The phenomenology of acute anosognosia for hemiplegia

Abstract

Objective: After attempting to move a plegic limb, patients with anosognosia for hemiplegia (AHP) may claim that limb movement occurred, even though the limb remained mo-tionless. The authors investigated the characteristics, natural history, and anatomical basis of AHP phenomenology. Methods: Twenty-nine right-hemisphere stroke patients with acute anosognosia for hemiplegia (AHP) were pro-spectively assessed for the presence and characteristics of movement claims and observable behavior during movement attempts. Results: AHP was transient, with the condition resolving in 68% of patients by 1 week. Patients made movement claims during 31% of unilateral movement attempts and 50% of bilateral movement attempts. Movement claims were idio-syncratic, lacked internal consistency within individual pa-tients, and even dissociated from explicit denial, as several patients made movement claims after they began to ex-plicitly acknowledge hemiplegia. Observable behavior during movement attempts revealed allochiria (moving the right arm instead of the left) in 31% of patients, signs of implicit knowledge of weakness in 24%, and intact intention in 34%. Lesion analysis revealed that allochiria was associated with inferior right parietal lobe damage. Conclusions: These results highlight that heterogeneity, phenomenological complexity, and transience are hall-marks of AHP. This advances clinical AHP assessment by showing that assessment of performance, rather than just verbal response, uncovers multiple dimensions of AHP. Allochiria emerges as an anatomically distinct sub-component of the disorder. These findings also have the-oretical implications, because they do not lend support to unitary pathogenic models proposing that illusions of movement or impaired intention form the basis of AHP. Most patients rapidly improve, which should invigorate the search for typical compensatory mechanisms un-derlying spontaneous recovery.