Dimensional Characterization of the Human Lumbar Interlaminar Space as a Guide for Safe Application of Minimally Invasive Dilators

BACKGROUND

The risk of interlaminar passage of a dilator into the lumbar spinal canal in minimally invasive approaches is currently unknown. Among anthropometric data reported in the medical literature, there is no cadaveric report of the interlaminar dimensions of the lumbar spine.

OBJECTIVE

To report the lumbar interlaminar dimensions in neutral, flexion, and extension postures.

METHODS

A total of 8 spines were sectioned into lumbar segments. Digitized coordinate data defining the locations and movements of chosen anatomic points on the laminar edges at a given spinal level were used to measure changes in the opening dimensions during static neutral posture and flexion-extension movements. Interlaminar dimensions were averaged and categorized for each vertebral level and spinal posture.

RESULTS

The mean interlaminar distance increased from neutral posture to flexion across all vertebral levels. The mean interlaminar distances in the neutral posture ranged from 12.21 mm (L5-S1) to 14.88 mm (L1-L2). In flexion, the range was from 17.15 mm (L5-S1) to 18.50 mm (L4-L5). These measurements are greater than the first several diameters of dilators in all minimally invasive dilator sets.

CONCLUSION

The precise measurements of the lumbar interlaminar space are valuable to minimally invasive spine surgeons for the dilatation phase of the operation. The risk of interlaminar passage of a minimally invasive dilator is greatest in flexion with dilators that have a diameter of 16 mm or less. There is considerably less risk of interlaminar passage in patients positioned on an extended Jackson table.

Access to Neurosurgery in the Era of Narrowing Insurance Networks: Statewide Analysis of Patient Protection and Affordable Care Act Marketplace Plans in Arizona

OBJECTIVE

The Patient Protection and Affordable Care Act (ACA) sought to expand access to health care for 46 million uninsured Americans. Increasing consumer coverage and ensuring affordability of care have raised concerns about ACA Marketplace plans with limited in-network physician coverage (narrow network plans). We assessed the neurosurgery coverage of ACA Marketplace plans in Arizona.

METHODS

The Health Insurance Marketplace website was used to identify ACA Marketplace plans in Arizona. Plan-specific details were examined to search for in-network neurosurgeons (2016-2019). Physician- and patient-level information was obtained using Intellimed health care databases, which provide specific neurosurgery diagnosis-related group information.

RESULTS

Although 5 insurance providers offered plans on the ACA Marketplace in Arizona, only 1 plan was available in 13 of 15 counties (87%). Evaluation of in-network coverage found that all in-network outpatient neurosurgery providers are in 5 of 15 counties (33%). Most of the other counties (9 of 10) have neurosurgery facilities, but do not have in-network access to neurosurgical care within the county (∼1.1 million people or 15% of the state population).

CONCLUSIONS

By narrowing the network of providers, insurance companies are attempting to maintain fiscal viability of their ACA Marketplace products. However, 10 of the 15 counties (67%) in Arizona do not have access to outpatient neurosurgical care through these plans despite the presence of neurosurgical facilities in most counties. Access to neurosurgical care requires consideration of network coverage in policies designed to expand coverage and coverage options for patients insured through the ACA Marketplace.

Dimensional Characterization of the Human Cervical Interlaminar Space as a Guide for Safe Application of Minimally Invasive Dilators

BACKGROUND

The risk of interlaminar passage of a dilator into the cervical spinal canal in minimally invasive approaches is currently unknown. Among the various anthropometric data reported in the literature, there is no report of the interlaminar dimensions in the cervical spine.

OBJECTIVE

To report the cervical interlaminar dimensions in neutral, flexion, and extension.

METHODS

A total of 8 spines were sectioned into cervical (C2-T1) segments. Digitized coordinate data defining the locations and movements of chosen anatomic points on the laminar edges at a given spinal level were used to compute the dimensions during a static neutral posture, flexion, and extension positions to mimic the positions during surgery. Interlaminar dimensions were averaged and categorized for each vertebral level and spinal posture.

RESULTS

Based on the reported measurements, the smallest diameter dilator in commonly used dilator sets has the potential to traverse the interlaminar space at all levels in flexion. In a neutral posture, the average interlaminar distance at C2-3, C6-7, and C7-T1 was still greater than 2.0 mm, the smallest diameter of the initial dilator. The largest interlaminar distance was at C6-7 in flexion (7.68 ± 1.60 mm).

CONCLUSION

Because dilators pass directly onto the cervical lamina without visualization of the midline structures, the interlaminar distances have increased relevance in the minimally invasive cervical approaches of foraminotomy and laminectomy. The data in this report demonstrate the theoretical risk of interlaminar passage with small diameter dilators in posterior minimally invasive approaches to the cervical spine.

