Lyme disease is a tick-borne illness caused by three pathogenic species of the spirochete Borrelia (B. burgdorferi, B. afzelii and B. garinii). B. burgdorferi is the sole cause of the disease in the United States. All three pathogenic species occur in Europe, and two (B. afzelii and B. garinii) have been identified in Asia. Lyme disease has a broad spectrum of clinical manifestations, and it also varies in severity due, in part, to differences in the infecting species.
The neurologic manifestations of Lyme disease will be reviewed here. Other aspects of Lyme disease are discussed separately. (See "Clinical manifestations of Lyme disease in adults" and "Lyme disease: Clinical manifestations in children" and "Diagnosis of Lyme disease" and "Treatment of Lyme disease".)
Borrelia burgdorferi, the organism responsible for the multisystem infectious disease known as Lyme disease, appears to preferentially affect several organ systems. Skin, the site of inoculation, is involved in 80 percent or more of infected individuals . Joint involvement occurs frequently in patients in the United States , but less commonly in Europe. The third most common site is the nervous system, which is involved in 10 to 15 percent of infected individuals in both Europe and the United States . (See "Clinical manifestations of Lyme disease in adults".)
Just as in neurosyphilis, nervous system involvement begins during early disseminated Lyme disease, when spread of the spirochetes can result in meningeal seeding . As in syphilis, untreated Borrelia infection probably subsides in some patients but becomes chronic in others. Also as in syphilis, appropriate antimicrobial treatment results in microbiologic cure in the overwhelming majority of patients, regardless of the duration of the infection.
Much of the confusion and controversy surrounding Lyme disease relates to misunderstandings about what does and does not constitute evidence of nervous system infection. Many patients with Lyme disease develop nonspecific symptoms, including headache, fatigue, cognitive slowing, and memory difficulty. However, these symptoms are not indicative of central nervous system infection [4,5] and, moreover, are common in many other infectious and inflammatory states. At any point in time, indistinguishable cognitive symptoms occur in as many as 2 percent of otherwise healthy people , in whom they can have a significant negative impact on the quality of life.