Writing-specific sites in frontal areas: a cortical stimulation study

Abstract

Object. The aim of this study was to determine whether cortical areas involved in the writing process are associated with reading or naming areas in patients undergoing surgery for brain tumors in frontal areas. This study was undertaken to spare all language areas found in patients during surgery. Methods. Fourteen patients (eight women and six men [mean age 47 years] of whom 12 were right handed, two left handed, 12 monolingual, and two bilingual) who harbored brain tumors in the left (11 patients) or right (three patients) frontal gyri or in rolandic areas, were tested by direct stimulation by using the awake surgery technique for direct brain mapping. Mapping of the frontal gyri was performed using naming, reading, and writing under dictation tasks in the appropriate language(s). Considerable individual variability in language organization among patients was observed. Interferences in writing were found during direct stimulation in the frontal gyri, in cortical sites common or not common to interferences in naming or reading. In dominant regions, patterns of writing dysfunctions were variable and included writing arrest, illegible script, letter omissions, and paragraphia. These dysfunctions were nonspecific (stimulation-induced eye movements) in nondominant frontal regions and in rolandic gyri (hand contractions). In the same patient, different writing impairments could sometimes be observed during stimulation of different sites. As is the case for naming or reading interference sites, writing interference sites could be extremely localized (1 cm2 in diameter). In this group of patients, writing interference sites found in Broca areas were associated with other sites of language interference, whereas writing-specific interference sites were found twice in the dominant middle frontal gyrus. Conclusions. In this series, we found that writing interference sites could be detected by direct cortical stimulation in dominant inferior and middle frontal gyri regardless of whether they were associated with naming or reading interference sites. Writing disorders elicited by direct stimulation in the frontal lobes are varied and probably depend on the functional status of the stimulated cortical area.