Category: Pain

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Subacute vision loss after microvascular decompression for trigeminal neuralgia

Acta Neurochirurgica (2021) 163:1635–1638

Microvascular decompression is the surgery of choice for typical trigeminal neuralgia (TN) that fails conservative medical management. Visual loss after MVD is a rare complication that has not been reported.

In this article, we present a patient who developed delayed visual loss and papilledema from transverse sinus stenosis resulting from bone wax compression after MVD for TN.

While waxing the edges of a retrosigmoid craniotomy may seem mundane, meticulous care should be taken to ensure that there is no compression of the venous sinuses, as this could lead to intracranial hypertension.

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Young‐onset trigeminal neuralgia: a clinical study and literature review

Acta Neurochirurgica (2021) 163:1617–1621

Trigeminal neuralgia (TN) primarily occurs in elderly adults and is thought to be induced by neurovascular compression. However, a few children and young adults may present with the clinical features of TN. In this study, we aim to retrospectively assess the data of young patients with TN from a single center.

Methods Of 783 consecutive patients with TN treated at our center between 2007 and 2017, 11 young patients under the age of 30 years with TN met the inclusion criteria and were enrolled. Their clinical records, surgical treatments, and long-term outcomes were obtained and analyzed.

Results All the 11 patients with TN underwent microvascular decompression (MVD). The average age at symptom onset was 24 years (range, 14–29 years), and the average age at the time of surgery was 28.9 years (range, 25–35 years). Further, 5 patients had left-sided symptoms, and 6 had right-sided symptoms. Surgery revealed only venous compression in 3 patients, only arterial compression in 5 patients, and both venous and arterial compression in 3 patients. The average duration of symptoms was 4.9 years, and the average follow-up duration was 7.4 years (range, 4.5–12.9 years). The long-term outcome was excellent in 9 patients and good in 2 patients, and there were no long-term complications.

Conclusions The symptoms and surgical findings presented in this cohort for young-onset TN are similar to those reported in elderly adults. MVD appears to be a safe and effective treatment for young patients with TN.

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Microvascular decompression for trigeminal neuralgia attributable to the vertebrobasilar artery

Acta Neurochirurgica (2021) 163:1037–1043

Separation of the vertebrobasilar artery (VBA) from the trigeminal nerve root in microvascular decompression (MVD) is technically challenging. This study aimed to review the clinical features of VBA involvement in trigeminal neuralgia and evaluate surgical decompression techniques in the long term.

Methods We retrospectively reviewed the surgical outcomes of 26 patients (4.4%) with VBA involvement in 585 consecutive MVDs for TGN using a Teflon roll for repositioning the VBA. The final operative status of the nerve decompression was categorized into two groups: the separation group and the contact group. Separation of the VBA from the nerve root was completed in 13 patients in the separation group, and slight vascular contact remained in the remaining 13 patients of the contact group. The clinical features of VBA-related TGN were investigated and the operative results were analyzed.

Results Multiple arteries are involved in neurovascular compression (NVC) in most cases. The anterior inferior cerebellar artery was the most common concomitant artery (69%). The site of the NVC varies from the root entry zone to the distal portion of the root. All patients were pain-free immediately after surgery and maintained medication-free status during the follow-up period, except for one patient (3.8%) who had recurrent facial pain 8 years after surgery. Postoperative facial numbness was observed in six patients (23%). Of these, one patient showed improvement within 3 months and the other five patients had persistent facial numbness (19.2%). Other neurological deficits include one dry eye, one diplopia due to trochlear nerve palsy, two decreased hearing (< 50 db), two facial weaknesses, and two cerebellar ataxia. Although most of them were transient, one dry eye, two hearing impairments, and one cerebellar ataxia became persistent deficits. Statistical analyses revealed no difference in surgical efficacy or complications in the long term between the two groups.

Conclusions Slightly remaining vascular contact does not affect pain relief in the long term. Our study indicated that once the tense trigeminal nerve is loosened, further attempts to mobilize the VBA are not necessary.

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Congress of Neurological Surgeons Systematic Review and Evidence-Based Guideline on Neuroablative Procedures for Patients With Cancer Pain

Neurosurgery 88:437–442, 2021

Managing cancer pain once it is refractory to conventional treatment continues to challenge caregivers committed to serving those who are suffering from a malignancy. Although neuromodulation has a role in the treatment of cancer pain for some patients, these therapies may not be suitable for all patients. Therefore, neuroablative procedures,whichwere once a mainstay in treating intractable cancer pain, are again on the rise. This guideline serves as a systematic review of the literature of the outcomes following neuroablative procedures.