Left Far Lateral Craniotomy for Clipping of a Posterior Inferior Cerebellar Artery Aneurysm

Objectives  The complex anatomical relationships of neurovascular structures at the craniovertebral junction make the clipping of a posterior inferior cerebellar artery (PICA) aneurysm surgically challenging. We demonstrate the clipping of a PICA aneurysm in the video.

Design, Setting, and Participant  A 65-year-old woman presented with a nonsymptomatic unruptured left PICA aneurysm; follow-up angiography showed an increase in its size. Preoperative angiography demonstrated a PICA aneurysm with the neck close to the origin of the PICA. A daughter sac of the aneurysm was also noted. A left far lateral approach was performed. The vagoaccessory triangle was exposed after opening the arachnoid membrane. The origin of the PICA and the aneurysm were revealed after exploration. The aneurysm neck was identified both proximally and distally. Two fenestrated clips were applied; subsequent indocyanine green (ICG) videoangiography demonstrated that the PICA was obstructed. One clip was adjusted, and repeated ICG videoangiography showed the PICA was patent. An endoscope was used before and after the clip application to better understand the anatomy of the aneurysm and inspect clip positions ( Fig. 1 ).

Outcome  The patient was neurologically intact postoperatively and was discharged on postoperative day 4.

Conclusion  PICA aneurysms require careful treatment. Impingement of adjacent structures can cause severe complications. Lower cranial nerve damage can cause dysphagia, and compromised vertebral/PICA circulation can cause brainstem symptoms, such as Wallenberg's syndrome. Intraoperative ICG videoangiography should be used to evaluate vessel patency, and the endoscope should be used to fully inspect the aneurysm and evaluate the clip application.

The link to the video can be found at: https://youtu.be/dKxFQTRA89g .

Far Lateral Craniotomy for Resection of Foramen Magnum Meningioma

Objective  Foramen magnum meningiomas present a formidable challenge to resection due to frequent involvement of the lower cranial nerves and vertebrobasilar circulation. The video shows the use of a far lateral craniotomy to resect a foramen magnum meningioma.

Design, Setting, and Participant  A 49-year-old woman presented with neck pain and was found to have a large foramen magnum meningioma ( Fig. 1A, B ). Drilling of the posterior occipital condyle was required to gain access to the lateral aspect of the brain stem. The amount of occipital condyle resection varies by patient and pathology.

Outcome/Result  Maximal total resection of the tumor was achieved ( Fig. 1B, C ), and the patient was discharged on postoperative day 4 with no neurologic deficits. The technique for tumor microdissection ( Fig. 2 ) is shown in the video.

Conclusion  Given the close proximity of foramen magnum meningiomas to vital structures at the craniocervical junction, surgical resection with careful microdissection and preservation of the overlying dura to prevent postoperative pseudomeningocele is necessary to successfully manage this pathology in those patients who are surgical candidates.

The link to the video can be found at: https://youtu.be/Mds9N1x2zE0 .

Quantitative Endoscopic Comparison of Contralateral Interhemispheric Transprecuneus and Supracerebellar Transtentorial Transcollateral Sulcus Approaches to the Atrium

OBJECTIVE

The contralateral interhemispheric transprecuneus approach (CITP) and the supracerebellar transtentorial transcollateral sulcus approach (STTC) are 2 novel approaches to access the atrium of the lateral ventricle. We quantitatively compared the 2 approaches.

METHODS

Both approaches were performed in 6 sides of fixed and color-injected cadaver heads. We predefined the 6 targets in the atrium for measurement and standardization of the approaches. Using a navigation system, we quantitatively measured the working distance, cortical transgression, angle of attack, area of exposure, and surgical freedom.

RESULTS

The distances from the craniotomy edge to the posterior pole of the choroid plexus of the CITP (mean ± standard deviation, 67 ± 5.3 mm) and STTC (mean, 57 ± 4.0 mm) differed significantly (P < 0.01). Cortical transgression with the CITP (mean, 27 ± 2.8 mm) was significantly greater than that with the STTC (mean, 21 ± 6.7 mm; P = 0.03). The CITP showed a significantly wider rostrocaudal angle of attack than that with the STTC (P = 0.01). The STTC showed a significantly wider mediolateral angle (P < 0.01). No significant difference was found for surgical freedom of any target except for point E, for which the CITP was larger. The exposure area did not differ significantly between the 2 approaches (P = 0.07).

