Middle Meningeal Artery Embolization for Subdural Hematoma: An Institutional Cohort and Propensity Score-Matched Comparison with Conventional Management.

BACKGROUND: The treatment of non-acute subdural hematoma (NASDH) is challenging due to its high recurrence rates and comorbidities of mostly elderly patients. Middle meningeal artery embolization (MMAE) recently emerged as an alternative to surgery in the treatment of NASDH. OBJECTIVE: To describe a single center's experience of MMAE with Onyx for NASDH and compare it to a surgically treated historical cohort. METHODS: We performed a retrospective analysis of patients undergoing MMAE for NASDH from 2019 to 2021. MMAE was performed with ethylene vinyl alcohol copolymer (Onyx). Comparisons were made with a historical cohort from 2010 to 2018 who underwent surgical evacuation only, before and after propensity score matching. Outcomes were assessed clinically and radiographically. RESULTS: We included 44 consecutive patients (55 MMAEs) who underwent MMAE, with a median follow-up of 63.5 days. Twenty-four NASDHs underwent upfront embolization, 17 adjunctive, and 14 for recurrence after prior surgical evacuation, with no significant differences in hematoma and mRS reduction between them. Two patients died during hospitalization and 2 during follow-up, unrelated to the procedure. Mean SDH thickness decreased by 48.3% ± 38.1% (P < 0.001) on last follow-up, which did not correlate with the amount of Onyx injected. Six (13.6%) patients required surgical rescue after embolization. There were no procedure-related complications. The mean modified Rankin Scale (mRS) on admission was 2.8 ± 1.5, which decreased significantly to 1 [1,4] at the last follow-up (P = 0.033). The MMAE (41 hematomas; upfront and adjunctive embolization) and Surgical Evacuation-only (461 hematomas) cohorts were balanced with propensity score mathing. Matching was successful for 41 MMAE and 41 surgical-only hematoma pairs, and only hypertension remained significantly different between the two groups, but there was no significant difference in any outcome. CONCLUSION: MMAE for NASDH seems safe and effective in appropriately selected patients, non-inferior to surgery, and may become a minimally-invasive alternative. Given our encouraging results, large-scale clinical randomized trials are warranted.

Machine learning for outcome prediction of neurosurgical aneurysm treatment: Current methods and future directions.

INTRODUCTION: Machine learning algorithms have received increased attention in neurosurgical literature for improved accuracy over traditional predictive methods. In this review, the authors sought to assess current applications of machine learning for outcome prediction of neurosurgical treatment of intracranial aneurysms and identify areas for future research. METHODS: A PRISMA-compliant systematic review of the PubMed, MEDLINE, and EMBASE databases was conducted for all studies utilizing machine learning for outcome prediction of intracranial aneurysm treatment. Patient characteristics, machine learning methods, outcomes of interest, and accuracy metrics were recorded from included studies. RESULTS: 16 studies were ultimately included in qualitative synthesis. Studies primarily analyzed angiographic outcomes, functional outcomes, or complication prediction using clinical, radiological, or composite variables. The majority of included studies utilized supervised learning algorithms for analysis of dichotomized outcomes. CONCLUSIONS: Commonly included variables were demographics, presentation variables (including ruptured or unruptured status), and treatment used. Areas for future research include increased generalizability across institutions and for smaller datasets, as well as development of front-end tools for clinical applicability of published algorithms.

Treatment of cerebral aneurysms with the FRED Jr flow-diverting stent: A case series and meta-analysis.

