Unlike other types of pain, pain arising from damage to the nerves or nervous system can occur for what seems like no reason. Muscular pain, for example, usually occurs because of a specific incident that the patient will be aware of. This isn’t necessarily the case with nerve damage. It can result from repetitive stress, toxic exposure or even other medications that the patient takes for other conditions. As a result, neuropathy can be a mystery, seeming to come out of nowhere.
The nervous system and brain use electricity to communicate, and anything that uses electricity is also capable of short circuiting, as in a seizure, or misfiring, as in phantom limb syndrome, where a patient still suffers pain in a limb that is no longer part of the body.
Nerve damage or neuropathy normally occurs when myelin degenerates. This is the outer sheathing and the protective covering of nerve cells. Without this protection the electrical signals are not transferred properly just like if you stripped the covering off of the electrical wires in your house. When the insulation begins to crumble, the unprotected “wire” will start short-circuiting.
As the damage gets worse, the nerves lose either their ability to transmit information, which results in numbness in the area, or they start sending false signals causing pain or a tingling sensation. Neuropathy is the condition where the nerves have sustained enough damage that numbness, pain or tingling have become noticeable to the patient. The term is almost always used to mean “peripheral neuropathy,” implying that it refers to nerve damage outside of the core.
There are three types of nerves that can be affected by neuropathy. These are the sensory nerves, autonomic nerves and motor nerves. What kind of symptoms you suffer is dependent on which types of nerves that have suffered damage.
Neuropathy can also affect either a single or one set of nerves or a number of nerves. The first is mononeuropathy, and when a number of nerves are affected, it is called polyneuropathy.
The majority of cases of neuropathy affect the motor and sensory nerves. Patients generally experience initial symptoms on their feet, hands, arms and legs. This is called Sensorimotor Polyneuropathy. Signs and symptoms of this type of neuropathy include:
- Pins and needles in the affected parts of the body. This might be described as a tingling or prickling sensation.
- A burning sensation in the skin of the feet and legs. This starts in the lower extremities, but, as it progresses, it will spread to the hands and arms as well.
- Sharper, stabbing pains which grow more intense at night. These sensations feel electrical or shocking in nature. Like the burning sensations, they also generally start in the feet and legs before spreading to the upper body.
- Muscle weakness
- Coordination problems
- Increased susceptibility to problems with feet, including ulcers and skin infections.
Peripheral neuropathy can also eventually develop into something called dysesthesia which is often accompanied by a more intense tingling sensation, burning sensation and by hyper-sensitivity of the skin. A patient may experience intense pain simply from contact with a towel or bedding.
When the autonomic nerves have been damaged, autonomic neuropathy occurs. Patients suffering from autonomic neuropathy may experience the following:
- Bowel incontinence
- Bladder incontinence
- Coordination problems
- Dysphagia – swallowing difficulties
- Hypotension – low blood pressure. The patient may feel dizzy when getting up from sitting or lying down
- Impotence – erectile dysfunction
- Problems emptying the bladder completely
- Problems with balance
- Tachycardia – accelerated heartbeat
When a single or one group of nerves are affected, then the condition is called mononeuropathy, and may cause patients to experience the following:
- Eye pain or vision problems which often include difficulty focusing or double vision.
- Bell’s palsy meaning that one side of the face is paralyzed or responds weakly to stimulus
- Various types of pain, including chest, shin or foot pain
- Carpal tunnel syndrome or pain and numbness from the wrist to the lower palm.
Causes of neuropathy
Physical trauma, repetitive injury, infection, metabolic problems and exposure to toxins and some drugs can all lead to peripheral neuropathy.
Diabetes often leads to neuropathic conditions and is the leading cause of neuropathy in the US. Estimates vary, but about half of all people with diabetes also have some level of neuropathy. The excess blood glucose levels in people with diabetes can, over a number of years, injure the walls of the small vessels that supply blood to nerves. This kind of damage is especially prevalent in the legs. Because one of the consequences of nerve damage is numbness, the inability to feel pain can often cause injuries to the feet or legs to go unnoticed by people with diabetes. Diabetic neuropathy is the primary cause of foot problems and ulcers in diabetics.
Diabetes is the most common cause of neuropathy, but other medical conditions can also be the underlying cause of nerve damage.
- Chronic liver or kidney disease
- AIDS and HIV infection
- Prolonged and excessive alcohol intake
- Nutritional deficiencies, especially Vitamin B
- Cancer – lymphoma or multiple myeloma
- Lyme disease, a tick-borne bacterial infection
- Charcot-Marie-Tooth disease, a genetic condition that causes nerve damage in the lower limbs
- Guillain-Barré syndrome, a rare and very serious condition that damages peripheral nerves
- Diphtheria, a common bacterial infection in tropical areas of the globe, but rare in other parts of the world.
Toxic and drug causes
Neuropathy can also be caused by toxins or drugs. Toxic causes are often through exposure to lead, mercury, arsenic or thalium through a workplace, but there are a variety of other sources of toxins. Industrial compounds are sometimes abused and exposure to them is deliberate, as in glue sniffing. Finally, some herbal medicines, especially Chinese medicines, contain toxins that are known to cause neuropathy.
Nearly forty drugs are also known to cause neuropathy. Neuropathy is a common side effect of certain medications, especially those used to treat HIV/AIDS and those used in chemotherapy, to fight cancer. Always consult a pharmacist or doctor if you suspect neuropathic side-effects of a medication.
One of the major differences between neuropathy and muscle pain is that neuropathy does not necessarily stem from some form of trauma or injury. Since muscle pain can be treated with standard pain-killers and is less likely to be chronic, it is important to try to recognize when pain is neuropathic rather than muscular.