Monitoring von semantischer Assoziation in Hirntumorpatienten mit Kategoriebenennung/-beschreibung: Anatomische Korrelate und intraoperative Machbarkeit

Most tools for intraoperative speech mapping and monitoring are based on picture/ verb naming tests or biographical speech. However these tests do not capture the ability of contextual association reliably, which is critical to communication. Semantic association tasks like the pyramid and palm tree test (PPTT) are a promising option but, yet, there is little evidence regarding the suitability of different task instructions to depict dysfunction in distinct parts of the semantic network, and the respective functional network correlates. Therefore, we investigated the robustness, functional-anatomical correlation and intraoperative feasibility of a PPTT adaptation with different instruction types.

42 images were composed of one reference object on top and two choice objects below (triplet format), taken from the Cologne Naming Test (CoNaT). The task consisted in the forced choice/association of the semantically associated pair. Three instruction types were tested: (a) semantic choice via button-press, (b) overt naming of the semantically related object, and (c) overt naming or description of the common semantic category or description. First, the influence of the instruction type on response robustness and delay as well as on the functional cortex activations were investigated via video-based online interviews in 24 healthy adults stratified by age and gender and task-related fMRI (3T, clustered sparse acquisition; SPM 12) in 20 subjects. Thereafter, clinical feasibility was tested before and during awake surgery monitoring of glioma patients. The corresponding functional-anatomical regions were used as origin regions for tractography.

Results showed an association of age with latency, particularly the older group (p<0.005). Moreover, a significant impact of gender and age on difficulty and total test time was observed (p<0.001). Interim fMRI data showed mainly left-hemispheric activations, similar to non-verbal semantic tasks (middle and inferior frontal gyrus, anterior superior temporal gyrus; MFG, IFG, aSTG). Comparing the instruction conditions, overt category naming led to the most comprehensive activation patterns, notably extending to the frontal association network, and proved well-feasible in the clinical context.

Semantic association tasks, and category naming instructions in particular, are a promising tool for intraoperative monitoring and mapping of communication functions, especially for tumours involving the left MFG/IFG and the aSTG.