Extraventricular long-axis cannulation of the hippocampus: technical considerations

Area of Science:

• Neurosurgery
• Epilepsy Treatment
• Stereotactic Procedures

Background:

• Hippocampal epileptogenic foci may benefit from targeted intracranial monitoring and treatments.
• Longitudinal hippocampal cannulation offers greater coverage for therapies like electrical stimulation and laser ablation.
• Extraventricular trajectories minimize risks associated with brain shift and hemorrhage.

Purpose of the Study:

• To establish a standardized protocol for extraventricular longitudinal hippocampal cannulation.
• To provide detailed technical guidance for this neurosurgical procedure.

Main Methods:

• Retrospective review of 25 patients with 27 implanted longitudinal hippocampal devices.
• Simulated planning of bilateral occipital trajectories on 50 trajectories from 25 patients with mesial temporal sclerosis.
• Validation of a derived entry point on 50 trajectories from 25 additional patients.

Main Results:

• Extraventricular long-axis hippocampal implantation requires a specific lateral-to-medial and cephalad-to-caudal trajectory.
• A consensus entry point was identified from 64 trajectories, successfully facilitating 50 test trajectories.
• The entry point was validated in 4 patients requiring long-axis hippocampal cannulation.

Conclusions:

• A recommended entry point is approximately 5.5 cm superior to the external occipital protuberance and 5.5 cm lateral to midline for adult patients.
• Individual trajectory tailoring is essential for optimal patient outcomes.
• Accurate identification of the entry point is crucial for stereotactic frame positioning.