OBJECTIVE: To establish clinical practice guidelines for the use of neuroablative procedures to treat patients with cancer pain.

METHODS: A systematic review of neuroablative procedures used to treat patients with cancer pain from 1980 to April 2019 was performed using the United States National Library of Medicine PubMed database, EMBASE, and Cochrane CENTRAL. After inclusion criteria were established, full text articles that met the inclusion criteria were reviewed by 2 members of the task force and the quality of the evidence was graded.

RESULTS: In total, 14 646 relevant abstracts were identified by the literature search, from which 189 met initial screening criteria. After full text review, 58 of the 189 articles were included and subdivided into 4 different clinical scenarios. These include unilateral somatic nociceptive/neuropathic body cancer pain, craniofacial cancer pain,midline subdiaphragmatic visceral cancer pain, and disseminated cancer pain. Class II and III evidence was available for these 4 clinical scenarios. Level III recommendations were developed for the use of neuroablative procedures to treat patients with cancer pain.

CONCLUSION: Neuroablative procedures may be an option for treating patients with refractory cancer pain. Serious adverse events were reported in some studies, but were relatively uncommon. Improved imaging, refinements in technique and the availability of new lesioning modalities may minimize the risks of neuroablation even further. The full guidelines can be accessed at https://www.cns.org/guidelines/browse-guidelinesdetail/ guidelines-on-neuroablative-procedures-patients-wi.

 

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Prognostic nomogram for microvascular decompression–treated trigeminal neuralgia

Neurosurgical Review (2021) 44:571–577

This study aimed to establish an effective prognostic nomogram for microvascular decompression (MVD)–treated trigeminal neuralgia (TN). The nomogram was based on a retrospective cohort study of 1054 patients with TN.

During the period 2005– 2014, 845 patients at our department treated TN with MVD and served as a development cohort. The predictive accuracy and discriminative ability of the nomogram were determined by concordance index (C-index) and calibration curve. The model was externally validated by 209 TN patients during 2014–2016.

Multivariate cox analysis suggested that the patient’s age, atypical pain, vascular type, number of offending vessels, and second MVD were significant factors influencing the prognosis of MVDtreated TN. The C index of nomogram in the development cohort was 0.767 (95%CI, 0.739–0.794), and 0.749 (95%CI, 0.688– 0.810) in the validation cohort.

We developed and validated a nomogram to predict 3-year overall remission rate after MVD treatment of TN. The nomogram can be used in clinical trials to determine the likelihood of pain recurrence in TN patients treated with MVD for 3 years to aid in the comprehensive treatment of TN.

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Neurosurgical Choice for Glossopharyngeal Neuralgia: A Benefit–Harm Assessment of Long-Term Quality of Life

Neurosurgery 88( 1) 2021: 131–139

Microvascular decompression (MVD) and vagoglossopharyngeal rhizotomy (VGR) are effective treatment for glossopharyngeal neuralgia (GN). However, surgical choice is controversial due to the need to maximize pain relief and reduce complications.

OBJECTIVE: To retrospectively compare safety, efficacy, long-term quality of life (QOL), and global impression of change following MVD and VGR for treatment of GN. METHODS: Patient database reviews and telephone surveys were conducted to assess baseline characteristics and long-term outcomes. The effects of pain and complications on QOL were assessed using Brief Pain Inventory-Facial (BPI-Facial) questionnaire. Complication tolerance and surgery satisfaction were sorted using the global impression of change survey.

RESULTS: Of 87 patients with GN, 63 underwentMVD alone, 20 underwent VGR alone, and 4 underwent VGR following a failed MVD. The long-term rate of pain relief was slightly, but not significantly, lower following MVD than VGR (83.6% vs 91.7%, P = .528). However, long-term complications occurred much more frequently following VGR (3.0% vs 50.0%, P < .001). The BPI-Facial, which evaluates pain and complications, showed that MVD had better postoperative QOL than VGR (P < .001). However, 91.7% of patients who underwent VGR experienced no or mild complications. There was no significant difference in the overall satisfaction rates between the groups (83.3% vs 83.6%, P > .99).

CONCLUSION: Although VGR resulted in lower postoperative QOL due to a high complication rate, most of these complications were mild. The overall satisfaction rates for the 2 surgeries were similar.

