Anesthesia Dolorosa Research Articles

Computed tomography-guided trigeminal tractotomy-nucleotomy for refractory chronic craniofacial pain: a case report

BackgroundRefractory chronic craniofacial pain is a debilitating condition with limited treatment options. This case report presents the use of percutaneous computed tomography-guided trigeminal tractotomy-nucleotomy under general anesthesia in a patient with refractory trigeminal neuralgia and post-treatment anesthesia dolorosa. This case report expands the use of TR-NC to include treatment-resistant post-treatment anesthesia dolorosa and introduces real-time verification under anesthesia, potentially broadening access and improving precision, while highlighting the need for further research on long-term efficacy and patient selection for this promising technique.Case presentationA 50-year-old woman with 12 years of chronic facial pain in the opthalmic and maxillary trigeminal branches despite multiple surgical and medical interventions underwent computed tomography-guided trigeminal tractotomy-nucleotomy under general anesthesia. Initial pain relief was significant, but symptoms gradually returned within 12 months. Transient mild ataxia was the only complication.ConclusionThis case suggests trigeminal tractotomy-nucleotomy under general anesthesia with real-time verification may be a valuable option for patients with refractory post-treatment anesthesia dolorosa. However, the transient nature of pain relief necessitates further investigation of long-term outcomes and optimal patient selection.

Retrogasserian trigeminal radiofrequency-thermorhizotmoy for trigeminal neuralgia

Based on a personal experience of 4200 surgeries, radiofrequency thermocoagulation is useful lesional treatment for those trigeminal neuralgias (TNs) not amenable to microvascular decompression (idiopathic or secondary TNs). Introduced through the foramen ovale, behind the trigemnial ganglion in the triangular plexus, the needle is navigated by radiology and neurophysiological testing to target the retrogasserian fibers corresponding to the trigger zone. Heating to 55–75 °C can achieve hypoesthesia without anaesthesia dolorosa if properly controlled. Depth of anaesthesia varies dynamically sedation for cannulation and lesioning, and awareness during neurophysiologic navigation. Proper technique ensures long-lasting results in more than 75% of patients.

Safety and Efficacy of Radiofrequency Ablation of Gasserian Ganglion in Trigeminal Neuralgia

Background: Trigeminal neuralgia (TN) is characterized by intractable pain in one or more division of trigeminal nerve. Pharmacologic management is first line treatment for TN, when it fails interventional treatment options are considered like percutaneous procedures or micro vascular decompression. Radio frequency thermoscoagulation is an effective option for medically refractory cases to control pain.Objective: To evaluate the safety and efficacy of Radiofrequency thermocoagulation of the gasserian ganglion for the treatment of trigeminal neuralgia.Methods: Total 44 patients were included in this prospective obsarvational study who were already diagnosed with trigeminal neuralgia and refractory to medical management. All patients were treated by radiofrequency thermocoagulation after confirming the position of needle tip by sensory and motor stimuli. Three lesions were created at 60-70oC for 90 second each. Patients were assessed for pain relief, corneal reflex, numbness and masticatory muscle weakness at immediate post procedural stage, 1 week, 1 month and at 6 months.Results: Twenty eight patients had pain over both mandibular (V3) and maxillary (V2) division, 12 patients had mandibular (V3) and 4 patients had only maxillary (V2) division involvement. Excellent pain relief was archived in 38 (86.36%) patients, 4 patients (9.09%) have good pain control and 2 (4.54%) patient developed poor pain control with development of Anesthesia dolorosa in 1 patient. None of them develop complete facial numbness, 41 patients developed tolerable numbness and 2 patients develop somewhat bothersome, Facial numbness. Three patients developed unilateral masseter muscle weakness however no patients developed corneal ulcers, blindness or other complications.Conclusion: Temperature controlled thermocoagulation is a safe and effective treatment options for trigeminal neuralgia.

Expect the Unexpected!! – Transient Cranial Nerve Palsies after Radiofrequency Ablation of Gasserian Ganglion for Trigeminal Neuralgia

