Torin Karsonovich, Allyson Alexander, Sarah Graber, and Brent R. O’Neill
Stereotactic electroencephalography (SEEG) is an increasingly common technique that neurosurgeons use to help identify the epileptogenic zone. The anchor bolt, which typically secures the electrode to the skull, can be problematic in very thin bone or in electrodes placed in the occiput.
A technique is described to place electrodes without the use of an anchor bolt. Accuracy data for entry point, target point, and depth were collected and compared between electrodes placed with and those placed without an anchor bolt.
A total of 58 patients underwent placement of 793 electrodes, of which 25 were boltless. The mean entry and depth errors at target were equivalent, although there was a trend toward greater depth error with boltless electrodes (3.4 mm vs 2.01 mm and 2.59 mm in the bolted groups, respectively). The mean lateral target error was slightly but significantly smaller for boltless electrodes. The majority (60%) of boltless leads were placed into thin temporal squamous bone. The average skull thickness at the entry point for all boltless leads was 1.85 mm.
Boltless SEEG electrodes can be placed through thin bone, adjacent to a cranial defect, or in the occiput with equivalent accuracy to electrodes placed with anchor bolts.
Ros Whelan, Eric Prince, David M. Mirsky, Robert Naftel, Aashim Bhatia, Benedetta Pettorini, Shivaram Avula, Susan Staulcup, Allyson L. Alexander, Maxene Meier, and Todd C. Hankinson
Pediatric adamantinomatous craniopharyngiomas (ACPs) are histologically benign brain tumors that confer significant neuroendocrine morbidity. Previous studies have demonstrated that injury to the hypothalamus is associated with worsened quality of life and a shorter lifespan. This insight helps many surgeons define the goals of surgery for patients with ACP. Puget and colleagues proposed a 3-tiered preoperative and postoperative grading system based on the degree of hypothalamic involvement identified on MRI. In a prospective cohort from their institution, the authors found that use of the system to guide operative goals was associated with decreased morbidity. To date, however, the Puget system has not been externally validated. Here, the authors present an interrater reliability study that assesses the generalizability of this system for surgeons planning initial operative intervention for children with craniopharyngiomas.
A panel of 6 experts, consisting of pediatric neurosurgeons and pediatric neuroradiologists, graded 30 preoperative and postoperative MRI scans according to the Puget system. Interrater reliability was calculated using Fleiss’ κ and Krippendorff’s α statistics.
Interrater reliability in the preoperative context demonstrated moderate agreement (κ = 0.50, α = 0.51). Interrater reliability in the postoperative context was 0.27 for both methods of statistical evaluation.
Interrater reliability for the system as defined is moderate. Slight refinements of the Puget MRI grading system, such as collapsing the 3 grades into 2, may improve its reliability, making the system more generalizable.