We report the case of a 76-year old woman, who presented with signs of a meningoencephalitis. The result of lumbar puncture showed a mononuclear pleocytosis. Empirical antimicrobial treatment was promptly initiated. Nevertheless a comatose state complicated the clinical course. The diagnosis of neuroborreliosis was made serologically and by molecular biology. Under adequate therapy with intravenous ceftriaxone the patient showed a slow but full recovery. This case illustrates that potentially reversible diseases need very careful decision making regarding therapeutic activities and that neuroborreliosis is a potentially reversible cause of severe neurologic impairment.