Trigeminal neuralgia is the most common type of craniofacial neuralgia, characterized by paroxysmal lancinating electric shock-like pain confined to the somatosensory distribution of the trigeminal nerve. Fluoroscopy-guided Radiofrequency Ablation of Gasserian Ganglion (RFA-GG) is the commonly performed minimally invasive pain intervention in these patients. Various complications such as masseter weakness, corneal anesthesia, dysesthesia, anesthesia dolorosa, keratitis, and cranial nerve deficits have been reported during the procedure. We present the case of a 58-year-old male diagnosed with left-sided trigeminal neuralgia involving mandibular division of trigeminal nerve (V3 division) with a Numerical Rating Scale of 9/10 at the time of presentation. As the patient was unresponsive to medical management, RFA of the V3 division of GG was performed with acceptable sensory and motor stimulation. Postablation, 1 ml of 1.0% Lidocaine injection with 2 mg injection dexamethasone was given. After the procedure, the patient complained of dizziness, left-sided hearing loss, and double vision on looking toward the left side. On examination, deviation of the angle of the mouth toward the right side, reduced blink reflex on the left side, and incomplete closure of the left eyelid were observed. Vitals were stable and there was no respiratory discomfort. The patient was reassured and monitored in the recovery room. Signs and symptoms were transient and the patient recovered completely after 45 min. Clinical findings were suggestive of the involvement of three cranial nerves: the abducens nerve, the facial nerve, and the vestibulocochlear nerve. Spillage of local anesthetic solution into adjacent cranial nerves surrounding the GG might be the causative mechanism for transient cranial nerve palsies in this case.

Causalgia: A Review of Nerve Resection, Amputation, Immunotherapy, and Amputated Limb CRPS II Pathology.

Causalgia and complex regional pain syndrome (CRPS) type II with nerve injury can be difficult to treat. Surgical peripheral nerve denervation for causalgia has been largely abandoned by pain clinicians because of a perception that this may aggravate a central component (anesthesia dolorosa). We selectively searched Pubmed, Cochrane, MEDLINE, EMBASE, CINAHL Plus, and Scopus from 1947 for articles, books, and book chapters for evidence of surgical treatments (nerve resection and amputation) and treatment related to autoimmunity and immune deficiency with CRPS. Reviews were found for the treatment of causalgia or CRPS type II (n = 6), causalgia relieved by nerve resection (n = 6), and causalgia and CRPS II treated by amputation (n = 8). Twelve reports were found of autoimmunity with CRPS, one paper of these on associated immune deficiency and autoimmunity, and two were chosen for discussion regarding treatment with immunoglobulin and one by plasma exchange. We document a report of a detailed and unique pathological examination of a CRPS type II affected amputated limb and related successful treatment with immunoglobulin. Nerve resection, with grafting, and relocation may relieve uncomplicated causalgia and CRPS type II in some patients in the long term. However, an unrecognized and treatable immunological condition may underly some CRPS II cases and can lead to the ultimate failure of surgical treatments.

Percutaneous balloon compression for trigeminal neuralgia: experience and surgical techniques from a single institution

ObjectiveThe treatment experience and the technical skill with percutaneous balloon compression (PBC) for treatment of primary trigeminal neuralgia (TN) were summarised in a single institution.MethodsThis is a retrospective review including consecutive patients with typical symptoms of uni-lateral primary TN who underwent PBC from June 2020 to September 2021 in our institution. We excluded secondary aetiologies of TN. Patient demographics, surgical techniques and outcomes were reviewed. All included patients were initially managed with carbamazepine before PBC.ResultsA total of 70 patients were included. The mean length of follow-up was 10.6 months. Sixty-nine (98.6%) were successfully treated, and only one patient failed due to particularly narrow foramen ovale. Amongst successfully treated patients, 68 (97.1%) had immediate pain relief, with one having delayed relief. Sixty-eight patients (97.1%) had immediate facial numbness post-operatively and one (1.4%) presented delayed numbness 7 days after surgery. In the last follow-up, regarding facial numbness, 22 (31.9%) patients had complete resolution, whilst 46 (67.6%) had different degrees of benefit. Forty-nine (71.0%) patients developed masseter muscle weakness with recovery at 3-month follow-up. No anaesthesia dolorosa, keratitis, intracranial infection or death occurred in this study.ConclusionPBC for treatment of TN has quick and effective result, and could be safely performed under general anaesthesia without discomfort to the patient. The common postoperative complications are facial numbness and masseter muscle weakness, with most being improved or recovered at follow-up.

Feasibility and Morbidity for the Use of MR-Guided Laser-Induced Thermotherapy for the Treatment of Skull Base Tumors: A Report of Three Cases

Background Laser-induced thermotherapy (LITT) is a minimally invasive technique that has been demonstrated as an effective treatment of many pathologies; however, it has never been investigated for the use in skull base tumors. Case Series Three patients underwent LITT for treatment of skull base meningiomas. All three patients were determined to be poor candidates for open resection. Each patient was treated with a single laser fiber. Postoperative imaging confirmed ablation zones along the tract of the catheter in all three patients. Ablation zones were estimated to be 9 to 20% of the intended to treat tumor volume. Two of three treated patients suffered cranial nerve injury following the procedure with one patient diagnosed with neurotrophic keratitis and one patient with symptoms consistent with anesthesia dolorosa. Conclusion LITT is a technically feasible, minimally invasive treatment modality for skull base lesions. Significant risk to cranial nerves and small ablation zones afforded by a single cannula placement proposes serious obstacles. Further investigation is warranted prior to using this technique outside of a palliative indication.

