Moscow Wada protocol: an optimised protocol for language and memory lateralization

The Wada test is an invasive procedure used to assess language and memory lateralization. Despite the widespread use of the Wada test in the population of people with epilepsy, the two existing standardized protocols for conducting the procedure are methodologically different and do not fully account for language comprehension as a separate domain. In this study, we presented a novel, optimized Wada protocol developed and tested using Russian language stimuli, with an English adaptation provided to support crosslinguistic application. The protocol was applied to a cohort of eight patients undergoing presurgical evaluation, demonstrating consistent lateralization patterns: language comprehension was predominately bilateral, while production was unilaterally localized in most patients, and memory representation was either bilaterally and right-hemisphere organized. Postoperative outcomes available for four patients confirmed the protocol's ability to identify eloquent hemispheres, as patients with unilateral language dominance showed transient language deficits after surgery, whereas those with bilateral representation did not. Furthermore, the intraoperative mapping results also corroborate the obtained outcomes. These findings support the protocol's enhanced applicability for determining individual patterns of language and memory lateralization, offering valuable insights to improve presurgical planning and treatment strategy selection for epilepsy patients.