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Michael D. Staudt, Holger Joswig, Gwynedd E. Pickett, Keith W. MacDougall and Andrew G. Parrent

OBJECTIVE

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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Hormuzdiyar H. Dasenbrock, Timothy R. Smith and Shenandoah Robinson

OBJECTIVES

The goal of this study was to evaluate clinical predictors of abnormal preoperative laboratory values in pediatric neurosurgical patients.

METHODS

Data obtained in children who underwent a neurosurgical operation were extracted from the prospective National Surgical Quality Improvement Program–Pediatrics (NSQIP-P, 2012–2013) registry. Multivariable logistic regression evaluated predictors of preoperative laboratory values that might require further evaluation (white blood cell count < 2000/μl, hematocrit < 24%, platelet count < 100,000/μl, international normalized ratio > 1.4, or partial thromboplastin time > 45 seconds) or a preoperative transfusion (within 48 hours prior to surgery). Variables screened included patient demographics; American Society of Anesthesiologists (ASA) physical designation classification; comorbidities; recent steroid use, chemotherapy, or radiation therapy; and admission type. Predictive score validation was performed using the NSQIP-P 2014 data.

RESULTS

Of the 6556 patients aged greater than 2 years, 68.9% (n = 5089) underwent laboratory testing, but only 1.9% (n = 125) had a critical laboratory value. Predictors of a laboratory abnormality were ASA class III–V; diabetes mellitus; hematological, hypothrombotic, or oncological comorbidities; nutritional support; recent chemotherapy; systemic inflammatory response syndrome; and a nonelective hospital admission. These 9 variables were used to create a predictive score, with a single point assigned for each predictor. The prevalence of critical values in the validation population (NSQIP-P 2014) of patients greater than 2 years of age was 0.3% with a score of 0, 1.0% in those with a score of 1, 1.6% in those with a score of 2, and 6.2% in those with a score ≥ 3. Higher score was predictive of a critical value (OR 2.33, 95% CI 1.91–2.83, p < 0.001, C-statistic 0.76) and with the requirement of a perioperative transfusion (intraoperatively or within 72 hours postoperatively; OR 1.42, 95% CI 1.22–1.67, p < 0.001) in the validation population. Moreover, when the same score was applied to children aged 2 years or younger, a greater score was predictive of a critical value (OR 2.47, 95% CI 2.15–2.84, p < 0.001, C-statistic 0.76).

CONCLUSIONS

Critical laboratory values in pediatric neurosurgical patients are largely predicted by clinical characteristics, and abnormal preoperative laboratory results are rare in patients older than 2 years of age without comorbidities who are undergoing elective surgery. The NSQIP-P critical preoperative laboratory value scale is proposed to indicate patients with the highest odds of an abnormal value. The scale can assist with triaging preoperative testing based on the surgical risk, as determined by the treating surgeon and anesthesiologist.

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I. Jonathan Pomeraniec, Davis G. Taylor, Or Cohen-Inbar, Zhiyuan Xu, Mary Lee Vance and Jason P. Sheehan

OBJECTIVE

Gamma Knife radiosurgery (GKRS) provides a safe and effective management option for patients with all types of pituitary adenomas. The long-term adverse effects of targeted radiation to the hypothalamic-pituitary axis in relationship to radiation dose remain unclear. In this retrospective review, the authors investigated the role of differential radiation doses in predicting long-term clinical outcomes and pituitary function after GKRS for pituitary adenomas.

METHODS

A cohort of 236 patients with pituitary tumors (41.5% nonfunctioning, 58.5% functioning adenomas) was treated with GKRS between 1998 and 2015. Point dosimetric measurements, with no minimum volume, to 14 consistent points along the hypothalamus bilaterally, pituitary stalk, and normal pituitary were made. Statistical analyses were performed to determine the impact of doses to critical structures on clinical, radiological, and endocrine outcomes.

