Incidence and diagnosis of anosognosia for hemiparesis revisited

Background and Purpose: In previous studies, the incidence of anosognosia for hemiparesis varied between 17% and 58% in samples of brain damaged patients with hemiparesis. One explanation for this wide variation might be different criteria used for the diagnosis of anosognosia.

Methods: The present study investigated a group of 128 acute stroke patients with hemiparesis or hemiplegia. The patients were tested for anosognosia for hemiparesis using the anosognosia scale of Bisiach et al. (Neuropsychologia 1986:24:471–482).

Results: Analysis revealed that 94% of those patients rated having „mild anosognosia“, i.e. who did not acknowledge their hemiparesis spontaneously following a general question about their complaints, suffered from and mentioned other neurological deficits, such as dysarthria, ptosis, or headache. However, they immediately acknowledged their paresis when they were asked about the strength of their limbs. Obviously other deficits had a higher impact for these subjects. In fact, they had significantly milder paresis compared to patients who denied their disorder even when asked about the limbs.

Conclusions: The data suggest that patients who do not mention their paresis spontaneously but directly when addressed by the examiner should not be diagnosed having „anosognosia“. If this more conservative cut-off criterion is applied to the data of the present as well as of previous studies, a frequency between 10% and 18% for anosognosia for hemiparesis is obtained in unselected samples of acute, hemiparetic stroke patients. The incidence of anosognosia for hemiparesis thus seems to be less frequent than previously assumed.