Mini-open lateral retropleural thoracic discectomy approach.

The lateral retropleural approach provides an eloquent, mini-open, safe corridor to address various pathologies in the thoracolumbar spine, including herniated thoracic discs. Traditional approaches (e.g., transpedicular, costotransversectomy, or transthoracic) have their own benefits and pitfalls but are generally associated with significant morbidity and often require instrumentation. In this video, the authors highlight the retropleural approach and its nuances, including patient positioning, surgical planning, relevant anatomy, surgical technique, and postoperative care. The video can be found here: https://stream.cadmore.media/r10.3171/2022.3.FOCVID2217.

Supracerebellar Infratentorial Approach for a Malignant Pineal Region Tumor Mimicking a Cavernous Malformation.

A man in his early 20s presented with diplopia. Imaging revealed a pineal region hemorrhagic lesion, suggestive of cavernous malformation.1-6 The patient underwent an endoscopic third ventriculostomy and was transferred to our institution. In the sitting position, he underwent a supracerebellar infratentorial approach. Gross total resection was achieved without new neurological deficits. Pathologic diagnosis was consistent with a mixed germ cell tumor. The patient was referred to the radiation oncology department. Gravity retraction of the cerebellum was achieved with the supracerebellar infratentorial approach in the sitting position, torcular craniotomy exposed the major sinuses, and drainage of cerebrospinal fluid widened the surgical corridor and facilitated resection of this lesion (Video 1). Histopathological findings are critical to establish the correct diagnosis because magnetic resonance imaging findings can be misleading. The patient provided written informed consent for the procedure.

Barrow Innovation Center: A 5-Year Update and Future Direction.

OBJECTIVE: The rich history of neurosurgical innovation served as a model for the Barrow Innovation Center's establishment in 2016. The center's accomplishments are summarized in hopes of fostering the development of similar centers and initiatives within the neurosurgical and broader medical community. METHODS: A retrospective review (January 2016-July 2021) of patent filings, project proposals, and funding history was used to generate the data presented in this operational review. RESULTS: Through the 5-year period of analysis, 55 prior art searches were conducted on new patentable ideas. A total of 87 provisional patents, 25 Patent Cooperation Treaty applications, and 48 national stage filings were submitted. In partnership with Arizona State University, the University of Arizona, California Polytechnic State University, and Texas A&M University, a total of 27 multidisciplinary projects were conducted with input from multispecialty engineers and scientists. These efforts translated into 1 startup company and 2 licensed patents to commercial companies, with most remaining ideas and project efforts awaiting interest from industry. CONCLUSIONS: The multidisciplinary collaborative environment embodied by the Barrow Innovation Center has revolutionized the innovative and entrepreneurial environment of its home institution and enabled neurosurgical residents to get a unique educational experience within the realm of innovation. The bottleneck within the workflow of ideas from conception to commercialization appears to be the establishment of commercial partners; therefore, future efforts within the center will be to establish a panel of industry partnerships to enhance the exposure of ideas to interested companies.

Outpatient outcomes of patients with femoral nerve neurapraxia after prone lateral lumbar interbody fusion at L4-5.

