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Mosby's dictionary defines neuropathy as inflammation or degeneration of the peripheral nerves.1 Degeneration obviously refers to the gradual deterioration of normal cells and function.
Focal Neuropathy (Mononeuropathy) is a single nerve lesion; however it may develop into multiple nerve lesions afterwards, most commonly caused by entrapment. Mononeuropathies are severe and have a rapid onset.2
Multifocal Neuropathy (Mononeuritis multiplex) multiple nerve root, peripheral or cranial nerve lesions occur, they can occur either serially or concurrently. The pathology is caused by either the involvement of the vasa nervorum or to malignant infiltration of the nerves.2
Generalised neuropathy (Polyneuropathy) occurs in the longest peripheral nerves first, therefore affecting the distal lower limbs first before the upper limbs.2
Chronic Polyneuropathy evolves over months or years and is the most common form of neuropathy.2
Diabetic Neuropathy is a noninflammatory disease process that can occur with diabetes mellitus, and it is characterized by motor and/or sensory disturbances in the peripheral nervous system. Diabetes is associated with many types of neuropathy.1
Other neuropathies also exist such as Guillain-Barre Syndrome and Chronic demyelinating Polyneuropathy etc.
HOW NERVE CONDUCTION IS AFFECTED BY NEUROPATHY
Nerve conduction in Neuropathy is affected in two main ways and therefore has different results on conduction speeds. They are then categorized as axonal neuropathies and demylinating neuropathies3.
In this form nerve conduction is slowed down but more mildly than demylinating neuropathy4. This is due to the loss of large nerve fibres in the affected areas and small ones remaining behind. This loss of fibres also makes the nerve smaller further aiding in loss of conduction speeds4. In axonal neuropathy the amplitude of action potentials/hyperpolarization is decreased this leads to a reduction in threshold level4. This should ideally be a compensatory mechanism, as conduction speeds will increase. Due to axonal fibres being broken down and not regenerating they over power this process and thus conduction speeds decrease4.
This is further subdivided into uniform demylination (this indicates its hereditary) and segmental demylination (this indicates its acquired) 3. It is basically in a nutshell the break down of myelin sheaths surrounding the axon or the disturbance of Schwann cells to produce or maintain these sheaths. The decrease in myelin sheath around the axon decreases the propagation speeds of action potentials5. This is due to the action potential being unable to "hop" from node to node in its usual way, which generally increases the speed of the action potential (this is called salutatory propagation5). In demylinating neuropathies it now works by the same form in some segments as an unmylinated axon (continuous propagation5), which slows down the speed of the action potential as it has to "pass" through each adjacent segment that isn't mylinated and cant hop to a node.
In most neuropathies seen however normally there is both axonal and demylinating neuropathies present5.
SYMPTOMS OF NEUROPATHY
Symptoms in Diabetes6-10
Ø Bilateral small fibre neuropathy
Ø Hyperalgesias(Described as a burning pain by the patients)6-10
Ø Have normal reflexes but lowered sensory levels.
Neuropathy can effect various organs and present with different symptoms associated with those organs or systems for e.g. the intestinal tract can be effected and cause diarrhea6. The list below is just general symptoms not specific organs or systems.
Ø Starts with the peripheral nerves
Ø Follows a characteristic coarse
Ø Slow nerve conduction(tested at peronel nerve)
Ø Then you start getting "restless leg syndrome"
Consisits of :
Ø Perculiar feeling in leg relieved by walking
Ø Then secondary symptoms occur
Ø Paresthesias in first the toes, foot then in leg
Ø Then fingers and toes
Ø It then affects the motor nerves and you get foot drop
Ø Paraplegia then occurs due to the loss of myelin
Ø Most of these symptoms are found with chronic renal failure.
CAUSES OF NEUROPATHY (RISK FACTORS)
Neuropathy can be inherited or acquired6. There is a vast array of causes or potential causes of neuropathy. There also seems to be a variety of subclasses that are derived from the various causes or types of nerve fibers involved.
Ø Trauma/physical injury6-10
Ø Diabetes is a big cause of neuropathy (mainly peripheral neuropathy). It can come about with both type 1 and type 2 diabetes. The risk for peripheral neuropathy increases if a person has a constant elevated blood sugar level that is uncontrolled (This is due to glucose affecting certain pathways e.g. glycolitic pathway as well as the polyol pathway) 6-10.
Ø Lyme disease (tick bites) 6,9
Ø HIV 6,7,9
Ø Alcoholism 6,7,9
Ø Certain cancers 6-10
Ø Cancer medications or treatment (such as medications containing Platinum compounds, Taxanes, Vinca alkaloids, Thalidomide, Velcade, Cytosine arabinoside, Misonidazole, Interferon.) 7,10
Ø Inherited neuropathy 9
Ø Family history 9
Ø Vasculitis 9 (inflammation within vascular system).
Ø Guillain-Barre syndrome 8,9 the bodies' own immune system attacks the peripheral nervous system.
Ø Various genetic disorders.8,9
Ø Circulatory problems 6-10
Ø Hypothyroidism and other hormone imbalances 6-10
Ø Hepatitis B 9
Ø Leprosy 7,9
Ø Vitamin deficiency (E, B1, B6, B12, and niacin).6
Ø Renal and/or liver failure 6,9
Ø Toxins 6-10
Ø Certain diseases 6-10
The treatment and diagnoses of neuropathy is dependent on the underlying causes, and if done in a timely manner permanent nerve damage can be prevented.11 Examples are that of diabetes and the control thereof can reduce diabetic neuropathy, another is renal dialysis in a chronic renal failure patient.11
Treatment options in reducing pain may vary from medication, injection therapy, and physical therapy. In some cases surgery needs to be performed like in that of carpal tunnel syndrome
Analgesic medication (aspirin, panado, ect) doesn't work in reducing pain in neuropathy and therefore treatment often involves medication that target nerve cells.11
Medications that are sometimes used are anticonvulsants, anti-depressants, local anesthetics, and anti-arrythmatics. With focal neuropathy a tropical cream with capsaicin is generally used.11
This involves the injection of a nerve block (e.g., lidocaine) into the area that surrounds the affected nerves and thus preventing the nerve from sending an impulse to the brain and so temporarily reducing symptoms. It is often used with other treatments like medications.11
If a neuropathy is caused by toxins or medication the discontinue thereof would be the first order of treatment. Vitamin supplements are used to treat nutritional neuropathy.
These can be from exercise to messages and also common is acupuncture to treat the symptoms. There are support groups that help the patient to regain a social and psychological wellness.
Prognosis depends on several factors like early diagnosis
Conditions like idiopathic neuropathy new research has been done on anodyne therapy, which entails electrowaves and infrared lights and is proving to be successful for all neuropathies, although this is still being researched.12