The Merging Tracks of Anosognosia and Neglect.

ABSTRACT

Anosognosia and hemineglect are among the most startling neurological phenomena identified during the 20th century. Though both are associated with right hemisphere cerebral dysfunction, notably stroke, each disorder had its own distinct literature. Anosognosia, as coined by Babinski in 1914, describes patients who seem to have no idea of their paralysis, despite general cognitive preservation. Certain patients seem more than unaware, with apparent resistance to awareness. More extreme, and qualitatively distinct, is denial of hemiplegia. Various interpretations of pathogenesis are still deliberated. As accounts of its captivating manifestations grew, anosognosia was established as a prominent symbol of neurological and psychic disturbance accompanying (right-hemisphere) stroke. Although reports of specific neglect-related symptomatology appeared earlier, not until nearly 2 decades after anosognosia's inaugural definition was neglect formally defined by Brain, paving a path spanning some years, to depict a class of disorder with heterogeneous variants. Disordered awareness of body and extrapersonal space with right parietal lesions, and other symptom variations, were gathered under the canopy of neglect. Viewed as a disorder of corporeal awareness, explanatory interpretations involve mechanisms of extinction and perceptual processing, disturbance of spatial attention, and others. Odd alterations involving apparent concern, attitudes, or belief characterize many right hemisphere conditions. Anosognosia and neglect are re-examined, from the perspective of unawareness, the nature of belief, and its baffling distortions. Conceptual parallels between these 2 distinct disorders emerge, as the major role of the right hemisphere in mental representation of self is highlighted by its most fascinating syndromes of altered awareness.