Validierung der lateralisierenden Aktivierung von Wada-Test Paradigmen mittels funktioneller transkranieller Dopplersonographie

Within the pre-surgical diagnosis of patients with therapy-resistant epilepsies, the knowledge of the localisation and the laterality of the eloquent cortex is of great importance. Up to now, the Wada-test is concidered the gold-standard for the examination of the localisation of both the language and the memory at the pre-surgical diagnosis of epilepsies. With the non-invasive functional transcranial Doppler-sonography (fTCD) one can, correlating the events, register the relative variability of the blood-stream (CBFV) of arterial vessels in the brainand, by comparing the sides, can also examine whether the functions of the brain are lateralised. Therefore, the fTCD is suitable for defining the hemispherical dominance of cognitive functions. Hitherto, the hemispherical lateralisation of the language has been intensively explored and numerous studies show good relations to the results of the Wada-test and the functional magnet-resonance-tomography (fMRT). In manx cases of the pre-surgical diagnosis fTCD can replace the Wada-test for lateralising the language. However, so far it has scarcely been examined whether fTCD can also be used for the lateralisation of non-verbal functions of the memory and how far a hemispherically specific activation occurs by means of Wada-test paradigms. It is the intention of this study to clearify whether the paradigms of the Wada-test invoke a lateralised activation which can be proved by an fTCD examination. Moreover, it has been scrutinised whether fTCD can be employed for the lateralisation of the verbal and the non-verbal memory. In this study four different Wada-paradigms have been investigated with 40 healthy test persons. Parallel to this, the CBFV of the two arteriae cerebri was continuously measured and tested with regard to the hemispherical dominance. The lateralisation of the verbal memory was tested by means of the sub-tests “encoding faces” and “recalling faces”. In order to validate these results the lateralisation of the language was examined and compared with those already established, and with the Wada-test and with the fMRT correlated word-generating paradigms. The results of this study constitute a stable external criterion for a comparison. The study confirms a significant dominance of the sinistro-cerebral hemisphere at the examination of the paradigms of the word-generation. By 37 of the 40 testpersons (=92,5%) a relative increase of the CBFV of the left arteria cerebri media was measured. When examining the localisation of the non-verbal memory, no significant hemispherical dominance was found, but- in comparison with the test for “generating words”- a significantly lower activation of the left hemisphere was discovered. Consequently, a bi-hemispherical representation of the non-verbal memory-contest must be assumed. By 27 of the 40 test-person (=67,5%) the examinatin of the localisation of the verbal memory showed a sinistro-cerebral dominance, 2 test-persons (=5%) showed a dextro-cerebral dominance and 11 test-persons (=27,5%) no lateralising activation. Summarising this study, it can be stated that the paradigms “encoding words” and “recalling words”, which were used in the Wada-test, induce an activation of the left hemisphere, the paradigms “encoding faces” and “recalling faces”, however, show rather more a bi-hemispherical representation. These results coincide with the hitherto existing examinations described in the medical literature, where a stable, right-hemispherically activating paradigm in fTCD-studies has not been found so far. With this study no clear lateralising activation of the non-verbal Wada-test paradigms has been ascertained. On the basis of these results the optimizing of the paradigms used in the Wada-test should be taken into consideration. Here fTCD could serve as a screening method to find an appropriate paradigm.