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Development and validation of a clinical prediction score for poor postoperative pain control following elective spine surgery

J Neurosurg Spine 34:3–12, 2021

Thirty percent to sixty-four percent of patients experience poorly controlled pain following spine surgery, leading to patient dissatisfaction and poor outcomes. Identification of at-risk patients before surgery could facilitate patient education and personalized clinical care pathways to improve postoperative pain management. Accordingly, the aim of this study was to develop and internally validate a prediction score for poorly controlled postoperative pain in patients undergoing elective spine surgery.

METHODS A retrospective cohort study was performed in adult patients (≥ 18 years old) consecutively enrolled in the Canadian Spine Outcomes and Research Network registry. All patients underwent elective cervical or thoracolumbar spine surgery and were admitted to the hospital. Poorly controlled postoperative pain was defined as a mean numeric rating scale score for pain at rest of > 4 during the first 24 hours after surgery. Univariable analysis followed by multivariable logistic regression on 25 candidate variables, selected through a systematic review and expert consensus, was used to develop a prediction model using a random 70% sample of the data. The model was transformed into an eight-tier risk-based score that was further simplified into the three-tier Calgary Postoperative Pain After Spine Surgery (CAPPS) score to maximize clinical utility. The CAPPS score was validated using the remaining 30% of the data.

RESULTS Overall, 57% of 1300 spine surgery patients experienced poorly controlled pain during the first 24 hours after surgery. Seven significant variables associated with poor pain control were incorporated into a prediction model: younger age, female sex, preoperative daily use of opioid medication, higher preoperative neck or back pain intensity, higher Patient Health Questionnaire–9 depression score, surgery involving ≥ 3 motion segments, and fusion surgery. Notably, minimally invasive surgery, body mass index, and revision surgery were not associated with poorly controlled pain. The model was discriminative (C-statistic 0.74, 95% CI 0.71–0.77) and calibrated (Hosmer-Lemeshow goodness-of-fit, p = 0.99) at predicting the outcome. Low-, high-, and extreme-risk groups stratified using the CAPPS score had 32%, 63%, and 85% predicted probability of experiencing poorly controlled pain, respectively, which was mirrored closely by the observed incidence of 37%, 62%, and 81% in the validation cohort.

CONCLUSIONS Inadequate pain control is common after spine surgery. The internally validated CAPPS score based on 7 easily acquired variables accurately predicted the probability of experiencing poorly controlled pain after spine surgery.

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Long-term pain outcomes in elderly patients with trigeminal neuralgia: comparison of first-time microvascular decompression and stereotactic radiosurgery

Neurosurg Focus 49 (4):E23, 2020

Common surgical treatments for trigeminal neuralgia (TN) include microvascular decompression (MVD) and stereotactic radiosurgery (SRS). The use of MVD in elderly patients has been described but has yet to be prospectively compared to SRS, which is well-tolerated and noninvasive. The authors aimed to directly compare long-term pain control and adverse event rates for first-time surgical treatments for idiopathic TN in the elderly.

METHODS A prospectively collected database was reviewed for TN patients who had undergone treatment between 1997 and 2017 at a single institution. Standardized collection of preoperative demographics, surgical procedure, and postoperative outcomes was performed. Data analysis was limited to patients over the age of 65 years who had undergone a first-time procedure for the treatment of idiopathic TN with at least 1 year of follow-up.

RESULTS One hundred ninety-three patients meeting the study inclusion criteria underwent surgical procedures for TN during the study period (54 MVD, 24 MVD+Rhiz, 115 SRS). In patients in whom an artery was not compressing the trigeminal nerve during MVD, a partial sensory rhizotomy (MVD+Rhiz) was performed. Patients in the SRS cohort were older than those in the MVD and MVD+Rhiz cohorts (mean ± SD, 79.2 ± 7.8 vs 72.9 ± 5.7 and 70.9 ± 4.8 years, respectively; p < 0.0001) and had a higher mean Charlson Comorbidity Index (3.8 ± 1.1 vs 3.0 ± 0.9 and 2.9 ± 1.0, respectively; p < 0.0001). Immediate or short-term postoperative pain-free rates (Barrow Neurological Institute [BNI] pain intensity score I) were 98.1% for MVD, 95.8% for MVD+Rhiz, and 78.3% for SRS (p = 0.0008). At the last follow-up, 72.2% of MVD patients had a favorable outcome (BNI score I–IIIa) compared to 54.2% and 49.6% of MVD+Rhiz and SRS patients, respectively (p = 0.02). In total, 0 (0%) SRS, 5 (9.3%) MVD, and 1 (4.2%) MVD+Rhiz patients developed any adverse event. Multivariate Cox proportional hazards analysis demonstrated that procedure type (p = 0.001) and postprocedure sensory change (p = 0.003) were statistically significantly associated with pain control.

