What is neuropathy?

Neuropathy means a physical problem with nerve(s) of the body. It is not about the emotional sense of “nerves” we use in conversation. Physical nerves are like electric wires in our body (in comparison to the arteries and veins). So the problem with nerves is with the electrical system of the body, not with its plumbing.

What is the function of a nerve in the body?

Like wiring in a circuit, the main function of a nerve is to transmit a signal, both electrical and chemical types. For example the sensory nerves in our foot transmit signals up to the brain for us to know something may be touching it. The signal from brain travels through motor nerves towards the muscles controlling the foot, so that we can pull it away from any harm.

What are different types of nerves?

Nerves can be divided mainly in two ways: a. based upon their size, and b. based upon their function. Based upon size, nerves can be divided into large size, intermediate size, and small size or small fiber type. Based upon their function, they are divided into motor, sensory, and autonomic types.

What are the symptoms of neuropathy?

Symptoms depend upon which nerve is affected. In most cases, both motor and sensory nerves are affected, but sometimes it is of either of one type. It also depends if one or a few nerves are involved or almost every nerve is involved.

Problem with sensory part of the nerve or the sensory nerve can cause numbness (loss of sensation), abnormal sensations (tingling, burning, aching, itching, cold or hot feeling, sensitivity to touch, and many other abnormal feelings), unsteadiness and dizziness. Problem with a motor nerve can cause weakness and loss of function. Problem with autonomic nerves depends upon the location of the affected nerves.

What is peripheral neuropathy?

The word peripheral here means away from the brain and the spinal cord. Nerves originate from the brain or the spinal cord and spread to every part of the body. The term peripheral neuropathy is used when the nerves that are farther away are affected, in comparison to a problem in the brain or the spinal cord.

If a diffuse process like diabetes or alcohol drinking affects them they get affected based upon their length; the longer ones first. This is the reason that usual initial symptoms of peripheral neuropathy start in toes and feet. Also it is not just one or two nerves that get affected, the diffuse process may affect all nerves. This is in comparison to a nerve problem caused by a local process like an injury in the wrist, which can selectively affect a single nerve causing Carpal tunnel syndrome. To differentiate between the two, neurologists sometimes use the term entrapment for this focal type of neuropathy.

What are different types of peripheral neuropathy?

To understand this, a general understanding of the structure of a nerve is helpful. Every nerve is in fact a cell, some very small in width and breadth, and can only be seen by a microscope. Though extremely thin, the nerve fiber that goes to our feet can be more than a meter long. The body of the nerve going to our feet resides up in the back while the nerve itself is an extension of the body, like a very long arm. It is called an axon. This is similar to the metallic inside of an electric wire. Myelin, a fatty type material similar to the plastic of common electric wires, covers axons. Electrical signal travels in the axon protected by the myelin around it. Following is how neuropathy types are usually described:

A: Based upon the part of nerve(s) affected: Neuropathy that selectively affects axons is called axonal neuropathy. In a different type of neuropathy it is myelin that is selectively affected, and it is called demyelinating neuropathy. The third variety is the mixture of the two, called axonal and demyelinating type.

B: Based upon type of nerves affected: In most cases of peripheral neuropathy both sensory and motor nerves are involved, and it is called sensory and motor neuropathy Sometimes it is only motor and at times only sensory type. Similarly, another type of neuropathy affects autonomic nerves and is called autonomic neuropathy.

C: Based upon size of nerves affected: Nerves can be divided into large, intermediate, and small fiber type. Most neuropathies involve all three types of nerves but sometimes there is selective involvement, e.g., small fiber neuropathy.

What causes peripheral neuropathy?

Most common cause of peripheral neuropathy in USA is diabetes. Diabetes causes multiple types of neuropathy. Other common causes are alcohol drinking, chemotherapy, kidney failure, immune system diseases, infections (like Lyme or HIV), severe prolonged illness (like COMA), genetic conditions, and mechanical reasons (like in Carpal tunnel syndrome). In day-to-day practice, a precise cause is difficult to determine or not found in almost 1/3rd of cases. This number may vary with better results in a neurology clinic specializing in nerve and muscle disorders.

How peripheral neuropathy is diagnosed?

Neuropathy presents with a particular set of symptoms such as numbness, tingling, burning, sensitivity, unsteadiness or weakness. With that kind of complaints, examination is done to assess strength, sensations, and reflexes. If they are abnormal, a diagnosis of neuropathy is made. To confirm the diagnosis, and especially to find more details about its type and severity, a test called EMG (electromyogram) and NCS (nerve conduction study) is done. Rarely, a biopsy of a nerve or skin is helpful.

What is EMG (electromyogram) and Nerve conduction study (NCS)?

