[Somatoparaphrenia. A positive variant of anosognosia for hemiplegia]

Abstract

Anosognosia for hemiplegia (AHP), i.e., unawareness of motor deficits and associated disorders, has been frequently reported, pre-dominantly following right hemispheric lesions. To a smaller extent, there are case reports of patients who give accounts of a feeling of strangeness concerning the contralesional limbs and sometimes attribute them to other persons. This "positive-variant" of AHP has been labeled "somatoparaphrenia" (SP). We report a case of SP in a 85-year-old woman with infarction of the right posterior cerebral artery and posterior parts of the right thalamus. She showed AHP and described her left side alternatively as her handicapped nephew and a clumsy cat. Misidentification of her daughter also occurred. With respect to the literature the predominant neuroanatomical features involved are lesions including right parietal cortex and/or posterior parts of the thalamus. Theories concerning the pathogenesis of this phenomenon comprise a denial of the illness, a lack of awareness caused by reduced sensory feedback and neglect, a misidentification or disturbance of the active discovery process considered necessary for realizing one's disorder.