In the wooded and grassy areas of the upper midwest and northeastern United States, bites by deer ticks, which are small, black-legged insects, can sometimes occur. While some bites won't cause lasting harm, others can result in a bacterial infection called Lyme disease. If left untreated, the disease can lead to neurological problems and rheumatoid arthritis. 

The discovery of Lyme disease is credited to two Yale physicians who identified the mysterious inflammatory disease after a rash of illnesses cropped up during the summer of 1975. Yale Medicine scientists are now exploring the different causes of nerve damage, and developing new ways to regrow damaged nerve cells.

If you're bitten by an infected deer tick you'll first see a skin rash, which appears in a “bull’s eye” pattern around the area of the tick bite. If the rash is not detected and the infection is not treated, symptoms of Lyme disease will appear within a few weeks.

The initial symptoms may seem like the flu and could include fever, lymph-node inflammation, fatigue, aches, and headaches. If left untreated, the bacteria can, in a few weeks or months, spread to the heart, bones, and nervous system.

If the infection spreads to those organs, patients might experience pain, weakness, headaches, memory problems, pinkeye, joint pain and swelling, or rapid heartbeat. And if the infection is never treated, it can lead to such joint problems as arthritis and neurological problems such as memory loss.

Some Lyme disease diagnoses are straightforward and no specific tests are needed. If you remember that you were bitten by a tick while hiking and see the characteristic “bull’s eye” rash, a doctor will probably prescribe antibiotics without any additional tests.

But sometimes people have no idea that they’ve been bitten by a tick. Ticks usually only stick around for a few days before dropping off to look for a new host. In the weeks and months following a bite, a person might develop symptoms that could be confused with another condition.

Some people are misdiagnosed with chronic fatigue syndrome, arthritis, Crohn’s disease, or a variety of other ailments. To know for sure, a doctor will usually order a blood test that looks for the antibodies produced by the body’s immune system to fight the bacterial infection.

Typically, three main neurological complications develop in people with untreated Lyme disease.

• Cranial neuropathy: If the infection affects nerves of the face, some patients might experience cranial neuropathy—or dysfunction of the peripheral nerves—causing drooping or swelling. The most common form of cranial neuropathy is Bell’s palsy, which is muscle drooping on one side of the face.
• Meningitis: If the bacterial infection reaches the meninges, or the tissue lining the brain and spinal column, it may cause inflammation and tissue damage. Patients with meningitis are likely to experience fevers, headache, fatigue, and stiff neck. 
• Radiculoneuritis: If the bacterial infection reaches the nerve root, or the part of the nerve cells that attaches to the central nervous system (spine and brain), it can cause severe pain, numbness, and other abnormal sensations.

People who do not know they have been infected. So it’s important to check for deer ticks after outdoor activities, especially in the northeast or midwest parts of the country.

Ticks sometimes bite in such inconspicuous places as the hairline or back. Lyme disease is treated with antibiotics at any stage of illness to eradicate the bacterial infection. However, some people might still be at risk for lingering neurological complications if the bacteria has traveled to the tissue of the central nervous system.

In most cases, the more quickly a patient is treated, the better the chances are for recovery. In the early stages of infection, before any potential neurological complications, oral antibiotic drugs will be prescribed to kill the infection—a combination of doxycycline and amoxicillin.

For Lyme disease that has begun to affect the nervous system, there is strong evidence that parenteral (injected) antibiotics work well to combat infection. These parenteral antibiotics include ceftriaxone, cefotaxime, and penicillin.

If neurological symptoms persist for months after initial treatment, patients will be treated with antibiotics again. But patients will not be treated with antibiotics for more than four weeks, because there is no evidence that prolonged treatment improves the symptoms of lingering neurological complications.

The discovery of Lyme disease is actually credited to two Yale physicians, who identified it after a rash of illnesses cropped up during the summer of 1975. That year, two mothers living in Old Lyme, Conn., refused to accept the diagnosis of rheumatoid arthritis among the children living in their town.

The mothers reached out to the Connecticut State Department of Health and the Yale School of Medicine for help, starting a study that would ultimately uncover the bacterial infection transmitted by ticks. Today, doctors in Yale Medicine’s neurology department provide care for patients who have infections that affect the nervous system.

Thanks to a powerful partnership with research programs at Yale Medicine, patients benefit from the most recent advantages in treatment.