Reversible Horner's syndrome and Lyme disease.

Neurologic manifestations of Lyme disease are common, often debilitating, and potentially treatable. We document a case of Borrelia infection of the nervous system manifesting as a reversible Horner's syndrome. The search for Lyme disease should be part of the evaluation of an isolated central or preganglionic Horner's syndrome or any unexplained pupillary abnormality.