Making sense of cerebral dominance and syndromes of the nondominant hemisphere.

Knowing the special function of each half of the brain is important to the clinician. If he doesn't understand what damage to the nondominant hemisphere can do, he may mistake the resulting syndrome for a psychiatric illness or generalized dementia, and the patient won't get proper treatment and counseling. The tendency is to think of dominance in terms of language, but other functions are asymmetrically located even though their input and output are bilateral. Generally, lesions in the left hemisphere cause problems with language and those in the right disrupt visual and spatial skills, attention, and emotional behavior. By far the most common syndrome in right hemisphere lesions is neglect of the left side. A patient may show lack of concern about his illness or he may deny that he is sick or even that the left side of his body belongs to him. Patients with left hemisphere lesions may neglect the right side but rarely to this extreme.