Abstracts

Rationale: During the Wada procedure, memory tests are performed with a series of objects shown to a patient after sodium amobarbital is injected directly into the right or left internal carotid artery. When the drug wears off, the recall of those objects is tested. We explored if objects shown were distinctly more memorable than others. Methods: 135 Consecutive adult Wada tests were performed from 1997-2004 in a standardized manner with sodium amobarbital injections into the right or left carotid artery with an 8 object memory exercise per side. After drug metabolism the 8 objects were tested for recognition intermixed with 16 different foil objects to test for false recognition (guessing). For study purposes, only first side injections were analyzed. At our center, all Wada tests start with amytal injections on the side of suspected disease burden. The majority of patients tested were undergoing surgical epilepsy work-ups. Item memory errors were compared between hemispheres via Chi square statistics by side of injection with two-tailed p tests and significance <0.05. No concession was made for side of language dominance. Results: Irrespective of side injected, targets were correctly identified between 73-88% of the time. When left injections were done, right sided recalls showed clear and consistent trends for greater memory difficulties, with correct target identification medians of 77.5%. Conversely, testing recognitions with right sided injections, median correct identifications were 93%. Object recognition errors were apparent in all items, occuring more often when the left side was injected, and were most notable for the following 3 of 16 items: comb (p=0.02), frog and clothespin (both p= 0.04). False positive recognitions of foil items, although less common, showed similar errors with left sided injections, and of the 32 items, only the binder clip p = 0.01 and green dinosaur p = 0.05 were statistically notable. Conclusions: Some objects shown during standardized Wada testing may be easier to recall than others, yet that effect is more notable when information is presented and encoded to the awake left hemisphere, where memory may be both visually and verbally encoded in the majority of patients.