BACKGROUND: With the development of the Flow Re-Direction Endoluminal Device Junior (FRED Jr), treatment of distal aneurysms and/or aneurysms with small parent vessels has become a viable option. OBJECTIVES: To assess the efficacy and safety of FRED Jr in the treatment of distal aneurysms with small parent vessels. METHODS: This is a single center retrospective study and meta-analysis of patients treated with FRED Jr for intracranial aneurysms. The primary outcome was complete aneurysm occlusion at final follow-up. Secondary outcomes included stroke rates, mortality rates, need for retreatment and clinical outcomes. RESULTS: There were a total of 7 patients with 7 aneurysms treated with FRED Jr. Mean aneurysm neck, width, height, and parent artery diameter were 2.6 ± 0.8 mm, 3.1 ± 0.9 mm, 2.5 ± 1.0 mm, and 1.8 ± 0.6 mm respectively. The complete occlusion rate was 57.1 % at 6 months, and favorable outcome (mRS 0-2) was observed in all patients in follow-up. Stroke complication occurred in none of the patients. Seven studies from 1360 articles were identified for inclusion in the meta-analysis, comprising 227 patients with 244 aneurysms treated with FRED Jr. Mean aneurysm height, width, neck and parent artery diameter were 6.9 ± 3.3 mm (pooled=5.6 [<0.1-11.47] mm), 6.6 ± 2.2 mm (pooled=6.6 [4.2-9.1] mm), 4.4 ± 1.4 mm (pooled=4.1 [3.3 -4.9] mm), and 2.0 ± 0.2 mm (pooled=2.1 [1.7-2.5]), respectively. At final follow-up, the pooled complete occlusion and complication rates were 69.9 % and 0 %, respectively. CONCLUSION: FRED Jr demonstrated moderate efficacy and good safety in the treatment of distal aneurysms with small parent vessels at mid-term follow-up.

Rescue stenting for acute ischemic stroke with refractory emergent large vessel occlusion in the modern thrombectomy era.

BACKGROUND AND PURPOSE: Rescue stenting is used as a bailout technique during mechanical thrombectomy for stroke. We performed a retrospective study analyzing outcomes of patients that received a stent as a bailout measure and compared results to a control group. METHODS: We identified all patients who underwent a mechanical thrombectomy for a large vessel occlusion between January 2010 and October 2019. Subjects with mTICI 0-2 A after at least three passes were defined as failed MT and constituted the control group (NSG-controls). Patients that received a rescue stent (RSG) formed the study group. RESULTS: Comparative analysis of patient demographics between NSG-controls and SRG was performed. Baseline characteristics and comorbidities were not significantly different between both groups. NIHSS at admission and IV t-PA were not significantly different among both groups (16.5 vs. 14.2, p = 0.19) and (39.4% vs. 29.4%, p = 0.30), respectively. There was no significant difference in procedural and post-procedural complications between both the groups. In the RSG, 24 patients (82.4%) achieved favorable revascularization outcomes. NIHSS at discharge (p = 0.01) was higher in the NSG-controls, while favorable functional outcome at three months (12% vs. 39.2%, p = 0.01) was observed at a higher proportion in the RSG. There was also a significant mortality difference, with 15.2% mortality in the RSG compared to 35.1% mortality in the NSG-controls (p = 0.03). In multivariate analysis, stenting was an independent predictor of favorable outcome (OR: 10.0, p = 0.009). CONCLUSION: Herein, we demonstrated that rescue stenting is a feasible, safe, and effective procedure to improve stroke outcomes and should be seriously considered if the primary mechanical thrombectomy is not successful.

The Woven EndoBridge (WEB) device: feasibility, techniques, and outcomes after FDA approval.

OBJECTIVE: Wide-neck bifurcation cerebral aneurysms have historically required either clip ligation or stent- or balloon-assisted coil embolization. This predicament led to the development of the Woven EndoBridge (WEB) aneurysm embolization system, a self-expanding mesh device that achieves intrasaccular flow disruption and does not require antithrombotic medications. The authors report their operative experience and 6-month follow-up occlusion outcomes with the first 115 aneurysms they treated via WEB embolization. METHODS: The authors reviewed the first 115 cerebral aneurysms they treated by WEB embolization after FDA approval of the WEB embolization device (from February 2019 to January 2021). Data were collected on patient demographics and clinical presentation, aneurysm characteristics, procedural details, postembolization angiographic contrast stasis, and functional outcomes. RESULTS: A total of 110 patients and 115 aneurysms were included in our study (34 ruptured and 81 unruptured aneurysms). WEB embolization was successful in 106 (92.2%) aneurysms, with a complication occurring in 6 (5.5%) patients. Contrast clearance was seen in the arterial phase in 14 (12.2%) aneurysms, in the capillary phase in 16 (13.9%), in the venous phase in 63 (54.8%), and no contrast was seen in 13 (11.3%) of the aneurysms studied. Follow-up angiography was performed on 60 (52.6%) of the aneurysms, with complete occlusion in 38 (63.3%), neck remnant in 14 (23.3%), and aneurysmal remnant in 8 (13.3%). Six (5.5%) patients required re-treatment for persistent aneurysmal residual on follow-up angiography. CONCLUSIONS: The WEB device has been successfully used for the treatment of both unruptured and ruptured wide-neck bifurcation aneurysms by achieving intrasaccular flow diversion. Here, the authors have shared their experience with its unique technical considerations and device size selection, as well as critically reviewed complications and aneurysm occlusion rates.