Multivariate models to predict pain recurrence and sensitive complications after percutaneous balloon compression in trigeminal neuralgia.

Percutaneous balloon compression (PBC) is a popular treatment option for trigeminal neuralgia. However, the efficacy of PBC is widely considered to be associated with the occurrence of sensitive complications, although neither this correlation nor the underlying mechanisms have been established. The objectives of the present study were to identify factors predicting time to pain recurrence after PBC and identify factors predicting a severe sensitive complication. The authors conducted a retrospective study on patients who underwent PBC for the first time between 1985 and 2019 in two French hospitals. Data were retrieved from patients' medical records. Potential clinical and radiological predictors for time to pain recurrence and severe sensitive complication were evaluated using a Cox model and a logistic regression, respectively. A total of 131 patients were included in the study, with a median follow-up of 3.0 years. Pain recurrence occurred in 77 patients, and the median time to pain recurrence was 2.0 years. In the multivariate analysis, six independent factors predicting pain recurrence were identified: 1) longer duration of presurgical symptoms; 2) localization of the pain along the mandibular branch of the trigeminal nerve (V3); 3) atypical pain; 4) diagnosis of multiple sclerosis; 5) use of a medical device not specifically adapted for trigeminal neuralgia surgery; and 6) duration of balloon compression > 60 seconds. Regarding the secondary objective, 26 patients presented a severe sensitive complication after PBC, which the authors defined as the development of a new sensitivity disorder of the cornea, deafferentation pain known as anesthesia dolorosa, and/or long-lasting hypoesthesia augmentation characterized by the new appearance or increase in size or intensity of an area of hypoesthesia in the face for at least 3 months. The only predictor associated with a severe sensitive complication in the multivariate analysis was compression duration > 60 seconds. These results show that the risk of postoperative complications can be assessed at the patient level, the most important modifiable parameter being the time of compression by the balloon. Although this study shows the relevance of a personalized medicine approach, its clinical application remains to be validated.

Clinical Outcome of Partial Sensory Rhizotomy in Negative-Exploration Trigeminal Neuralgia and Technical Nuances

Background: Microvascular decompression is considered to be a potential treatment for most trigeminal neuralgia cases with obvious neurovascular conflict. Partial sensory rhizotomy (PSR) is an alternate option in cases of negative investigation for neurovascular conflict, although its effectiveness and technical complexity are still being debated. Objective: To evaluate the therapeutic efficacy of PSR following negative-exploration trigeminal neuralgia (NETN) in terms of pain control, adverse effects from sensory fiber destruction, and patient satisfaction in the short-term or after 1 month, and in the long-term or after 12 months. In addition, technical nuances were highlighted to mitigate the negative effects of PSR. Materials and Methods: The present study enrolled 27 NETN patients, and all were operated by the same neurosurgeon. The patients underwent surgery via a keyhole retromastoid technique, with extensive exploration for any possible intraoperative neurovascular conflict. A modified PSR approach was used to operate on these negative exploration cases, and this entailed cutting fewer than 1/5 of the trigeminal sensory fibers. The short-term or within one month, and long-term or after one-year intervals were used to track all instances. The therapeutic efficacy of employing pain score and subjective sensation in terms of pain control, adverse consequences from sensory fiber destruction, and patient satisfaction were investigated. Results: Eighty-five point two percent of patients reported excellent pain control following PSR, in terms of both pain score and total pain alleviation. Despite having their trigeminal nerve fibers severed, not all of the patients experienced numbness, and 45% of patients recovered to some extent on their own within a year. Only 13% of patients had Anesthesia Dolorosa in the present trial, which could be attributable because only 1/5 of the trigeminal nerve fibers were severed. There was no relationship between pain distribution and pain alleviation efficacy before and after PSR. When PSR was effective, most patients should notice an improvement within a month of the surgery. Conclusion: For patients with negative exploration following keyhole suboccipital craniectomy, PSR proved to be therapeutic and effective in alleviating trigeminal neuralgic pain. The majority of the patients can tolerate the minor side effects from minute nerve destruction well, particularly numbness, which partially resolves on its own with time. Keywords: Negative exploration; Trigeminal neuralgia; Microvascular decompression; Partial sensory rhizotomy; Efficacy

The formalin test does not probe inflammatory pain but excitotoxicity in rodent skin.