OBJECTIVE: Single-position prone lateral lumbar interbody fusion (LLIF) improves the efficiency of staged minimally invasive lumbar spine surgery. However, laterally approaching the lumbar spine, especially L4-5 with the patient in the prone position, could increase the risk of complications and presents unique challenges, including difficult ergonomics, psoas migration, and management of the nearby lumbar plexus. The authors sought to identify postoperative femoral neurapraxia after single-position prone LLIF at L4-5 to better understand how symptoms evolve over time. METHODS: This retrospective analysis examined a prospectively maintained database of LLIF patients who were treated by two surgeons (J.S.U. and J.D.T.). Patients who underwent single-position prone LLIF at L4-5 and percutaneous pedicle screw fixation for lumbar stenosis or spondylolisthesis were included if they had at least 6 weeks of follow-up. Outpatient postoperative neurological symptoms were analyzed at 6-week, 3-month, and 6-month follow-up evaluations. RESULTS: Twenty-nine patients (16 women [55%]; overall mean ± SD age 62 ± 11 years) met the inclusion criteria. Five patients (17%) experienced complications, including 1 (3%) who had a femoral nerve injury with resultant motor weakness. The mean ± SD transpsoas retractor time was 14.6 ± 6.1 minutes, the directional anterior electromyography (EMG) threshold before retractor placement was 20.1 ± 10.2 mA, and the directional posterior EMG threshold was 10.4 ± 9.1 mA. All patients had 6-week clinical follow-up evaluations. Ten patients (34%) reported thigh pain or weakness at their 6-week follow-up appointment, compared with 3/27 (11%) at 3 months and 1/20 (5%) at 6 months. No association was found between directional EMG threshold and neurapraxia, but longer transpsoas retractor time at L4-5 was significantly associated with femoral neurapraxia at 6-week follow-up (p = 0.02). The only case of femoral nerve injury with motor weakness developed in a patient with a retractor time that was nearly twice as long as the mean time (27.0 vs 14.6 minutes); however, this patient fully recovered by the 3-month follow-up evaluation. CONCLUSIONS: To our knowledge, this is the largest study with the longest follow-up duration to date after single-position prone LLIF at L4-5 with percutaneous pedicle screw fixation. Although 34% of patients reported ipsilateral sensory symptoms in the thigh at the 6-week follow-up evaluation, only 1 patient sustained a nerve injury; this resulted in temporary weakness that resolved by the 3-month follow-up evaluation. Thus, longer transpsoas retractor time at L4-5 during prone LLIF is associated with increased ipsilateral thigh symptoms at 6-week follow-up that may resolve over time.

Should Somatosensory and Motor Evoked Potential Monitoring Be Used Routinely in All Posterior Cervical Operations for Degenerative Conditions of the Cervical Spine?

OBJECTIVE: Intraoperative neuromonitoring (IONM) is useful during spinal cord operations, but whether IONM is necessary for posterior cervical surgeries for degenerative conditions is unknown. We evaluated the utility of somatosensory evoked potential (SSEP) and motor evoked potential (MEP) monitoring as a tool for predicting new postoperative neurologic deficits during posterior decompression and fusion for degenerative cervical spine conditions. METHODS: We retrospectively reviewed posterior cervical operations performed at our institute over a 4-year period. Patients with postoperative neurologic deficits were identified, and a detailed analysis performed to ascertain whether SSEP or MEP monitoring accurately predicted the onset of new postoperative deficits. RESULTS: Overall, 498 patients were included in the analysis (median age 66 years; range: 22-93 years). SSEP monitoring was performed in all patients, and both SSEP and MEP monitoring were performed in 121 patients (24%). Twenty-one patients (4.2%) had new postoperative neurologic deficits. SSEP had significantly higher specificity (90%) but lower sensitivity (33%) than MEP (74% specificity [P = 0.008], 50% sensitivity [P = 0.01]) for detecting neurologic compromise intraoperatively. For SSEP, the positive predictive value (PPV) and negative predictive value (NPV) in detecting intraoperative changes that translated to new postoperative neurological deficits were 12% and 97%, respectively, whereas for MEP, the PPV and NPV were 6% (P = 0.009) and 98% (P = 0.20), respectively. CONCLUSIONS: IONM during posterior cervical operations for degenerative conditions of the spine is not reliable at predicting new postoperative neurologic deficits in patients treated for degenerative conditions, but may provide peace of mind to the surgeon intraoperatively when no abnormalities are detected.

Predictors of indirect neural decompression in minimally invasive transpsoas lateral lumbar interbody fusion.