Nerves are like electric wires and to check their integrity certain techniques are used that are similar to an electrician checking a home’s electrical system. Electrodes are put on two locations of a nerve and minor amount of electric current is sent from one side to the other. A computer helps to find the time it takes for electricity to travel and this is compared to normal standards for patient’s age. This part of the test is called nerve conduction study (NCS). But not all nerves are accessible to put electrodes on them, like the nerves in the neck and the back. They are tested in an indirect manner, though the principle is still the same. A contraption that looks like a needle, but in fact is a needle in a needle, is used. This has both electrodes close to each other in the shape of a needle. This double-electrode needle is inserted in the muscle supplied by a particular nerve. It can detect minor electrical changes in a muscle and provides information about its health and nerve supply. This electrical activity and the noise it makes are compared to the normal patterns to determine integrity of the muscle and the nerve. This part is called EMG or electromyogram. EMG is helpful in diagnosing both nerve and muscle diseases.

EMG and nerve conduction studies are complimentary to each other and are done together. The test is somewhat un-comfortable (for some, it is painful), though most people tolerate it without any significant issue. Generally speaking, there is no particular side effect of the test other than discomfort, or minor bruises where the needle goes in. Having a pacemaker, an electrical stimulator, or similar equipment in the body does not affect the test, or the equipment. No anesthesia is used for the test. It can be done in a patient taking blood thinners.

EMG and nerve conduction study is a sensitive test, but its findings shall be carefully interpreted based upon patient’s complaints and the finding on examination. Many times there are findings that are not significant to take any action, or are not related to patient’s complaint or problem. Another caveat is that this type of test is different than having an X-ray or CT scan, which take pictures, and having the pictures taken at different places may not change the data collected. A physician does EMG/Nerve conduction study with help from a technologist, and its technique may differ in different places. One lab’s data may not exactly be the same as the other one. But, if done right, the findings should not differ between different laboratories.

Electrical test, or EMG/nerve conduction study, can help to figure out the type of neuropathy and its extent. Figuring out the type of neuropathy help physicians narrow down its possible cause, and further tests are done for confirmation.

How is the cause of neuropathy found?

Different conditions cause different types and pattern of neuropathy. At the end, after getting appropriate data, a process of pattern recognition is used to reach a conclusion. After taking history and performing examination, tests are ordered based upon possible causes. It may include EMG and nerve conduction study, blood tests, spinal fluid analysis, and rarely a nerve or skin biopsy.

How is peripheral neuropathy treated?

Treatment of peripheral neuropathy depends upon its type and the cause. Many neuropathies do not have any specific treatment at this time, other than treating the underlying disease and its symptoms. Some neuropathies are treatable and usually, if left untreated, they are the ones that can make patients much worse. For example, a common neuropathy Carpal tunnel syndrome is treated differently than neuropathy caused by Lyme disease.

What is Guillain-Barre Syndrome?

The new and better term for this condition is AIDP or Acute Inflammatory Demyelinating Polyneuropathy. This is a type of neuropathy occurring after an infection, and caused by a defect of immune system. General understanding is that it is triggered by an abnormal immune response to a common viral infection. Once infected, immune system triggers certain antibody formation, which starts attacking body’s own myelin, the protective coating around the nerve. Once reaching a critical state, it can progress rather quickly and may involve the whole body. Typically, after a few weeks of an infection, patient notices tingling and numbness in feet and legs followed by worsening weakness and unsteadiness. In severe cases, it can affect nerves controlling muscles for breathing, swallowing, or eye control.

Diagnosis of AIDP is made with appropriate history, findings on examination, and sometimes further testing including spinal fluid analysis, and EMG and nerve conduction studies. Many patients may recover without specific treatment, but many others require admission to an ICU and a breathing tube for a few days. It is treated either by a blood product called IV Ig, or by a procedure called plasmapheresis.

What is CIDP?

Compared to AIDP above, it is Chronic Inflammatory Demyelinating Polyneuropathy. It is when AIDP does not completely go away, or seem to come back with worsening symptoms. It is diagnosed using similar approach and similar tests, though its diagnosis is somewhat trickier than AIDP. Its treatment is also on similar lines with added oral medicines like prednisone.

What is nerve pain or neuropathic pain?

Pain caused by injury to nervous system, a nerve, brain or spinal cord, is called neuropathic pain. This pain is different from more common pain from injury to other tissues like joints. Unlike usual pain from trauma or inflammation, e.g., leg pain after a fracture, when the problem is exactly where the pain is, neuropathic pain may not be at the site of problem. A pinched nerve in the back may cause neuropathic pain in the leg and the foot, which is far away from the site of the problem. It also seems not to respond to regular painkillers, which mostly are anti-inflammatory drugs. It can become chronic problem requiring long-term use of medicines. It is also a difficult pain to treat, and a source of frustration for patients and their physicians.

Neuropathic pain is a common symptom of peripheral neuropathy. In this condition, patients typically complain of an uncomfortable numbness, burning, shooting, knife-like, or aching pain. It seems to occur or felt more at rest, at the end of the day or during sleep. It is felt more with stress, anxiety or depression, change in barometric pressure, or with lack of sleep. It can just be a mild numbness not requiring any treatment or it can be severe debilitating pain syndrome not responsive to available medications.

How is pain caused by neuropathy treated?

