Trigeminal Rhizotomy Research Articles

Abnormal bone outgrowths and osseous structures around the foramen ovale may leads to mandibular compression or entrapment neuropathy

Foramina ovale is an important opening on the infratemporal surface of the posterior part of the greater wing of the sphenoid bone, any bone outgrowths and osseous structures around it could influence the anatomical organisation of the nerves and vessels that run through this opening. Accordingly the present study was designed to find out the bony outgrowths and osseous structures around the foramen ovale in available dried adult human skulls. The study was carried out using 100 dried adult human skulls irrespective of sex were obtained from the Department of Anatomy-Santhiram Medical College Nandyal, Department of Anatomy-Melaka Manipal Medical College (MMMC)-Manipal and Department of Anatomy- Viswabharati Medical College Kurnool. Among 100 dry adult skulls studied, sixty one (61%) of the skulls had neither any abnormal bony outgrowths nor osseous structures around the foramen ovale. Abnormal bone outgrowths in 22 skulls (22%) and osseous structures in seventeen skulls (17%) around the foramen ovale were noted. Anatomical knowledge of such abnormal bone outgrowths and osseous structures around the foramen ovale is important for neurosurgical procedures involving the percutaneous trigeminal rhizotomy for trigeminal neuralgia, transfacial fine needle aspiration technique in perineural spread of tumour and electroencephalographic analysis for seizure.

SU‐E‐J‐58: Lens Exposure During Percutaneous Trigeminal Nerve Radiofrequency Rhizotomy Guided by Computed Tomography with Three‐Dimensional Image Reconstruction

Purpose: The eye lens is one of the most radiosensitive tissues; it is an issue to estimate the lens dose during the percutaneous trigeminal nerve radiofrequency rhizotomy guided by computed tomography. The purpose of this abstract was to prove the CTDI(computed tomography dose index) peripheral (CTDIp) could be provided a reference value for the eye lens dose. Methods: There are two methods for estimate the eye lens dose in this study. The first is CTDIp calculated and second is ImPACT software which is common used in CT dose calculation. We Collected the CTDIv in dose report which create from CT scanner automatically. Ten patients who performed the trigeminal neuralgia underwent computed tomography (CT)‐guided percutaneous radiofrequency trigeminal rhizotomy was included. In order to find out the factor of CTDIv and CTDIp, we measured the CTDIv and CTDIp using ion‐chamber and 16‐cm diameter CTDI dose phantom. On the other hand, we also apply the ImPACT software to estimate the eye lens dose, and compare the two values, CTDIp and the eye lens dose from ImPACT. Results: The factor of CTDIv to CTDIp is 1.02. The average CTDIp in 10 patients is 116.65 mGy, and the average lens dose from ImPACT is 124 mGy. It is only 6% error. Conclusion: CTDIp can be provided a reference value for the eye lens dose. And the CTDIv can display in modern CT scanner in time, the radiologist can monitor the radiation dose during the exam. However,how to reduce the lens dose in this process would be next important issue foe us.

Role of Cranial and Spinal Virtual and Augmented Reality Simulation Using Immersive Touch Modules in Neurosurgical Training

Recent studies have shown that mental script-based rehearsal and simulation-based training improve the transfer of surgical skills in various medical disciplines. Despite significant advances in technology and intraoperative techniques over the last several decades, surgical skills training on neurosurgical operations still carries significant risk of serious morbidity or mortality. Potentially avoidable technical errors are well recognized as contributing to poor surgical outcome. Surgical education is undergoing overwhelming change, as a result of the reduction of work hours and current trends focusing on patient safety and linking reimbursement with clinical outcomes. Thus, there is a need for adjunctive means for neurosurgical training, which is a recent advancement in simulation technology. ImmersiveTouch is an augmented reality system that integrates a haptic device and a high-resolution stereoscopic display. This simulation platform uses multiple sensory modalities, re-creating many of the environmental cues experienced during an actual procedure. Modules available include ventriculostomy, bone drilling, percutaneous trigeminal rhizotomy, and simulated spinal modules such as pedicle screw placement, vertebroplasty, and lumbar puncture. We present our experience with the development of such augmented reality neurosurgical modules and the feedback from neurosurgical residents.