OBJECTIVE: An advantage of lateral lumbar interbody fusion (LLIF) surgery is the indirect decompression of the neural elements that occurs because of the resulting disc height restoration, spinal realignment, and ligamentotaxis. The degree to which indirect decompression occurs varies; no method exists for effectively predicting which patients will respond. In this study, the authors identify preoperative predictive factors of indirect decompression of the central canal. METHODS: The authors performed a retrospective evaluation of prospectively collected consecutive patients at a single institution who were treated with LLIF without direct decompression. Preoperative and postoperative MRI was used to grade central canal stenosis, and 3D volumetric reconstructions were used to measure changes in the central canal area (CCA). Multivariate regression was used to identify predictive variables correlated with radiographic increases in the CCA and clinically successful improvement in visual analog scale (VAS) leg pain scores. RESULTS: One hundred seven levels were treated in 73 patients (mean age 68 years). The CCA increased 54% from a mean of 0.96 cm2 to a mean of 1.49 cm2 (p < 0.001). Increases in anterior disc height (74%), posterior disc height (81%), right (25%) and left (22%) foraminal heights, and right (12%) and left (15%) foraminal widths, and reduction of spondylolisthesis (67%) (all p < 0.001) were noted. Multivariate evaluation of predictive variables identified that preoperative spondylolisthesis (p < 0.001), reduced posterior disc height (p = 0.004), and lower body mass index (p = 0.042) were independently associated with radiographic increase in the CCA. Thirty-two patients were treated at a single level and had moderate or severe central stenosis preoperatively. Significant improvements in Oswestry Disability Index and VAS back and leg pain scores were seen in these patients (all p < 0.05). Twenty-five (78%) patients achieved the minimum clinically important difference in VAS leg pain scores, with only 2 (6%) patients requiring direct decompression postoperatively due to persistent symptoms and stenosis. Only increased anterior disc height was predictive of clinical failure to achieve the minimum clinically important difference. CONCLUSIONS: LLIF successfully achieves indirect decompression of the CCA, even in patients with substantial central stenosis. Low body mass index, preoperative spondylolisthesis, and disc height collapse appear to be most predictive of successful indirect decompression. Patients with preserved disc height but severe preoperative stenosis are at higher risk of failure to improve clinically.

Multimodal Sensing Capabilities for the Detection of Shunt Failure.

Hydrocephalus is a medical condition characterized by the abnormal accumulation of cerebrospinal fluid (CSF) within the cavities of the brain called ventricles. It frequently follows pediatric and adult congenital malformations, stroke, meningitis, aneurysmal rupture, brain tumors, and traumatic brain injury. CSF diversion devices, or shunts, have become the primary therapy for hydrocephalus treatment for nearly 60 years. However, routine treatment complications associated with a shunt device are infection, obstruction, and over drainage. Although some (regrettably, the minority) patients with shunts can go for years without complications, even those lucky few may potentially experience one shunt malfunction; a shunt complication can require emergency intervention. Here, we present a soft, wireless device that monitors distal terminal fluid flow and transmits measurements to a smartphone via a low-power Bluetooth communication when requested. The proposed multimodal sensing device enabled by flow sensors, for measurements of flow rate and electrodes for measurements of resistance in a fluidic chamber, allows precision measurement of CSF flow rate over a long time and under any circumstances caused by unexpected or abnormal events. A universal design compatible with any modern commercial spinal fluid shunt system would enable the widespread use of this technology.

When Indirect Decompression Fails: A Review of 220 Consecutive Direct Lateral Interbody Fusions and Unplanned Secondary Decompression.

STUDY DESIGN: A consecutive series of patients who underwent minimally invasive spinal surgery by a single surgeon at a high-volume academic medical center were studied. OBJECTIVE: The objective of this study was to identify the prevalence, radiographic features, and clinical characteristics of patients who require unplanned secondary decompressive laminectomy or foraminotomy after lateral lumbar interbody fusion (LLIF). SUMMARY OF BACKGROUND DATA: LLIF indirectly decompresses the spinal canal, lateral recess, and neural foramen when properly performed. However, indirect decompression relies on endplate integrity, reasonable bone quality, and sufficient contralateral release so that ligament distraction can occur. Some patients have insufficient decompression, resulting in persistent axial low back pain or radiculopathy. METHODS: Patients undergoing LLIF for radiculopathy or refractory low back pain were enrolled in a prospective registry. Preoperative and postoperative imaging, clinical presentation, and operative reports were reviewed from this registry. RESULTS: During registry collection, 122 patients were enrolled (220 lumbar levels treated), with nearly even representation between men (64/122, 52.5%) and women (58/122, 47.5%). Overall, right-sided lumbar spinal approaches (74/122, 60.7%) were more common. Ultimately, 4.1% (five of 122) of patients required unplanned direct decompressive laminectomy or foraminotomy because of refractory radiculopathy and persistent radiographic evidence of compression at the index LLIF level. All patients for whom indirect decompression failed were men who underwent stand-alone LLIF and had radiculopathy contralateral to the side of the LLIF approach. Most patients (59.8%, 73/122) had evidence of graft subsidence (grade 0 or 1) or osteoporosis. CONCLUSION: We report a 4.1% rate of return to the operating room for failed indirect decompression after LLIF for refractory radiculopathy. Graft subsidence and osteoporosis were common in these patients. All five patients who required secondary decompressive laminectomy or foraminotomy underwent stand-alone primary LLIF, and the persistent radiculopathy was consistently contralateral to the initial side of the LLIF approach.Level of Evidence: 4.