The most widely used formalin test to screen antinociceptive drug candidates is still apostrophized as targeting inflammatory pain, in spite of strong opposing evidence published. In our rat skin‐nerve preparation ex vivo, recording from all classes of sensory single‐fibers (n = 32), 30 units were transiently excited by formaldehyde concentrations 1–100 mM applied to receptive fields (RFs) for 3 min, C and Aδ‐fibers being more sensitive (1–30 mM) than Aβ−fibers. From 30 mM on, ~1% of the concentration usually injected in vivo, all RFs were defunctionalized and conduction in an isolated sciatic nerve preparation was irreversibly blocked. Thus, formaldehyde, generated a state of ‘anesthesia dolorosa’ in the RFs in so far as after a quiescent interphase all fibers with unmyelinated terminals developed a second phase of vigorous discharge activity which correlated well in time course and magnitude with published pain‐related behaviors. Sural nerve filament recordings in vivo confirmed that higher formalin concentrations (> 42 mM) have to be injected to the skin to induce this second phase of discharge. Patch‐clamp and calcium‐imaging confirmed TRPA1 as the primary transducer of formaldehyde (10 mM) effects on mouse sensory neurons. However, stimulated CGRP release from isolated skin of TRPA1+/+ and TRPA1–/– mice showed a convergence of the saturating concentration‐response curves at 100 mM formaldehyde, which did not occur with nerve and trachea preparations. Finally, skin‐nerve recordings from C and Aδ‐fibers of TRPA1–/– mice revealed a massive reduction in formaldehyde (30 mM)‐evoked discharge. However, the remaining activity was still biphasic, thus confirming additional unspecific excitotoxic actions of the fixative that diffuses along still excitable axons as previously published. The multiplicity of formaldehyde's actions requires extensive discussion and literature review, leading to a fundamental reevaluation of the formalin test.

Results of a third Gamma Knife radiosurgery for trigeminal neuralgia.

Gamma Knife radiosurgery (GKRS) is a commonly used procedure for medically refractory trigeminal neuralgia (TN), with repeat GKRS routinely done in cases of pain relapse. The results of a third GKRS in cases of further pain relapse have not been well described. In this study, the authors report the largest series of patients treated with a third GKRS for TN to date. Retrospective review of institutional electronic medical records and a GKRS database was performed to identify patients who had been treated with a third GKRS at the authors' institution in the period from 2010 to 2018. Telephone interviews were used to collect long-term follow-up data. Pain outcomes were measured using the Barrow Neurological Institute (BNI) pain intensity scale, with a score ≤ IIIb indicating successful treatment. Twenty-two nerves in 21 patients had sufficient follow-up to determine BNI pain score outcomes. Eighteen of 22 cases had a successful third GKRS, with a median durability of pain relief of 3.88 years. There was no significant difference in the durability of pain relief after a third GKRS compared with those of institutional historical controls of prior series of first and second GKRS procedures. Ten cases had new or worsening facial numbness, with 1 case being bothersome. Four cases of toxicity other than facial numbness were reported, including 1 case of corneal abrasions and possible neurotrophic keratopathy. No cases of anesthesia dolorosa were reported. No factors predicting treatment success or the durability of pain relief were identified. Nonnumbness toxicity was more common in those with a proximally placed shot at the third GKRS. A third GKRS is an effective treatment option for TN patients who have pain relapse after repeat GKRS. Pain outcomes of a third GKRS are similar to those following a first or second GKRS. Toxicity is tolerable in patients with a distally placed shot at the third GKRS.

Trigeminal root massage in microsurgical treatment of trigeminal neuralgia patients without arterial compression: When, how and why