Management of bilateral trigeminal neuralgia with trigeminal radiofrequency rhizotomy: a treatment strategy for the life-long disease

The objective of this study was to evaluate the effectiveness of percutaneous controlled radiofrequency trigeminal rhizotomy (RF-TR) in patients with bilateral trigeminal neuralgia (BTN). Patients were analyzed after RF-TR in terms of outcome, safety and complications. Eighty-nine BTN patients underwent 186 RF-TR procedures. Eighty-seven patients had idiopathic trigeminal neuralgia (ITN) and two patients had multiple sclerosis (2.2%). Fifty-six (62.9%) were women and 33 (37.1%) were men. Ages ranged from 29 to 85 years. Anesthesia was administered at a determined optimal level, allowing patient cooperation for controlled and selective lesioning. The mean follow-up period was 101.71 ± 77.7 months. Familial occurrence was seen in two (2.2%) patients. Synchronized pain was observed in 25 (28.2%) patients. Pain occurrence on the contralateral side was observed with an average duration of 124.7 ± 87.13 months. Fifty-four of the 89 patients underwent 146 RF-TR procedures for both sides and 35 underwent 40 RF-TR procedures for one side. Complete pain relief or partial satisfactory pain relief was achieved on the medically treated side in 35 patients. During follow-up, 36 patients required the second procedure and 7 required the third procedure. Acute pain relief was reported in 86 (96.6%) patients. Early (<6 months) pain recurrence was observed in 11 (12.3%) and late (>6 months) recurrence in 25 (28.0%) patients. Complications included diminished corneal reflex in four (2.1%) patients, keratitis in two (1.1%), masseter dysfunction in four (2.1%), dysesthesia in two (1.1%), and anesthesia dolorosa in one (0.5%). RF-TR is an effective, selective, well-controlled, and effortlessly repeatable procedure for treating BTN, especially in the elderly, in terms of low morbidity and mortality rates and high rate of satisfactory pain relief.

Application of intraoperative computed tomography in a neurosurgical operating theatre

Background and purposeThe authors describe their own experience in use of intraoperative computed tomography (CT) with the Siemens SOMATOM Sensation in 125 cases. Material and methodsIntraoperative CT of the head was most often used in functional neurosurgery for stereotactic planning in 32 cases and for control of deep brain stimulation electrode placement in 18 cases. In spine surgery, CT was used most often in spine stabilization to control the placement of implants. ResultsThe implant had to be corrected in 7 cases (17% of 41 procedures), and in those cases the need for a revision procedure was therefore avoided. Intraoperative CT was also widely used in emergency procedures and perioperative complications in 13 cases, for control of intraventricular catheter or Rickham port placement in 8 cases, for evaluation of extent of tumour resection in 4 cases, for verification of electrode placement during percutaneous trigeminal rhizotomy in 3 cases, for evaluation of decompression after cervical corpectomy and thoracic discopathy in 3 cases, in complex fractures in 2 cases and as angio-CT after aneurysm clipping in 1 case. There was no significant prolongation of procedure duration. Intraoperative CT proved to be safe for a patient and for personnel. During the three-year evaluation period, the increasing use and indications for intraoperative CT were noted. Integration of CT with navigation is planned in the near future. ConclusionsIntraoperative CT is a very useful tool in spine surgery as well as in functional neurosurgery and neurooncology.

