Diabetic neuropathy is the term that refers to damage of the sensory nerves that affect the sensation of the body. This is a common complication of diabetes. Diabetes can damage the nerves in a number of ways, but all the problems are basically related to blood sugar being too high for prolonged period of time.
Diabetic neuropathy or nerve damage caused by diabetes can be painful, but the pain is not severe in most of the cases.
Pathophysiology of Diabetic Neuropathy
Research indicates that both metabolic and vascular factors are involved in pathogenesis of diabetic neuropathy. Animal and in-vitro experiments link enzymatic and non-enzymatic pathways in glucose metabolism to initiation as well as progression of diabetic neuropathy. These include:
- Imbalance of Redox due to increased aldose reductase activity.
- Increased oxidative and nitrosative stress.
- Impairment of Protein Kinase-C activity.
- Non-enzymatic glycation of structural nerve proteins.
- Impaired synthesis of nitric oxide as well as endothelial dysfunction.
- Alteration in cyclo-oxygenase activity and subsequent perturbation in prostaglandin metabolism.
- Poly (ADP-ribose) polymerase (PARP) activation.
- Deficiency of neurotrophic support of neuron and deficiency of C-peptide.
- Alteration in mitogen activated Protein Kinase and NF-kB signaling pathways.
- Oxidised LDL cholesterol-mediated injury.
This metabolic and vascular disruption impedes mitochondrial function and neurotrophic support to nerve tissue, and mediates injury to neurons and Schwann cells resulting in progressive injury and loss of peripheral nerve fibers and impairment of sensory functions.
Epidemiology of Diabetic Neuropathy
Diabetes is known to be the leading cause of neuropathy in developed countries, and neuropathy is the most common complication and greatest source of morbidity and mortality in diabetics. Prevalence of neuropathy is estimated to be approximately 20% in diabetic patients. Diabetic neuropathy is implicated in 50–75% of nontraumatic amputations.
Hyperglycemia is the main risk factor for diabetic neuropathy. According to Diabetes Control and Complications Trial study, the annual incidence of neuropathy is 2% per year, but dropped to 0.56% with intensive treatment of Type 1 diabetes. The progression of neuropathy is depends on the degree of glycemic control both in Type 1 and Type 2 diabetes. Age, duration of diabetes, hypertension, cigarette smoking, height and hyperlipidemia are also risk factors for diabetic neuropathy.
There may be more than 3 million people with painful diabetic neuropathy in United States. 20-30% of type 2 diabetics develop neuropathy. Type 1 diabetics usually develop neuropathy after more than 10 years of getting affected with diabetes.
Classification and Types of Diabetic Neuropathy
Diabetic Neuropathy Can Be Classified Mainly Into Four Types :
- Diabetic Peripheral Neuropathy: Legs and feet are the most commonly affected areas of body. Nerve damage in the feet can result in loss of sensation in feet thereby increasing risk of foot issues such that any injury and sore in the feet can go unrecognized due to loss of sensation. Therefore, appropriate skin and foot care needs to be practiced. Other areas of body like arms, back, abdomen can also get affected but this happens in rarity.
- Diabetic Autonomic Neuropathy: This mostly affects digestive system, specially the stomach, urinary system, blood vessels, and reproductive organs. Continuous check on blood sugars and keeping them well controlled can help prevent autonomic neuropathy.
- Diabetic Proximal Neuropathy: This causes pain in hips or thighs. It may also result in weakness of legs. Pain is generally on one side of body. Treatment of pain and weakness includes medication as well as physical therapy. Recuperation depends on type of nerve damage. Keeping blood sugars under tight control is the best way to avoid this ailment.
- Diabetic Focal Neuropathy: This can appear out of the blue and affect specific nerves, most often head, torso, and leg resulting in muscle weakness and pain. This disease is unpredictable; however, it generally improves on its own within weeks or months and does not cause any long term damage.
Diabetes also can lead to other nerve related problems like nerve compression or entrapment neuropathy. Carpal tunnel syndrome is one of the most common type of nerve compression which causes numbness and tingling in the wrist sometimes resulting in muscle weakness or pain.
Tight control of blood sugars helps prevent almost all of diabetes related problems.
