Does Lyme disease affect the brain and nervous system?

Lyme disease affects the nervous system. This statement is both accurate and terrifying since, for many of us, damage to the brain is the most feared consequence of disease. However, when it comes to Lyme disease, much of this fear is misplaced. Lyme disease can affect the lining of the brain, a disorder known as meningitis. Other than causing fever and bad headaches, this form of meningitis is remarkably benign; nobody has ever died of it, and it has rarely — if ever — caused significant damage to any patient’s brain. On extremely rare occasions, the infection can involve the brain or spinal cord, disorders that are now extraordinarily rare. Other patients can develop inflammation of various nerves, e.g., the nerves that control the muscles on one side of the face (Bell’s palsy); this might occur in about 5% of untreated individuals. Other nerves can be affected, but even less frequently.

When considering these disorders, it is essential to recognize some key facts. First, the infection is highly responsive to antibiotics. Second, if the facial nerve has been severely damaged, there may be some residual weakness after treatment. However it is extraordinarily rare for there to be any permanent damage to the brain itself.

More importantly, there are many symptoms that occur in patients with Lyme disease and most other infections that may make one think there is a problem with the brain; however, that is not the case. Headaches, which are remarkably common in individuals with fever of any cause, are rarely due to a brain infection. Slowed thinking, with difficulty in concentrating, remembering or mentally focusing occurs to a greater or lesser extent in virtually everyone with an active inflammatory condition; however, it is almost never due to the disease affecting the brain itself. Rather, these are the effects of chemicals produced by the body in response to an infection or inflammation. These effects disappear as soon as the infection or inflammation resolves.

Since some patients with Lyme disease develop fatigue and thinking difficulties, some have suggested that these symptoms in isolation– are strongly suggestive of this infection. However, this is misguided thinking. Studies have shown that symptoms such as these, which are severe enough to affect day-to-day functioning but are never due to nervous system disease, occur in over 2% of the population at large at any given time. In the U.S., this amounts to 6,000,000 people! Since there only about 30,000 cases of Lyme disease are reported each year, patients with Lyme disease obviously represent only a very tiny fraction of the total number of individuals with these symptoms.