All Diseases

Narcolepsy is a chronic sleep disorder characterized by overwhelming daytime drowsiness and sudden attacks of sleep. People with narcolepsy often find it difficult to stay awake for long periods of time, regardless of the circumstances. Narcolepsy can cause serious disruptions in your daily routine.

Contrary to what some people believe, narcolepsy isn't related to depression, seizure disorders, fainting, simple lack of sleep or other conditions that may cause abnormal sleep patterns.

Narcolepsy is a chronic condition for which there's no cure. However, medications and lifestyle changes can help you manage the symptoms. Support from others — family, friends, employer, teachers — can help you cope with narcolepsy.

Nasal polyps are soft, painless, noncancerous growths on the lining of your nasal passages or sinuses. They hang down like teardrops or grapes. They result from chronic inflammation due to asthma, recurring infection, allergies, drug sensitivity or certain immune disorders.

Small nasal polyps may not cause symptoms. Larger growths or groups of nasal polyps can block your nasal passages or lead to breathing problems, a lost sense of smell, and frequent infections.

Nasal polyps can affect anyone, but they're more common in adults. Medications can often shrink or eliminate nasal polyps, but surgery is sometimes needed to remove them. Even after successful treatment, nasal polyps often return.

Nasopharyngeal (nay-zo-fuh-RIN-gee-uhl) carcinoma is cancer that occurs in the nasopharynx, which is located behind your nose and above the back of your throat.

Nasopharyngeal carcinoma is rare in the United States. In other parts of the world — specifically Southeast Asia — nasopharyngeal carcinoma occurs much more frequently.

Nasopharyngeal carcinoma is difficult to detect early. That's probably because the nasopharnyx isn't easy to examine and symptoms of nasopharyngeal carcinoma mimic those of other more common conditions.

Treatment for nasopharyngeal carcinoma usually involves radiation therapy, chemotherapy or a combination of the two. You can work with your doctor to determine the exact approach depending on your particular situation.

Nearsightedness (myopia) is a common vision condition in which you can see objects near to you clearly, but objects farther away are blurry.

The degree of your nearsightedness affects your ability to focus on distant objects. People with severe nearsightedness can see clearly only objects just a few inches away, while those with mild nearsightedness may clearly see objects up to several yards away.

Nearsightedness may develop gradually or rapidly, often worsening during childhood and adolescence. Nearsightedness tends to run in families.

A basic eye exam can confirm nearsightedness. You can easily correct the condition with eyeglasses or contact lenses. Another treatment option for nearsightedness is surgery.

Neck pain is a common complaint. Neck muscles can be strained from poor posture — whether it's leaning into your computer at work or hunching over your workbench at home. Wear-and-tear arthritis also is a common cause of neck pain.

Rarely, neck pain can be a symptom of a more serious problem. Seek medical care if your neck pain is accompanied by numbness or loss of strength in your arms or hands or if you're experiencing shooting pain into your shoulder or down your arm.

Nephrotic syndrome is a kidney disorder that causes your body to excrete too much protein in your urine.

Nephrotic syndrome is usually caused by damage to the clusters of small blood vessels in your kidneys that filter waste and excess water from your blood. Nephrotic syndrome causes swelling (edema), particularly in your feet and ankles, and increases the risk of other health problems.

Treatment for nephrotic syndrome includes treating the underlying condition that's causing it and taking medications. Nephrotic syndrome can increase your risk of infections and blood clots. Your doctor may recommend medications and dietary changes to prevent these and other complications of nephrotic syndrome.

Neuroblastoma is a cancer that develops from immature nerve cells found in several areas of the body. Neuroblastoma most commonly arises in and around the adrenal glands, which have similar origins to nerve cells and sit atop the kidneys. However, neuroblastoma can also develop in other areas of the abdomen and in the chest, neck and near the spine, where groups of nerve cells exist.

Neuroblastoma most commonly affects children age 5 or younger, though it may rarely occur in older children.

Some forms of neuroblastoma go away on their own, while others may require multiple treatments. Your child's neuroblastoma treatment options will depend on several factors.

Neurodermatitis starts with a patch of itchy skin, but scratching it makes the area even itchier. Eventually you may scratch simply out of habit. This cycle of chronic itching and scratching can cause the affected skin to become thick and leathery.

Neurodermatitis — also known as lichen simplex chronicus — isn't serious, but breaking the itch-scratch cycle is challenging.

Successful treatment of neurodermatitis depends on identifying and eliminating factors that may be aggravating the problem. Over-the-counter and prescription creams can help ease neurodermatitis symptoms.

Neurofibromatosis is a genetic disorder that disturbs cell growth in your nervous system, causing tumors to form on nerve tissue. These tumors may develop anywhere in your nervous system, including in your brain, spinal cord and nerves. Neurofibromatosis is usually diagnosed in childhood or early adulthood.

The tumors are usually noncancerous (benign), but in some cases these tumors become cancerous (malignant) tumors. People with neurofibromatosis often experience only mild symptoms. Effects of neurofibromatosis can range from hearing loss, learning impairment, and heart and blood vessel (cardiovascular) complications to severe disability due to nerve compression by tumors, loss of vision and severe pain.

Neurofibromatosis treatment aims to maximize healthy growth and development and to manage complications as soon as they arise. When neurofibromatosis causes large tumors or tumors that press on a nerve, surgery may help ease symptoms. Some people may benefit from other therapies, such as stereotactic radiosurgery, medications to control pain or physical therapy.

Nickel allergy is one of the most common causes of allergic contact dermatitis — an itchy rash that appears when your skin touches a usually harmless substance.

Nickel allergy is commonly associated with earrings and other jewelry, particularly jewelry associated with body piercings. But nickel can be found in many everyday items — from coins to zippers, from cellphones to eyeglass frames.

Nickel allergy can affect people of all ages. A nickel allergy usually develops after repeated or prolonged exposure to items containing nickel. Treatments can reduce the symptoms of nickel allergy. Once you develop nickel allergy, however, you will always be sensitive to the metal and need to avoid contact.