Selective posterior cerebral artery amobarbital test: a predictor of memory following subtemporal selective amygdalohippocampectomy.

BACKGROUND: The selective posterior cerebral artery (PCA) amobarbital test, or PCA Wada test, is used to predict memory impairment after epilepsy surgery in patients who have previously had a failed internal carotid artery (ICA) amobarbital test. METHODS: Medical records from 2012 to 2018 were retrospectively reviewed for all patients with seizures who underwent a selective PCA Wada test at our institution following a failed or inconclusive ICA Wada test. Standardized neuropsychological testing was performed before and during the Wada procedure and postoperatively in patients who underwent resection. RESULTS: Thirty-three patients underwent a selective PCA Wada test, with no complications. Twenty-six patients with medically refractory epilepsy had a seizure focus amenable to selective amygdalohippocampectomy (AHE). Six patients (23%, n=26) had a failed PCA Wada test and did not undergo selective AHE, seven (27%) declined surgical resection, leaving 13 patients who underwent subtemporal selective AHE. Hippocampal sclerosis was found in all 13 patients (100%). Twelve patients (92%) subsequently underwent formal neuropsychological testing and all were found to have stable memory. Ten patients (77%) were seizure-free (Engel Class I), with average follow-up of 13 months. CONCLUSION: The selective PCA Wada test is predictive of memory outcomes after subtemporal selective AHE in patients with a failed or inconclusive ICA Wada test. Furthermore, given the low risk of complications and potential benefit of seizure freedom, a selective PCA Wada test may be warranted in patients with medically intractable epilepsy who are candidates for a selective AHE and who have a prior failed or inconclusive ICA Wada test.

Standardized Ventriculostomy Protocol without an Occlusive Dressing: Results of an Observational Study in Patients with Aneurysmal Subarachnoid Hemorrhage.

BACKGROUND: Catheter-related infections are a potentially life-threatening complication of having an external ventricular drain (EVD). Patients with aneurysmal subarachnoid hemorrhage (aSAH) are at increased risk of infection associated with prolonged ventricular drainage, with a reported mean infection rate of 6%. We report the EVD-associated infection rate among patients with aSAH managed with a unique standardized treatment protocol without an occlusive EVD dressing. METHODS: Patients with aSAH admitted from August 2015 through August 2017 were retrospectively analyzed for EVD placement. Cerebrospinal fluid (CSF) samples were obtained twice weekly for culture and routine studies. EVD-associated infection was defined as growth of CSF cultures. RESULTS: During the 2-year study period, 122 patients presented with an aSAH, with 91 (74.6%) having EVD placement. In patients with EVDs, the mean age was 57.9 years (68% women); 88% of aSAHs were Fisher grade III or IV. Mean duration of EVD was 14 days, and 13% of patients required EVD replacement. Endovascular coiling and surgical clipping were performed in 34 (37%) and 53 (58%) patients with EVD, respectively. A total of 347 CSF studies were performed with no EVD-associated infections. There were 3 CSF samples with false-positive Gram stain results but no growth on concurrent or multiple repeat cultures. CONCLUSIONS: Using a standardized protocol for placement and management of EVDs in patients with aSAH is associated with low risk of CSF infection. Our study demonstrates that occlusive EVD dressings are not necessary and that routine CSF sampling in patients with EVD may lead to false-positive findings and unnecessary antibiotic administration.

