Frontal lobe syndromes

Introduction Because of its large size and dependence on both anterior and middle cerebral arteries, the frontal lobes are commonly involved in ischemic strokes. Frontal lobe strokes produce a wide variety of symptoms, which can be challenging even to the experienced clinician. Presentations range from profound akinesia and mutism to subtle changes in emotional processing and personality. The human frontal lobes are especially important for many higher cognitive skills, such as planning and reasoning. They play a crucial role in most processes underlying human adaptation and social behavior. Frontal lobe strokes can be quite devastating to the patient and family. With better acute stroke therapies available, it becomes important to recognize these stroke syndromes early and initiate treatment. This chapter addresses both organizational and clinical aspects of the frontal lobes, particularly those signs, symptoms, and cerebrovascular lesion patterns that clinicians are likely to encounter. Anatomical and organizational features of the frontal lobe The frontal lobes comprise multiple functional entities and can be subdivided into three major divisions: primary motor, premotor, and prefrontal cortical areas. The motor and premotor regions are considered distinctive functional units, whereas the prefrontal cortex is more complex and requires further subdivision. Based on its cytoarchitecture, its connections to other areas, as well as its functional distinctions, the prefrontal cortex can be differentiated into orbitofrontal, dorsolateral, and medial frontal/anterior cingulate regions. Each of these prefrontal regions mediates a separate set of skills and produces a unique clinical syndrome when affected, although pure syndromes are rare and there is often overlap. Figure 17.1 contains drawings that show the various subdivisions of the frontal lobes seen from different surfaces with the Brodman area numbers assigned to each of these regions.