Diabetic Neuropathy: Classification, Types, Causes, Risk Factors, Signs, Symptoms, Treatment

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.

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.

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 to 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.

1. 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.
2. 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.
3. 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.
4. 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.

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.

• Cranial nerves or nerves in the skull.
• Nerves from the spinal column and their branches.

Nerves that help the body to manage vital organs such as the heart, stomach, bladder and intestines as in autonomic neuropathy.

Symptoms often develop slowly over a period of several years. Symptoms vary depending on the nerves affected.

• 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.

• Bloating, Heartburn, Swallowing problems, Nausea, Vomiting, Diarrhea, Constipation, Feeling full after small meals.

• 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.

• Unable to completely empty the bladder.
• Bloating.
• Leakage of urine or incontinence.
• Increased urination at night.

• 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.

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.

• 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.

• Consuming smaller meals.
• Medication.

• Avoiding standing up too quickly.
• Medications.
• Wearing special stockings.

• Counseling.
• Vacuum erection device.
• Penile implant.
• Penile injections.
• Medication.

• Counseling.
• Lubricants.
• Vaginal estrogen creams, suppositories, and rings.

• Medication.
• Self-catheterization or inserting a catheter into the bladder to release urine.
• Surgery as a last resort.

• Antidepressants such as doxepin, amitriptyline, or duloxetine.
• Antiepileptic drugs such as carbamazepine, valproate, gabapentin, and pregabalin.
• Pain medicines.

• Medicines to help food move more quickly through the stomach and intestines.
• Sleeping with the head elevated.
• Consuming smaller meals at more frequent intervals.

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.

• Nerve conduction studies.
• Electromyography.
• Ultrasound.

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