Neuropsychological Outcomes After Insular Tumor Resection: Focus on Neurologically Intact Patients Following Transsylvian–Transinsular Resection in the Dominant Hemisphere

Background Gliomas of the dominant insular lobe represent functionally critical tumors in which overt neurological deficits may be absent despite involvement of language-related and associative networks. In such cases, standard neurological examination does not always adequately reflect the status of higher cognitive functions, underscoring the importance of neuropsychological assessment for a comprehensive evaluation of functional outcomes following surgical treatment. Objective To evaluate neuropsychological outcomes in patients with gliomas of the dominant insular lobe, with particular emphasis on a functional analysis of the subgroup undergoing resection via the transsylvian–transinsular approach, aiming to identify subclinical cognitive alterations in the absence of clinically significant neurological deficits. Materials and Methods A prospective, single-center observational cohort study was conducted between January 2023 and December 2025. Thirty-one patients aged 18–52 years were included. Hemispheric dominance was determined clinically based on handedness. All tumors were classified as gliomas according to the WHO classification (LGG/HGG). In 12 patients, the tumor was located in the left insular lobe; among them, 8 patients underwent resection via the transsylvian–transinsular approach, which was applied in individuals with a clinically preserved preoperative neurological status allowing standardized neuropsychological assessment. The extent of resection comprised subtotal resection (STR) in 9 patients and gross total resection (GTR) in 3 patients. Neuropsychological evaluation was performed in all patients during the preoperative and postoperative periods; in patients with transient motor aphasia, testing was conducted after regression of the speech deficit. One illustrative clinical case is presented using intraoperative images. Results In the early postoperative period, transient neurological disturbances were observed in three patients with dominant insular tumors who underwent resection via the transsylvian–transinsular approach: motor deficits in two patients and motor aphasia in one patient. No new permanent neurological deficits were identified compared with the preoperative status, and all transient deficits completely resolved during follow-up. Neuropsychological assessment revealed cognitive alterations in a subset of patients both in the early postoperative period and during subsequent follow-up, including patients with clinically preserved or recovered neurological status. The profile and severity of neuropsychological impairments varied across patients and time points, as detailed in the corresponding tables. Conclusion Within the framework of this prospective study, it was demonstrated that a clinically preserved neurological status after surgical treatment of dominant insular gliomas does not necessarily reflect the integrity of higher cognitive functions. Despite the absence of permanent motor or language deficits, neuropsychological assessment identified cognitive alterations in a subset of patients, including those with an otherwise neurologically intact clinical presentation. In this context, neuropsychological testing proved to be more sensitive than standard neurological examination in detecting subclinical cognitive impairments following tumor resection via the transsylvian–transinsular approach.