RESULTS

With a median follow-up duration of 42.9 months, 18.6% of patients developed new loss of pituitary function. The median time to endocrinopathy was 21 months (range 2–157 months). The median dose was 2.1 Gy to the hypothalamus, 9.1 Gy to the pituitary stalk, and 15.3 Gy to the normal pituitary. Increasing age (p = 0.015, HR 0.98) and ratio of maximum dose to the pituitary stalk over the normal pituitary gland (p = 0.013, HR 0.22) were independent predictors of new or worsening hypopituitarism in the multivariate analysis. Sex, margin dose, treatment volume, nonfunctioning adenoma status, or ratio between doses to the pituitary stalk and hypothalamus were not significant predictors.

CONCLUSIONS

GKRS offers a low rate of delayed pituitary insufficiency for pituitary adenomas. Doses to the hypothalamus are low and generally do not portend endocrine deficits. Patients who are treated with a high dose to the pituitary stalk relative to the normal gland are at higher risk of post-GKRS endocrinopathy. Point dosimetry to specific neuroanatomical structures revealed that a ratio of stalk-to-gland radiation dose of 0.8 or more significantly increased the risk of endocrinopathy following GKRS. Improvement in the gradient index toward the stalk and normal gland may help preserve endocrine function.

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Lourdes C. Eco, Alison Brayton, William E. Whitehead and Andrew Jea

Chordomas are histologically benign tumors with local aggressive behavior. They arise from embryological remnants of the notochord at the clivus, mobile spine, and sacrum. Chordomas are rare tumors in the pediatric age group. Their surgical management is difficult, given their propensity for inaccessible anatomical regions, and proximity to critical neurovascular structures. While en bloc resection with surgical margins has been advocated as the preferred approach for chordomas, tumor characteristics and violation of adjacent anatomical boundaries may not allow for safe en bloc resection of the tumor. Here, the authors present the case of a C1 chordoma in a 5-year-old boy with epidural and prevertebral extension. The patient’s treatment consisted of a far-lateral approach for resection of the tumor and C1 arch, followed by circumferential reconstruction of the craniocervical junction with an expandable cage spanning the skull base to C2, and posterior occipitocervical spinal instrumentation. At 42 months after surgery, the patient remains neurologically intact with stable oncological status, and no evidence of craniocervical junction instrumentation failure.

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Adam T. Leibold, Jonathan Weyhenmeyer and Albert Lee

OBJECTIVE

Intrathecal drug delivery devices (IDDDs) are a mainstay in the treatment of spasticity and refractory pain. While these devices have been shown to greatly improve the quality of life for patients, they also have a high perioperative complication and failure rate. A major complication of IDDD implantation is infection. The current standard of care in the treatment of IDDD infection necessitates that the pump be explanted and the infection treated prior to implantation of a new IDDD. This process leads to long hospital stays, interruptions in optimal medical management, and a high risk for dangerous drug withdrawals. The authors describe a technique that allows for the explantation of the infected pump and implantation of a new pump concurrently, which they have named the “Turner Switch” technique in honor of its inventor.

METHODS

The authors conducted a retrospective analysis of cases of infected IDDDs in which patients underwent simultaneous explantation of the infected pump and implantation of a new pump. Demographics and clinical data were collected.

RESULTS

Data from a total of 17 patients (11 male, 6 female) who underwent simultaneous IDDD explantation and implantation to treat infections were analyzed from a 3-year period. No patients experienced infection of the newly implanted pump or catheter. Of the 17 patients, 14 (82.4%) had baclofen pumps to treat spasticity and 3 (17.6%) had fentanyl pumps to treat chronic pain. The median hospital stay was 7 days, with 16 of 17 (94.1%) patients able to be discharged home or to a facility with a level of care similar to their preoperative care. All patients ultimately experienced complete resolution of their initial infections. Five patients (29.4%) required a return to the operating room within the next 5 months (for repair of a CSF leak in 2 cases, for treatment of infection at the old pump site in 2 cases, and for treatment of a CSF leak compounded with infection in 1 case). No patient experienced infection of the newly implanted pump or catheter.