Comparison of Anesthetic Agents Dexmedetomidine and Midazolam During Mechanical Thrombectomy.

OBJECTIVES: The ideal anesthetic for mechanical thrombectomy (MT) is a subject of debate. Recent studies have supported the use of monitored anesthesia care (MAC), but few have attempted to compare MAC neuroanesthetics. Our study directly compares midazolam and dexmedetomidine (DEX) on blood pressure control during thrombectomy and functional outcomes at discharge. MATERIALS AND METHODS: We performed a retrospective review of an MT database, which consisted of 612 patients admitted between 2010-2019 to our tertiary stroke center. 193 patients who received either midazolam or DEX for MAC induction were identified. Primary and secondary outcomes were >20% maximum decrease in mean arterial pressure during MT and functional independence respectively. RESULTS: 146 patients were administered midazolam, while 47 were administered DEX. Decrease in blood pressure (BP) during MT was associated with lower rates of functional independence at last follow-up (p=0.034). When compared to midazolam, DEX had significantly higher rates of intraprocedural decrease in MAP at the following cut-offs: >20% (p<0.001), >30% (p=0.001), and >40% (p=0.006). On multivariate analysis, DEX was an independent predictor of >20% MAP decrease (OR 7.042, p<0.001). At time of discharge, NIHSS scores and functional independence (mRS 0-2) were statistically similar between DEX and midazolam. Functional independence at last known follow-up was statistically similar between DEX and midazolam (p = 0.643). CONCLUSIONS: Use of DEX during MT appears to be associated with increased blood pressure volatility when compared to midazolam. Further investigation is needed to determine the impact of MAC agents on functional independence.

Independent Predictors of Revision Lumbar Fusion Outcomes and the Impact of Spine Surgeon Variability: Does It Matter Whether the Primary Surgeon Revises?

BACKGROUND: There is a paucity of information regarding treatment strategies and variables affecting outcomes of revision lumbar fusions. OBJECTIVE: To evaluate the influence of primary vs different surgeon on functional outcomes of revisions. METHODS: All elective lumbar fusion revisions, March 2018 to August 2019, were retrospectively categorized as performed by the same or different surgeon who performed the primary surgery. Oswestry Disability Index (ODI) and clinical variables were collected. Multiple logistic regression identified multivariable-adjusted odds ratio (OR) of independent variables analyzed. RESULTS: Of the 130 cases, 117 (90%) had complete data. There was a slight difference in age in the same (median: 59; interquartile range [IQR], 54-66) and different surgeon (median: 67; IQR, 56-72) groups (P = .02); all other demographic variables were not significantly different (P > .05). Revision surgery with a different surgeon had an ODI improvement (median: 8; IQR, 2-14) greater than revisions performed by the same surgeon (median: 1.5; IQR, -3 to 10) (P < .01). Revisions who achieved minimum clinically important difference (MCID) performed by different surgeon (59.7%) were also significantly greater than the ones performed by the same surgeon (40%) (P = .042). Multivariate analysis demonstrated that a different surgeon revising (OR, 2.37; [CI]: 1.007-5.575, P = .04) was an independent predictor of MCID achievement, each additional 2 years beyond the last surgery conferred a 2.38 ([CI]: 1.36-4.14, P < .01) times greater odds of MCID achievement, and the anterior lumbar interbody fusion approach decreased the chance of achieving MCID (OR, 0.19; [CI]: 0.04-0.861, P = .03). CONCLUSION: All revision lumbar spinal fusion approaches may not achieve the same outcomes. This analysis suggests that revision surgeries may have better outcomes when performed by a different surgeon.

Clinical outcomes in revision lumbar spine fusions: an observational cohort study.

