Placement of leads for stereotactic electroencephalography without the use of anchor bolts: Technical note

Objective: 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. Methods: 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. Results: 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. Conclusions: 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.