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To determine the clinical spectrum and incidence of neuroborreliosis in the Netherlands.
All neurological practices in 106 hospital locations in the Netherlands were asked to look for patients with the codes ‘other neurological infections’ or ‘Borrelia burgdorferi’ in their Diagnosis & Treatment Combinations registration or the Neurological Coding System, respectively, concerning the year 2001, then to identify the patients with neuroborreliosis and to send a copy of the correspondence with the family doctor and the laboratory data on these patients, after making them anonymous, for data extraction. Pleocytosis in the cerebrospinal fluid combined with a positive test for IgM or IgG antibodies of B. burgdorferi in the serum or cerebrospinal fluid was used as the criterion for the diagnosis neuroborreliosis.
Forty-seven (44%) neurological practices did not respond and twenty-two (21%) either did not use any kind of diagnosis registration system or linkage between the registration and the patient file was impossible. Of the 37 (35%) neurological practices that provided information, 17 had diagnosed neuroborreliosis in 30 patients, 20 of whom met the specified criteria. Fifteen (75%) patients had a radiculopathy, 8 (40%) a peripheral facial palsy and 3 (15%) a myelopathy.
The clinical spectrum of patients with neuroborreliosis was consistent with that described in Denmark. The incidence of neuroborreliosis found was 3.6 per million inhabitants. The real incidence was probably higher because the registration systems used allowed patients with neuroborreliosis to be booked under other (symptomatic) diagnostic codes, paediatricians were not involved in the study, and relatively few participating neurologists practiced in high-risk areas for tick bites and erythema migrans. The low incidence of neuroborreliosis in combination with a high background level of seropositivity in the population implies a low predictive value of positive Borrelia serology. It is therefore essential that when neuroborreliosis is suspected, the cerebrospinal fluid should always be investigated.