Association of Angiotensin-Converting Enzyme Inhibitors with Increased Mortality Among Patients with Isolated Severe Traumatic Brain Injury.

BACKGROUND: Traumatic brain injury (TBI) is associated with one-third of all deaths from trauma. Preinjury exposure to cardiovascular drugs may affect TBI outcomes. Angiotensin-converting enzyme inhibitors (ACEIs) exacerbate brain cell damage and worsen functional outcomes in the laboratory setting. ß-blockers (BBs), however, appear to be associated with reduced mortality among patients with isolated TBI. OBJECTIVE: Examine the association between preinjury ACEI and BB use and clinical outcome among patients with isolated TBI. METHODS: A retrospective cohort study of patients age ≥ 40 years admitted to an academic level 1 trauma center with isolated TBI between January 2010 and December 2014 was performed. Isolated TBI was defined as a head Abbreviated Injury Scale (AIS) score ≥ 3, with chest, abdomen, and extremity AIS scores ≤ 2. Preinjury medication use was determined through chart review. All patients with concurrent BB use were initially excluded. In-hospital mortality was the primary measured outcome. RESULTS: Over the 5-year study period, 600 patients were identified with isolated TBI who were naive to BB use. There was significantly higher mortality (P = .04) among patients who received ACEI before injury (10 of 96; 10%) than among those who did not (25 of 504; 5%). A multivariate stepwise logistic regression analysis revealed a threefold increased risk of mortality in the ACEI cohort (P < .001), which was even greater than the twofold increased risk of mortality associated with an Injury Severity Score ≥ 16. A second analysis that included patients who received preinjury BBs (n = 98) demonstrated slightly reduced mortality in the ACEI cohort with only a twofold increased risk in multivariate analysis (P = .05). CONCLUSIONS: Preinjury exposure to ACEIs is associated with an increase in mortality among patients with isolated TBI. This effect is ameliorated in patients who receive BBs, which provides evidence that this class of medications may provide a protective benefit.

Iatrogenic pseudoaneurysm rupture of the anterior cerebral artery after placement of an external ventricular drain, treated with clip-wrapping: a case report and review of the literature.

External ventricular drains (EVDs) are often placed emergently for patients with hydrocephalus, which carries a risk of hemorrhage. Rarely, rupture of a pseudoaneurysm originating from an EVD placement precipitates such a hemorrhage. An EVD was placed in a patient with a ruptured left posterior communicating artery aneurysm who later underwent endovascular coil embolization. On post-bleed day 20, a distal right anterior cerebral artery pseudoaneurysm along the EVD tract ruptured, which was successfully treated via clip-wrapping. Although EVD-associated pseudoaneurysms are rare, they have a high propensity for rupture. Early treatment of these lesions should be considered to prevent neurologic deterioration.

Biomechanical Testing of a 3D-printed L5 Vertebral Body Model.

Background We examined the biomechanical performance of a three-dimensional (3D)-printed vertebra on pedicle screw insertional torque (IT), axial pullout (APO), and stiffness (ST) testing. Materials and methods Seventy-three anatomically identical L5 vertebral body models (146 pedicles) were printed and tested for IT, APO, and ST using single-threaded pedicle screws of equivalent diameter (6.5 mm), length (40.0 mm), and thread pitch (2.6 mm). Print properties (material, cortical thickness [number of shells], cancellous density [in-fill], in-fill pattern, print orientation) varied among models. One-way analysis of variance was performed to evaluate the effects of variables on outcomes. Results The type of material significantly affected IT, APO, and ST (P < 0.001, all comparisons). For acrylonitrile butadiene styrene (ABS) models, in-fill density (25-35%) had a positive linear association with APO (P = 0.002), ST (P = 0.008), and IT (P = 0.10); similarly for the polylactic acid (PLA) models, APO (P = 0.001), IT (P < 0.001), and ST (P = 0.14). For the nylon material type, in-fill density did not affect any tested parameter. For a given in-fill density, material, and print orientation, the in-fill pattern significantly affected IT (P = 0.002) and APO (P = 0.03) but not ST (P = 0.23). Print orientation also significantly affected IT (P < 0.001), APO (P < 0.001), and ST (P = 0.002). Conclusions 3D-printed vertebral body models with specific print parameters can be designed to perform analogously to human bone on pedicle screw tests of IT, APO, and ST. Altering the material, in-fill density, in-fill pattern, and print orientation of synthetic vertebral body models could reliably produce a model that mimics bone of a specific bone mineral density.