CONCLUSIONS In this study cohort, patients who had undergone MVD had a statistically significantly longer duration of pain freedom than those who had undergone MVD+Rhiz or SRS as their first procedure. Fewer adverse events were seen after SRS, though the MVD-associated complication rate was comparable to published rates in younger patients. Overall, the results suggest that both MVD and SRS are effective options for the elderly, despite their advanced age. Treatment choice can be tailored to a patient’s unique condition and wishes.

 

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First application of 7-T ultra–high field diffusion tensor imaging to detect altered microstructure of thalamic-somatosensory anatomy in trigeminal neuralgia

J Neurosurg 133:839–847, 2020

Trigeminal neuralgia (TN) is a debilitating neurological disease that commonly results from neurovascular compression of the trigeminal nerve (CN V). Although the CN V has been extensively studied at the site of neurovascular compression, many pathophysiological factors remain obscure. For example, thalamic-somatosensory function is thought to be altered in TN, but the abnormalities are inadequately characterized. Furthermore, there are few studies using 7-T MRI to examine patients with TN. The purpose of the present study was to use 7-T MRI to assess microstructural alteration in the thalamic-somatosensory tracts of patients with TN by using ultra–high field MRI.

METHODS Ten patients with TN and 10 age- and sex-matched healthy controls underwent scanning using 7-T MRI with diffusion tensor imaging. Structural images were segmented with an automated algorithm to obtain thalamus and primary somatosensory cortex (S1). Probabilistic tractography was performed between the thalamus and S1, and the microstructure of the thalamic-somatosensory tracts was compared between patients with TN and controls.

RESULTS Fractional anisotropy of the thalamic-somatosensory tract ipsilateral to the site of neurovascular compression was reduced in patients (mean 0.43) compared with side-matched controls (mean 0.47, p = 0.01). The mean diffusivity was increased ipsilaterally in patients (mean 6.58 × 10 −4 mm 2 /second) compared with controls (mean 6.15 × 10 −4 mm 2 / second, p = 0.02). Radial diffusivity was increased ipsilaterally in patients (mean 4.91 × 10 −4 mm 2 /second) compared with controls (mean 4.44 × 10 −4 mm 2 /second, p = 0.01). Topographical analysis revealed fractional anisotropy reduction and diffusivity elevation along the entire anatomical S1 arc in patients with TN.

CONCLUSIONS The present study is the first to examine microstructural properties of the thalamic-somatosensory anatomy in patients with TN and to evaluate quantitative differences compared with healthy controls. The finding of reduced integrity of these white matter fibers provides evidence of microstructural alteration at the level of the thalamus and S1, and furthers the understanding of TN neurobiology.

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Diffusion tensor imaging reveals microstructural differences between subtypes of trigeminal neuralgia

J Neurosurg 133:573–579, 2020

Trigeminal neuralgia (TN) is an uncommon idiopathic facial pain syndrome. To assist in diagnosis, treatment, and research, TN is often classified as type 1 (TN1) when pain is primarily paroxysmal and episodic or type 2 (TN2) when pain is primarily constant in character. Recently, diffusion tensor imaging (DTI) has revealed microstructural changes in the symptomatic trigeminal root and root entry zone of patients with unilateral TN. In this study, the authors explored the differences in DTI parameters between subcategories of TN, specifically TN1 and TN2, in the pontine segment of the trigeminal tract.

METHODS The authors enrolled 8 patients with unilateral TN1, 7 patients with unilateral TN2, and 23 asymptomatic controls. Patients underwent DTI with parameter measurements in a region of interest within the pontine segment of the trigeminal tract. DTI parameters were compared between groups.

RESULTS In the pontine segment, the radial diffusivity (p = 0.0049) and apparent diffusion coefficient (p = 0.023) values in TN1 patients were increased compared to the values in TN2 patients and controls. The DTI measures in TN2 were not statistically significant from those in controls. When comparing the symptomatic to asymptomatic sides in TN1 patients, radial diffusivity was increased (p = 0.025) and fractional anisotropy was decreased (p = 0.044) in the symptomatic sides. The apparent diffusion coefficient was increased, with a trend toward statistical significance (p = 0.066).

CONCLUSIONS Noninvasive DTI analysis of patients with TN may lead to improved diagnosis of TN subtypes (e.g., TN1 and TN2) and improve patient selection for surgical intervention. DTI measurements may also provide insights into prognosis after intervention, as TN1 patients are known to have better surgical outcomes than TN2 patients.