Treatment of Severe Trigeminal Headache in Patients With Pituitary Adenomas

The incidence of headache in patients with pituitary adenomas is high, and the underlying pathological mechanisms are not completely understood. We tested the efficacy of percutaneous ganglion block and trigeminal rhizotomy in the treatment of severe trigeminal/autonomic headache associated with pituitary tumors. Eleven patients treated surgically for pituitary adenomas in whom intractable trigeminal headaches developed were enrolled in the study and underwent ictal cerebral single-photon emission computed tomography before starting treatment. Initially, all patients underwent a 6-month medical treatment trial. Patients who did not experience improvement in headache severity, addressed by the Headache Impact Test-6 scale, underwent trigeminal percutaneous ganglion blockade. Two patients subsequently underwent trigeminal balloon rhizotomy. Among the 11 patients, 6 did not have improved Headache Impact Test-6 scale scores after 6 months of treatment with medications and underwent trigeminal ganglion blockade. Significant improvement in headache severity was noted in 3 of them. Long-term response was obtained in 1 patient, and the other 2, in whom the response was transient, were then successfully treated with trigeminal rhizotomy. Cerebral single-photon emission computed tomography showed increased uptake in the thalamus/hypothalamus region in patients who responded well to manipulation of the trigeminal-hypothalamic system. Percutaneous ganglion blockade and trigeminal rhizotomy may be promising alternative options for the treatment of severe headache in selected patients with pituitary adenomas.

Foramen ovale cannulation guided by intra-operative computed tomography with integrated neuronavigation for the treatment of trigeminal neuralgia

Radiofrequency rhizotomy of the Gasserian ganglion for the treatment of trigeminal neuralgia via percutaneous cannulation of the foramen ovale is facilitated by various localization modalities. In our preliminary study, we described the feasibility of computed tomography (CT) using an integrated neuronavigation system to cannulate the foramen ovale. Analysis was performed on 42 consecutive patients who underwent cannulation of the foramen ovale for radiofrequency trigeminal rhizotomy guided by CT using an integrated neuronavigation system. The reproducibility and safety of the neuronavigation-guided procedure were evaluated. Overall, the average dimension of the foramen ovale was 7.1 (1.5) × 4.7 (1.1) mm, and it was successfully cannulated by neuronavigation guidance in 31 (73.8%) patients with a mean cannulation time of 3.1 (0.7) min and an overall procedure time of 68.2 (16.4) min. The remaining 11 (26.2%) patients required subsequent CT guidance for successful puncture of the foramen ovale. These data demonstrate that neuronavigation-guided cannulation of the foramen ovale can be executed both quickly and safely on an outpatient basis. Additionally, the use of CT with integrated neuronavigation technology provides superior visual-spatial information compared to conventional fluoroscopy, the process of CT scanning, object planning, and neuronavigation-guided intervention can be completed in the same locale, and its application is easy to master and has the potential to enhance procedure tolerability of awake patients.

Incidence, morphology and morphometry of the foramen of Vesalius: complementary study for a safer planning and execution of the trigeminal rhizotomy technique

The foramen of Vesalius (FV) is located in the greater wing of the sphenoid bone between the foramen ovale (FO) and the foramen rotundum in an intracranial view. The FO allows the passage of the mandibular branch of trigeminal nerve, which is the target of the trigeminal radiofrequency rhizotomy. We analyzed its location, morphology, morphometry and interrelation among other foramina. 400 macerated adult human skulls were examined. A digital microscope (Dino-Lite plus) was used to capture images from the FV. A digital caliper was used to perform the measurements of the distance between the FV and other foramina (FO, foramen spinosum and the carotid canal) in an extracranial view of the skull base. In the 400 analyzed skulls, the FV was identified in 135 skulls (33.75%) and absent on both sides in 265 skulls (66.25%). The FV was observed present bilaterally in 15.5% of the skulls. The incidence of unilateral foramen was 18.25% of the skulls of which 7.75% on right side and 10.5% on left side. The diameter of the FV was measured and we found an average value of 0.65 mm, on right side 0.63 mm and on the left side 0.67 mm. We verified that positive correlations were statistically significant among the three analyzed distances. This study intends to offer specific anatomical data with morphological patterns (macroscopic and mesoscopic) to increase the understanding of the FV features as frequency, incidence and important distances among adjacent foramina.