OBJECTIVE: The authors compared primary lumbar spine fusions with revision fusions by using patient Oswestry Disability Index (ODI) scores to evaluate the impact of the North American Spine Society (NASS) evidence-based medicine (EBM) lumbar fusion indications on patient-reported outcome measures of revision surgeries. METHODS: This study was a retrospective analysis of a prospective observational cohort of patients who underwent elective lumbar fusion between January 2018 and December 2019 at a single quaternary spine surgery service and had a minimum of 6 months of follow-up. A prospective quality improvement database was constructed that included the data from all elective lumbar spine surgeries, which were categorized prospectively as primary or revision surgeries and EBM-concordant or EBM-discordant revision surgeries based on the NASS coverage EBM policy. In total, 309 patients who met the inclusion criteria were included in the study. The ODIs of all groups (primary, revision, revision EBM concordant, and revision EBM discordant) were statistically compared. Differences in frequencies between cohorts were evaluated using chi-square and Fisher's exact tests. The unpaired 2-tailed Student t-test and the Mann-Whitney U-test for nonparametric data were used to compare continuous variables. Logistic regression was performed to determine the associations between independent variables (surgery status and NASS criteria indications) and functional outcomes. RESULTS: Primary lumbar fusions were significantly associated with improved functional outcomes compared with revisions, as evidenced by ODI scores (OR 1.85, 95% CI 1.16-2.95 to achieve a minimal clinically important difference, p = 0.01). The percentage of patients whose functional status had declined at the 6-month postoperative evaluation was significantly higher in patients who had undergone a revision surgery than in those who underwent a primary surgery (23% vs 12.3%, respectively). An increase in ODI score, indicating worse clinical outcome after surgery, was greater in patients who underwent revision procedures (OR 2.14, 95% CI 1.17-3.91, p = 0.0014). Patients who underwent EBM-concordant revision surgery had significantly improved mean ODI scores compared with those who underwent EBM-discordant revision surgery (7.02 ± 5.57 vs -4.6 ± 6.54, p < 0.01). CONCLUSIONS: The results of this prospective quality improvement program investigation illustrate that outcomes of primary lumbar fusions were superior to outcomes of revisions. However, revision procedures that met EBM guidelines were associated with greater improvements in ODI scores, which indicates that the use of defined EBM guideline criteria for reoperation can improve clinical outcomes of revision lumbar fusions.

Simultaneous bilateral mechanical thrombectomy in a patient with COVID-19.

Owing to systemic inflammation and widespread vessel endotheliopathy, SARS-CoV-2 has been shown to confer an increased risk of cryptogenic stroke, particularly in patients without any traditional risk factors. In this report, we present a case of a 67-year-old female who presented with acute stroke from bilateral anterior circulation large vessel occlusions, and was incidentally found to be COVID-positive on routine hospital admission screening. The patient had a large area of penumbra bilaterally, and the decision was made to pursue bilateral simultaneous thrombectomy, with two endovascular neurosurgeons working on each side to achieve a faster time to recanalization. Our study highlights the utility and efficacy of simultaneous bilateral thrombectomy, and this treatment paradigm should be considered for use in patients who present with multifocal large vessel occlusions.

Discrepancies in Stroke Distribution and Dataset Origin in Machine Learning for Stroke.

BACKGROUND: Machine learning algorithms depend on accurate and representative datasets for training in order to become valuable clinical tools that are widely generalizable to a varied population. We aim to conduct a review of machine learning uses in stroke literature to assess the geographic distribution of datasets and patient cohorts used to train these models and compare them to stroke distribution to evaluate for disparities. AIMS: 582 studies were identified on initial searching of the PubMed database. Of these studies, 106 full texts were assessed after title and abstract screening which resulted in 489 papers excluded. Of these 106 studies, 79 were excluded due to using cohorts from outside the United States or being review articles or editorials. 27 studies were thus included in this analysis. SUMMARY OF REVIEW: Of the 27 studies included, 7 (25.9%) used patient data from California, 6 (22.2%) were multicenter, 3 (11.1%) were in Massachusetts, 2 (7.4%) each in Illinois, Missouri, and New York, and 1 (3.7%) each from South Carolina, Washington, West Virginia, and Wisconsin. 1 (3.7%) study used data from Utah and Texas. These were qualitatively compared to a CDC study showing the highest distribution of stroke in Mississippi (4.3%) followed by Oklahoma (3.4%), Washington D.C. (3.4%), Louisiana (3.3%), and Alabama (3.2%) while the prevalence in California was 2.6%. CONCLUSIONS: It is clear that a strong disconnect exists between the datasets and patient cohorts used in training machine learning algorithms in clinical research and the stroke distribution in which clinical tools using these algorithms will be implemented. In order to ensure a lack of bias and increase generalizability and accuracy in future machine learning studies, datasets using a varied patient population that reflects the unequal distribution of stroke risk factors would greatly benefit the usability of these tools and ensure accuracy on a nationwide scale.

