The Anatomy And Clinical Study Of Percutaneous Radiofrequency Thermocoagulation Therapy In Trigeminal Neuralgia Under Neuronavigation

Primary trigeminal neuralgia(TN) is defined by the International Association for the Study of Pain(IASP) as "a sudden,severe,brief stabbing,recurrent pain localization in the distribution of one or more branches of the fifth cranial nerve." The incidence rate of the disease is 3 to 5 per 100,000 per year.The pathogenesy of it is unknown.TN usually falls ill after the middle age.The median age at diagnosis is about 67 years.The incidence rate of female is higher than that of male.The pain ususlly located in the single lateral,the right is more than the left,and the bilaterality pain is little.The pain usually appears on the branchⅡ,Ⅲof the trigeminal nerve, and little on the branchⅠ.The diagnosis of TN depends strictly on clinical criteria.There are no objective laboratory or pathological tests,no apparent structural disease or functional disease by various kinds of imaging examination and it show no present neurologic sign.There are many kinds of treatment methods for the primary trigeminal neuralgia. The anticonvulsant drug carbamazepine is considered the drug of first choice. However,carbamazepine's effective may taper,and side effects are major problem. Several other drugs,usually other anticonvulsants used for neuropathic pain,are also some what side effects.Many patients who eventually become refractory to medication are candidates for one of several surgical options.The surgery methods include ethanol or butanol injection trigeminal ganglion, microvascular decompression(MVD),peripheral neurotomy,percutaneous microballoon compression(PMC),percutaneous radiofrequency thermocoagulation (PRFT) and stereotactic radiosurgery Gamma knife.Every method show some effects and related shortcomings.The mechanism of percutaneous radiofrequency thermocoagulation of the trigeminal ganglion is that the action potentials of small nociceptive fibers(A-delter and C fibers) are blocked at lower temperature than those of the larger tactile fibers(A-alpha and A-beta fibers)during surgical procedure,through the procedure the nociceptive fibers were damaged and tactual fibers were retained.Although percutaneous radiofrequency thermocoagulation of the trigeminal ganglion may affect the function of the trigeminal nerve to some extent,it is accepted by many patients because of its safety and simplicity.Moreover,the surgery is highly selective for the trigeminal ganglion damage leading to a low complication rate. Therefore,some neurosurgeons regard it as the first choice for most patients with intractable TN.Correct puncture of the oval foramen is one of the most important step in PRFT. Conventionally,PRFT is guided by intermittent fluoroscopy,which cannot be used to achieve precise location of the oval foramen consistently.Complications reported by many authors.Later computed tomography(CT) fluoroscopy-guided oval foramen puncture,and stereotactic radiofrequency thermocoagulation have been used to improve the accuracy of puncture and minimize the complications.As a simply and rapid localization tool,neuronavigation technique broadens the field of stereotactic neurosurgery,and prompts the development of neurosurgery greatly.It can provide us a real-time link between digitized neuroradiological images and anatomic structures.Theoretically,neuronavigation system can make the target points be viewable and monitor the trail of the surgery,so it provide us the possibility of precise localization of oval foramen.But if the neuronavigation system can precisely reflect the individual detail anatomical characteristics and if the system show its satisfactory stability,these problems puzzled the neurosurgeons constantly.This study began with the anatomy research,evaluated the precision and stability of neuronavigation system in reflecting the individual detail anatomical characteristics. Meanwhile,the study selected 21 primary trigeminal neuralgia cases who candicated for percutaneous radiofrequency thermocoagulation under neuronavigation, investigated the effects of navigation in the treatment of primary trigeminal neuralgia, provided theoretically basis for treating trigeminal neuralgia with radiofrequency thermocoagulation.In the anatomy parts,25 adults'(50 sides) cadaveric head were dissected and exposed the skull base and had continuous thin-slice CT scans.CT images were then transferred to the computer workstation via an optical disk,labeled the important structure such as foramen ovale of skull base and reconstructed.The cadaveric head were registered by Z-touch laser scanning.Observed the shape,size and position of foramen ovale,measured the diameters of foramen ovale and the depth of needle in trigeminal ganglion blocking with different surgery methods through neuronavigation system,CT images and standard scientific calipers respectively,evaluated the equivalence and stability of the three measurement methods.The results shew that foramen ovale is much varied in different individual on cadaveric heads,CT images and neuronavigation system.Neuronavigation system and CT images can reflect the individual detail anatomical characteristics of oval foramen.Compared with the values measured on cadaveric heads,the values of oval foramen parameters measured both on CT images and on neuronavigation shew no statistic difference(p＞0.2).The coefficient of variation of CT image measurement was smaller than the other two methods.In the clinical parts,21 patients with trigeminal neuralgia had continuous and thin-slice CT scans before surgery.The CT datas were transported to the neuronavigation system,the important structure such as foramen ovale of skull base were labeled and reconstructed and radiofrequency thermocoagulation was then performed on the patients.Routine monitoring during surgery included electrocardiography,heart rate,mean arterial blood pressure and pulse oximetry.All hemodynamic changes were monitored continuously and recorded throughout the surgical procedure.The results shew that neuronavigation assistance ensured precise puncture of oval foramen and successful targeting of oval foramen in all patients,the accuracy rate of puncturing is 100%.The value of numerical rating scales (NRS),decreased significantly from 8.7 to 2.5,1.7,2.0,2.2 at 1 hour,7 days,3 months,7 months after operation respectively.Also,the value of quality of life declined markedly.Serious complication wasn't observed.Conclusions:1) The foramen ovale is much varied in different individual.CT images on skull base before operation can reflect the shape and size of foramen oval and evaluate the difficult degree of puncturing foramen ovale.2) Neuronavigation system can show the individual anatomy characteristics of oval foramen objectively, measure the diameters of foramen ovale of cranial base and the depth of needle in trigeminal ganglion blocking precisely.3) When the anatomic structure is located precisely and objectively,the datas measured on CT images are more stable than that of the other two methods.4) Neuronavigation-guided radiofrequency thermocoagulation is very useful in puncturing the oval foramen and minimizing serious complications for primary trigeminal neuralgia.