Subarachnoid bleeding into the superior cerebellopontine cistern after radiofrequency trigeminal rhizotomy: case report

Sir, We would like to report an unusual case of a patient suffering from trigeminal neuralgia, who underwent percutaneous radiofrequency trigeminal rhizotomy (RF-TR), and complicated with subarachnoidal bleeding in the superior cerebellopontine cistern. A 68-year-old woman had been suffering from medically intractable trigeminal neuralgia. She had a 6-year history of trigeminal neuralgia at the ophthalmic and maxillary branches of the left trigeminal nerve. Cranial magnetic resonance imaging scans revealed no structural or vascular abnormality. Routine preoperative analyses, including coagulation studies, were normal. The patient underwent RF-TR under intravenously administered sedation and analgesia. The localization was confirmed within the nerve by electrical stimulation at 0.5 V (100 Hz, 0.2 m); and a lesion was made at a temperature of 70°C for 60 s. After the procedure, the patient’s pain resolved completely. However, 12 h after the procedure, sudden onset of severe headache, vomiting and neck stiffness occurred. The initial cranial computed tomography (CT) scan was normal. Lumbar puncture examination revealed bloody cerebrospinal fluid (CSF); the lymphocyte and monocyte proportions were normal. The control cranial CT scan showed subarachnoidal bleeding in the left superior cerebellopontine cistern (Fig. 1). The patient underwent conservative treatment, and neck stiffness and headache improved. She was discharged 7 days after the procedure. Trigeminal RF-TR is an effective and commonly performed procedure for control of medically refractory pain. Surgical procedures, such RF-TR, microvascular decompression, etc, may lead to serious complications. Anesthesia dolorosa, painful dysesthesia, absence of corneal reflex, corneal keratitis, masseter paralysis, septic-aseptic meningitis, cranial nerve palsy (cranial nerves III, IV, VI, VII, and VIII), blindness, carotid puncture, and carotidcavernous fistulae are all potential complications of the RFTR procedure [2]. Thus, all surgeons should be aware of these risks and not consider any of these methods as easy and safe. Meckel’s cave and root entry zone, which are the focus of these intervention methods, are at the same time the areas where multiple anatomic variations and vital structures are located [3]. Meckel’s cave opens through a porus into the cerebellopontine cistern. Meckel’s segment of the trigeminal nerve, which begins at the porus and extends to the trigeminal ganglion, is differentiated from the cavernous segment in the wall of the cavernous sinus. Meckel’s segment is narrower adjacent to the porus and fans out as it approaches the posterior edge of the gasserian ganglion, which is embedded in the dura just anterior to the anterior edge of Meckel’s cave. The superior petrosal sinus extends medially through the upper edge of the porus of Meckel’s cave and above the trigeminal nerve to join the cavernous sinus [1]. Some superior petrosal veins may join the sinus on the medial side of the trigeminal nerve. The SCA A. Savas Department of Neurosurgery, School of Medicine, Ankara University, Ankara, Turkey

Virtual reality imaging technique in percutaneous radiofrequency rhizotomy for intractable trigeminal neuralgia

Trigeminal neuralgia (TN) is the most common facial neuralgia, and is extremely painful. We evaluate the effectiveness of percutaneous controlled radiofrequency trigeminal rhizotomy (RFTR) assisted by a virtual reality (VR) imaging technique for idiopathic TN. A total of 2769 patients with TN underwent RFTR procedures between June 1986 and March 2007, with VR assisted guiding and electrode positioning in 26 patients from January 2006 to March 2007. A laminal basicranial CT scan (2 mm slice, 16 slices/s) was used during RFTR. The three-dimensional (3D) position of the electrode needle tip and the oval foramen can be seen clearly using this VR technique. The position and depth of the needle was adjusted according to the virtual 3D-CT scan. CT scanning was performed repeatedly until the needle tip was situated in the oval foramen. Usually, the tip of the electrode was adjusted once or twice. Acute pain relief was accomplished in the 26 patients who underwent a single RFTR procedure assisted with VR. No recurrence of pain was noted except in one patient after 16 months. There were no permanent complications or mortality. VR-assisted RFTR represents a minimally invasive, low-risk technique with a higher efficacy compared with traditional RFTR.