CONCLUSIONS

Both approaches were feasible for accessing the atrium. The STTC provided a shorter working distance and wider mediolateral angle, CITP provided a wider rostrocaudal angle of attack and better exposure and maneuverability to the anterior and superior atrium. In contrast, the STTC was more favorable for the inferior and posterior regions.

Changing Paradigms in the Endovascular Management of Ruptured Anterior Communicating Artery Aneurysms

BACKGROUND

Approximately 17% of ruptured anterior communicating artery (ACoA) aneurysms were deemed unsuitable for coil embolization during the Barrow Ruptured Aneurysm Trial (BRAT), most commonly due to unfavorable dome-to-neck ratio or small size.

OBJECTIVE

To compare patients treated by coil embolization for ruptured ACoA aneurysms during the trial to those treated after the trial to determine whether advances in endovascular techniques have allowed for effective treatment of these lesions.

METHODS

All cases of ruptured ACoA aneurysms treated by endovascular modalities during BRAT (2003-2007) and post-BRAT (2007-2012) were reviewed for patient and aneurysm characteristics, treatment types, and clinical and angiographic outcomes at 3-yr or last follow-up.

RESULTS

The BRAT ACoA cohort included 39 patients treated with coiling (excluding those crossed over to clipping). The post-BRAT cohort included 93 patients who were significantly older (mean age, 59.5 vs 52.8 yr, P = .005) than the BRAT cohort; there were no significant cohort differences in sex, Hunt and Hess grade, or mean aneurysm size. The use of balloon remodeling was significantly higher in the post-BRAT cohort (31.2% [29/93] vs 5.1% [2/39], P = .001), as was the proportion of wide-necked aneurysms treated (66.7% [62/93] vs 30.8% [12/39], P < .001). There was no significant difference in clinical outcome or retreatment rate between the 2 cohorts (P = .90 and P = .48, respectively).

CONCLUSION

ACoA lesions thought unamenable to endovascular therapy in an earlier randomized trial are now successfully coiled with increased use of adjunctive techniques, without sacrificing patient outcome or treatment durability.

Dolichoectatic aneurysms of the vertebrobasilar system: clinical and radiographic factors that predict poor outcomes

OBJECTIVE

Fusiform dolichoectatic vertebrobasilar aneurysms are rare, challenging lesions. The natural history of these lesions and medium- and long-term patient outcomes are poorly understood. The authors sought to evaluate patient prognosis after diagnosis of fusiform dolichoectatic vertebrobasilar aneurysms and to identify clinical and radiographic predictors of neurological deterioration.

METHODS

The authors reviewed multiple, prospectively maintained, single-provider databases at 3 large-volume cerebrovascular centers to obtain data on patients with unruptured, fusiform, basilar artery dolichoectatic aneurysms diagnosed between January 1, 2000, and January 1, 2015.

RESULTS

A total of 50 patients (33 men, 17 women) were identified; mean clinical follow-up was 50.1 months and mean radiographic follow-up was 32.4 months. At last follow-up, 42% (n = 21) of aneurysms had progressed and 44% (n = 22) of patients had deterioration of their modified Rankin Scale scores. When patients were dichotomized into 2 groups— those who worsened and those who did not—univariate analysis showed 5 variables to be statistically significantly different: sex (p = 0.007), radiographic brainstem compression (p = 0.03), clinical posterior fossa compression (p < 0.001), aneurysmal growth on subsequent imaging (p = 0.001), and surgical therapy (p = 0.006). A binary logistic regression was then created to evaluate these variables. The only variable found to be a statistically significant predictor of clinical worsening was clinical symptoms of posterior fossa compression at presentation (p = 0.01).

CONCLUSIONS

Fusiform dolichoectatic vertebrobasilar aneurysms carry a poor prognosis, with approximately one-half of the patients deteriorating or experiencing progression of their aneurysm within 5 years. Despite being high risk, intervention—when carefully timed (before neurological decline)—may be beneficial in select patients.

Misplacement of Stent Into Epidural Venous Plexus With Resultant Cauda Equina Syndrome and Open Surgical Treatment: A Case Report

BACKGROUND AND IMPORTANCE

Endovascular therapy has proven to be a safe, minimally invasive treatment for multiple etiologies, but proper precautions must be taken to avoid complications. When complications occur, they should be promptly identified and corrected when possible. This case report describes endovascular stents misplaced into the epidural spinous venous plexus rather than the iliofemoral arteries, causing cauda equina syndrome, as well as the spinal procedure performed to treat the resulting spinal canal compression.

