A 74-year-old woman presented with gait impairment, urinary incontinen
ce, and dementia. She showed lymphocytic CSF pleocytosis and pronounce
d intrathecal Borrelia burgdorferi antibody production, indicating act
ive Lyme neuroborreliosis. The syndrome of normal-pressure hydrocephal
us (NPH) fully remitted after ceftriaxone treatment. Lyme neuroborreli
osis may cause NPH by interfering with subarachnoid CSF flow.