Inion not a reliable landmark of the torcula in posterior fossa craniotomies

Abstract

Background: Sub-occipital craniotomies are used in surgical approaches into the posterior cranial fossa. The inion is used as an extracranial landmark of the torcula in burr hole placement. However, inadvertent damage to the torcula and the related sinuses due to variant intracranial location of the torcula has been reported. This study aimed at determining the position of the torcula in relation to the inion.

Method: 40 adult open skulls were obtained and the positional relationship between the inion and the torcula assessed. Results: The torcula was at the same level with the inion in half of the cases (50%), below it in 12 cases (30%), and above in 8 cases (20%). The position above the inion ranged from 0.38 to 2.40 cm and below it from 0.75 to 2.45 cm.

Conclusion: The torcula lies either at the level of the inion in only half of the cases. The surgeon should augment this physical landmark with radiographs to avoid iatrogenic injuries