Peripheral neuropathy, often shortened to neuropathy, is damage or disease affecting the nerves. Damage to nerves may impair sensation, movement, gland function, 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 such as of vitamin B12, medication (e.g., chemotherapy, or commonly prescribed antibiotics including metronidazole and 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")"neuropathy". Online Etymology Dictionary. without modifier usually means peripheral neuropathy.
Neuropathy affecting just one nerve 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 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 the affected glands and organs, but common symptoms are poor bladder control, abnormal blood pressure or heart rate, and reduced ability to sweat normally.
Classification 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 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 exam completion.
Mononeuropathy
Mononeuropathy is a type of neuropathy that only affects a single nerve. Diagnostically, it 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. Diabetes mellitus is a confounding example due to its diabetic lumbosacral radiculoplexus neuropathy variant, presenting as a single-nerve femoral neuropathy though additional signatures indicate it is not a true femoral neuropathy.
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
"Polyneuropathy" 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 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 axons' ability to conduct electrical impulses. The third and least common pattern directly affects the cell bodies of neurons. 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 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 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 toxicants (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 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 prediabetes. 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 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 Mononeuritis multiplex, occasionally termed polyneuritis multiplex, 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 the pattern of early symptoms is important.
Mononeuritis multiplex is sometimes associated with a deep, aching pain that worsens 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 weakness of anterior muscle and loss of knee reflex.
Electrodiagnostic medicine studies will show multifocal sensory motor axonal neuropathy.
It is caused by, or associated with, several medical conditions:
Autonomic neuropathy
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 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 types 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 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: Urinary bladder conditions: bladder incontinence or urine retention Gastrointestinal tract: dysphagia, abdominal pain, nausea, vomiting, malabsorption, fecal incontinence, gastroparesis, diarrhoea, constipation Cardiovascular system: disturbances of heart rate (tachycardia, bradycardia), orthostatic hypotension, inadequate increase of heart rate on exertion Respiratory system: impairments in the signals associated with regulation of breathing and gas exchange (central sleep apnea, hypopnea, bradypnea). Skin: thermal regulation, dryness through sweat disturbances Other areas: hypoglycemia unawareness, genital impotence
Neuritis Neuritis is a general term for inflammation of a nerve or the general inflammation of 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 Physical injury Infection Diphtheria Herpes zoster (shingles) Leprosy Lyme disease Chemical injury such as chemotherapy Radiation therapy
Types of neuritis include Brachial neuritis Cranial neuritis such as Bell's palsy Optic neuritis Vestibular neuritis Wartenberg's migratory sensory neuropathy Underlying conditions including: Alcoholism Autoimmune disease, especially multiple sclerosis and Guillain–Barré syndrome Beriberi (vitamin B1 deficiency) Cancer Celiac disease Non-celiac gluten sensitivity Diabetes mellitus (Diabetic neuropathy) Hypothyroidism Porphyria Vitamin B12 deficiency Vitamin B6 excess
Signs and symptoms Those with diseases or dysfunctions of their nerves may have problems with 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. Positive symptoms include pain, itching, crawling, tingling, 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).