The trigeminal ganglion (TG) contains a large number of cell bodies of primary sensory neurons, including unmyelinated fibers, large myelinated fibers, and small fibers. Painful myelinated fibers conduct pain sensation, triggering frequent and persistent severe neuralgia in the oral and facial areas. Everyday activities such as brushing teeth, talking, eating, and washing the face can all potentially trigger trigeminal neuralgia (TN)[8]. According to the research results from the American Academy of Neurology and the European Federation of Neurological Societies (AAN-EFNS) "Trigeminal Neuralgia Treatment Guidelines," if patients with trigeminal neuralgia (TN) experience adverse drug reactions or inadequate therapeutic effects following treatment with medications such as carbamazepine or oxcarbazepine, prompt surgical intervention should be considered[9]。Currently, PBC targeting the trigeminal ganglion has become a research hotspot for treating trigeminal neuralgia (TN)[8]. The mandibular branch of the trigeminal nerve passes through the foramen ovale, where it converges with the maxillary branch and ophthalmic branch to form the large trigeminal ganglion (TG) on the impression of the petrous part of the temporal bone. It crosses the petrous ridge to form the trigeminal nerve root entering the middle cranial fossa. Within the middle cranial fossa, the inner layer of the dura mater wraps around the TG in a sac-like structure, known as Meckel's cave[10]. The Meckel's cave is the site where the trigeminal ganglion and the trigeminal nerve root meet, and effective compression by the balloon catheter at this location is crucial for ensuring postoperative clinical efficacy of PBC treatment. Meckel's cave typically has a round or oval shape, with the petrous part of the temporal bone below it and the sphenoid bone in front of it[11]. Due to the bony barrier, when contrast agent is injected into the balloon through the catheter, if the volume of the contrast agent exceeds the capacity of Meckel's cave, the balloon can only cross the petrous ridge and enter the trigeminal nerve root. The protruding part appears like a "nipple" on DSA, and the entire balloon takes on a "pear" shape. The appearance of the "pear" shape indicates that the balloon is within Meckel's cave and has filled it. In PBC, the balloon is positioned within Meckel's cave. After injecting the contrast agent and achieving a pear shape, mechanical compression of the three branches of the trigeminal ganglion (TG) can be realized. This allows for selective destruction of large myelinated nerve fibers within the TG, leading to evident demyelination and focal axonal injury in these fibers. Within 6 months, the self-repair function of the myelin sheath and axons results in the formation of normally functioning nerve fibers. Damage to unmyelinated and fine fibers involved in the corneal reflex is minimal. Therefore, PBC has advantages such as minimal trauma, rapid recovery, excellent efficacy, and fewer complications.
Traditional PBC usually targets the foramen ovale and uses the Hartel approach for puncturing under the assistance of DSA, CT, or simple stereotactic instruments. Although this approach improves the accuracy of puncture positioning to a certain extent, there are still some deficiencies in precision. Successful puncture requires surgeons to have rich clinical experience and superb operational skills. In TPBC, the two-dimensional images of the foramen ovale provided by DSA and CT have certain deviations, and in some patients, due to significant anatomical variations and deep positions of the foramen ovale, puncture becomes challenging, necessitating repeated X-ray imaging for positioning and puncture. Prolonged exposure to X-rays increases the risk of nerve and vascular damage. Precise positioning and puncture remain challenging and crucial aspects of PBC. Currently, due to the high precision of neurosurgical robotic procedures (error less than 1.0mm), they have been widely used in various neurosurgical fields such as brain abscess, DBS, hypertensive intracerebral hemorrhage, or intracranial lesion biopsy. The neurosurgical intelligent robot system Remebot software can reconstruct the three-dimensional structure of the foramen ovale and Meckel's cave based on preoperative CT, MRI, and other imaging data. It helps surgeons visually and dynamically observe the puncture position, reduce damage to surrounding tissues, and can be used to assist in treating PTN with IPBC.
