Sammendrag
Visuo-spatial neglect is a behavioural syndrome occurring after brain injury and involves the inability to report, respond or orient to stimuli, generally in the contralesional space. Paper-and-pencil tests are commonly used in formal assessments of visuo-spatial neglect in patients. However, some patients who after formal assessment are believed to be fully recovered still experience neglect-related problems in everyday life. The present pilot study explored the neuronal correlates of visuo-spatial neglect using event related potentials [ERPs], which could be used as a biological marker of neglect, possibly being more sensitive than traditional tests. 20 right medial cerebral artery stroke patients were recruited, 15 had varied degree of visuo-spatial neglect as determined by neuropsychological tests and behavioural assessment in daily life situations and 5 did not. Time since stroke varied from 8 years to 3 months. In addition 35 healthy age matched controls were examined. Event related potentials were recorded from 19 electrodes distributed on the scalp according to the international 10-20 system during a visual continuous performance test. The test consisted of 400 trials with pictures of animals, plants and humans presented for 100 ms each and with an inter stimulus interval of 1000 ms. The entire task lasted 20 minutes. Participants were instructed to respond as quickly as possible by pressing a response button each time two consecutive pictures of an animal were presented [25% of all trials]. Patients with visuo-spatial neglect, as compared to other stroke patients and healthy controls, displayed markedly increased amplitude of the P2 component [180-250ms] in a grand average ERP analysis. This phenomenon was most pronounced over the right posterior temporal region [T6]. Single subject data revealed that significantly increased P2 amplitude in T6 was detectable in all patients with visuo-spatial neglect, but not in the patients with right hemisphere stroke without neglect or healthy controls. Furthermore, there was a significant negative correlation between P2 amplitude and time since stroke. Our results suggest that the P2 component have qualities that can provide supplementary information in clinical assessments of spatial neglect. Further investigation is required to determine sensitivity, specificity, and positive and negative predictive values of increased P2 amplitude as an electrophysiological marker for visuo-spatial neglect.
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