 

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Significance of degree of neurovascular compression in surgery for trigeminal neuralgia

J Neurosurg 133:411–416, 2020

The aim of this study was to identify preoperative imaging predictors of surgical success in patients with classic trigeminal neuralgia (cTN) undergoing microvascular decompression (MVD) via retrospective multivariate regression analysis.

METHODS All included patients met criteria for cTN and underwent preoperative MRI prior to MVD. MR images were blindly graded regarding the presence and severity (i.e., mild or severe) of neurovascular compression (NVC). All patients were contacted by telephone to determine their postoperative pain status.

RESULTS A total of 79 patients were included in this study. Sixty-two patients (78.5%) were pain-free without medication following MVD. The following findings were more commonly observed with the symptomatic nerve when compared to the contralateral asymptomatic nerve: NVC (any form), arterial compression alone, NVC along the proximal trigeminal nerve, and severe NVC (p values < 0.0001). The only imaging variable that was a statistically significant predictor of being pain-free without medication following MVD was severe NVC. Patients with severe NVC were 6.36 times more likely to be pain-free following MVD compared to those without severe NVC (p = 0.007).

CONCLUSIONS In patients with cTN undergoing MVD, severe NVC on preoperative MRI is a strong predictor of an excellent surgical outcome.

 

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Neurosurgical ablative procedures for intractable cancer pain

J Neurosurg 133:144–151, 2020

Cancer patients suffering from severe refractory pain may benefit from targeted ablative neurosurgical procedures aimed to disconnect pain pathways in the spinal cord or the brain. These patients often present with a plethora of medical problems requiring careful consideration before surgical interventions. The authors present their experience at an interdisciplinary clinic aimed to facilitate appropriate patient selection for neurosurgical procedures, and the outcome of these interventions.

METHODS This study was a retrospective review of all patients who underwent neurosurgical interventions for cancer pain in the authors’ hospital between March 2015 and April 2018. All patients had advanced metastatic cancer with limited life expectancy and suffered from intractable oncological pain.

RESULTS Sixty patients underwent surgery during the study period. Forty-three patients with localized pain underwent disconnection of the spinal pain pathways: 34 percutaneous-cervical and 5 open-thoracic cordotomies, 2 stereotactic mesencephalotomies, and 2 midline myelotomies. Thirty-nine of 42 patients (93%) who completed these procedures had excellent immediate postoperative pain relief. At 1 month the improvement was maintained in 30/36 patients (83%) available for follow-up. There was 1 case of hemiparesis. Twenty patients with diffuse pain underwent stereotactic cingulotomy. Nineteen of these patients reported substantial pain relief immediately after the operation. At 1 month good pain relief was maintained in 13/17 patients (76%) available for follow-up, and good pain relief was also found at 3 months in 7/11 patients (64%). There was no major morbidity or mortality.

CONCLUSIONS With careful patient selection and tailoring of the appropriate procedure to the patient’s pain syndrome, the authors’ experience indicates that neurosurgical procedures are safe and effective in alleviating suffering in patients with intractable cancer pain.

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Hypertrophic Interstitial Neuropathy of the Trigeminal Nerve

Neurosurgery 87:E41–E47, 2020

Hypertrophic interstitial neuropathy (HIN) is an uncommon, non-neoplastic lesion typically affecting peripheral nerves. Cranial nerve (CN) involvement is exceedingly rare. We present a case of isolated trigeminal nerve HIN manifesting with V3 distribution neuralgia.

CLINICAL PRESENTATION: A 50-yr-old male presented with left sided trigeminal neuralgia refractory to medical management. The patient underwent retromastoid craniectomy for possible microvascular decompression. Intra-operatively, the trigeminal nerve appeared to be focally enlarged with a sausage-like configuration. We selectively resected 1 fascicle which was predominantly involved. Histopathological examination revealed onion bulb formations composed of Schwann cells around centrally placed axons. A diagnosis of HIN was made. Postoperatively, the patient experienced complete resolution of symptoms.

CONCLUSION: This is the third case of isolated trigeminal nerve HIN in the literature. We performed a selective resection in a patient presenting with trigeminal neuralgia, resulting in complete resolution of symptoms. It is reported here with intraoperative microscope images, along with a review and analysis of this topic as it related to CN.

