Surgical timing guided by progressive cognitive decline in a left insular tumor without neurological deficits: A case report.

Background: Insular brain tumors may remain clinically silent for prolonged periods without producing focal neurological deficits. In such cases, subtle cognitive changes may be underestimated despite their potential impact on daily functioning and quality of life. We present a clinical case of a left insular tumor in which the timing of surgical intervention was guided by the combination of progressive neuropsychological decline, radiological tumor growth, and concern that continued progression could increase surgical complexity and postoperative risk. Case Description: A 48-year-old woman with a cognitively demanding academic occupation was incidentally found to have a left insular tumor with medial extension on magnetic resonance imaging (MRI). During follow-up, she remained neurologically intact and seizure-free. Baseline and repeat neuropsychological assessments performed approximately 18 months later, including the Montreal Cognitive Assessment and Trail Making Test (parts A and B), showed preserved cognitive function. Approximately 3.5 years after the initial diagnosis, she developed progressive memory difficulties, impaired decision-making, and reduced professional performance. Repeat testing demonstrated mild cognitive impairment, predominantly affecting executive function and attention. Surgery was initially deferred; however, continued cognitive decline, interval tumor growth on serial MRI, and concern that further progression could increase surgical complexity supported operative intervention. After preoperative MRI, diffusion tensor imaging, and 3D time-of-flight angiography, subtotal resection was performed via a transsylvian transinsular approach under intraoperative neuromonitoring, with preservation of tumor portions adjacent to critical subcortical tracts. No postoperative focal neurological deficits or seizures occurred. Early transient cognitive worsening was followed by partial recovery on serial assessments through 6 months. Conclusion: This case illustrates that progressive cognitive decline may precede focal neurological deficits in patients with insular tumors and may represent an important early functional sign in clinically silent lesions. Rather than cognitive impairment alone, the timing of surgical intervention in this patient was guided by the combination of progressive neuropsychological decline, radiological tumor growth, and concern that continued progression could increase surgical complexity and postoperative risk. Systematic neuropsychological assessment may therefore help identify clinically meaningful functional deterioration and contribute to more timely and individualized surgical decision-making.