Season is an unreliable predictor of Lyme neuroborreliosis.

INTRODUCTION Lyme neuroborreliosis (LNB) is a tick-borne infection of the nervous system caused by the spirochete Borrelia burgdorferi sensu lato. The primary symptoms are usually painful radiculitis, facial palsy and lymphocytic meningitis. The aim of this study was to provide data on the seasonal variation, anamnesis, symptoms, laboratory data and course of the disease in adults (≥ 16 years). METHODS The medical records of 69 patients with confirmed LNB who attended the Department of Neurology, Lillebaelt Hospital, Vejle, Denmark, were analysed. The diagnosis was confirmed by the presence of leucocytosis in the cerebrospinal fluid and intrathecal production of immunoglobulin M and/or G anti-B. burgdorferi antibodies. RESULTS Onset of neurological symptoms in LNB occurred year round in the Region of Southern Denmark. Only half of the patients had a history of a tick bite or erythema migrans (EM). Half of the patients who observed a tick bite subsequently reported EM. The duration from the onset of neurological symptoms to referral to hospital was remarkably long for patients with radiculoneuritis, whereas the onset of facial palsy led to a swift referral. Patients who were ≥ 50 years old had a significantly lower age-related risk of facial palsy without radicular symptoms. CONCLUSION In this study, winter as a low-risk season was not a reliable factor in ruling out LNB. This finding may be relevant when investigating the cause of facial palsy and radicular symptoms.