BackgroundDuring the microsurgical exploration of trigeminal root in the pontocerebellar angle in patients with primary trigeminal neuralgia (TN) without an evident arterial compression, the surgeon is in an engaged situation because there are not well-established surgical strategies. The aim of this study is to describe in these cases the surgical maneuver we call “trigeminal root massage” (TRM). Methods52 consecutive patients with primary trigeminal neuralgia who had undergone a microsurgical suboccipital retrosigmoid exploration of trigeminal root were reviewed. Among them we found 10 patients without an evident arterial compression after a thorough microsurgical exploration. In the great majority of these 10 cases, we noticed a venous contact to the trigeminal root along this cisternal trajectory, in most cases we have had to coagulate the compressive vein/s and then cut. All underwent a simple trigeminal root massage, without interposition of any material implant. ResultsAll 10 patients experienced immediate pain disappearance and the postoperative course was uneventful except one case with a severe complication: cerebellar swelling, meningitis and hydrocephaly. The recurrence rate was 40%. Six patients achieved pain relief without specific medication with an average follow-up period of 5 years. There have been no mortalities nor any postoperative anesthesia dolorosa. ConclusionsThe described maneuver provides an easy and simple alternative way in cases where during a microsurgical exploration of trigeminal root, where we don’t find a clear arterial compression, with similar results than other possibilities such as partial sensory rhizotomy or more complicated and time consuming surgery as “nerve combing”. Nevertheless, a 40% of pain recurrence after an average follow-up of 5 years means that is a good alternative, but not a definitive technique at the moment for permanent cure of trigeminal neuralgia without arterial compression.

Gamma Knife radiosurgery for bilateral trigeminal neuralgia

OBJECTIVEA small subset of patients with trigeminal neuralgia (TN) will experience bilateral symptoms. Treatment in these patients is controversial because the population is heterogeneous and patients may have nonvascular etiologies of their pain. This study reports treatment outcomes in the largest cohort of patients with bilateral TN who have undergone Gamma Knife radiosurgery (GKRS) to date.METHODSA retrospective chart review identified 51 individual nerves in 34 patients with bilateral TN who were treated with GKRS at the authors’ institution between 2001 and 2015, with 12 nerves in 11 patients undergoing repeat GKRS for recurrent or persistent symptoms. Long-term follow-up was obtained by telephone interview. Pain outcomes were measured using the Barrow Neurological Institute (BNI) pain scale, with BNI IIIb or better considered a successful treatment.RESULTSThere was sufficient follow-up to determine treatment outcomes for 48 individual nerves in 33 patients. Of these nerves, 42 (88%) achieved at least BNI IIIb pain relief. The median duration of pain relief was 1.9 years, and 1-, 3-, and 5-year pain relief rates were 64%, 44%, and 44%, respectively. No patients experienced bothersome facial numbness, and 1 case of anesthesia dolorosa and 2 cases of corneal dryness were reported. Patients with a history of definite or possible multiple sclerosis were significantly more likely to experience BNI IV–V relapse. There was no statistically significant difference in treatment outcomes between patients in this series versus a large cohort of patients with unilateral TN treated at the authors’ institution. There was sufficient follow-up to determine treatment outcomes for 11 individual nerves in 10 patients treated with repeat GKRS. Ten nerves (91%) improved to at least BNI IIIb after treatment. The median duration of pain relief was 2.8 years, with 1-, 3-, and 5-year rates of pain relief of 79%, 53%, and 53%, respectively. There was no statistically significant difference in outcomes between initial and repeat GKRS. One case of bothersome facial numbness and 1 case of corneal dryness were reported, with no patients developing anesthesia dolorosa with retreatment.CONCLUSIONSGKRS is a safe, well-tolerated treatment for patients with medically refractory bilateral TN. Efficacy of treatment appears similar to that in patients with unilateral TN. GKRS can be safely repeated in this population if necessary.

Trigeminal root massage in microsurgical treatment of trigeminal neuralgia patients without arterial compression: When, how and why.

During the microsurgical exploration of trigeminal root in the pontocerebellar angle in patients with primary trigeminal neuralgia (TN) without an evident arterial compression, the surgeon is in an engaged situation because there are not well-established surgical strategies. The aim of this study is to describe in these cases the surgical maneuver we call "trigeminal root massage" (TRM). 52 consecutive patients with primary trigeminal neuralgia who had undergone a microsurgical suboccipital retrosigmoid exploration of trigeminal root were reviewed. Among them we found 10 patients without an evident arterial compression after a thorough microsurgical exploration. In the great majority of these 10 cases, we noticed a venous contact to the trigeminal root along this cisternal trajectory, in most cases we have had to coagulate the compressive vein/s and then cut. All underwent a simple trigeminal root massage, without interposition of any material implant. All 10 patients experienced immediate pain disappearance and the postoperative course was uneventful except one case with a severe complication: cerebellar swelling, meningitis and hydrocephaly. The recurrence rate was 40%. Six patients achieved pain relief without specific medication with an average follow-up period of 5 years. There have been no mortalities nor any postoperative anesthesia dolorosa. The described maneuver provides an easy and simple alternative way in cases where during a microsurgical exploration of trigeminal root, where we don't find a clear arterial compression, with similar results than other possibilities such as partial sensory rhizotomy or more complicated and time consuming surgery as "nerve combing". Nevertheless, a 40% of pain recurrence after an average follow-up of 5 years means that is a good alternative, but not a definitive technique at the moment for permanent cure of trigeminal neuralgia without arterial compression.

