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Awake Craniotomy Cortical Mapping — FRCA Final MCQ

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HardNeuroanaesthesiaAwake Craniotomy Cortical MappingFRCA Final

During awake cortical mapping for resection of a dominant left temporal glioma, stimulation of the same cortical point reproducibly causes complete interruption of counting. There is no facial, mandibular or laryngeal movement, and electrocorticography shows no afterdischarge. What is the most accurate interpretation?

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Correct answer: E — A language-positive site within the distributed speech network has been functionally identified

Reproducible interruption of counting without orofacial motor activity or an electrocorticographic afterdischarge is a positive language-mapping response. Speech arrest identifies functionally important cortex within a distributed speech network and should influence the surgical boundary. It does not, by itself, prove stimulation of either classical Broca's or Wernicke's area: speech-arrest sites occur in ventral precentral and inferior frontal cortex, supplementary motor cortex, and posterior temporoparietal regions. Primary motor-cortex stimulation would be expected to produce movement or motor speech impairment rather than isolated arrest without muscle activity. A stimulation-induced seizure is less likely because no afterdischarge or evolving clinical activity is present. A reproducible positive response also does not itself establish that the current is excessive.

Reference: Lu J et al. Functional maps of direct electrical stimulation-induced speech arrest and anomia: a multicentre retrospective study. Brain. 2021;144:2541–2553. https://pubmed.ncbi.nlm.nih.gov/33792674/