Lyme disease is caused by an infection with the spirochete Borrelia burgdorferi transmitted via tick bites ( Ixodes ricinus in Europe and Ixodes scapularis in the United States). Primary infection is normally associated with an erythematous ring-shaped “bullseye” rash (erythema migrans); fever, headaches, and fatigue may also occur. Neurologic involvement (neuroborreliosis) occurs in 10%–15% of patients, and is more common in the absence of early treatment for primary infection. Onset of neurologic symptoms beyond the first few months after initial infection is rare.
Meningitis, cranial neuropathies, and painful radiculitis are common neurologic manifestations of Lyme disease. Approximately two-thirds of patients with neurologic involvement will develop meningitis with slowly progressive headache and neck stiffness and a lymphocytic pleocytosis in the cerebrospinal fluid (CSF). Cranial nerve involvement occurs with similar frequency. While almost any cranial nerve can be affected, facial nerve involvement is by far the most frequent, and may occasionally be bilateral. A painful radiculitis occurs in ~ 50% of patients with neuroborreliosis. It is an acute-onset radicular pain, often involving more than one dermatome.
Intracranial hypertension and encephalomyelitis are very rare neurologic manifestations of Lyme disease. Intracranial hypertension, seen more commonly in children than adults, presents with headaches and occasionally vision loss, with papilledema present on examination. Unlike typical benign intracranial hypertension (pseudotumor cerebri), the CSF demonstrates pleocytosis consistent with meningitis, which is felt to be the operative mechanism. Encephalomyelitis may be associated with focal signal abnormalities on magnetic resonance imaging; there is often associated radiculitis. It appears to be more common in Europe than in the United States. Mild cognitive impairment, often associated with fatigue and generalized nonspecific malaise, is common with active disseminated Lyme disease (as it is with many infectious/inflammatory diseases) but does not indicate active brain infection and should not be considered Lyme encephalitis.
The Ixodes tick, carrier of the tick-borne spirochetes that cause Lyme disease, are endemic across temperate regions of northern and central Europe and Asia and the northeast and north-central United States. Among the three spirochete species, Borrelia garinii , Borrelia afzelii , and Borrelia burgdorferi sensu stricto , only B. burgdorferi sensu stricto is found in the United States. Lyme disease should be considered only in those with plausible exposure to an Ixodes tick, recognizing that both tick bite and erythema migrans may go unnoticed by patients.
Serologic testing for Lyme disease starts with a screening enzyme-linked immunosorbent assay (ELISA). If this is negative, no further testing is indicated. If positive, confirmatory western blot testing for immunoglobulin (Ig)G and IgM antibodies is performed. IgM antibodies generally are present by about 2 weeks after infection, with IgG antibodies taking up to 6 weeks to appear. In patients with symptom duration of 6 weeks or greater, positive IgM but negative IgG testing is likely to represent a false-positive test.
Individuals with a history of a recent tick bite and characteristic erythema migrans (“bullseye” rash, Fig. 110.1 ) who have neurologic symptoms suspected due to Lyme disease may be tested with a serum Lyme titer but should be treated regardless of the results. While the vast majority of cases will be seropositive by the time neurologic symptoms of Lyme develop, occasionally a detectable antibody response is delayed for up to 6 weeks. Note that negative serologic testing is common early in the disease course when only rash is present, particularly if treated with antibiotics.