[Preoperative diagnosis: the Wada test with SPECT control for localizing brain function in therapy-refractory...

Extensive diagnostic measures are necessary to clarify the indication for surgery in patients suffering from epilepsy that is refractory to treatment. Within the overall framework of neuropsychological diagnosis we conducted the Wada test, injecting 200 mg (or 3 mg/kg body weight) of sodium amytal on different days, in each case into the left or right internal carotid artery. This results in a 3-5 minute anaesthesia of the relevant hemisphere. By means of a neuropsychological short test it is possible to determine the performance of the non-blocked hemisphere. The extent of the blocking is also determined by simultaneous i.v. injection of HM-PAO (hexamethyl propylene amine oxime) labelled with 99m Tc, the uptake of which by various cerebral regions is visualised via SPECT. The Wada test supplies information on the lateralisation of cognitive functions (speech, memory etc.) whereas the SPECT examination enables additional determinations not only of processes that must be characterised as diaschisis, but also on the extent of blocking of a hemisphere. The results supply clues to expected postoperative cognitive deficits and thus enable a differentiated assessment of the indication for surgery. This is discussed on the basis of two clinical cases.