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Ossification of the pterygoalar and pterygospinous ligaments: a computed tomography analysis of infratemporal fossa anatomical variants relevant to percutaneous trigeminal rhizotomy

J Neurosurg 132:1942–1951, 2020

Ossification of pterygoalar and pterygospinous ligaments traversing the superior aspect of the infratemporal fossa results in formation of osseous bars that can obstruct percutaneous needle access to the trigeminal ganglion through the foramen ovale (FO), interfere with lateral mandibular nerve block, and impede transzygomatic surgical approaches. Presence of these ligaments has been studied on dry skulls, but description of their radiological anatomy is scarce, in particular on cross-sectional imaging. The aim of this study was to describe visualization of pterygoalar and pterygospinous bars on computed tomography (CT) and to review their prevalence and clinical significance.

METHODS The authors retrospectively reviewed 200 helical sinonasal CT scans by analyzing 0.75- to 1.0-mm axial images, maximum intensity projection (MIP) reconstructions, and volume rendered (VR) images, including views along the anticipated axis of the needle in percutaneous Hartel and submandibular approaches to the FO.

RESULTS Ossified pterygoalar and pterygospinous ligaments were readily identifiable on CT scans. An ossified pterygoalar ligament was demonstrated in 10 patients, including 1 individual with bilateral complete ossification (0.5%), 4 patients with unilateral complete ossification (2.0%), and 5 with incomplete unilateral ossification (2.5%). Nearly all patients with pterygoalar bars were male (90%, p < 0.01). An ossified pterygospinous ligament was seen in 35 patients, including 2 individuals with bilateral complete (1.0%), 8 with unilateral complete (4%), 8 with bilateral incomplete (4.0%), 12 with bilateral incomplete (6.0%) ossification, and 5 (2.5%) with mixed ossification (complete on one side and incomplete on the contralateral side). All pterygoalar bars interfered with a hypothetical needle access to the FO using the Hartel approach but not the submandibular approach. In contrast, 54% of complete and 24% of incomplete pterygospinous bars impeded the submandibular approach to the FO, without affecting the Hartel approach.

CONCLUSIONS This study provides the first detailed description of cross-sectional radiological and applied surgical anatomy of pterygoalar and pterygospinous bars. Our data are clinically useful during skull base imaging to predict potential obstacles to percutaneous cannulation of the FO and assist in the choice of approach, as these two variants differentially impede the Hartel and submandibular access routes. Our results can also be useful in planning surgical approaches to the skull base through the infratemporal fossa.

 

 

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Percutaneous glycerol rhizotomy for trigeminal neuralgia in patients with multiple sclerosis

J Neurosurg 132:1405–1413, 2020

The prevalence of trigeminal neuralgia (TN) in patients with multiple sclerosis (MS-TN) is higher than in the general population (idiopathic TN [ITN]). Glycerol rhizotomy (GR) is a percutaneous lesioning surgery commonly performed for the treatment of medically refractory TN. While treatment for acute pain relief is excellent, long-term pain relief is poorer. The object of this study was to assess the efficacy of percutaneous retrogasserian GR for the treatment of MS-TN versus ITN.

METHODS A retrospective chart review was performed, identifying 219 patients who had undergone 401 GR procedures from 1983 to 2018 at a single academic institution. All patients were diagnosed with medically refractory MS-TN (182 procedures) or ITN (219 procedures). The primary outcome measures of interest were immediate pain relief and time to pain recurrence following initial and repeat GR procedures. Secondary outcomes included medication usage and presence of periprocedural hypesthesia.

RESULTS The initial pain-free response rate was similar between groups (p = 0.726): MS-TN initial GR 89.6%; MS-TN repeat GR 91.9%; ITN initial GR 89.6%; ITN repeat GR 87.0%. The median time to recurrence after initial GR was similar between MS-TN (2.7 ± 1.3 years) and ITN (2.1 ± 0.6 years) patients (p = 0.87). However, there was a statistically significant difference in the time to recurrence after repeat GR between MS-TN (2.3 ± 0.5 years) and ITN patients (1.2 ± 0.2 years; p < 0.05). The presence of periprocedural hypesthesia was highly predictive of pain-free survival (p < 0.01).

CONCLUSIONS Patients with MS-TN achieve meaningful pain relief following GR, with an efficacy comparable to that following GR in patients with ITN. Initial and subsequent GR procedures are equally efficacious.

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Retrosigmoid approach for glycerin rhizotomy in the treatment of trigeminal neuralgia without overt arterial compression

J Neurosurg 132:1227–1233, 2020

Trigeminal neuralgia (TN) is a neuropathic pain disorder characterized by severe, lancinating facial pain that is commonly treated with neuropathic medication, percutaneous rhizotomy, and/or microvascular decompression (MVD). Patients who are not found to have distinct arterial compression during MVD present a management challenge. In 2013, the authors reported on a small case series of such patients in whom glycerin was injected intraoperatively into the cisternal segment of the trigeminal nerve. The objective of the authors’ present study was to report their updated experience with this technique to further validate this novel approach.

