Approach to a focal neurological deficit

What it is

A focal neurologic deficit consists of a set of symptoms or signs in which causation can be localized to an anatomic site in the central nervous system. That is what makes it focal: the signs point to a site, rather than to the brain as a whole.

How it presents

Once a deficit occurs, it may remain stable, may continue to worsen in a continuous or steplike fashion, or may resolve. Deficits may also be unifocal, implying a single lesion, or multifocal, suggesting multiple discrete lesions.