Behavioral neurology is an essential complement to the psychiatric approach for evaluating cognition and behavior. Both disciplines seek to more fully understand the most complex of human behaviors, thoughts, and abilities and to apply that knowledge helping those impaired by diseases affecting those functions.

Neuropathology has always been fundamental to the neurologist’s understanding of the link from structure to function. The psychiatric approach uses a mental status examination describing insight, judgement, and the like; the behavioral neurology approach parallels the general neurological strategy by determining the location of dysfunction, based on the pattern of cognitive deficits. Localization then assists with narrowing the differential diagnosis.

Focal pathologic conditions such as strokes, tumors, or traumatic brain injury have given way to the lesion method for correlating structure to function. Focal cognitive signs and symptoms can be just as useful and precise for localization as weakness or visual loss. Multifocal or degenerative illnesses can also cause a combination of behavioral, cognitive, and other neurological manifestations that, while less attributable to a single anatomical correlate, can aid in diagnosis and treatment.

This section on behavioral neurology is organized around the general functional geography of the four lobes, with an emphasis on disease processes manifesting in dysfunction in one or more of these regions. Topics covered will be weighted according to their relative exposure potential in a clinical setting.

Some principles can help in forming a construct for brain-behavior relationships. Cognitive functions are subserved by networks of brain regions, so although these rules oversimplify the complexity of cognitive function, they have clinical utility (Figs. 6.1 and 6.2).