METHODS The authors performed a retrospective analysis of data obtained in patients in whom glycerin was directly injected into the inferior third of the cisternal portion of the trigeminal nerve. Seventy-four patients, including 14 patients from the authors’ prior study, were identified, and demographic information, intraoperative findings, postoperative course, and complications were recorded. Fisher’s exact test, unpaired t-tests, and Kaplan-Meier survival curves using Mantel log-rank test were used to compare the 74 patients with a cohort of 476 patients who received standard MVD by the same surgeon.

RESULTS The 74 patients who underwent MVD and glycerin injection had an average follow-up of 19.1 ± 18.0 months, and the male/female ratio was 1:2.9. In 33 patients (44.6%), a previous intervention for TN had failed. On average, patients had an improvement in the Barrow Neurological Institute Pain Intensity score from 4.1 ± 0.4 before surgery to 2.1 ± 1.2 after surgery. Pain improvement after the surgery was documented in 95.9% of patients. Thirteen patients (17.6%) developed burning pain following surgery. Five patients developed complications (6.7%), including incisional infection, facial palsy, CSF leak, and hearing deficit, all of which were minor.

CONCLUSIONS Intraoperative injection of glycerin into the trigeminal nerve is a generally safe and potentially effective treatment for TN when no distinct site of arterial compression is identified during surgery or when decompression of the nerve is deemed to be inadequate.

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Sex-dependent posterior fossa anatomical differences in trigeminal neuralgia patients with and without neurovascular compression: a volumetric MRI age- and sex-matched case-control study

J Neurosurg 132:631–638, 2020

The pathophysiology of trigeminal neuralgia (TN) in patients without neurovascular compression (NVC) is not completely understood. The objective of this retrospective study was to evaluate the hypothesis that TN patients without NVC differ from TN patient with NVC with respect to brain anatomy and demographic characteristics.

METHODS Six anatomical brain measurements from high-resolution brain MR images were tabulated; anterior-posterior (AP) prepontine cistern length, cerebellopontine angle (CPA) cistern volume, nerve-to-nerve distance, symptomatic nerve length, pons volume, and posterior fossa volume were assessed on OsiriX. Brain MRI anatomical measurements from 232 patients with either TN type 1 or TN type 2 (TN group) were compared with measurements obtained in 100 age- and sex-matched healthy controls (control group). Two-way ANOVA tests were conducted on the 6 measurements relative to group and NVC status. Bonferroni adjustments were used to correct for multiple comparisons. A nonhierarchical k-means cluster analysis was performed on the TN group using age and posterior fossa volume as independent variables.

RESULTS Within the TN group, females were found to be younger than males and less likely to have NVC. The odds ratio (OR) of females not having NVC compared to males was 2.7 (95% CI 1.3–5.5, p = 0.017). Patients younger than 30 years were much less likely to have NVC compared to older patients (OR 4.9, 95% CI 1.3–18.4, p = 0.017). The mean AP prepontine cistern length and symptomatic nerve length were smaller in the TN group than in the control group (5.3 vs 6.5 mm and 8.7 vs 9.7 mm, respectively; p < 0.001). The posterior fossa volume was significantly smaller in TN patients without NVC compared to those with NVC. A TN group cluster analysis suggested a sex-dependent difference that was not observed in those without NVC. Factorial ANOVA and post hoc testing found that findings in males without NVC were significantly different from those in controls or male TN patients with NVC and similar to those in females (female controls as well as female TN patients with or without NVC).

CONCLUSIONS Posterior fossa volume in males was larger than posterior fossa volume in females. This finding, along with the higher incidence of TN in females, suggests that smaller posterior fossa volume might be an independent factor in the pathophysiology of TN, which warrants further study.

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Pain Outcomes Following Microvascular Decompression for Drug-Resistant Trigeminal Neuralgia: A Systematic Review and Meta-Analysis

Neurosurgery, Volume 86, Issue 2, February 2020, Pages 182–190

Microvascular decompression (MVD) is a potentially curative surgery for drug-resistant trigeminal neuralgia (TN). Predictors of pain freedom after MVD are not fully understood. OBJECTIVE: To describe rates and predictors for pain freedom following MVD.