CONCLUSIONS

IDDD infections represent a large portion of morbidity associated with these devices. The current standard of care for deep pump infections requires pump explantation and a course of antibiotics prior to reimplantation of the IDDD. The authors demonstrate the effectiveness of a procedure involving simultaneous explantation of an infected pump and implantation of a new pump on the contralateral side in the treatment of IDDD infections.

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Daniel Dutra Cavalcanti, Bárbara Albuquerque Morais, Eberval Gadelha Figueiredo, Robert F. Spetzler and Mark C. Preul

OBJECTIVE

The brainstem is a compact, delicate structure. The surgeon must have good anatomical knowledge of the safe entry points to safely resect intrinsic lesions. Lesions located at the lateral midbrain surface are better approached through the lateral mesencephalic sulcus (LMS). The goal of this study was to compare the surgical exposure to the LMS provided by the subtemporal (ST) approach and the paramedian and extreme-lateral variants of the supracerebellar infratentorial (SCIT) approach.

METHODS

These 3 approaches were used in 10 cadaveric heads. The authors performed measurements of predetermined points by using a neuronavigation system. Areas of microsurgical exposure and angles of the approaches were determined. Statistical analysis was performed to identify significant differences in the respective exposures.

RESULTS

The surgical exposure was similar for the different approaches—369.8 ± 70.1 mm2 for the ST; 341.2 ± 71.2 mm2 for the SCIT paramedian variant; and 312.0 ± 79.3 mm2 for the SCIT extreme-lateral variant (p = 0.13). However, the vertical angular exposure was 16.3° ± 3.6° for the ST, 19.4° ± 3.4° for the SCIT paramedian variant, and 25.1° ± 3.3° for the SCIT extreme-lateral variant craniotomy (p < 0.001). The horizontal angular exposure was 45.2° ± 6.3° for the ST, 35.6° ± 2.9° for the SCIT paramedian variant, and 45.5° ± 6.6° for the SCIT extreme-lateral variant opening, presenting no difference between the ST and extreme-lateral variant (p = 0.92), but both were superior to the paramedian variant (p < 0.001). Data are expressed as the mean ± SD.

CONCLUSIONS

The extreme-lateral SCIT approach had the smaller area of surgical exposure; however, these differences were not statistically significant. The extreme-lateral SCIT approach presented a wider vertical and horizontal angle to the LMS compared to the other craniotomies. Also, it provides a 90° trajectory to the sulcus that facilitates the intraoperative microsurgical technique.

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Jakub Godzik, Jennifer N. Lehrman, Anna G. U. S. Newcomb, Ram Kumar Menon, Alexander C. Whiting, Brian P. Kelly and Laura A. Snyder

OBJECTIVE

Transforaminal lumbar interbody fusion (TLIF) is commonly used for lumbar fusion, such as for foraminal decompression, stabilization, and improving segmental lordosis. Although many options exist, surgical success is contingent on matching design strengths with surgical goals. The goal in the present study was to investigate the effects of an expandable interbody spacer and 2 traditional static spacer designs in terms of stability, compressive stiffness, foraminal height, and segmental lordosis.

METHODS

Standard nondestructive flexibility tests (7.5 N⋅m) were performed on 8 cadaveric lumbar specimens (L3–S1) to assess intervertebral stability of 3 types of TLIF spacers at L4–5 with bilateral posterior screw-rod (PSR) fixation. Stability was determined as range of motion (ROM) in flexion-extension (FE), lateral bending (LB), and axial rotation (AR). Compressive stiffness was determined with axial compressive loading (300 N). Foraminal height, disc height, and segmental lordosis were evaluated using radiographic analysis after controlled PSR compression (170 N). Four conditions were tested in random order: 1) intact, 2) expandable interbody cage with PSR fixation (EC+PSR), 3) static ovoid cage with PSR fixation (SOC+PSR), and 4) static rectangular cage with PSR fixation (SRC+PSR).

