Neuropathy

Neuropathy (Dutch: neuropatie) is damage to one or more peripheral nerves, leading to dysfunction in the parts of the body those nerves innervate. This damage can be caused by traumatic injuries, infections, metabolic problems, exposure to poisons, and autoimmune diseases. Diabetes mellitus is a common cause of peripheral neuropathy, as are several medications. Peripheral neuropathy produces various symptoms depending on which types of nerves are affected. Symptoms range from numbness and tingling sensations in the extremities to pain, paralysis, and organ dysfunction.

Symptoms

The symptoms of peripheral neuropathy depend on which nerves are damaged. Common symptoms include:

• Numbness, prickling, or tingling in the hands and feet
• Sharp pains or cramps
• Increased sensitivity to touch
• Loss of reflexes
• Muscle weakness and atrophy
• Paralysis if motor nerves are affected
• Organ dysfunction such as constipation, urinary retention, or erectile dysfunction

Peripheral neuropathy affecting the sensory nerves (sensory neuropathy) often first presents with symptoms of numbness or tingling in the toes or fingers, which then spread gradually towards the center of the body. As the disease progresses, sufferers may experience pain, usually described as burning, throbbing, shooting, or electrical in nature. In advanced stages, they may also develop muscle weakness, loss of reflexes, and other neurological symptoms such as difficulty walking or coordinating movements. Motor neuropathy (neuralgic amyotrophy) can present with sudden and severe pain followed by progressive muscle weakness and atrophy. Autonomic neuropathy affects the nerves that control involuntary functions such as digestion, blood pressure regulation, and sweating. Symptoms can include constipation, urinary retention, erectile dysfunction, and orthostatic hypotension (dizziness upon standing).

Types

There are several types of peripheral neuropathy based on the nerves affected and the causes. The most common forms include:

1. Diabetic neuropathy: This type of neuropathy is commonly associated with diabetes mellitus and is one of the complications of long-standing diabetes. It can affect any nerve in the body but most commonly affects the peripheral nerves leading to symptoms such as numbness, tingling, burning pain, and muscle weakness in the feet and legs.
2. Peripheral neuropathy due to nutritional deficiencies: Vitamin B12, thiamine (Vitamin B1), niacin (Vitamin B3), vitamin E, and other nutritional deficiencies can lead to peripheral neuropathy. Alcoholism is a common cause of nutritional neuropathy due to malnutrition.
3. Toxic neuropathy: Exposure to certain toxins such as heavy metals (lead, mercury), industrial chemicals (organophosphates), chemotherapeutic drugs (vincristine), and alcohol can cause peripheral neuropathy.
4. Inflammatory neuropathy: This type of neuropathy is caused by inflammation of the nerve tissue due to autoimmune disorders such as rheumatoid arthritis, lupus erythematosus, Sjögren's syndrome, Guillain-Barré syndrome, and Chronic inflammatory demyelinating polyneuropathy (CIDP). Inflammatory neuropathies can present with a variety of symptoms including numbness, tingling, muscle weakness, pain, and autonomic dysfunction.
5. Metabolic disorders: Certain genetic conditions such as porphyria can lead to neuropathy due to abnormalities in enzyme function and metabolism. Hemochromatosis and Wilson's disease can also cause neuropathy due to iron overload or copper deficiency.
6. Hereditary neuropathies: Some forms of peripheral neuropathy are inherited genetically and are called hereditary neuropathies. Examples include Charcot-Marie-Tooth disease and Friedreich's ataxia. These disorders are characterized by progressive muscle wasting, weakness, and numbness in the arms and legs.
7. Compressive neuropathies: Compression or trauma to a nerve can lead to localized neuropathy such as carpal tunnel syndrome or sciatica. Repetitive motion injuries such as tendonitis can also result in nerve compression and subsequent neuropathy.
8. Idiopathic neuropathies: In some cases, the cause of peripheral neuropathy remains unknown despite a thorough evaluation. These cases are referred to as idiopathic neuropathies.
9. Proximal diabetic neuropathy: Also known as diabetic amyotrophy or proximal neurolysis with mononeuritis multiplex, this condition affects the proximal muscles of the limbs resulting in progressive thigh muscle wasting (proximal weakness), weight loss and abdominal pain. This type of diabetic neuropathy tends to occur more frequently in type 2 diabetes mellitus patients over the age of 40 years old.
10. Peripheral neuropathic pain in feet: This type of neuropathic pain can be caused by several factors including diabetes mellitus, chemotherapy agents such as vincristine or paclitaxel, Lyme disease, HIV infection, alcoholism and other conditions that damage the peripheral nerves supplying sensation to the feet. Symptoms can include burning pain, tingling sensations, sensitivity to touch and even extreme sensitivity to temperature changes. Treatment options for this condition include pain medications such as gabapentin or pregabalin, antidepressants such as tricyclic antidepressants or serotonin-norepinephrine reuptake inhibitors (SNRIs), topical creams containing lidocaine or capsaicin, physical therapy and nerve block injections. Lifestyle modifications such as quitting smoking, controlling blood sugar levels in diabetes mellitus patients and limiting alcohol consumption can also help alleviate symptoms of peripheral neuropathic pain in feet.

Diagnosis

A diagnosis of peripheral neuropathy is typically based on the patient's medical history and physical examination findings such as numbness, tingling sensations, muscle weakness and reflex changes. Various tests can be used to confirm the diagnosis and determine the underlying cause including:

1. Electromyography (EMG): This test measures electrical activity in the muscles during rest and contraction. It can help identify denervation (loss of innervation) and establish whether motor nerves are affected. EMG is particularly useful for distinguishing between peripheral neuropathies and other conditions that mimic nerve damage such as myopathies and radiculopathies.
2. Nerve conduction studies (NCS): NCS measure the speed at which electrical signals travel through nerves. Abnormal results suggest that there is damage or slowing of conduction in a particular nerve. NCS are often performed along with EMG when evaluating for peripheral neuropathy.
3. Blood tests: Blood tests can help identify potential causes of peripheral neuropathy such as vitamin deficiencies, diabetes mellitus, thyroid disease or kidney disease. Additionally, blood tests can help screen for infectious causes of peripheral neuropathy such as Lyme disease or HIV infection. Genetic testing may also be useful in identifying hereditary forms of peripheral neuropathy.
4. Imaging studies: Imaging studies such as MRI or CT scans may be ordered if there is suspicion for an underlying compressive lesion causing peripheral neuropathy such as a tumor or herniated disc. Imaging studies are also useful for evaluating for other conditions that can mimic peripheral neuropathy such as multiple sclerosis or spinal cord lesions.
5. Autonomic function testing: Autonomic function tests can help evaluate for autonomic dysfunction associated with peripheral neuropathies such as cardiovascular instability, gastrointestinal motility disorders or sexual dysfunction. Autonomic function tests may include heart rate variability studies, sweat tests or tilt table testing.

Treatment

Treatment for peripheral neuropathy depends on the underlying cause and severity of symptoms. The goal of treatment is to manage symptoms and prevent further nerve damage if possible. Treatment options may include:

1. Medications: Pain medications such as opioids or non-opioid analgesics may be prescribed for managing painful symptoms associated with peripher