Cottonoid-Guided Dynamic Ultrasound Navigation During Brain Surgery: A Technical Note and Case Series

Intraoperative ultrasound (ioUS) provides real-time imaging during cranial surgery and may be particularly useful when the reliability of conventional neuronavigation is reduced by brain shift, tissue distortion, or registration challenges. Cottonoid patties have previously been described as echogenic markers for intraoperative orientation, but their use has remained limited. In this technical note and case series, we describe a simple technique combining cottonoids with ioUS to provide a dynamic intraoperative reference during tumor resection. By exploiting the intrinsic hyperechogenicity of cottonoids and their readily identifiable movement during gentle manipulation, the technique was used to confirm surgical trajectories, support depth perception, and assist with spatial orientation throughout the procedure. We report a consecutive series of 12 patients with intracranial tumors in different anatomical locations and surgical positions, with particular emphasis on posterior fossa and occipital lesions. Rather than introducing a novel concept, the present Technical Note extends previous proof-of-concept experience by describing the practical transferability of cottonoid-guided ioUS to an independent consecutive adult cohort and by detailing its repeated use throughout the operative workflow, from initial trajectory confirmation to resection-cavity assessment. Trajectory confirmation was estimated by the operating surgeon to require less than 30 s in all cases, and no complications attributable to the technique were observed. Gross-total resection, assessed by postoperative magnetic resonance imaging, was achieved in all patients. The series also provides practical experience with posterior fossa and prone-position procedures, settings that remain comparatively underrepresented in the published literature. Our experience suggests that cottonoid-guided ioUS is a feasible, inexpensive, and practical adjunct to conventional neuronavigation, providing a dynamic reference that reflects current intraoperative anatomy.