When pain accompanies an illness, it is usually because the disease has inflamed an organ and irritated the ends of the pain nerves, or pain fibres. However, there are certain conditions in which the nerves themselves become inflamed. Such nerve inflammation is called neuritis. If the irritation affects a nerve that carries pain fibres, severe pain will be perceived by the brain, which is the central ‘receiving station’ for all pain nerve fibres. We usually speak of this pain as neuralgia.
When nerves that do not carry pain fibres, such as the motor nerves to muscles, are destroyed by the polio virus, there may be total paralysis without any pain.
The peripheral nerves connect the brain and spinal cord with the muscles, organs, skin, eyes, and so on. The peripheral nerves may be affected by a variety of diseases and injuries. When a peripheral nerve is involved, the condition may be either neuritis or neuralgia.
The peripheral nerves usually contain both pain and motor fibres. Thus, a disease that affects the peripheral nerves would be expected to, and usually does, cause painful symptoms plus some paralysis of muscle power.
Special types of neuritis and neuralgia
Frequently, instead of a generalized irritation of the nerves, only one nerve is afflicted. For example, a person may be sleeping in a cold draught that blows on the left side of the face. The next morning, the side of the face that is ‘powered’ by muscles controlled through the facial nerve may be temporarily paralysed. This type of paralysis is called facial palsy, or Bell’s palsy. Most often, such a paralysis will clear up after some days or weeks. Sometimes, a tumour presses on the nerve and causes facial palsy, or the nerve may be injured by a blow, a cut, or a bullet. In such cases, the results of treatment will depend on the success in treating the tumour or injury. If the cause of facial palsy is not apparent, or the condition does not improve, your doctor is justified in sending you to a neurologist for his opinion.
The sciatic nerve is the widest and longest nerve in the body; it runs from the spinal column to the lower leg, where it divides into two branches. It is exposed to many different kinds of injury in the back, in the pelvis, and even along its course in the lower legs. Injury or inflammation of the sciatic nerve causes pain that travels down the leg from the thigh or the back into the feet and toes. Certain muscles of the leg may be partly or completely paralysed, making it difficult to move the thigh and leg. When this occurs, the doctor makes a careful search for the origin of the sciatica. He knows that this will generally reveal some definite reason for the neuralgic pain. There may be a back injury or irritation from arthritis of the spine, or pressure on the nerve that occurs during some types of work. Certain diseases, such as diabetes or gout, may be the inciting factor. It is true that some cases of sciatica will turn out to be the idiopathic variety—that is, without known cause.
If the cause has been located, the cure will be facilitated by correcting the underlying trouble. In addition, sedatives and physiotherapy may be required to relieve the pain or disability.
Shingles (herpes zoster)
Herpes zoster, or shingles (the word ‘herpes’ means ‘creeping,’ and ‘zoster’ means ‘girdle’), is a terribly painful inflammation of the sections of the nerves that have just emerged from the spinal cord.
This illness is caused by a virus. Fever and prostration may accompany the pain when shingles first develops. After the illness starts, small blisters, or vesicles, usually—but not always—appear on the skin along the course of the affected nerves. Frequently, this will be on the chest. There is a form of shingles that inflames the nerves leading to the face and eyes; this form is especially dangerous because it may cause damage to the vision.
The ordinary attack of shingles runs its painful course in a matter of days or weeks and does not leave any residual difficulties. In some instances, most frequently in elderly people, there is a persistence of pain that may be terribly disabling.
Neuritis and neuralgia of other spinal nerves
Any one of the many nerves travelling out from the spine may be affected by injury or disease. For example, the nerves that lie between the ribs may become inflamed and cause pain in the chest that may resemble pleurisy or even a heart attack. This form of nerve ailment is called intercostal neuritis or neuralgia. Similarly, the nerves travelling down the neck to the arm may be subject to various injuries and diseases. For example, a chronic pain in the hand or arm is sometimes traced to the irritation caused by the pressure of an extra rib in the neck. Doctors call this the cervical rib syndrome. Sometimes too vigorous pulling on the nerves in the neck, such as might occur in difficult obstetrical deliveries, causes the condition known as brachial nerve palsy, which may lead to paralysis of the arm.
Neuritis and neuralgia of the cranial nerves
I have mentioned ailments like sciatica that strike at the spinal-cord nerves. However, there are also 12 pairs of important nerves leading directly from the brain, called the cranial nerves. I have described Bell’s palsy, which results from inflammation of the facial, or seventh cranial, nerve. There is another nerve, the trigeminal, or fifth cranial, nerve, which also ends in the face and jaws.
This nerve may be the source of a neuralgia that causes spasms of pain on one side of the face. This trigeminal neuralgia is also called tic douloureux. It may be set off by a draught of cold air, by chewing, or by other factors.
The nerves leading to the retina of the eye may be involved in various ailments. This condition is called optic neuritis and, because of its potential danger to vision, requires immediate treatment. Any of the other cranial nerves may be damaged by infections, tumours, and toxins. Any disturbance of vision, hearing, balancing, swallowing, taste, or speech may be a signal of trouble in the cranial nerves and should be mentioned to a physician at once.
Injuries to nerves
The peripheral nerves may be cut, bruised, or torn by fractured bones, blows, or gunshot wounds. Nerves have a capacity to heal and regenerate. A torn or cut nerve should be treated by a surgeon who specializes in such work. If necessary, go hundreds of miles for such treatment if your doctor advises it, rather than take a chance on paralysis and other serious consequences of nerve injuries.