A Quantitative Assessment of the Accuracy and Reliability of Robotically Guided Percutaneous Pedicle Screw Placement: Technique and Application Accuracy.

BACKGROUND: Minimally invasive surgery (MIS) and anterior (ALIF), transforaminal (TLIF), or lateral lumbar interbody fusion (LLIF) often require percutaneous pedicle screw fixation (PSF) to achieve circumferential fusion. Robotic guidance technology may augment workflow to improve screw placement and decrease operative time. OBJECTIVE: To report surgical experience with robotically assisted percutaneous screw placement following LLIF. METHODS: Data from fusions with robotically assisted PSF in prone or lateral decubitus positions was reviewed. A CT-guided robotic guidance arm was used for screw placement (Excelsius GPS™, Globus Medical Inc, Audubon, Pennsylvania). Postoperative CT imaging facilitated screw localization. 3-dimensional and 2-dimensional coordinates of the screw tip and tail were calculated and compared with a target trajectory to calculate targeting errors. Breach was defined as a violation of the lateral or medial pedicle wall. RESULTS: Robotic-guided screw placement was successful in 28/31 patients. In those patients, 116/116 screws were successfully implanted. The breach rate was 3.4% (4/116). Across 17 patients (70 screws), mean 3-D accuracy was 5.0 ± 2.4 mm, mean 2-D accuracy was 2.6 ± 1.1 mm, and mean angular offset was 5.6 ± 4.3° with corresponding intraclass correlation coefficients (ICC) of 0.775 and 0.693. 3-dimensional accuracy correlated with age (R = 0.306, P = .011) and BMI (R = 0.252, P = .038). Accuracy did not significantly differ among vertebral body levels (P > .22). Mean operative time for MIS-TLIF and percutaneous screws was 277 ± 52 and 183 ± 54 min, respectively. Operative time did not significantly decrease across either group (P > .187). CONCLUSION: The Excelsius GPS™ robotic guidance system allows accurate PSF in most cases with 2 mm 2-D accuracy. Future studies are needed to demonstrate the utility of this novel guidance system and workflow improvement.

Use of a wrist-mounted device for continuous outpatient physiologic monitoring after transsphenoidal surgery: a pilot study.

PURPOSE: Patients who undergo transsphenoidal surgery can experience hormonal, electrolyte, and fluid disturbances in the postoperative period leading to outpatient readmissions for medical management. Our goal was to determine whether use of a wrist-mounted physiologic tracking device is feasible in this setting and whether changes or trends in these parameters after discharge can help predict aberrant physiology in these patients. METHODS: Wrist-mounted physiologic tracking devices that transmit data via Bluetooth to a mobile device were used to monitor patients. Preoperative baseline data and postoperative data were aggregated daily to compare within-patient and between-patient trends. RESULTS: Of 11 patients enrolled in the study, 1 was readmitted for symptomatic hyponatremia. Device data completeness ranged from 78 to 93% with the exception of oxygen saturation (25% completeness). The patient with hyponatremia had a significantly lower baseline level of activity compared with other patients. Nonreadmitted patient activity variables (steps, calories, and distance) decreased by 48-52% after the operation (P < 0.001). The activity variables for the patient with hyponatremia were statistically unchanged after the operation; however, the patient did experience a significant decrease in heart rate compared with baseline. CONCLUSION: Deployment of a wrist-based physiologic tracking device is feasible for surgical patients in elective clinical practice. Overall, the device was associated with good patient adherence and high patient satisfaction. Patient activity significantly decreased after surgery. A significant decrease in heart rate was detected in a patient with hyponatremia who required readmission, which reflects the known intravascular volume expansion in this state.