Results of a Third or Fourth Radiosurgery for Trigeminal Neuralgia

Stereotactic Radiosurgery SRS is an accepted option for treatment of medically refractory trigeminal neuralgia (TN) with a median duration of pain relief of 5 years. Repeat SRS for recurrent pain has been well described with similar results. Data regarding the use of a third or fourth SRS for recurrent pain are limited. Here we report the largest series to date on the use of a third or fourth SRS for TN. Retrospective review of a single institution SRS database identified 24 cases of unilateral TN in 23 patients who were treated with 3 sessions of SRS from 1999 to 2018. 3 patients underwent a fourth SRS. Background history, treatment outcomes and toxicity, and dosimetric data were obtained by chart review and telephone interview. Pain relief was defined using the Barrow Neurological Institute (BNI) scale. Categorical variables were compared using the chi square or Fisher’s exact test. Duration of at least BNI IIIB pain relief was estimated using the Kaplan-Meier method and compared with the log-rank test. Univariate cox proportional hazards were used to evaluate for predictors of pain relief. 22 of 24 cases had sufficient follow up to determine BNI pain outcomes. 18 of the 22 cases (82%) achieved at least BNI IIIb pain relief. At a median follow up of 1.96 years, the median duration of at least BNI IIIb pain relief after third SRS was 3.90 years, with 1, 3, and 5 year pain relief rates of 59%, 51%, and 38% respectively. New or worsening facial numbness was seen in 9 cases (41%) with 1 (4.5%) being reported as bothersome. 1 case (4.5%) of corneal abrasions requiring surgery and 2 cases (9%) of dry eye without vision loss or corneal abrasions, and 0 cases of anesthesia dolorosa were reported. The median dose at third SRS was 75 Gy (range 75-85). All 3 patients treated with a fourth SRS had at least BNI IIIb pain relief with no relapse at a median follow up of 2.54 years. No cases of severe numbness or toxicity were reported after fourth SRS. No factors predicting initial response to a third SRS were identified. Patients with a successful second SRS were less likely to experience pain relapse after third SRS (HR 0.12, p = .02). Third and fourth SRS had a longer durability of pain relief than first and second SRS (p = .02). No factors predictive of numbness after third SRS were identified. Non-numbness toxicity after third SRS was associated with a higher dose to the pons surface (median 41.6 Gy vs 16.9 Gy, p < .01) and decreased distance from the isocenter to the pons surface (median 2.9 mm vs 4.6 mm, p < .01). A third or fourth SRS is an effective treatment option for recurrent TN and may be more durable than the first or second SRS. Durable relief is more likely in patients with a successful second SRS. Toxicity rates appear to increase with third SRS, and dose to the pons should be limited to decrease this risk. The views expressed in this article are those of the author and do not reflect the official policy or position of the Department of the Army, Department of Defense, or the U.S. Government.

Effectiveness of tonic and burst motor cortex stimulation in chronic neuropathic pain.

Background: Motor cortex stimulation (MCS) is an intracranial, invasive method for treatment of chronic pain. Main indications for MCS are central post stroke pain, neuropathic facial pain, phantom limb pain and brachial plexus or spinal cord injury pain. Spinal cord stimulation (SCS) with burst waveform has been proved to be more effective than tonic mode in chronic pain. Necessity to replace depleted batteries of motor cortex tonic stimulators gave us an opportunity of applying burst stimulation. The objective of the pilot study was to evaluate the effects of burst stimulation applied on motor cortex in patients with chronic pain syndromes as well as comparison to tonic mode.Materials and methods: We have evaluated 6 patients (females N=3, males N=3) belonging to the group of 14 cases (females N=5, males N=9) who had undergone surgical procedure of MCS in years 2005–2017. Selected for the study were 6 patients with thalamic pain N=3, with facial pain N=3 (anaesthesia dolorosa and neuropathic trigeminal neuralgia). The patients were subjected to both modes of stimulation then they chose which one was better in relieving pain: tonic or burst. Pain intensity was assessed with the visual analogue scale (VAS) before the replacement of implanted pulse generator (IPG) and after the stimulation with tonic and burst modes.Results: In the study, 5 out of 6 patients with MCS found burst mode more effective than tonic mode. Baseline VAS score in patients that had at least 3 months depleted battery of tonic IPG was 95 mm. After implantation of a new IPG mean VAS score on tonic stimulation was 72 mm, on burst 53 mm.Conclusions: The most preferred option of MCS in selected group of patients was burst stimulation. This study has shown, that the burst stimulation of cerebral cortex is a promising modality when tonic stimulation is not sufficient in refractory, neuropathic pain.

