists of a series of ...
to ascertain the pattern of the disease process (such as arms, legs, distal, proximal), if they fluctuate, and what deficits and pain are involved. If pain is a factor, determining where and how long it has been present is important; one also needs to know what disorders are present within the family and what diseases the person may have. Although diseases often are suggested by the physical examination and history alone, tests that may be employed include electrodiagnostic testing, serum protein
electrophoresis Electrophoresis is the motion of charged dispersed particles or dissolved charged molecules relative to a fluid under the influence of a spatially uniform electric field. As a rule, these are zwitterions with a positive or negative net ch ...
,
nerve conduction studies A nerve is an enclosed, cable-like bundle of nerve fibers (called axons). 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 ...
,
urinalysis Urinalysis, a portmanteau of the words ''urine'' and ''analysis'', is a Test panel, panel of medical tests that includes physical (macroscopic) examination of the urine, chemical evaluation using urine test strips, and #Microscopic examination, m ...
, serum
creatine kinase Creatine kinase (CK), also known as creatine phosphokinase (CPK) or phosphocreatine kinase, is an enzyme () expressed by various tissues and cell types. CK catalyses the conversion of creatine and uses adenosine triphosphate (ATP) to create phos ...
(CK) and
antibody An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as pathogenic bacteria, bacteria and viruses, includin ...
testing; nerve biopsy is done sometimes. Other tests may be used, especially tests for specific disorders associated with polyneuropathies; quality measures have been developed to diagnose patients with distal symmetrical polyneuropathy (DSP).


Differential diagnosis

In terms of the differential diagnosis for polyneuropathy, the following must be considered:


Treatment

In the treatment of polyneuropathies one must ascertain and manage the cause, among management activities are: weight decrease, use of a walking aid, and
occupational therapist Occupational therapists (OTs) are health care professionals specializing in occupational therapy and occupational science. OTs and occupational therapy assistants (OTAs) use evidence-based practice, scientific bases and a Holism, holistic perspec ...
assistance. Additionally, BP control in those with diabetes is helpful, while intravenous
immunoglobulin An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as pathogenic bacteria, bacteria and viruses, includin ...
is used for multifocal motor neuropathy. According to Lopate, et al.,
methylprednisolone Methylprednisolone (Depo-Medrol, Medrol, Solu-Medrol) is a synthetic glucocorticoid, primarily prescribed for its anti-inflammatory and immunosuppressive effects. It is either used at low doses for chronic illnesses or used at high doses durin ...
is a viable treatment for chronic inflammatory demyelinative polyneuropathy (which can also be treated with intravenous immunoglobulin). The authors also indicate that
prednisone Prednisone is a glucocorticoid medication mostly used to immunosuppressive drug, suppress the immune system and decrease inflammation in conditions such as asthma, COPD, and rheumatologic diseases. It is also used to treat high blood calcium ...
has greater adverse effects in such treatment, as opposed to intermittent (high-doses) of the aforementioned medication. According to Wu, et al., in critical illness polyneuropathy supportive and preventive therapy are important for the affected individual, as well as, avoiding (or limiting)
corticosteroids Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are invol ...
.


See also


References


Further reading

* * *


External links

{{Medicine Peripheral nervous system disorders