Small fiber peripheral neuropathy
Encyclopedia
Small fiber peripheral neuropathy is a type of neuropathy that occurs from damage to the small unmyelinated peripheral nerve fibers. These fibers, categorized as C fibers, are present in skin, peripheral nerves and organs. The role of these nerves is to innervate the skin (somatic fibers) and help control autonomic function (autonomic fibers). It is estimated that 15-20 million people in the United States suffer from some form of peripheral neuropathy.
, dysesthesias, and insensitivity to pain. Paresthesias are abnormal sensations. They are often described as numbness, burning, cold, prickling, pins and needles along with other symptoms. Dysesthesias are altered normal sensations. A light breeze, the feeling of clothes, or even a soft touch can cause pain. Insensitivity to pain can be particular problem. One may be bleeding or have a skin injury without even knowing it.
It is often a disorder diagnosed by ruling out everything else. In fact, nerve conduction tests
and electromyography
(EMG tests), which are good in diagnosing other neuropathies, are usually bad in detecting small fiber neuropathies. Quantitative sensory testing (QST) can be used to measure more objective changes in the temperature sensation. An elevated heat-detection threshold, heat-pain threshold, a reduced cold detection threshold or cold pain threshold may indicate a small-fiber neuropathy. A conventional nerve biopsy
is not useful, since in this procedure mostly large-fiber nerves are studied. A skin biopsy
(with the measurement of intraepidermal nerve fiber density) can be used for a diagnosis, but is not commonly available. This test allows for direct visualization of the un-myelinated nerve fibers (the "small fibers") in the epidermal layer of the skin, and requires taking a small skin sample.
, Sjögren's syndrome
, Lupus
, vasculitis
, sarcoidosis
, nutritional deficiency, Celiac disease, Lyme disease
, HIV
, Fabry disease, amyloidosis
and alcoholism
. A 2008 study reported that in approximately 40% of patients no cause could be determined after initial evaluation. When no cause can be identified, the neuropathy is called idiopathic
. A recent study revealed dysfunction of a particular sodiumchannel (Nav1.7
) in a significant portion of the patient population with an idiopathic small fiber neuropathy.
There is no current treatment to cure small fiber peripheral neuropathy, but Intravenous immunoglobulin
(IVIG) is often used as well as plasmapheresis
.
Symptoms
Sensory symptoms of small fiber neuropathy are highly variable. Common complaints include paresthesiasParesthesia
Paresthesia , spelled "paraesthesia" in British English, is a sensation of tingling, burning, pricking, or numbness of a person's skin with no apparent long-term physical effect. It is more generally known as the feeling of "pins and needles" or of a limb "falling asleep"...
, dysesthesias, and insensitivity to pain. Paresthesias are abnormal sensations. They are often described as numbness, burning, cold, prickling, pins and needles along with other symptoms. Dysesthesias are altered normal sensations. A light breeze, the feeling of clothes, or even a soft touch can cause pain. Insensitivity to pain can be particular problem. One may be bleeding or have a skin injury without even knowing it.
Topographic pattern
Like many polyneuropathies, the symptoms usually start in the longer nerves and progressively attack shorter nerves. This means that most often the symptoms start in the feet and progress upwards, and usually symptoms are more severe in the feet. However, patients with Fabry disease have isolated small fiber engagement, and can have a more widespread small fiber disruption.Diagnosis
This neuropathy is considered a separate clinical entity from a regular large-fiber polyneuropathy. Small fibers are difficult to diagnose. The diagnosis of a large-fiber (common) polyneuropathy is much easier. Many large-fiber polyneuropathies have minor small-fiber engagement, and small-fiber engagements are often implied if the patient has minor small-fiber symptoms in addition to large-fiber symptoms. The clinical picture of an isolated small-fiber neuropathy is characteristic, but the diagnosis is not always easy.It is often a disorder diagnosed by ruling out everything else. In fact, nerve conduction tests
Nerve conduction study
A nerve conduction study is a test commonly used to evaluate the function, especially the ability of electrical conduction, of the motor and sensory nerves of the human body.Nerve conduction velocity is a common measurement made during this test...
and electromyography
Electromyography
Electromyography is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph, to produce a record called an electromyogram. An electromyograph detects the electrical potential generated by muscle...
(EMG tests), which are good in diagnosing other neuropathies, are usually bad in detecting small fiber neuropathies. Quantitative sensory testing (QST) can be used to measure more objective changes in the temperature sensation. An elevated heat-detection threshold, heat-pain threshold, a reduced cold detection threshold or cold pain threshold may indicate a small-fiber neuropathy. A conventional nerve biopsy
Nerve biopsy
In medicine, a nerve biopsy is an invasive procedure in which a piece of a nerve is removed from an organism and examined microscopically. A nerve biopsy can lead to the discovery of necrotizing vasculitis, amyloidosis, sarcoidosis, leprosy, metabolic neuropathies, inflammation of the nerve, loss...
is not useful, since in this procedure mostly large-fiber nerves are studied. A skin biopsy
Skin biopsy
Skin biopsy is a biopsy technique in which a skin lesion is removed and sent to the pathologist to render a microscopic diagnosis. It is usually done under local anesthetic in a physician's office, and results are often available in 4 to 10 days. It is commonly performed by dermatologists. Skin...
