Tag: entry point

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Optimal entry point for endoscopic colloid cyst resection

Endoscopic approach to colloid cysts

J Neurosurg 121:790–796, 2014

An optimal entry point and trajectory for endoscopic colloid cyst (ECC) resection helps to protect important neurovascular structures. There is a large discrepancy in the entry point and trajectory in the neuroendoscopic literature.

Methods. Trajectory views from MRI or CT scans used for cranial image guidance in 39 patients who had undergone ECC resection between July 2004 and July 2010 were retrospectively evaluated. A target point of the colloid cyst was extended out to the scalp through a trajectory carefully observed in a 3D model to ensure that important anatomical structures were not violated. The relation of the entry point to the midline and coronal sutures was established. Entry point and trajectory were correlated with the ventricular size.

Results. The optimal entry point was situated 42.3 ± 11.7 mm away from the sagittal suture, ranging from 19.1 to 66.9 mm (median 41.4 mm) and 46.9 ± 5.7 mm anterior to the coronal suture, ranging from 36.4 to 60.5 mm (median 45.9 mm). The distance from the entry point to the target on the colloid cyst varied from 56.5 to 78.0 mm, with a mean value of 67.9 ± 4.8 mm (median 68.5 mm). Approximately 90% of the optimal entry points are located 40–60 mm in front of the coronal suture, whereas their perpendicular distance from the midline ranges from 19.1 to 66.9 mm. The location of the “ideal” entry points changes laterally from the midline as the ventricles change in size.

Conclusions. The results suggest that the optimal entry for ECC excision be located at 42.3 ± 11.7 mm perpendicular to the midline, and 46.9 ± 5.7 mm anterior to the coronal suture, but also that this point differs with the size of the ventricles. Intraoperative stereotactic navigation should be considered for all ECC procedures whenever it is available. The entry point should be estimated from the patient’s own preoperative imaging studies if intraoperative neuronavigation is not available. An estimated entry point of 4 cm perpendicular to the midline and 4.5 cm anterior to the coronal suture is an acceptable alternative that can be used in patients with ventriculomegaly.

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Optimal trajectory of endoscopic third ventriculostomy

J Neurosurg 116:1153–1157, 2012. http://thejns.org/doi/abs/10.3171/2012.2.JNS111287

An optimal entry point for endoscopic third ventriculostomy (ETV) helps protect critical structures from undue manipulation. A commonly accepted ideal entry point is 3 cm from the midline and 1 cm anterior to the coronal suture. The authors of this study reexamine this ideal entry point.

Methods. Trajectory views from MR images or CT scans used for cranial image guidance in 53 patients (age range 3–85 years) who had undergone ETV were retrospectively evaluated. The trajectory from the tuber cinereum back through the center of the foramen of Monro was projected to the surface of the head. The relation of the entry point to the midline and the coronal suture was established.

Results. The mean perpendicular distance from the ideal entry point to the midline was 30.1 ± 7 mm (median 31.9 mm, range 12.5–42.2 mm). The mean perpendicular distance to the coronal suture was 8.9 ± 14.1 mm posterior (median 10.4 mm), ranging from 30.6 mm anterior to 35.8 mm posterior. The entry point tended to be located more posteriorly in women and adults: 5.8 ± 15.4 mm posterior in males versus 13.1 ± 13.2 mm posterior in females (p = 0.08) and 9.1 ± 14.8 mm posterior in adults versus 8.2 ± 11.7 mm posterior in children (p = 0.84).

Conclusions. While the entry point may need to be modified from the ideal trajectory for other anatomical reasons, such as a trajectory through the motor cortex, in general, the authors found that the optimal entry point for ETV was more posterior than previously published and highly variable. Using image guidance or a customized trajectory based on analysis of a patient’s own imaging is highly preferable to using an empirical ideal trajectory.

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