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 & needles), paresis (weakness), hypoesthesia (numbness), anesthesia, paralysis, wasting, and disappearance of the reflexes. Causes include:

1) Physical injury. One common cause of neuritis and subsequent inflammation of the nerves to the toes is the wearing of high-heeled shoes or ill-fitting shoes that bind the toes painfully. This can cause temporary numbness and pain in the affected toes for several days.

2) Infection:

A) Herpes simplex
B) Shingles
C) Leprosy
D) Guillain-Barre syndrome
E) Lyme Disease
F) Chemical injury
G) Radiation

3) Underlying conditions causing localized neuritis (affecting a single nerve):

A) Diphtheria
B) Localized injury
C) Diabetes

4) Underlying conditions causing polyneuritis (affecting multiple nerves):

A) Beriberi
B) Vitamin B12 deficiency
C) Vitamin B6 excess
D) Metabolic diseases
E) Diabetes
F) Herpes zoster
G) Hypothyroidism
H) Porphyria
I) Infections, bacterial and/or viral
J) Autoimmune disease, especially Multiple Sclerosis
K) Cancer
L) Alcoholism
M) Wartenbergs migratory sensory neuropathy

Types of neuritis include:

1) Polyneuritis or Multiple neuritis (not to be confused with multiple sclerosis)
2) Brachial neuritis
3) Optic neuritis
4) Vestibular neuritis
5) Cranial neuritis, often representing as Bell's Palsy
6) Arsenic neuritis

Signs and symptoms

Those with diseases or dysfunctions of their peripheral nerves can present with problems in any of the normal peripheral nerve functions.

In terms of sensory function, there are commonly loss of function (negative) symptoms, which include numbness, tremor, and gait abnormality.

Gain of function (positive) symptoms include tingling, pain, itching, crawling, and pins and needles. Pain can become intense enough to require use of opioid (narcotic) drugs (i.e., morphine, oxycodone).

Skin can become so hypersensitive that patients are prohibited from having anything touch certain parts of their body, especially the feet. People with this degree of sensitivity cannot have a bedsheet touch their feet or wear socks or shoes, and eventually become housebound.

Motor symptoms include loss of function (negative) symptoms of weakness, tiredness, heaviness, and gait abnormalities; and gain of function (positive) symptoms of cramps, tremor, and muscle twitch
(fasciculations).

There is also pain in the muscles (myalgia), cramps, etc., and there may also be autonomic dysfunction. During physical examination, specifically a neurological examination, those with generalized peripheral neuropathies most commonly have distal sensory or motor and sensory loss, though those with a pathology (problem) of the peripheral nerves may be perfectly normal; may show proximal weakness, as in some inflammatory neuropathies like Guillain–Barré syndrome; or may show focal sensory disturbance or weakness, such as in mononeuropathies. Ankle jerk reflex is classically absent in peripheral neuropathy.

Causes

The causes are broadly grouped as follows:

1) Genetic diseases: Friedreich's ataxia, Charcot-Marie-Tooth syndrome
2) Metabolic/Endocrine: diabetes mellitus, chronic renal failure, porphyria, amyloidosis, liver failure, hypothyroidism
3) Toxic causes: Drugs (vincristine, phenytoin, nitrofurantoin, isoniazid, ethyl alcohol), organic metals, heavy metals, excess intake of vitamin B6 (pyridoxine)
4) Fluoroquinolone toxicity: Irreversible neuropathy is a serious adverse reaction of fluoroquinolone drugs
5) Inflammatory diseases: Guillain Barre syndrome, systemic lupus erythematosis, leprosy, Sjogrens syndrome, Lyme Disease, sarcoidosis,
6) Vitamin deficiency states: Vitamin B12 (cyanocobalamin), vitamin A, vitamin E, vitamin B1 (thiamin)
7) Physical trauma: compression, pinching, cutting, projectile injuries (i.e. gunshot wound), strokes including prolonged occlusion of blood flow, electric discharge, including lightning strikes
8) Others: shingles, malignant disease, HIV, radiation, chemotherapy

Many of the diseases of the peripheral nervous system may present similarly to muscle problems (myopathies), and so it is important to develop approaches for assessing sensory and motor disturbances in patients so that a physician may make an accurate diagnosis.

Treatment

Many treatment strategies for peripheral neuropathy are symptomatic. Some current research in animal models has shown that neurotrophin-3 can oppose the demyelination present in some peripheral neuropathies.

A range of drugs that act on the central nervous system such as drugs originally intended as antidepressants and antiepileptic drugs have been found to be useful in managing neuropathic pain. Commonly used treatments include using a tricyclic antidepressant (such as amitriptyline) and antiepileptic therapies such as gabapentin or sodium valproate. These have the advantage that besides being effective in many cases they are relatively low cost.

A great deal of research has been done between 2005 and 2010 which indicates that synthetic cannabinoids and inhaled cannabis are effective treatments for a range of neuropathic disorders. Research has demonstrated that the synthetic oral cannabinoid Nabilone is an effective adjunct treatment option for neuropathic conditions, especially for people who are resistant, intolerant, or allergic to common medications. Orally, opiate derivatives were found to be more effective than cannabis for most people. Smoked cannabis has been found to provide relief from HIV-associated sensory neuropathy. Smoked cannabis was also found to relieve neuropathy associated with CRPS type I, spinal cord injury, peripheral neuropathy, and nerve injury.

Pregabalin is an anticonvulsant drug used for neuropathic pain. It has also been found effective for generalized anxiety disorder. It was designed as a more potent successor to gabapentin but is significantly more expensive, especially now that the patent on gabapentin has expired and gabapentin is available as a generic drug. Pregabalin is marketed by Pfizer under the trade name Lyrica.

Duloxetine, a serotonin-norepinephrine reuptake inhibitor, is also being used to reduce neuropathic pain.TENS (Transcutaneous Electrical Nerve Stimulation) therapy may be effective and safe in the treatment of diabetic peripheral neuropathy. A recent review of three trials involving 78 patients found some improvement in pain scores after 4 and 6 but not 12 weeks of treatment, and an overall improvement in neuropathic symptoms at 12 weeks. symptoms, with 38% of patients in one trial becoming asymptomatic. The treatment remains effective even after prolonged use, but symptoms return to baseline within a month of treatment cessation.

Adopted from wikipedia.com