Gabriele Miceli - Università degli Studi di Trento, Italy
2D3
My talk starts from two considerations:
a. Spelling (and reading) skills are critical in everyday life, due to the massive use of computers, tablets, smartphones, etc. In the recent past, increasing interest in the cognitive neuroscience of spelling has resulted in detailed neuroanatomical and functional hypotheses, that can account for normal and pathological spelling performance, and guide the diagnosis and treatment of dysgraphias.
b. Awake surgery is increasingly popular in the treatment of gliomas. It allows extensive removal of tumour tissue, while at the same time monitoring and preserving language and communicative skills. Preoperative neuropsychological testing identifies items to be administered during surgery. Intraoperative mapping pinpoints the cortical and subcortical regions involved in language, to be spared during surgery. Postoperative and follow-up assessments allow monitoring the outcome of surgery and guiding speech-language therapy, if needed. In short, awake surgery is an individually-tailored set of procedures that aims at removing the largest extent of tumour tissue while preserving the patient’s quality of life.
Notwithstanding these facts, language testing during awake surgery procedures is still largely restricted to speech (automatic series, object naming, spontaneous narratives). Reports on writing are exceedingly rare.
A thorough search of the awake surgery literature only yields 23 studies that mention writing, and only 9 that report interpretable spelling performance. However, even such a small database provides relevant information. Dysgraphia was observed post-operatively in 26.9% of the patients with intact pre-operative writing, and persisted at follow-up in 45% of these. Intra-operative stimulation interfered only with writing in 48.1% of the cases. Coherent with data from stroke and fMRI investigations, a network of frontal, parietal and temporal regions was found to be critical for writing. Interestingly, while damage to some regions affected both ‘central’ and ‘peripheral’ spelling processes, damage to other areas selectively interfered with ‘central’ or with ‘peripheral’ stages.
A retrospective study from our group shows that subjects in whom spelling was mapped intraoperatively had a better prognosis and/or recovered pre-operative spelling skills more quickly and fully than subjects in whom no assessment had been carried out. A prospective study on the impact of intraoperative mapping of reading on postoperative reading and writing skills shows that the procedure does preserve reading, but protects spelling only in some cases. In contrast, dedicated intraoperative mapping of spelling results in intact postoperative performance.
Cognitive neuroscience of spelling and awake surgery practice can fruitfully interact in at least two critical areas. From a clinical perspective, current knowledge of the functional neuroanatomy of spelling can inform awake surgery at all stages (pre-, intra, post-operative and follow-up) – for example, by selecting patients for whom the intraoperative assessment of spelling is mandatory, advisable or redundant. From the perspective of cognitive neuroscience, carefully designed intraoperative mapping might shed light on stages of spelling (e.g., modality-specific spelling skills, like written spelling, oral spelling, typing), that are largely unamenable to testing in stroke cases, due to the nature of vascular lesions.
Gabriele Miceli
