Development of a Neuronavigation-Compatible System for Selective Access of Trigeminal Rootlets in Radiofrequency Lesioning: A Cadaveric Morphometric Study

Introduction: Radiofrequency lesioning (RFL) is a safe and effective treatment modality for medically refractory trigeminal neuralgia (TN). Due in large part to the work of Dr. John Tew, RFL gained mainstream neurosurgical acceptance in the 1970s; however, the technique has remained relatively unchanged, relying on lateral fluoroscopy. We have previously reported on the feasibility of using neuronavigation in lieu of lateral fluoroscopy for selective targeting of trigeminal rootlets during radiofrequency lesioning and proposed that it may allow for more selectivity. We have since added to our dataset and improved upon our model. Additionally, we set forth in designing and developing a fully neuronavigation-compatible RFL system, expanding upon and modernizing Dr. Tew’s pioneering work.

Methods:

Part 1:

Twenty RFL procedures were performed on embalmed cadaveric specimens. After pre-procedural thin-cut CT scans were obtained, specimens were registered to neuronavigation and frontotemporal craniotomy was performed to facilitate direct visualization of the Gasserian ganglion. Pre-planned trajectories were created using an “entry” 2.5 cm lateral to oral commissure and “target” at FO. A 19-gauge TEW Cannula was retrofit to the modified end of a navigation probe, adjusting the “offset” function to permit real-time tracking. Using Hartel’s technique, the cannula was advanced through FO to the navigated posterior clival line (nPCL). A curved TEW electrode was inserted and oriented inferolaterally for V3 and superomedially for V2. For V1, the cannula was advanced 5 mm beyond the nPCL and the curved electrode was oriented inferomedially. At each position, a surgical microscope was used to evaluate whether successful contact was achieved. Relevant distances and trajectory angles were measured and recorded.

Part 2:

To design a neuronavigation-compatible system for RFL, we worked in conjunction with an engineering team to design and 3D print a prototype component which would be compatible both with an existing RFL Kit and with neuronavigation.

Results: Successful contact with V3, V2, and V1 was made in 95, 90, and 85% of attempts, respectively. The mean distance from entry point to FO was 7.61 cm ± 0.74 cm. The mean distance from FO to the nPCL was 1.26 cm ± 0.25 cm. The mean coronal and sagittal trajectory angles were 22.8° ± 6.6° and 50.6° ± 6.2°, respectively.

Discussion: Using neuronavigation and relying on the nPCL as an anatomic reference point, we were able to contact each trigeminal rootlet with high rates of success. The algorithm we used for selective targeting was slightly modified from that which was originally described by Dr. Tew; however, it may be better suited for use with neuronavigation. Our morphometric data, particularly the distance from FO to the nPCL, was highly uniform between specimens, indicating its potential as a key parameter. While issues relating to cost and resource utilization are valid, we believe incorporating neuronavigation into RFL will improve operative efficiency, accuracy, and ultimately improve outcomes ([Figs 1]–[4]).

Conclusions: Neuronavigation can be used to perform RFL in lieu of lateral fluoroscopy and may provide more selectivity. Despite its limitations, our investigation represents an important and necessary first step.

Fig. 1

Fig. 2

Fig. 3

Fig. 4

Publikationsverlauf

Artikel online veröffentlicht:
05. Februar 2024