Gamma Knife Radiosurgery for Bilateral Trigeminal Neuralgia

Bilateral trigeminal neuralgia (BTN) makes up a small subset of patients with trigeminal neuralgia. These patients have a higher incidence of familial TN and multiple sclerosis and their management is controversial. Here we report a large single institution retrospective cohort of patients with BTN treated with stereotactic radiosurgery (SRS). SRS database review identified 78 nerves in 52 patients with BTN who underwent at least one SRS between 1999 and 2017. Background history, demographics, treatment outcomes, complications, and dosimetric data were obtained by retrospective chart review. Long-term follow-up was obtained by a standardized telephone interview performed by a physician. Successful treatment was defined as BNI IIIb or better pain relief. Time-to-failure outcomes were estimated by the Kaplan-Meier method. Hazard ratios (HR) associated with patient and treatment-related variables for time-to-failure outcomes were estimated by Cox proportional hazards methods. Of the 78 individual nerves treated with a first SRS, 77 had sufficient follow up data to determine BNI pain score outcomes. Sixty-seven of the 77 nerves (87%) achieved ≥ BNI IIIb pain relief, with 34 (44%) achieving BNI I pain relief. The median time to BNI IIIb pain relief was 3.5 weeks. At a median follow-up of 3.4 years, the median duration of ≥ BNI IIIb pain relief was 2.5 years. The estimated 1, 3, and 5-year rates of ≥ BNI IIIb pain relief were 71%, 43%, and 32%. Post-SRS facial numbness was seen in 33 (43%) cases, with five (6.5%) being bothersome. Two (2.6%) cases of anesthesia dolorosa (AD) and five (6.4%) cases of corneal numbness were reported. SRS with a maximal post procedure BNI of IIIb were more likely to experience pain relapse than those who achieved BNI I relief (HR 2.55, p = 0.04), as were those who had a history of prior ipsilateral microvascular decompression (MVD) (HR 2.64, p = 0.03). Left sided pain was more likely to relapse than right sided (HR 2.22, p = 0.02). Twenty-two nerves underwent repeat SRS for recurrent pain, of which 20 had sufficient follow up to determine BNI pain score outcomes. Of these, 19 (95%) had ≥ BNI IIIb pain relief, with 8 (40%) reaching BNI I relief. The median time to BNI IIIb pain relief was 8 weeks. At a median follow-up of 4.1 years, the median duration of BNI IIIb or better pain relief was 8 years, with estimated 1, 3, and 5-year rates of pain relief of 89%, 62%, and 62% respectively. Eleven (55%) experienced facial numbness after repeat SRS with four (20%) being bothersome. One case (5.6%) of corneal numbness and zero cases of AD were reported after repeat SRS. SRS is an effective, well-tolerated treatment modality for patients with BTN. Patients with prior MVD or SRS that resulted in maximal pain relief of BNI IIIb are more likely to experience pain relapse than those who achieved BNI I relief. Repeat SRS appears to have greater efficacy and durability than initial SRS, and despite increased bothersome facial numbness remains well tolerated.

Dedicated Linear Accelerator Radiosurgery for Classic Trigeminal Neuralgia: A Single-Center Experience with Long-Term Follow-Up

During the past decades, stereotactic radiosurgery, and Gamma Knife in particular, has proved its safety and efficacy for drug-resistant classic trigeminal neuralgia. However, few large series exist using linear accelerator (LINAC) reporting long-term follow-up. Between 2006 and 2015, 301 patients were treated by LINAC at our institution. The prescribed radiation dose was 90 Gy at the far anterior target. Clinical response was defined using the Barrow Neurological Institute scale. We considered grades I and IIIa as a successful response. Mean duration of follow-up was 54.6 months (range, 12-132 months). Two hundred and seventy-three patients (90.7%) were initially pain free, and 28 patients (9.3%) were unchanged. The actuarial probabilities of maintaining pain relief with or without medication (Barrow Neurological Institute grade I and IIIa) at 0.5, 1, 2, 4, 5, and 10 years were 88.7%, 85.0%, 76.1%, 68.8%, 65.8%, and 48.1%, respectively. Hypesthesia was present in only 26.2% of patients (very bothersome, 0.3%). No anesthesia dolorosa was reported. The actuarial probabilities of maintaining pain relief without further surgery at 0.5, 1, 2, 4, and 5 years were 99.3%, 98.3%, 95.8%, 91.0%, and 89.7%, respectively. Among all treated patients, 86.5% were satisfied by the procedure and would undergo stereotactic radiosurgery again. Stereotactic radiosurgery with dedicated LINAC is associated with high rates of long-term pain relief, with minimal invasiveness and rare complications. LINAC is a possible therapeutic alternative for drug-resistant trigeminal neuralgia and could be proposed to selected patients as the first intention therapy, among other surgical solutions.