RESULTS

All constructs demonstrated greater stability than the intact condition (p < 0.001). No significant differences existed among constructs in ROM (FE, AR, and LB) or compressive stiffness (p ≥ 0.66). The EC+PSR demonstrated significantly greater foraminal height at L4–5 than SRC+PSR (21.1 ± 2.6 mm vs 18.6 ± 1.7 mm, p = 0.009). EC+PSR demonstrated higher anterior disc height than SOC+PSR (14.9 ± 1.9 mm vs 13.6 ± 2.2 mm, p = 0.04) and higher posterior disc height than the intact condition (9.4 ± 1.5 mm vs 7.1 ± 1.0 mm, p = 0.002), SOC+PSR (6.5 ± 1.8 mm, p < 0.001), and SRC+PSR (7.2 ± 1.2 mm, p < 0.001). There were no significant differences in segmental lordosis among SOC+PSR (10.1° ± 2.2°), EC+PSR (8.1° ± 0.5°), and SRC+PSR (11.1° ± 3.0°) (p ≥ 0.06).

CONCLUSIONS

An expandable interbody spacer provided stability, stiffness, and segmental lordosis comparable to those of traditional nonexpandable spacers of different shapes, with increased foraminal height and greater disc height. These results may help inform decisions about which interbody implants will best achieve surgical goals.

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Michael E. Ivan, Michael M. Safaee, Nikolay L. Martirosyan, Ana Rodríguez-Hernández, Barbara Sullinger, Priyanka Kuruppu, Julian Habdank-Kolaczkowski and Michael T. Lawton

OBJECTIVE

Anterior communicating artery (ACoA) aneurysms are common intracranial aneurysms. Despite advances in endovascular therapy, microsurgical clipping remains an important treatment for aneurysms with broad necks, large size, intraluminal thrombus, complex branches, or previous coiling. Anatomical triangles identify safe corridors for aneurysm access. The authors introduce the A1-A2 junctional triangle and the A1-A1 precommunicating triangle and examine relationships between dome projection, triangular corridors of access, and surgical outcomes.

METHODS

Preoperative catheter and CT angiograms were evaluated to characterize aneurysm dome projection. Aneurysm projection was categorized into quadrants and octants. Preoperative, intraoperative, and postoperative factors were correlated to aneurysm dome projection and patient outcomes using univariate and multivariate analyses.

RESULTS

A total of 513 patients with microsurgically treated ACoA aneurysms were identified over a 13-year period, and 400 had adequate imaging and follow-up data for inclusion. Surgical clipping was performed on 271 ruptured and 129 unruptured aneurysms. Good outcomes were observed in 91% of patients with unruptured aneurysms and 86% of those with ruptured aneurysms, with a mortality rate < 1% among patients with unruptured aneurysms. Increasing age (p < 0.01), larger aneurysm size (p = 0.03), and worse preoperative modified Rankin Scale score (p < 0.01) affected outcomes adversely. Aneurysms projecting superiorly and posteriorly required dissection in the junctional triangle, and multivariate analysis demonstrated worse clinical outcomes in these patients (p < 0.01).

CONCLUSIONS

Anteriorly and inferiorly projecting aneurysms involve only the precommunicating triangle, are simpler to treat microsurgically, and have more favorable outcomes. Superior and posterior dome projections make ACoA aneurysms more difficult to visualize and require opening the junctional triangle. Added visualization through the junctional triangle is recommended for these aneurysms in order to facilitate dissection of efferent branch arteries, careful clip application, and perforator preservation. Dome projection can be determined preoperatively from images and can help anticipate dissection routes through the junctional triangle.

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Silviu Sabou, Apostolos Lagaras, Rajat Verma, Irfan Siddique and Saeed Mohammad

OBJECTIVE

Sagittal imbalance and loss of lumbar lordosis are the main drivers of functional disability in adult degenerative scoliosis. The main limitations of the classic posterior lumbar interbody fusion technique are increased risk of neurological injury and suboptimal correction of the segmental lordosis. Here, the authors describe the radiological results of a modified posterior lumbar interbody fusion and compare the results with a historical cohort of patients.