Intracranial Hemorrhage After Percutaneous Radiofrequency Trigeminal Rhizotomy

Radiofrequency thermocoagulation (RFT) of trigeminal ganglion is a commonly performed percutaneous procedure for the management of trigeminal neuralgia. However, it is not free from potentially life-threatening complications. A case of intracranial hemorrhage following RFT, which was managed conservatively, is reported. The authors suggest that coagulation parameters be normalized and intra-procedural blood pressure controlled while performing this technique. As RFT is carried out as an ambulatory procedure, absence of any intracranial complication must be ascertained clinically before the patient is discharged.

Oculo-motility defects and treated trigeminal neuralgia

Purpose: To report the ocular motility defects associated with the surgical treatment of trigeminal neuralgia. Methods: There were five patients who presented with ocular motility defects after surgical treatment of trigeminal neuralgia. In three patients the method of treatment was microvascular decompression (MVD) of the trigeminal ganglion. Two patients were treated with percutaneous controlled radiofrequency trigeminal rhizotomy (RF-TR). Results: There were four male patients. The mean age was 67.8 ± 9.1 years (median, 73years). In the three patients treated with MVD, two presented with fourth nerve palsy and one presented with sixth nerve palsy. All these patients made a complete recovery between 5 and 8 months. In the two patients treated with RF-TR one patient presented with a third nerve palsy that recovered completely over a 6 month period. The other patient presented with a complete third, fourth, and sixth nerve palsy. At the 7-month follow-up he continues to have a partially recovered third nerve palsy. Conclusions: The surgical treatment for trigeminal neuralgia may result in potentially serious ophthalmic side effects or complications. Ophthalmologists should be aware that ocular motor cranial neuropathies can occur after these procedures and that, although complete recovery is seen in the majority of cases, persisting palsies may also be encountered.

VGluT1- and GAD-immunoreactive terminals in synaptic contact with PAG-immunopositive neurons in principal sensory trigeminal nucleus of rat

To trace the origin of abundant vesicular glutamate transporter 1-like immunoreactive (VGluT1-LI) axon terminals in the dorsal division of the principal sensory trigeminal nucleus (Vpd) and the relationships between VGluT1-LI, as well as the glutamic acid decarboxylase (GAD)-LI axon terminals, and phosphate- activated glutaminase (PAG)-LI thalamic projecting neurons in the Vpd. Following unilateral trigeminal rhizotomy, triple-immunofluorescence histochemistry for VGluT1, GAD and PAG and the immunogold-silver method for VGluT1 or GAD, combined with the immunoperoxidase method for PAG were performed, respectively. After unilateral trigeminal rhizotomy, the density of VGluT1-like immunoreactivity (IR) in the Vpd on the lesion side was reduced compared to its contralateral counterpart. Under the confocal laser-scanning microscope, the VGluT1-LI or GAD-LI axon terminals were observed to be in close apposition to the PAG-LI thalamic projecting neuronal profiles, and further electron microscope immunocytochemistry confirmed that VGluT1- and GAD-LI axon terminals made asymmetrical and symmetrical synapses upon the PAG-LI neuronal structures. The present results suggest that the VGluT1-LI axon terminals, which mainly arise from the primary afferents of the trigeminal ganglion, along with the PAG-LI neuronal profiles, form the key synaptic connection involved in sensory signaling.

Review of complications due to foramen ovale puncture

We aim to evaluate the mechanisms responsible for complications during trigeminal rhizotomy via foramen ovale puncture. Ten dry skulls and 10 skull-base specimens were investigated in the present study. In cadaveric skull-base specimens, the anatomical relationships between the foramen ovale, mandibular nerve and Gasserian ganglion and the surrounding neurovascular structures were investigated intradurally. The distance between the foramen ovale and Gasserian ganglion was measured as 6 mm. The abducent nerve, adjacent to the anterior tail of the petrolingual ligament, was observed passing along the lateral wall of the cavernous sinus. Advancement of the catheter more than 10 mm from the foramen ovale is likely to damage the internal carotid artery and the abducent nerve at the medial side of the petrolingual ligament. Thermocoagulation of the lateral wall of the cavernous sinus may damage the cranial nerves by heat, giving rise to pareses.

