Clinical relevance of memory performance during Wada is stimulus type dependent.

OBJECTIVES

This study aimed to investigate whether different types of memory stimulus provide different information during the Wada or intracarotid amytal procedure (IAP) in patients with refractory medial temporal lobe epilepsy (MTLE).

METHODS

Eighty nine surgical candidates with documented MTLE and selected for left hemispheric language dominance underwent memory assessment with verbal and dually encodable stimuli during a presurgical IAP.

RESULTS

The overall IAP memory performance with the left hemisphere is significantly better than with the right hemisphere regardless of lesion side. This can be explained by the left hemispheric advantage of encoding all stimuli, whereas the right hemisphere has only limited resources to encode verbal stimuli. More importantly, it appeared that dually encodable items remain more readily recognised following injection ipsilateral to the lesion, whereas verbal items are always better recognised following right hemisphere injection regardless of lesion side.

CONCLUSIONS

Verbal IAP stimuli show left hemispheric sensitivity in left language dominant MTLE patients. The dually encodable items of the IAP appear lesion sensitive.