Uniportal full-endoscopic decompression of the posterior cranial fossa: a comparative anatomical study of defect assessment using ultrasonography versus radiography and computed tomography.

STUDY AIMS: The surgical treatment of symptomatic Arnold-Chiari malformation type I (CM-I) typically involves decompression of the posterior cranial fossa. A full-endoscopic approach is emerging as an alternative to traditional microsurgical techniques. However, this method presents challenges in intraoperative assessment of the decompression extent, potentially resulting in inadequate decompression. In neurosurgery, ultrasound is gaining increasing importance, as it avoids ionizing radiation and enables real-time examination. The aim of this anatomical study is to evaluate the suitability of ultrasound for assessing defect size compared to radiography and CT during uniportal full-endoscopic decompression of the posterior fossa.

MATERIAL AND

METHODS

Six fresh-frozen adult human cadavers underwent endoscopic decompression of the posterior fossa. The endoscope used featured an oval shaft with a diameter of 9.3 mm, a working length of 177 mm, a 20° viewing angle, and an eccentric 5.6 mm working channel. Computed tomography (CT), X-rays, and ultrasound images were obtained before and after decompression for measurement purposes.

RESULTS

The average endoscopic decompression in the sagittal plane as measured by ultrasound was 26 ± 2 mm, with fluoroscopy 27 ± 1 mm and using CT 26 ± 1 mm. A statistically significant Pearson correlation was found between ultrasound and CT (r = 0.94, p < 0.01); between ultrasound and fluoroscopy (r = 0.9, p < 0.05); and between fluoroscopy and CT (r = 0.8, p < 0.05). The average endoscopic decompression in the axial plane as measured by ultrasound was 37 ± 2 mm, with fluoroscopy 26 ± 2 mm and using CT 36 ± 1 mm. A statistically significant Pearson correlation was found only between ultrasound and CT (r = 0.95, p < 0.01).

CONCLUSION

The full-endoscopic approach enables effective decompression of the posterior fossa in an experimental setup. Intraoperative ultrasound proves reliable in assessing the extent of decompression, showing good correlation with X-rays and CT. This technique holds promise for wider use in CM-I treatment, particularly in pediatric neurosurgery, where ultrasound offers a radiation-free method for intraoperative evaluation of defect size.