Anosognosia and asomatognosia during intracarotid amobarbital inactivation

Background: Anosognosia (i.e., denial of hemiparesis) and asomatognosia (i. e., inability to recognize the affected limb as one's own) occur more frequ ently with right cerebral lesions. However, the incidence,, relative recove ry, and underlying mechanisms remain unclear. Methods: Anosognosia and asom atognosia were examined in 62 patients undergoing the intracarotid amobarbi tal procedure as part of their preoperative evaluation for epilepsy surgery . Additional questions were asked in the last 32 patients studied. Results: During inactivation of the non-language-dominant cerebral hemisphere, 88% of the 62 patients were unaware of their paralysis, and 82% could not recog nize their own hand at some point. Only 3% did not exhibit anosognosia or a somatognosia. In general, asomatognosia resolved earlier than anosognosia. When patients could not recognize their hand, they uniformly thought that i t was someone else's hand. Dissociations in awareness were seen in the seco nd series of 32 patients. Although 23 patients (72%) thought that both arms were in the air, 31% pointed to the correct position of the paralyzed arm on the table. Despite the inability of 24 of 32 patients (75%) to recognize their own hand, 21% of these patients were aware that their arm was weak, and 38% had correctly located their paralyzed arm on the angiography table. Conclusions. Anosognosia and asomatognosia are both common during acute dy sfunction of the non-language-dominant cerebral hemisphere. Dissociations o f perception of location, weakness, and ownership of the affected limb are frequent, as are misperceptions of location and body part identity. The dis sociations suggest that multiple mechanisms are involved.