Microvascular decompression has been considered as an effective and safe method for treatment of primary trigeminal neuralgia for decades. So far, most surgeons performed MVD with microscope. A recent multicenter study showed that the complete pain relief was found in 79% patients who underwent microscopic MVD with a recurrence rate of about 20% after follow-up.[26] However, not all the offending vessels could always be discovered under microscope due to its limited illumination and view. Sometimes, to visualize potential neurovascular conflicts in deep position under microscope, it required to increase the traction of cerebellum which could injury the facial nerve, vestibulocochlear nerve, or lower cranial nerves. Omission of neurovascular conflict and incomplete decompression were the important cause of failure and recurrence after MVD operation.[38] Compared to the microscope, endoscope could provide panoramic view and bright illumination which were very helpful for surgeons to identify the offending vessels. Therefore, some surgeons began to perform MVD with endoscope-assisted technique due to its advantages mentioned above.[1, 2, 8, 15, 25, 28, 36] Although endoscope-assisted technique improved the observation of deep structures without significant retraction of cerebellum and brain stem, it prolonged the operation time due to changing from microscope to endoscope, and back to microscope. The first fully endoscopic microvascular decompression for primary TN treatment was reported by Jarrahy in 2002.[16] In the following decade, it has been reported in several other single-center series and considered as an effective and save method to treat primary TN.[5, 10, 17, 27, 35]
In this study, we performed fully endoscopic MVD from dura was opened to be closed. Unlike to most surgeons who preferred to fix the endoscope to a holder during MVD operation,[5, 16, 18, 35] the assistant held endoscope in our department. So, position of endoscope could be adjusted at any time by the assistant according to the surgeon’s needs and a continual and dynamic visualization was obtained. It is not rare that the petrous vein or its tributaries block the way to the root of trigeminal nerve via traditional infratentorial superior-lateral cerebellar approach. It was very important to preserve these large veins because sometimes sacrifice of these veins may lead to serious complications such as, cerebellar and brain stem infraction, coma or even death.[12, 23, 37] To avoid such issue, our department presented a cerebellar-fissure approach by which the surgeon could detour the petrous vein or its tributaries and reach the REZ of trigeminal nerve directly.[40] This approach is more important for fully endoscopic MVD for TN, because sometimes assistant has to let endoscope detour these veins so that it could get closed to the REZ for more clear observation. Once the neurovascular conflict was identified, a piece of moist gelatin sponge was placed between offending vessel and the fifth nerve to expand the space between them owing to gelatin sponge swelling (Fig. 2b and c). It facilitated Teflon sponge interposition through the enlarging space. In addition, it reduced excessive dissection and retraction around neurovascular conflict area, which would result in the nerve or vessels injury. This method also called gelatin-assisted technique is especially fit for veinous compression.[12] The fully endoscopic MVD procedure for venous compression in this study was highlighted in Video 2. The recurrence of TN after MVD is not rare and it is still a challenge for surgeons. Teflon adhesion and its granuloma development have been considered as two of the important reasons for TN recurrence after MVD.[6, 14, 29, 32] Some studies by other surgeons have found that Teflon implants could result in chronic inflammation and fibrosis.[24, 32] Recently, our department demonstrated that placing the moist gelatin sponge between Teflon sponge and the facial nerve could remarkably reduce the incidence of hemifacial spasm recurrence.[7] We speculate that it will play the same role in reducing the incidence of TN recurrence because Teflon adhesion and its granuloma development were also the cause of TN recurrence, although there is no study report the outcome of this method in TN MVD.
With the help of bright illumination and panoramic view provided by endoscope, we explored every potential neurovascular conflict carefully and found SCA was the most common offending vessel (68.6%), similar to the other endoscopic MVD studies.[10, 18, 26, 27] In this study, the complete pain relief was found in 93 patients (97.9%) immediate postoperatively and 89 patients (93.7%) at the end of follow-up (Table 3). In 2013, Pradeep Setty et al. reported that 47 of 57 patients (82%) achieved complete pain relief (BNI score of I) immediately after fully endoscopic MVD operation. [33] Yadav et al. reported 46 of 51 patients (90.2%) who underwent fully endoscopic MVD had complete pain relief postoperatively.[39] A recent study reported by Pak et al. in 2022 described 22 of 22 patients (100%) have immediate postoperative complete pian relief (BNI score of I). [27] Complication after MVD operation is an issue the surgeon could not avoid. In this study, complication was found in 5 patients (5.3%) including facial numbness in 3 patients (3.2%), vertigo in one patient (1.1%), and headache in one patient (1.1%). There is no death, stroke, facial paralysis, hearing impairment, and CFS leak et al. The relatively low complication may attribute to the less dissection and retraction in cerebellopontine angle (CPA) that benefit from bright illumination and panoramic view provide by endoscope.
We think that the endoscope could play a very important role in MVD. It provides bright illumination and panoramic view which can help surgeons to observe the neurovascular structures in deep area of CPA without dead corner. Its lens could get access to the fifth nerve infinitely which facilitates surgeons to explore the neurovascular conflicts and prevent omission of offending vessels. For fully endoscopic MVD, the assistant could adjust the direction of endoscopic view at any time point as the surgeons’ needs which could keep the MVD operation dynamic and consistent. Moreover, the surgeon could decompress adequately using endoscope without excessive retraction of cerebellum and dissection of arachnoid membrane that would increase the risk of complication. However, there are some shortcomings we could not deny. The sense of depth is poor due to the two-dimensional view provided by endoscope. The fully endoscopic procedure requires the surgeon and assistant cooperate and synchronize well. Therefore, it will take relatively long time to overcome steep learning curve. More practice on model or cadaver is needed. Theoretically, the heat generated from the lens of endoscope may result in the injury of adjacent neurovascular structures.