Ultrastructural findings of idiopathic trigeminal neuralgia

Abstract Objective: To further investigate the ultrastructural features of trigeminal nerve root in patients with trigeminal neuralgia without vascular compression. Methods: Trigeminal nerve root biopsy specimens were excised from 12 patients scheduled to undergo posterior fossa craniotomy and root exploration. In 12 of 106 patients no vascular compression was detected. Partial trigeminal posterior rhizotomy was performed. A biopsy sample was taken from the cut portion of the root, followed by electron microscopic examination. Results: The primary finding was the pronounced involvement of the myelin sheath and Schwann cells. In 10 out of 12 specimens, there were some claviform steroid crystals in the Schwann cell cytoplasm. Myelin filled came to fill the liposomes. In all specimens, dysmyelination and demyelination were the main changes of the myelin sheath. Conclusion: Claviform steroid crystals in Schwann cell cytoplasm and lipid deposition in the inner myelin sheath of trigeminal root were found.

Stereotactic radiosurgery using CT cisternography and non-isocentric planning for the treatment of trigeminal neuralgia

Objective: Frame-based radiosurgical rhizotomy has been shown in clinical studies to be effective for managing trigeminal neuralgia (TN). To date, however, only a small pilot study has been published for the frameless, image-guided CyberKnife system. We present our preliminary experience with 29 trigeminal neuralgia patients treated with the frameless CyberKnife using X-ray image-guided targeting, a novel CT method for target definition, and non-isocentric planning.Materials and Methods: All 29 patients failed previous medical therapy and 14 had undergone prior surgical procedures. CT iohexal cisternography was used to identify the 6- to 8-mm segment of nerve to be lesioned. The marginal dose ranged from 60 to 70 Gy (median 66.4 Gy) as defined at an average 79th percentile. The corresponding Dmax varied from 71.4 to 86.4 Gy (median 77.91 Gy).Results: After a median 10-month follow-up, 26 of 29 (90%) patients rated their pain control as excellent and 3 (10%) reported no improvement. Median time to improvement was 6 days. No or only minor progression in numbness was reported by 22 of 29 (76%) patients, 4 of 29 (14%) patients reported worsening, and 3 of 29 (10%) reported the onset of severe ipsilateral facial numbness. Two patients whose target volume inadvertently included the semi-lunar ganglion developed painful dysethesias in the distribution of their numbness.Conclusion: Although the optimal dose and length of nerve to be lesioned are still being refined, this preliminary experience suggests that image-guided robotic radiosurgery can effectively lesion the trigeminal nerve. Further follow-up is needed to determine whether our method has advantages over the more commonly used procedure for radiosurgical trigeminal rhizotomy.

The Clinical Effectiveness and Selectivity of Radiofrequency Trigeminal Rhizotomy Using a 2 mm Active Tip Electrode for the Treatment of Trigeminal Neuralgia

Background: To minimize the side effects of radiofrequency trigeminal rhizotomy by making a more selective minimal lesion for the target division of a trigeminal rootlet, we performed this study to evaluate the effectiveness and the selectivity of radiofrequency trigeminal rhizotomy using a 2 mm active tip electrode as compared to a 5 mm active tip electrode. Methods: The authors evaluated 36 cases, in which radiofrequency thermocoagulation of a trigeminal rootlet was performed using a 2 mm active tip electrode or a 5 mm active tip electrode at for 60 seconds in patients suffering from trigeminal neuralgia. One month after each operation, we assessed the clinical effects, selectivity, and the side effects of these operations. Results: Of the 36 patients, 34 patients experienced loss of tic pain. In terms of effectiveness, no difference was found between the two groups. In terms of selectivity, some superiority was shown by the 2 mm active tip electrode, but this was not statistically significant. Masseter weakness or dysesthesia occurred in six patients who suffered from tic pain in the V3 region, and who were operated upon with a 5 mm active tip electrode. Major complications like anesthesia dolorosa, and corneal anesthesia were absent in any patients. Conclusions: For target specific lesion generation of trigeminal rootlets, single lesion generation using a 2 mm active tip electrode may be as clinically effective as a 5 mm tip and is more selective in use.