(with the measurement of intraepidermal nerve fiber density) can be used for a diagnosis, but is not commonly available. This test allows for direct visualization of the un-myelinated nerve fibers (the "small fibers") in the epidermal layer of the skin, and requires taking a small skin sample.
Causes
There are many possible causes of small fiber neuropathy. The most common cause is diabetes or glucose intolerance. Other possible causes include hypothyroidismHypothyroidism
Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone.Iodine deficiency is the most common cause of hypothyroidism worldwide but it can be caused by other causes such as several conditions of the thyroid gland or, less commonly, the pituitary gland or...
, Sjögren's syndrome
Sjögren's syndrome
Sjögren's syndrome , also known as "Mikulicz disease" and "Sicca syndrome", is a systemic autoimmune disease in which immune cells attack and destroy the exocrine glands that produce tears and saliva....
, Lupus
Lupus
Lupus most commonly refers to the disease systemic lupus erythematosus.Lupus may also refer to:-Medicine:* Lupus erythematosus, a chronic autoimmune disease with several different forms...
, vasculitis
Vasculitis
Vasculitis refers to a heterogeneous group of disorders that are characterized by inflammatory destruction of blood vessels. Both arteries and veins are affected. Lymphangitis is sometimes considered a type of vasculitis...
, sarcoidosis
Sarcoidosis
Sarcoidosis , also called sarcoid, Besnier-Boeck disease or Besnier-Boeck-Schaumann disease, is a disease in which abnormal collections of chronic inflammatory cells form as nodules in multiple organs. The cause of sarcoidosis is unknown...
, nutritional deficiency, Celiac disease, Lyme disease
Lyme disease
Lyme disease, or Lyme borreliosis, is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia. Borrelia burgdorferi sensu stricto is the main cause of Lyme disease in the United States, whereas Borrelia afzelii and Borrelia garinii cause most...
, HIV
HIV
Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...
, Fabry disease, amyloidosis
Amyloidosis
In medicine, amyloidosis refers to a variety of conditions whereby the body produces "bad proteins", denoted as amyloid proteins, which are abnormally deposited in organs and/or tissues and cause harm. A protein is described as being amyloid if, due to an alteration in its secondary structure, it...
and alcoholism
Alcoholism
Alcoholism is a broad term for problems with alcohol, and is generally used to mean compulsive and uncontrolled consumption of alcoholic beverages, usually to the detriment of the drinker's health, personal relationships, and social standing...
. A 2008 study reported that in approximately 40% of patients no cause could be determined after initial evaluation. When no cause can be identified, the neuropathy is called idiopathic
Idiopathic
Idiopathic is an adjective used primarily in medicine meaning arising spontaneously or from an obscure or unknown cause. From Greek ἴδιος, idios + πάθος, pathos , it means approximately "a disease of its own kind". It is technically a term from nosology, the classification of disease...
. A recent study revealed dysfunction of a particular sodiumchannel (Nav1.7
Nav1.7
Nav1.7 is a sodium ion channel that in humans is encoded by the SCN9A gene. It is usually expressed at high levels in two types of neurons, the nociceptive neurons at dorsal root ganglion and trigeminal ganglion, and sympathetic ganglion neurons, which are part of the autonomic nervous system.-...
) in a significant portion of the patient population with an idiopathic small fiber neuropathy.
Treatment
Treatment is based on the underlying cause, if any. Where the likely underlying condition is known, treatment of this condition is indicated treated to reduce progression of the disease and symptoms. For cases without those conditions, there is only symptomatic treatment.There is no current treatment to cure small fiber peripheral neuropathy, but Intravenous immunoglobulin
Intravenous immunoglobulin
Intravenous immunoglobulin is a blood product administered intravenously. It contains the pooled IgG extracted from the plasma of over one thousand blood donors. IVIG's effects last between 2 weeks and 3 months...
(IVIG) is often used as well as plasmapheresis
Plasmapheresis
Plasmapheresis is the removal, treatment, and return of blood plasma from blood circulation. It is thus an extracorporeal therapy...
.
External links
- Peripheral Neuropathy Fact Sheet - NINDS
- Painful Feet: The Small Fiber Neuropathies
- Small Fiber Neuropathy Center Maastricht
See also
- Neuropathy
- PolyneuropathyPolyneuropathyPolyneuropathy is a neurological disorder that occurs when many peripheral nerves throughout the body malfunction simultaneously. It may be acute and appear without warning, or chronic and develop gradually over a longer period of time. Many polyneuropathies have both motor and sensory...
- Wartenbergs migratory sensory neuropathyWartenbergs migratory sensory neuropathyWartenberg's migratory sensory neuropathy is a rare condition identified by Robert Wartenberg in 1958 which is easy to confuse with the early stages of multiple sclerosis or Guillain-Barré syndrome...