Lessons Learned After 760 Neurointerventions via the Upper Extremity Vasculature: Pearls and Pitfalls.

BACKGROUND: The radial approach has been gaining more widespread use by neurointerventionalists fueled by data from the cardiology literature showing better safety and overall reduced morbidity. OBJECTIVE: To present our institution's experience with the radial approach for neuroendovascular interventions in 614 consecutive patients who underwent a cumulative of 760 procedures. METHODS: A retrospective analysis was performed and identified neuroendovascular procedures performed via the upper extremity vasculature access site. RESULTS: Amongst 760 procedures, 34.2% (260) were therapeutic, and 65.7% (500) were nontherapeutic angiograms. Access sites were 71.5% (544) via a conventional radial artery, 27.8% (211) via a distal radial artery, 0.5% (4) via an ulnar artery, and 0.1% (1) via the brachial artery. Most of the procedures (96.9%) were performed via the right-sided (737), 2.9% (22) via the left-sided, and 0.1% (1) via a bilateral approach. Major access site complications occurred at a rate of 0.9% (7). The rate of transfemoral conversion was 4.7% (36). There was a statistically higher incidence of transfemoral conversion when repeat procedures were performed using the same access site. Also, there was no significant difference between nontherapeutic procedures performed using the right and left radial access, and conventional versus distal radial access. Procedural metrics improved after completion of 14 procedures, indicating a learning curve that should be surpassed by operators to reach optimal outcomes. CONCLUSION: Radial artery catheterization is a safe and effective means of carrying out a wide range of neuroendovascular procedures associated with excellent clinical outcomes and an overall low rate of periprocedural complications.

Low diagnostic yield in follow-up MR imaging in patients with spontaneous intracerebral hemorrhage with a negative initial MRI.

PURPOSE: Follow-up MRI/MRA is historically obtained as outpatient when patients with a spontaneous intracerebral hemorrhage (ICH) have an initial MRI/MRA that is negative for an underlying structural lesion. However, the utility of repeating MR imaging in a delayed fashion remains uncertain. METHODS: We retrospectively reviewed 396 patients with spontaneous ICH admitted at our institution between 2015 and 2017 and selected those whose initial MRI/MRA was negative for an underlying structural lesion and those who underwent follow-up MR imaging in a delayed fashion. RESULTS: A total of 113 patients met the study criteria. The average age of those with negative follow-up MRI/MRA was 65.0 ± 12.6 (IQR: 55.0-74.0) years old. None of the 113 patients with a negative inpatient MRI/MRA had an underlying structural lesion on follow-up MRI/MRA (0%, 95% CI 0.0-0.032, p < 0.001). The mean time of the follow-up imaging from the initial study was 105.7 days (median: 62 days; IQR: 42.5-100.5). Of the 113, 83 (73.5%) underwent follow-up MRI with and without gadolinium, while 30 (26.5%) patients did not receive gadolinium. CONCLUSION: Delayed follow-up MRI in patients with a negative initial MRI/MRA for workup of spontaneous ICH was not diagnostic in any of the patients included in the study. Our study suggests that a routine follow-up MRI for this patient population is not necessary.

Carotid cutdown for mechanical thrombectomy in the setting of intravenous tissue plasminogen activator: A technical report.

Acute ischemic stroke (AIS) is a leading cause of mortality and morbidity in the world. Patients are usually treated with endovascular methods and access is often gained trans-femoral or trans-radial. In patients with difficult anatomy, in rare cases the approach must be done trans-cervical. Our case illustrates a patient who received IVTPA prior to attempted endovascular treatment, leading to a direct carotid cutdown for mechanical thrombectomy. Our patient presented with a left M1 occlusion and had received intravenous thrombolytic at the presentation of his symptoms. Due to unfavorable anatomy and tortuous aortic arch, conventional access could not be obtained. In order to achieve reperfusion while maintaining hemostasis, a decision was made to perform an open carotid cutdown to catherize the left internal carotid artery to successfully retrieve the thrombus. This resulted in a TICI2B revascularization. This is the first reported case of direct carotid access in the setting of acute ischemic stroke with IVTPA. Open technique allowed us to maintain hemostasis while bypassing the tortuous arch and achieving reperfusion and give the patient the best chance for a functional recovery.