METHODS: Using preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines, PubMed, Cochrane Library, and Scopus were queried for primary studies examining pain outcomes after MVD for TN published between 1988 and March 2018. Potential biases were assessed for included studies. Pain freedom (ie, Barrow Neurological Institute score of 1) at last follow-up was the primary outcome measure. Variables associated with pain freedom on preliminary analysis underwent formal meta-analysis. Odds ratios (OR) and 95% confidence intervals (CI) were calculated for possible predictors.

RESULTS: Outcome data were analyzed for 3897 patients from 46 studies (7 prospective, 39 retrospective). Overall, 76.0% of patients achieved pain freedom afterMVD with amean follow-up of 1.7 ± 1.3 (standard deviation) yr. Predictors of pain freedom on meta-analysis using random effectsmodels included (1) disease duration≤5 yr (OR=2.06, 95% CI=1.08- 3.95); (2) arterial compression over venous or other (OR = 3.35, 95% CI = 1.91-5.88); (3) superior cerebellar artery involvement (OR = 2.02, 95% CI = 1.02-4.03), and (4) type 1 Burchiel classification (OR = 2.49, 95% CI = 1.32-4.67).

CONCLUSION: Approximately three-quarters of patients with drug-resistant TN achieve pain freedom after MVD. Shorter disease duration, arterial compression, and type 1 Burchiel classification may predict more favorable outcome. These results may improve patient selection and provider expectations.

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Endoscopic endonasal treatment of maxillary nerve (V2) painful neuropathy: cadaveric study with clinical correlation

Acta Neurochirurgica (2020) 162:223–229

Surgical access to the second (V2, maxillary) and third (V3, mandibular) branches of the trigeminal nerve (V) has been classically through a transoral approach. Increasing expertise with endoscopic anatomy has achieved less invasive, more efficient access to skull base structures. The authors present a surgical technique using an endoscopic endonasal approach for the treatment of painful V2 neuropathy.

Methods Endoscopic endonasal dissections using a transmaxillary approach were performed in four formalin-fixed cadaver heads to expose the V2 branch of the trigeminal nerve. Relevant surgical anatomy was evaluated and anatomic parameters for neurectomy were identified.

Results Endoscopic endonasal transmaxillary approaches completed bilaterally to the pterygopalatine and pterygomaxillary fossae exposed the V2 branch where it emerged from the foramen rotundum. The anatomy defined for the location of neurectomy was determined to be the point where V2 emerged from the foramen rotundum into the pterygopalatine fossa. The technique was then performed in 3 patients with intractable painful V2 neuropathy.

Conclusions In our cadaveric study and clinical cases, the endoscopic endonasal approach to the pterygopalatine fossa achieved effective exposure and treatment of isolated V2 painful neuropathy. Important surgical steps to visualize the maxillary nerve and its branches and key landmarks of the pterygopalatine fossa are discussed. This minimally invasive approach appears to be a valid alternative for select patients with painful V2 trigeminal neuropathy.

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Somatosensory functional MRI tractography for individualized targeting of deep brain stimulation in patients with chronic pain after brachial plexus injury

Acta Neurochirurgica (2019) 161:2485–2490

The optimal targets for deep brain stimulation (DBS) in patients with refractory chronic pain are not clearly defined. We applied sensory functional MRI (fMRI)- and diffusion tensor imaging (DTI)-based DBS in chronic pain patients into 3 different targets to ascertain the most beneficial individual stimulation site.

Methods Three patients with incapacitating chronic pain underwent DBS into 3 targets (periventricular gray (PVG), ventroposterolateral thalamus (VPL), and posterior limb of the internal capsule according to fMRI and DTI (PLIC). The electrodes were externalized and double-blinded tested for several days. Finally, the two electrodes with the best pain reduction were kept for permanent stimulation. The patients were then followed up for 12 months. Outcome measures comprised the numerical rating scale (NRS), short-form McGill’s score (SF-MPQ), and health-related quality of life (SF-36).

Results Continuous pain (mean NRS 6.6) was reduced to NRS 3.6 after 12 months. Only with stimulation of the PLIC pain attacks, that occurred at least 3 times a week (mean NRS 9.6) resolved in 2 patients and improved in one patient concerning both intensity (NRS 5) and frequency (twice a month). The mean SF-MPQ decreased from 92.7 to 50. The health-related quality of life improved considerably.

Conclusion fMRI- and DTI-based DBS to the PLIC was the only target with a significant effect on pain attacks and seems to be the most promising target in chronic pain patients after brachial plexus injury. The combination with PVG or VPL can further improve patients’ outcome especially in terms of reducing the continuous pain.

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