Neuropathy is a condition that generally describes any disturbance of the structure or function of nerves. Neuropathies are largely classified by the location and type of nerves that are affected, as well as by the underlying causes of the nerve damage. The most common type of neuropathy is peripheral neuropathy, which affects the nerves outside of the brain and spinal cord, but there are also cranial, autonomic, and focal neuropathies as well. Pain is the most common presenting symptom, but it is rarely present without other symptoms as well, including numbness, tingling, gait imbalance, and weakness.
Causes of Neuropathy
While the mechanisms that drive neuropathy are very complex, at a very high level the issue is that damaged or impaired nerves are not able to function properly, lowering their input to the central nervous system. This, in turn, causes a variety of issues with the nerves that can cause pain or paresthesia. Some of the most common causes of the nerve damage that drives neuropathy include:
- Diabetes – by far the most common cause of neuropathy, as over one-third of cases are tied to diabetes. Neuropathy is generally worse in people who have a difficult time controlling their diabetes, are overweight, or suffer from other comorbidities.
- Alcohol Use – the next most common cause of neuropathy. Alcohol use is thought to trigger neuropathy through the damage alcohol inflicts on the nerves themselves, as well as by the lifestyle habits that often accompany alcohol use, like vitamin deficiencies and poor diet.
- Medications – there are a variety of medications, most notably common cancer treatments like chemotherapy or radiation therapy, that can cause neuropathy. While these treatments play an absolutely vital role in the management of our most deadly diseases, their indiscriminate nature can inflict unintended damage to otherwise healthy anatomy, including nerves, and can lead to neuropathy and other conditions.
- Trauma – direct injury to nerves or nerve fibers, especially prolonged pressure on a bundle of nerves, can cause neuropathy. Ischemia, or reduced blood flow to nerves, can also cause neuropathy.
- Vitamin deficiency – nutritional deficiencies, specifically in the B vitamins and folate, can cause neuropathy by leading to damaged nerves.
- Autoimmune disease – certain autoimmune diseases like rheumatoid arthritis, lupus, and Guillain-Barre syndrome can cause neuropathies as they progress.
- Infection – serious infections, specifically HIV/AIDs, Lyme disease, leprosy, and syphilis, can cause nerve damage that culminates in neuropathy.
Symptoms of Neuropathy
Peripheral neuropathies typically present with a gradual sensory loss in what is known as a stocking and glove distribution, meaning they affect the toes and fingers first. This makes sense when one considers that the longest nerve fibers are the easiest to be injured or damaged. As neuropathy progresses, it begins to affect the next longest fibers, leading to numbness, tingling, and pain in the arms, shoulders, and, finally, the chest. If motor neurons are affected, neuropathy can lead to issues with movement, including walking, extremity weakness, and loss of muscle tone and dexterity.
The loss of sensory input can lead to the development of blisters or sores on the feet and hands, particularly in patients with diabetic neuropathy. In severe cases, these sores can deepen and lead to amputation if left untreated.
The single most important test when diagnosing neuropathy is a comprehensive physical examination, as this will allow the practitioner to fully gauge the extent of the nerve damage. This exam should include a full neurological workup, to include testing of the reflexes and functioning of peripheral nerves.
In addition to the physical exam, your provider may order additional tests, including but not limited to blood work, x-rays, CT scans, MRI scans, EMG/nerve conduction velocity tests, and nerve biopsies. They will then take all of the data points gleaned from these tests and synthesize them with the results of their physical examination to arrive at a cause for your neuropathy.
The treatment for neuropathy will vary based on the extent of the condition and the underlying causes of the nerve damage. In general, treatment will focus on managing the symptoms of neuropathy–the pain, numbness, and tingling–while working to address the underlying causes of the nerve damage. In some cases, treatment of the underlying causes–be it diabetes, medication/treatments, or autoimmune disorders–can greatly reduce the symptoms of neuropathy. However, other cases may require more intense interventions to attack the symptoms, including medication, minimally-invasive interventions, or surgery.