Endoscopic transsphenoidal resection of a recurrent petrous apex cholesterol granuloma: Operative video.

BACKGROUND: Cholesterol granulomas (GC) of the petrous apex are benign cystic lesions that occur due to a foreign body reaction to blood by-products and cholesterol crystals. They cause erosion and expansion of the petrous apex and lead to cranial nerve deficits. CASE DESCRIPTION: We present an operative video of a 28-year-old male whose work-up for horizontal diplopia revealed a right petrous apex GC. He originally underwent a subtemporal and later a transmastoid approach at outside institutions before he presented to us with diplopia due to recurrence. An endoscopic transsphenoidal transclival approach was done for drainage and resection of the GC. The patient did well and his diplopia resolved. A follow-up MRI showed no recurrence of the granuloma. CONCLUSION: This case illustrates an endoscopic transsphenoidal transclival approach for a recurrent petrous apex CG, which may lead to symptom resolution if done in a timely fashion.

Comparison of Outcomes in Level I vs Level II Trauma Centers in Patients Undergoing Craniotomy or Craniectomy for Severe Traumatic Brain Injury.

BACKGROUND: Traumatic brain injury (TBI) carries a devastatingly high rate of morbidity and mortality. OBJECTIVE: To assess whether patients undergoing craniotomy/craniectomy for severe TBI fare better at level I than level II trauma centers in a mature trauma system. METHODS: The data were extracted from the Pennsylvania Trauma Outcome Study database. Inclusion criteria were patients > 18 yr with severe TBI (Glasgow Coma Scale [GCS] score less than 9) undergoing craniotomy or craniectomy in the state of Pennsylvania from January 1, 2002 through September 30, 2017. RESULTS: Of 3980 patients, 2568 (64.5%) were treated at level I trauma centers and 1412 (35.5%) at level II centers. Baseline characteristics were similar between the 2 groups except for significantly worse GCS scores at admission in level I centers (P = .002). The rate of in-hospital mortality was 37.6% in level I centers vs 40.4% in level II centers (P = .08). Mean Functional Independence Measure (FIM) scores at discharge were significantly higher in level I (10.9 ± 5.5) than level II centers (9.8 ± 5.3; P < .005). In multivariate analysis, treatment at level II trauma centers was significantly associated with in-hospital mortality (odds ratio, 1.2; 95% confidence interval, 1.03-1.37; P = .01) and worse FIM scores (odds ratio, 1.4; 95% confidence interval, 1.1-1.7; P = .001). Mean hospital and ICU length of stay were significantly longer in level I centers (P < .005). CONCLUSION: This study showed superior functional outcomes and lower mortality rates in patients undergoing a neurosurgical procedure for severe TBI in level I trauma centers.

Oculomotor neuropathy from an unruptured arteriovenous malformation in the frontal operculum: A case report.

BACKGROUND: Cerebral arteriovenous malformations (AVMs) are vascular lesions with a network of dysplastic vessels between an arterial and a venous tree with no intervening capillary bed. They most commonly present with an acute hemorrhage, seizures, or persistent headaches. CASE DESCRIPTION: The authors report the case of a 62-year-old male who presented with diplopia for 5 days. Magnetic resonance imaging and angiography demonstrated a Spetzler-Martin Grade 2 AVM located in the right frontal operculum with deep drainage into the basal vein of Rosenthal causing ipsilateral oculomotor neuropathy. The patient underwent staged embolizations of the feeding pedicles, which were derived from the internal as well as external carotid circulation. This was followed by a right pterional craniotomy for resection of the AVM. The patient reported complete resolution of the diplopia over 4 weeks with no recurrence at the 6-month follow-up appointment. CONLUSION: AVMs of the brain can present with atypical clinical symptoms that can be caused by the venous drainage pattern not the location. It is important to include vascular imaging studies in the work-up of patients who present with diplopia to rule out an AVM. Early diagnosis and treatment of the AVM can result in complete resolution of the diplopia.