Stereotactic Radiosurgery for Multiple Sclerosis Associated Trigeminal Neuralgia

Trigeminal neuralgia in the setting of multiple sclerosis (MS-TN) is a challenging condition to manage and frequently does not respond as well to medications or surgical intervention when compared with classic TN. Gamma Knife radiosurgery (GKRS) is a commonly used treatment modality for these patients, however, data regarding the efficacy of this treatment is limited. Here we report a large single institution retrospective analysis for MS-TN treated with GKRS. A retrospective review of our GKRS database was performed to identify patients with MS-TN treated with GKRS between 2001 and 2016. Seventy-seven cases of unilateral MS-TN (UMSTN) in 74 patients were treated with GKRS at our institution between 2001 and 2016. Background medical history, treatment outcomes and complications, and dosimetric data were obtained by retrospective chart reviews and telephone interviews. Time-to-failure outcomes were estimated using the Kaplan-Meier method. Cox proportional hazards methods were used to estimate the hazard ratios (HR) associated with patient and treatment-related variables for time-to-failure outcomes. Seventy-four of 77 cases of UMSTN had sufficient follow up to determine BNI pain score outcomes. Three patients had both nerves treated. Sixty-one out of 74 cases (82%) of UMSTN achieved BNI IIIb or better pain relief following initial GKRS, with 18 cases (24%) achieving BNI I pain relief. Median time to BNI IIIb pain relief was 1.8 weeks. At a median follow up of 2.5 years, the estimated median duration of BNI IIIb pain relief after initial GKRS was 1.1 years. Estimated rates of pain relief at 1, 3 and 5 years were 51%, 37%, and 27% respectively. Three cases (4.1%) developed bothersome numbness and three cases (4.1%) developed ipsilateral corneal anesthesia, although none experienced vision loss. No patients experienced anesthesia dolorosa. Thirty-seven of the original 77 cases of UMSTN were treated with repeat GKRS after initial treatment failure. Of 35 patients with sufficient follow up to determine pain outcomes, 30 (86%) achieved BNI IIIb or better pain relief, with 12 (34%) achieving BNI I following repeat GKRS. Median time to BNI IIIb pain relief was 4.5 weeks. At a median follow up of 2.3 years from repeat GKRS, the median duration of BNI IIIb pain relief after repeat GKRS was 2.8 years. Estimated rates of pain relief at 1 and 3 years were 67% and 49% respectively. One case (2.9%) developed bothersome numbness after repeat GKRS, and three cases (8.6%) developed new ipsilateral corneal anesthesia, but none reported vision loss. No patients developed anesthesia dolorosa. Patients with episodic pain were more likely to achieve a good pain outcome after repeat GKRS than those with atypical symptoms (HR 10.51, p = 0.03). GKRS is a viable, well tolerated treatment option for patients with MS-TN. More durable relief is often achieved with a second application of GKRS. Patients with episodic pain are more likely to have successful second procedure.

Neuromodulation and Devices in Trigeminal Neuralgia.

Trigeminal neuralgia is a severe facial pain disorder that has been studied for decades. Classical trigeminal neuralgia (CTN) is either idiopathic or caused by neurovascular compression. The related painful trigeminal neuropathies are often secondary to other causes, such as multiple sclerosis or trauma. Therapies for trigeminal neuralgia and neuropathy have often been pharmacologic or surgical. Pharmacologic therapies are not effective in some cases and often cause side effects, some substantial. Surgery can have comorbidity (such as anesthesia dolorosa, or painful differentiation of the affected nerve distribution) and also is not always effective. There is a desire, as in all chronic conditions, to find effective treatments with minimal morbidity and side effects. We review several devices including neuromodulation, ranging in invasiveness, for treatment of trigeminal neuralgia and neuropathy. We review existing data on sphenopalatine ganglion blocks, transcranial magnetic stimulation, transcortical direct stimulation, deep brain stimulation, spinal cord stimulation, peripheral nerve stimulation, and transcutaneous electrical stimulation for CTN and pain trigeminal neuropathies. We also offer hope for further research in this area with the goal of discovering a device that can provide treatment for many with few side effects and minimal morbidity.