This study confirms the validity of slinging the compressing vessel away from the trigeminal nerve as a viable alternative to the commonly employed technique of separating the compressing vessel from the trigeminal nerve using shreds of Teflon.
TN is typically a relapsing condition with pain-free intervals that might last months or years. The current standard of care begins with carbamazepine, which frequently relieves symptoms. Unfortunately, the comfort afforded by carbamazepine or other medicines may diminish over time, and adverse effects such as hyponatremia or trouble balancing may prompt discontinuation of the treatment. Approximately half of all patients will eventually require an operation to relieve their discomfort [14].
The patient characteristics in this series, such as gender, affected side, and affected division, were consistent with prior local and global reports [15, 16]. The pain was mostly right-sided (right to left ratio was 1.5:1), and the mandibular branch was the most affected.
MVD was standardized by Janetta where Teflon was inserted between the trigeminal nerve and the offending vessel. However, long-term follow-up studies revealed a gradual decline of the efficacy of MVD for treatment of TGN which occurred in 1–7% of cases where development of Teflon-induced granuloma and adhesions around the nerve caused by inflammatory response induced by Teflon was the suggested etiology [17,18,19,20,21]. Rzaev et al. [7] found that though Teflon granuloma is rare following MVD, it could lead to recurrence of symptoms mitigating initial improvement. Chronic inflammation without signs of bacterial infection can be induced by small amount of intraoperative bleeding which may lead to granuloma formation. Matsushima et al. [22] suggested the use of sling retraction instead of the interposing technique in fear of adhesion of the prosthesis to the nerve thus leading to recurrence. It is worth noting that Sindou et al. [23] compared the outcomes of patients with TN using two technical modalities in 330 patients and concluded that the ‘no touching’ procedure had a better long-term outcome than the ‘touching’ procedure.
In our study, we had 90% success rate and one case had recurrence of symptoms requiring reoperation, whereas Masuoka et al. found recurrence in 4% of patients undergoing the sling retraction technique [9, 24, 25]. The higher incidence of recurrence in our study is obviously due to the smaller pool of cases.
We encountered early improvement of symptoms in 90% of the cases nearly matching the results of Cheng J et al. who had immediate pain relief in 83% of cases, partial pain relief in 11% and failure in 5% [26].
Poshataev et al. stated that most cases of TGN are caused by arterial compression (90%) namely the SCA and AICA and rarely caused by venous compression by branches of superior petrosal vein [11, 27, 28]. Barker et al. found the SCA to be the main vessel in contact with the nerve (75.5%), the AICA was involved in 9.6%, the vertebral artery in 1.6%, the basilar and the posterior-inferior cerebellar artery (PICA) in 0.7% and the labyrinthine artery in 0.2%. A vein attributed to the compression in 68% of patients and was the only compressing vessel in 12% [12]. These results coincide with the results in our study where the SCA was the offending vessel in 75% of patients, AICA in 20% of patients, and in 5% of patients, the nerve compression was caused by the complex venous anatomy together with AICA, in which case the patient had facial numbness postoperatively notably caused by excessive manipulation needed for successful slinging and avoiding injury to the petrosal vein.
The technique of vascular transposition using sling retraction was originally developed by Fukushima [29], and a variety of sling retraction techniques have subsequently been reported using aneurysm clips [13], Gore-Tex tape [30] and fascia strips [31].
Steinberg et al. [1] published their large series of 45 patients who had MVD for trigeminal neuralgia using a tentorial sling technique where a 3- to 4-mm split-thickness strip of dura with a pedicle at the medial and deep aspect of the inferior tentorium was created. The dural sling is then wrapped around the compressive vessel and secured using a Weck® clip or a suture.
Although their results, similar to our cohort, are comparable to those of the traditional MVD technique, the unique tentorial sling method offers neurosurgeons an alternative surgical technique that can be used when reinforcing with foreign material alone does not provide adequate decompression.
On another hand Attabib et al. conducted a retrospective review of MVD operations in which the culprit vessel was transposed and then maintained in position with a fenestrated aneurysm clip secured in position by suturing it to the dura mater. Among a consecutive series of more than 450 MVD surgeries, the fenestrated aneurysm clip sling was used in eight cases: six for HFS and two for TN. Four of these six patients were undergoing reoperations [32]. Similarly, Shigeno [31] described his technique where Gore-Tex tape was directly snared around the artery and sutured over the petrous dura. However, both are technically demanding especially with availability of other options.
Limitations of the study
The retrospective design of the study is an obvious shortcoming. Ideally, a prospective double blinded study is the most informative, however, in the surgical context; it is difficult and may be unethical to conduct such a study. A small number of cases is another limitation due to low statistical power. However, significant advantages could still be reported from this small study group.