Percutaneous Radiofrequency Trigeminal Rhizotomy in a Patient with an Implanted Cardiac Pacemaker

Percutaneous radiofrequency ablation is a frequently used treatment for trigeminal neuralgia. Radiofrequency is another potential source of electromagnetic interference to implanted cardiac pacemakers. Our patient had a permanent pacemaker and underwent the procedure without incident.

Treatment of idiopathic trigeminal neuralgia: comparison of long-term outcome after radiofrequency rhizotomy and microvascular decompression. (Heidelberg College of Medicine, Heidelberg, Germany) Neurosurgery. 2001;48:1261-1267.

The purpose of this study was to evaluate the long-term outcome of patients after either percutaneous trigeminal rhizotomy or microvascular decompression (MVD) for idiopathic trigeminal neuralgia at a single institution. Overall, the results of the study showed that there was a 50% risk of recurrence of pain 2 years after percutaneous radiofrequency rhizotomy. Conversely, 64% of the patients who underwent MVD remained completely pain free 20 years postoperatively. Patients without sensory impairment after MVD were pain free significantly longer than patients who experienced postoperatively hypesthesia or partial rhizotomy. Conclude that because it is curative and nondestructive, MVD is considered the treatment of choice for trigeminal neuralgia in otherwise healthy people. In this study, it was proved to be a more effective and long-lasting procedure for patients with typical trigeminal neuralgia than radiofrequency rhizotomy. Patients without postoperative sensory deficit remained pain free significantly longer, which is a strong argument against the “trauma” hypothesis of this procedure. Comment by Ron Pawl, M.D. This paper is noteworthy in that comparing the follow-up on 225 of 378 patients who underwent microvascular decompression (MVD) with 206 of 316 who underwent radiofrequency thermocoagulation (RFT), the RFT group stood a 50% risk of recurrent pain by 2 years after the procedure, whereas 64% of those undergoing MVD were pain-free after 20 years. Furthermore, after MVD, those patients with no postoperative sensory deficit, measured with von Frey hairs, remained pain-free longer than those with a sensory deficit. This latter finding flies in the face of the concept that to be effective, surgery for trigeminal neuralgia must damage the nerve. The whole concept of RF lesioning of the nerve is to damage it enough to deaden the trigger zone of the affected nerve branch. However, in this study it is noted that postoperative hypesthesia was only temporary after RF lesioning, which might well explain the high rate of pain recurrence in this series. Although the long-term pain relief in the MVD group is excellent, it must be weighed against the complications. In the MVD group, there were 3 mortalities, diminished hearing in 5%, loss of hearing in 2.6%, facial paralysis in 4 patients, and tinnitus in 4 patients, none of which occurred in the RF group.

Trigeminal neuralgia due to multiple sclerosis: ultrastructural findings in trigeminal rhizotomy specimens.

Trigeminal neuralgia is a well-recognized complication of multiple sclerosis. In patients with neuralgia not responding to medical treatment or transcutaneous ablative procedures, the pain can often be treated successfully by partial rhizotomy of the trigeminal sensory root. We have examined partial trigeminal rhizotomy specimens from six multiple sclerosis patients, aged between 34 and 77 years, with intractable trigeminal neuralgia lasting between 18 months and 11 years. The rhizotomy specimens were placed in buffered glutaraldehyde immediately after resection, and subsequently processed for electron microscopy. In all cases, this revealed demyelination in the proximal (CNS) part of the nerve root, with associated gliosis and variable inflammation. A consistent feature was the presence of clusters of juxtaposed axons without intervening glial processes. Similar juxtaposition of axons was previously observed in trigeminal neuralgia due to vascular compression of the nerve root. Experimental studies indicate that this arrangement of demyelinated axons is conducive to both spontaneous impulse activity and ephaptic spread of excitation. The demyelination and associated juxtaposition of axons may therefore account for key aspects of the pathogenesis of trigeminal neuralgia.