Regular pain medicines or anti-inflammatory drugs seem not to work for neuropathic pain. Many medicines that are used for epilepsy have better effect, but complete pain control for neuropathic pain is rare. Patient needs proper education about what may be treatable and what may not be, and what may be the response of taking medicines. There is always a psychological side to pain management, with pain felt more or difficult to control with stress, anxiety and depression. Psychological issues may be the result of lack of pain control, or the ones making pain worse. In either case, it becomes a vicious cycle, one feeding into the other. Better pain management requires addressing both physical and psychological sides of patient’s problems.

Patients may try local creams or lotions, some prescription creams, or gel-patches with local anesthesia. All these measures only help for a short period of time, if they ever work, and are not practical for long-term pain control.

Many medicines that are used for epilepsy are helpful in controlling neuropathic pain. Common examples of such medicines are carbamazepine, gabapentin, or pregabilin. Some antidepressants may also help, like amitryptiline, nortryptiline, venlafaxine, and duloxetine. Many patients benefit from a combination of such medicines. Generally speaking, it is recommended to avoid medicines during daytime, when pain may not be that severe, and take medicine in the evening or before going to bed. Alternatively, sedating medicines should be taken at night and non-sedating during daytime.

Do medicines like gabapentin fix neuropathy?

Gabapentin or any other medicine used for pain control in peripheral neuropathy does not alter the nature of neuropathy. It does not stop, improve or resolve neuropathy. If pain is not interfering with day-to-day life, it is better to avoid taking such medicines. If taking such medicines, it is best to avoid taking them during daytime to avoid side effects. In most patients, there is more pain in the evening or at night when a medicine can be used. For reasons not completely understood, patients do not have same level of pain during daytime.

What are long-term complications of peripheral neuropathy?

Other than pain, neuropathy may cause permanent numbness, weakness, and loss of function; sometimes so severe that patient may not be able to walk or take care of day-to-day chores. This is the reason that tests are done to find any treatable cause of neuropathy to avoid disability.

What is autonomic neuropathy?

Our nervous system influences every part of our body. Some of it is in our voluntary control, but a large part is not. Nerves wrap around blood vessels in almost every part of our body but we have no control on them. All body organs from head to the toe have nerves but they are also not in our control. This part of the nervous system is called autonomic nervous system. It controls our ability to swallow, digest, clean, urinate, defecate, and maintain functions of organs like heart, lungs, eyes and ears. The circuitry for the autonomic system is running parallel to the system in our control.

What are the symptoms of autonomic neuropathy?

Autonomic is the part of nervous system that manages body functions not directly in our control. It works in the background to keep our heart beating, and other body organs functioning normally. It also maintains appropriate stiffness of blood vessels. Symptoms of autonomic neuropathy depend upon the specific organ affected. If it is heart, it can go into abnormal rhythm. If it is gut, it may not move and digest well; if it is the bladder, urination can be too frequent or not happen at all; and if it is genital organs, erection may not happen. From maintaining the size of our pupils to sweating of our feet, autonomic nervous system is continuously working, even during sleep. A common symptom of autonomic dysfunction is dizziness because of loss of muscle tone in blood vessels. Change in position from sitting to standing may lead to lightheadedness due to low blood flow to the brain.

What are common causes of autonomic neuropathy?

Diabetes mellitus is likely the most common cause, especially when not well controlled. Other causes included alcohol, an infection like HIV disease, kidney failure, amyloidosis, immune system dysfunction, exposure to certain types of chemotherapy, genetic causes, and in a significant number of patients where a cause may not be found.

How is autonomic neuropathy treated?

This depends upon the cause and the organ involved. Some causes are treatable but many are not, and the patient is left with permanent issue to manage. Dizziness due to low blood pressure is treated with medicines that can elevate the blood pressure. If heart is too slow, a pacemaker is inserted. If bladder malfunctions, certain medicines are used to help it out, and in case of erectile difficulties, some medicines or procedure are helpful.

What is small fiber neuropathy?

Nerves that start from the brain or the spinal cord travel to every area of the body. As they reach their destination, they give out smaller branches called dendrites. At these level nerves are very small and can only be seen or visualized with a microscope. Some conditions selectively affect these small nerves while the main part of the nerve remains intact, which is called small fiber neuropathy.

What are symptoms of small fiber neuropathy?

Typical symptoms of small fiber neuropathy are numbness, burning, tingling, aching, and many other abnormal sensations, but not weakness. It may cause unsteadiness due to loss of sensations.

How is small fiber neuropathy diagnosed?

It is diagnosed based upon typical symptoms and a pattern of examination findings. As far as tests are concerned, EMG and nerve conduction study cannot be done on nerves of this size. But it is still helpful and a needed test, because if it is normal in a patient with typical symptoms of neuropathy, one may consider small fiber neuropathy. If needed, a small piece of skin is taken and analyzed by a microscope to visualize any injury to the small nerves. This test is useful to confirm this diagnosis, and sometimes its cause.

Where can I get more information about neuropathy?

American Academy of Neurology