METHODS

Eighty-two consecutive patients underwent surgical treatment for degenerative scoliosis/kyphosis in a single tertiary referral center for complex spinal surgery. Fifty-five patients were treated using the classic multilevel posterior lumbar interbody fusion (MPLIF) technique and 27 were treated using the modified MPLIF technique to include a release of the anterior longitudinal ligament (ALL) and the annulus. A radiographic review of both series of patients was performed by two independent observers. Functional outcomes were obtained, and patients were registered in the European Spine Tango registry.

RESULTS

The mean L4–5 disc angle increased by 3.14° in the classic MPLIF group and by 12.83° in MPLIF plus ALL and annulus release group. The mean lumbar lordosis increased by 15.23° in the first group and by 25.17° in the second group. The L4–S1 lordosis increased on average by 4.92° in the classic MPLIF group and increased by a mean of 23.7° in the MPLIF plus ALL release group when both L4–5 and L5–S1 segments were addressed. There were significant improvements in the Core Outcome Measures Index and EQ-5D score in both groups (p < 0.001). There were no vascular or neurological injuries observed in either group.

CONCLUSIONS

The authors’ preliminary results suggest that more correction can be achieved at the disc level using posterior-based ALL and annulus release in conjunction with posterior lumbar interbody fusion. They demonstrate that ALL and annulus release can be performed safely using a posterior-only approach with minimal risk of vascular injury. However, the authors recommend that this approach should only be used by surgeons with considerable experience in anterior and posterior spinal surgery.

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Günther Deuschl, Kenneth A. Follett, Ping Luo, Joern Rau, Frances M. Weaver, Steffen Paschen, Frank Steigerwald, Lisa Tonder, Valerie Stoker and Domenic J. Reda

OBJECTIVE

Several randomized studies have compared the effect of deep brain stimulation (DBS) of the subthalamic nucleus with the best medical treatment in large groups of patients. Important outcome measures differ between studies. Two such major studies, the life-quality study of the German Competence Network for Parkinson’s disease (LQ study) and the US Veterans Affairs/National Institute of Neurological Disorders and Stroke trial (VA/NINDS trial), were compared here in order to understand their differences in outcomes.

METHODS

Unless otherwise noted, analyses were based on those subjects in each study who received a DBS implant (LQ study 76 patients, VA/NINDS trial 140 patients) and who had data for the measurement under consideration (i.e., no imputations for missing data), referred to hereafter as the “as-treated completers” (LQ 69 patients, VA/NINDS 125 patients). Data were prepared and analyzed by biostatisticians at the US Department of Veterans Affairs Cooperative Studies Program Coordinating Center, the Coordinating Center for Clinical Trials Marburg, and Medtronic, under the direction of two authors (G.D. and K.A.F.). Data were extracted from the respective databases into SAS data sets and analyzed using SAS software. Analyses were based on the 6-month follow-up data from both studies because this was the endpoint for the LQ study.

RESULTS

Pre-DBS baseline demographics differed significantly between the studies, including greater levodopa responsiveness (LDR) in the LQ study population than in the VA/NINDS group. After DBS, LQ subjects demonstrated greater improvement in motor function (Unified Parkinson’s Disease Rating Scale, Motor Examination [UPDRS-III]), activities of daily living (ADLs), and complications of therapy. Medication reduction and improvements in life quality other than ADLs were not significantly different between LQ and VA/NINDS subjects. When the two populations were compared according to pre-DBS LDR, the “full responders” to levodopa (≥ 50% improvement on UPDRS-III with medication) in the two studies showed no significant difference in motor improvement with DBS (LQ 18.5 ± 12.0–point improvement on UPDRS-III vs VA/NINDS 17.7 ± 15.6–point improvement, p = 0.755). Among levodopa full responders, ADLs improved slightly more in the LQ group, but scores on other UPDRS subscales and the Parkinson’s Disease Questionnaire-39 were not significantly different between the two studies.

CONCLUSIONS

This comparison suggests that patient selection criteria, especially preoperative LDR, are the most important source of differences in motor outcomes and quality of life between the two studies.