The goal of PBC treatment is to achieve pear-shaped balloon expansion during the procedure to effectively and precisely compress the trigeminal nerve[12]. Therefore, obtaining a satisfactory pear shape is a key factor for the effectiveness of PBC treatment[13]. In addition to the shape of the balloon, the clinical efficacy of patients undergoing PBC treatment is also related to the duration of balloon compression and the volume of the balloon. Currently, there is still a lack of unified international standards for these indicators, and further exploration and research are needed. In this study, IPBC reconstructed the three-dimensional structure of Meckel's cave using the Remebot software system, accurately calculating the volume of Meckel's cave. The authors believe that the optimal balloon volume is the volume of Meckel's cave plus 0.1ml, calculated based on the "nipple-like" part of the balloon. Through this method, the study can accurately calculate the optimal balloon volume to avoid the risk of excessive volume leading to balloon rupture or insufficient postoperative clinical efficacy. In addition, this study also used a method of applying balloon compression to the trigeminal nerve twice, with a 1-minute interval between compressions, each lasting 2.5 minutes. Both groups of patients achieved good clinical outcomes after the procedure. Before IPBC, the Remebot software system is used to reconstruct the three-dimensional structure of Meckel's cave and its bony landmarks such as the petrous bone, sella turcica, and slope, in order to understand their anatomical differences. This information is then utilized to adjust the angle and direction of the probing needle in a timely manner based on the imaging pictures[11]. If the balloon is funnel-shaped, oval-shaped, or of another shape, contrast agent should be promptly released and the position of the probing needle adjusted until the balloon expands pear-shaped upon contrast injection. In this study, 21 cases (63.64%) of TPBC patients exhibited a "pear" shape, while all 33 cases (100.00%) of IPBC patients showed this shape, significantly higher than TPBC, indicating the feasibility of IPBC. Theoretically, preoperative IPBC involves importing DICOM data from head CT and MRI scans into the Remebot software system of the Rui Mi neurosurgery robot to simulate the optimal surgical path. The target point is Meckel's cave, connected to the foramen ovale in a straight line. The extension of this line intersects with the facial skin, serving as the skin puncture point. With robotic assistance, the probing needle can be precisely guided along the foramen ovale bone wall into the mandibular nerve sheath, allowing the balloon catheter to smoothly enter Meckel's cave through the probing tube. This method is particularly suitable for patients with anatomical anomalies such as oversized or narrow foramen ovale that make manual puncture challenging. Currently, there are no reports on the use of IPBC for PTN treatment internationally. In the past, foramen ovale localization and puncture were key measures in PBC. The IPBC assistance system used in this study is the Remebot software system of the Rui Mi neurosurgery robot. All 33 patients treated with IPBC underwent only one puncture with the probing needle, significantly lower than the average number of punctures (4.73±2.55) with traditional manual puncture methods. This approach can greatly reduce the number of punctures, X-ray exposures, patient radiation exposure time, and postoperative complications, representing a major advantage of this study.
In addition to the advantages mentioned earlier, IPBC offers the following benefits: ①Reconstruction of three-dimensional images of Meckel's cave, foramen ovale, and surrounding crucial structures (such as the cavernous sinus, internal carotid artery, etc.) through the Remebot software system provides a more intuitive way to simulate the optimal surgical path. This allows for better avoidance of these critical structures and provides dynamic feedback on the puncture process, thereby enhancing the precision of PBC and reducing postoperative complications. ②The Remebot software system is user-friendly, making surgical planning more convenient and easy to operate. ③The system boasts high precision, with positioning errors less than 1mm, enabling precise guidance of the balloon catheter to reach Meckel's cave effortlessly. ④The Remebot software system exhibits characteristics of high intelligence, precision, and scalability. The robotic surgical operation is flexible and convenient, with the robotic arm offering a high degree of freedom. This minimizes the trauma to patients during minimally invasive surgery, reduces incision size, alleviates postoperative pain, shortens surgical duration, decreases surgical errors, lowers surgical risks, and improves clinical outcomes postoperatively.
In this study, postoperative complications in patients undergoing TPBC included facial numbness in 18 cases (54.46%), weakened masseter muscle in 11 cases (33.33%), keratitis in 4 cases (12.12%), diplopia in 2 cases (6.06%), and herpes zoster in 1 case (3.03%). For IPBC patients, the occurrences were as follows: facial numbness in 5 cases (15.15%), weakened masseter muscle in 3 cases (9.09%), keratitis in 1 case (3.03%), diplopia in 1 case (3.03%), and no cases of herpes zoster. There was a statistically significant difference between the two groups in terms of facial numbness and weakened masseter muscle, indicating a higher incidence of postoperative complications in TPBC patients. However, there was no statistical difference in keratitis, diplopia, and herpes zoster between the two groups. The author suggests that repeated punctures during PBC surgery are important factors leading to facial numbness and weakened masseter muscle in TPBC patients. The preoperative NRS scores for both groups were 5.45±2.80 and 5.70±2.60, respectively, with no statistical difference (P=0.72). On the first postoperative day, the NRS scores were 2.00±2.19 and 0.85±1.33, and at 1 month postoperatively, the NRS scores were 1.03±1.40 and 0.36±0.70, with a significant difference observed (P<0.001), indicating that IPBC is more beneficial in early pain relief for patients. However, there was no statistical difference in the 6-month postoperative NRS scores (0.24±0.45 and 0.09±0.29, P=0.107), and both groups had similar BNI grades postoperatively, suggesting that both groups achieved comparable clinical outcomes at 6 months.