Evaluating spelling in Glioma patients undergoing awake surgery: a systematic review

A main goal of awake surgery is to preserve language in order to facilitate return to work and maintain quality of life. Although spelling has become crucial in daily life, it has received little attention in awake surgery practice. We review assessments of spelling carried out in awake surgery studies, to inspect how current neurofunctional theories of spelling may guide pre-, intra- and post-operative neurosurgical practice. A systematic database search in Embase, Medline, PubMed and Web of Science identified studies reporting on spelling assessment in glioma patients undergoing awake surgery. Twenty-three studies were included, of which only 9 report details on spelling assessments. We evaluate the incidence of dysgraphia in glioma patients, the types of spelling errors as a function of tumor location, and the specificity of spelling sites with respect to other language functions. Post-operative dysgraphia arose in 26.9% of the patients with preserved pre-operative handwriting, and persisted in 45.0% of them at follow-up. Intra-operative stimulation interfered only with handwriting in 37.7% of the patients. A network of frontal, parietal and temporal regions was found to underlie central and peripheral spelling processes. Evidence on spelling performance in patients undergoing awake surgery for gliomas is surprisingly scarce. With the limitations inherent in the small number of observations, results converge with the neurofunctional knowledge accruing from studies of stroke cases. Such knowledge should be exploited in more thorough investigations of spelling skills in glioma patients. Implications for clinical and neuroscientific practice are discussed, as well as possible strategies to overcome current limitations.