Causes and Risk Factors of Diabetic Neuropathy
Nerve injuries are caused due to high blood sugar levels and decreased blood flow, the more likely cause being poor control of blood sugar levels. About half the people with diabetes develop nerve damage. Most of the times symptoms do not begin until 10 to 20 years of diabetes being diagnosed.
Nerve Injuries May Affect:
- Cranial nerves or nerves in the skull.
- Nerves from the spinal column and their branches.
Signs and Symptoms of Diabetic Neuropathy
Symptoms often develop slowly over a period of several years. Symptoms vary depending on the nerves affected.
Symptoms Of Diabetic Peripheral Neuropathy May Include :
- Numbness, Tingling, Burning (especially in the evening), Pain.
- Early symptoms of diabetic peripheral neuropathy in most of the cases will decrease when blood sugar is under good control. Medications can be taken to help control the discomfort if needed.
Diabetic Autonomic Neuropathy Of The Digestive System May Result In Following Symptoms :
- Bloating, Heartburn, Swallowing problems, Nausea, Vomiting, Diarrhea, Constipation, Feeling full after small meals.
Diabetic Autonomic Neuropathy Of The Blood Vessels May Lead To :
- Blacking out when standing, Increased heart rate, Low blood pressure, Light-headedness, Dizziness, Nausea, Vomiting, Early fullness.
- Autonomic neuropathy symptoms of male sex organs may include erectile dysfunction or being unable to have or maintain an erection and dry or reduced ejaculations. Symptoms of the female sex organs may include decrease in vaginal lubrication and lack or decrease in the number of orgasms.
Following Are The Common Symptoms With Regard To Urinary System :
- Unable to completely empty the bladder.
- Leakage of urine or incontinence.
- Increased urination at night.
Focal Neuropathy Symptoms May Include The Following :
- Eye pain.
- Double vision.
- Paralysis on one side of the face, also known as Bell's palsy.
- Severe pain in certain areas such as lower back or legs.
- Chest or abdominal pain that can sometimes be confused with another condition such as heart attack or appendicitis.
Treatment for Diabetic Neuropathy
The key factor in preventing diabetic neuropathy is to keep the blood sugar levels under tight control in a healthy range following the basic steps for management of diabetes, avoiding its complications, and staying as healthy as possible. Diet, exercise, and sometimes medicines are the mainstay of treatment.
Complications Of Peripheral Neuropathy Can Be Prevented By :
- Examining the feet and legs daily.
- Applying lotion if the feet are dry.
- Caring for the nails regularly.
- Wearing properly fitting footwear and wearing them constantly to prevent foot injury.
Autonomic Neuropathy Treatment Of The Digestive System May Include :
- Consuming smaller meals.
Autonomic Neuropathy Of The Blood Vessels May Be Treated By :
- Avoiding standing up too quickly.
- Wearing special stockings.
Autonomic Neuropathy Of The Male Sex Organs Can Be Treated By :
- Vacuum erection device.
- Penile implant.
- Penile injections.
Autonomic Neuropathy Of The Female Sex Organs Can Be Treated By :
- Vaginal estrogen creams, suppositories, and rings.
Autonomic Neuropathy Of The Urinary System May Be Treated By :
- Self-catheterization or inserting a catheter into the bladder to release urine.
- Surgery as a last resort.
The Following Medications May Be Used To Reduce Symptoms In The Feet, Legs, And Arms :
- Antidepressants such as doxepin, amitriptyline, or duloxetine.
- Antiepileptic drugs such as carbamazepine, valproate, gabapentin, and pregabalin.
- Pain medicines.
Treatments For Nausea And Vomiting May Include :
- Medicines to help food move more quickly through the stomach and intestines.
- Sleeping with the head elevated.
- Consuming smaller meals at more frequent intervals.
Investigations for Diabetic Neuropathy
Diabetic Neuropathy can be diagnosed on the basis of symptoms and physical exam.
Comprehensive foot exam needs to be done each year to check for peripheral neuropathy. Individuals diagnosed with peripheral neuropathy need more frequent foot exams.
Protective sensation or feeling in the feet is assessed by touching the foot with a nylon monofilament-similar to a bristle on a hairbrush attached to a wand or by pricking the foot with a pain.
Other Tests That Are Rarely Needed May Include :
- Nerve conduction studies.