A paradigm for awake intraoperative memory mapping during forniceal stimulation

Abstract

A case report is presented detailing the successful use of awake intraoperative memory testing while using white matter stimulation in order to isolate the fornix tracks involved in memory function. The identification of the white matter tracks of the fornix that were involved in memory function was used to tailor the neurosurgical resection of a third ventricle tumor that was impinging on the fornix in order to successfully preserve memory functioning in the patient.

Selection of intraoperative tasks for awake mapping based on relationships between tumor location and functional networks

“…42,120,122 Stimulation during encoding, storage, or retrieval has also been used to map memory function in awake procedures involving dominant premotor areas, left anterior temporal lobe, or fornix. 10,106,112 The frontal eye field, eliciting saccades and related to attention and working memory, has also been mapped. 100 Using a nonverbal semantic association test during intraoperative stimulation, it was possible to map the neural basis underlying multimodal (verbal and nonverbal) semantic processing.…”

“…Although the fornix is strongly related to memory function, EBM has been successfully used for memory mapping in an awake patient in order to tailor the resection of a tumor impinging on the fornix. 10 Association Pathways. Association fibers connect cortical centers within the same hemisphere and are subdivided into short (subcortical U-fibers) and long association fibers (deeper in the white matter).…”

“…106,112 The authors of a recent case report described the use of memory testing in an awake patient while performing white matter stimulation to isolate the fornix tracts involved in memory function. 10 Occipital Lobe. Visual pathways run from the lateral geniculate nucleus via optic radiations to the primary visual cortex, located in the banks of the calcarine sulcus.…”

Subcortical language and non-language mapping in awake brain surgery: the use of multimodal tests

“…Only very few studies have focussed on nonlanguage tasks for subcortical stimulation. A modified picturenaming task has been used to identify the visual pathways [24], a picture recognition task to identify the fornix tracts [5] and a line bisection task to identify the right superior longitudinal fascicle (SLF) [7]. Coello et al [7] recommended a combined task with picture naming and continuous movement to identify language networks, sensorimotor pathways and attentional processing/ working memory at the subcortical level.…”

Pushing the Limits of Glioma Resection Using Electrophysiologic Brain Mapping

“…Future developments in mapping techniques and instrumentation and functional intraoperative imaging are likely to improve the general utility of intraoperative neurosurgical charting of eloquent brain areas. While at this time most mapping consists in an intraoperative study of the effects of transient cortical inactivation and the mapping of evoked potential from cortical areas predicted to affect motor or sensory behavior, it is likely that future mapping and life imaging technologies will permit the mapping of higher functions of the brain, such as memory functions sustained by the hippocampus 53 , or higher cognitive functions 54,55 , such as those carried out by the frontal lobes 56–59 . Equally, improvements in the mapping of subcortical pathways 11,15,34,35,39,44,60 impinged upon by growing tumors will improve the capacity of neurosurgeons to increase resection while maintaining essential neuronal pathways 44,60,61 .…”