Trigeminal Neuralgia (TN) is a neuropathic disorder characterized by episodes of intense pain in the face, originating from the trigeminal nerve [4]. TN is not easily controlled but can be managed with a variety of treatment options. In curing TN, the medical treatment based on anodynes, anticonvulsants, muscle relaxants. Nerve block based on local anesthetic, alcohol or glycerol on trigeminal neural division and ganglion. Also, RadioFrequency (RF) coagulation and the MicroVascular Decompression (MVD) have been used to treat TN in elderly patients [24]. CyberKnife (Accuray Inc., Sunnyvale, CA, USA) is constituted by a linear accelerator (LINAC) and a robot arm having six joints [1]. In this study, We retrospectively analyzed the outcome of 28 elderly patients with intractable TN to evaluate whether CKRS is an effective and safe mode of therapy.

TN is caused by compression of the trigeminal nerve root by blood vessels, usually within a few millimeters of the junction between the trigeminal nerve root and the pons [4,6]. Dandy initially mentioned the theory of neurovascular compression in 1934. He reported that 66 (30.5%) out of 215 patients, who underwent surgeries through craniotomy, experienced perstriction toward the trigeminal nerve. Likewise, Jannetta advanced his theory for the better. The real frequency of the perstriction towards the trigeminal nerve, observed by occipital craniotomy, ran up from 11% to 96%. He reported that He should set the trigeminal neuralgia's neurovascular etiology and the penetrative way of the trigeminal nerve root to the therapeutic target [24].

The application of RS to treat TN dates back to1950s with Leksell, who first used stereotactic radiosurgerytargeting the gasserian ganglion in humans with encouraging results [10]. Nowadays, the RS technique is a well-established option for the treatment of TN, and the series reported confirm the efficacy and safety of this modality Northwest Neuroscience Institute’s Young et al. and Pollock et al., who have reported multi-institutional researches, dealt with safety and efficacy of radiosurgery in detail among their reports [3,15,16,21,23]. The same as this study, such reports claimed that the penetrative way of trigeminal nerve root is the target of RS [2,9,14,23].

The rationale about the trigeminal neuralgia relief after RS is related to the effect on nervous amyelinic, low caliber cells associated to nociceptive sensibility, and to the destruction of the ionic channels and relative blockade of the electrical conduction [12,22]. Hodaie et al. by using tractography has helped the neurologiocal community reach a better understanding of the effect of RS on the trigeminal nerve. The authors have observed that radial but not axial diffusivities changed markedly after RS, suggesting that this irradiation technique primarily affects myelin. Also, tractography seems to be a more sensitive imaging tool than conventional gadolinium-enhanced MR, as confirmed by the fact that, for patients with long-term follow-up, recovery of FA/RD correlated with pain recurrence [5].

The claim is based on the experiences achieved through microneurosurgery. We observed initial pain relief in 89.5% (24 out of 28) of the patients with TN. Our results are consistent with the reported rates from studies of gamma knife (Elekta AB, Stockholm, Sweden) and linear accelerator (LINAC) radiosurgery, which have reported initial pain relief of 50 to 96%. This study is the result derived from applying CKRS to treat TN. After CKRS, the pain relief was analyzed on the basis of VAS system. 28 patients showed excellent response within 7 days. The reason why their pain were alleviated so rapidly can be explained by several causes. First, its accuracy is higher than the existing instruments because the therapeutic target is set by using positive contrast CT cisternography. Second, treatment planning and irradiation can be performed without any restrictions because there is no stereotactic ring. Lastly, isodose distribution can be easily equalized along the trigeminal nerve [2,11,18]. At periods of 2 years follow-up, 68% of our patients continued to have excellent pain relief. This is also comparable to other modes of radiosurgery. At gamma knife centers, 40 to 59% sustained pain relief was observed at 2 to 5 years follow-up [3,12,15,20,22].

Hypoesthesia/dysesthesia is the most common adverse event. The median hypoesthesia rate ranges between 19% and 28%. Others toxicities including anesthesia dolorosa, dysgeusia, dry eye syndrome, hearing impairment, and masticator weakness are very rare [8,11,13,14,17,18,21]. Factors which may affect the toxicity are the target selection, the length of the irradiated nerve, and the dose. Some studies seem to suggest a potential advantage of the intracisternal target compared to the REZ in terms of complication rate. Some other authors found that longer portions of irradiated nerve as well as doses higher than 90 Gy may lead to a higher toxicity rate. This study reported a 32% increase of new hypesthesia symptoms in the follow-up period, which we observed mild to moderate numbness in the patients. The median time to the onset of numbness was 10 months (range, 2-16 months) [22].

The merit of CKRS is that homogeneous conformity can be formed, the ray can be accurately irradiated and the therapeutic target can be accurately set [1]. Specifically, it is impossible to get satisfactory dose distribution from the thin and long trigeminal nerve by performing one-time spherical irradiation [7]. Dose distribution can be satisfiably formed though repetitive irradiation based on secondary isocenter, but it increases morbidity [11,18]. The accuracy of CKRS is based on the accuracy of ray emitting and target positioning. The accuracy of ray emitting can be high by the robot arm with six joints and the image-seeking camera system. The accuracy of target positioning can be high by the mutual function between CT imaging and treatment planning [18,19]. According to a phantom research on CKRS, the collimation error scored 1.1±0.3 mm when CT-scanning intervals were 1.25 mm. The error emarkably improved in comparison with the collimation error of 5 mm, derived from the treatment planning of conformal radiosurgery on the basis of the data gotten by MRI. It is also reasonable to speculate that the short latency and excellent response obtained in this series stems from better treatment accuracy [1,7]. CKRS with CT cisternography may have enhanced overall accuracy, which in turn may have been manifested in greater treatment efficacy [18,19].

In conclusion, this clinical study suggests that CKRS is a safe and effective treatment for Elderly Patients with TN in this study. In most patients, the pain was relieved in seven days after CKRS, and no severe complications occurred. However, In older patients, CKRS could be considered as a treatment option for TN.