CLINICAL PRESENTATION

A 67-yr-old man had undergone what he thought was iliofemoral arterial stenting at an outside hospital for peripheral vascular disease. He presented 8 d later to our hospital with cauda equina syndrome comprising back pain, right L5 radiculopathy, perianal numbness, urinary retention, and constipation. Scans demonstrated stents deployed into the venous system, traversing the spinal canal and the right L5-S1 neural foramen, resulting in severe spinal canal stenosis, right L5-S1 foraminal stenosis, and moderate left S1-S2 foraminal stenosis. The patient underwent an L5-S1 laminectomy with full right L5-S1 facetectomy and left S1-S2 medial facetectomy, with associated L5-S1 posterolateral fusion with fixation to remove the stent and decompress the neural elements.

CONCLUSION

Although stent misplacement is an uncommon complication of endovascular therapy, this case demonstrates the importance of ensuring access to the proper vessel before stent placement. Once this complication was recognized, safe removal of the stents was possible and the patient demonstrated meaningful postoperative improvement in symptoms and strength.

Endovascular management of intracranial dural arteriovenous fistulas

Dural arteriovenous fistulas are a heterogeneous group of lesions that comprise 10-15% of intracranial vascular malformations. The treatment strategy is devised after careful consideration of the arterial supply, venous drainage, clinical presentation, and risk of progression, hemorrhage, or neurologic decline. With recent advancements in endovascular technology, the majority of dural arteriovenous fistulas can be treated with either transarterial or transvenous embolization. Those that cannot be fully treated by endovascular means are approached with either adjuvant surgery or radiotherapy.

Techniques and long-term outcomes of cotton-clipping and cotton-augmentation strategies for management of cerebral aneurysms

OBJECTIVE To address the challenges of microsurgically treating broad-based, frail, and otherwise complex aneurysms that are not amenable to direct clipping, alternative techniques have been developed. One such technique is to use cotton to augment clipping ("cotton-clipping" technique), which is also used to manage intraoperative aneurysm neck rupture, and another is to reinforce unclippable segments or remnants of aneurysm necks with cotton ("cotton-augmentation" technique). This study reviews the natural history of patients with aneurysms treated with cotton-clipping and cotton-augmentation techniques. METHODS The authors queried a database consisting of all patients with aneurysms treated at Barrow Neurological Institute in Phoenix, Arizona, between January 1, 2004, and December 31, 2014, to identify cases in which cotton-clipping or cotton-augmentation strategies had been used. Management was categorized as the cotton-clipping technique if cotton was used within the blades of the aneurysm clip and as the cotton-clipping technique if cotton was used to reinforce aneurysms or portions of the aneurysm that were unclippable due to the presence of perforators, atherosclerosis, or residual aneurysms. Data were reviewed to assess patient outcomes and annual rates of aneurysm recurrence or hemorrhage after the initial procedures were performed. RESULTS The authors identified 60 aneurysms treated with these techniques in 57 patients (18 patients with ruptured aneurysms and 39 patients with unruptured aneurysms) whose mean age was 53.1 years (median 55 years; range 24-72 years). Twenty-three aneurysms (11 cases of subarachnoid hemorrhage) were treated using cotton-clipping and 37 with cotton-augmentation techniques (7 cases of subarachnoid hemorrhage). In total, 18 patients presented with subarachnoid hemorrhage. The mean Glasgow Outcome Scale (GOS) score at the time of discharge was 4.4. At a mean follow-up of 60.9 ± 35.6 months (median 70 months; range 10-126 months), the mean GOS score at last follow-up was 4.8. The total number of patient follow-up years was 289.4. During the follow-up period, none of the cotton-clipped aneurysms increased in size, changed in configuration, or rebled. None of the patients experienced early rebleeding. The annual hemorrhage rate for aneurysms treated with cotton-augmentation was 0.52% and the recurrence rate was 1.03% per year. For all patients in the study, the overall risk of hemorrhage was 0.35% per year and the annual recurrence rate was 0.69%. CONCLUSIONS Cotton-clipping is an effective and durable treatment strategy for intraoperative aneurysm rupture and for management of broad-based aneurysms. Cotton-augmentation can be safely used to manage unclippable or partially clipped intracranial aneurysms and affords protection from early aneurysm re-rupture and a relatively low rate of late rehemorrhage.

Intraprocedural abciximab bolus versus pretreatment oral dual antiplatelet medication for endovascular stenting of unruptured intracranial aneurysms

Background

Standard pretreatment with dual antiplatelet medication (DAPM) was compared with a standalone intraprocedural abciximab bolus for the prevention of thromboembolic and hemorrhagic events during endovascular stenting of unruptured intracranial aneurysms.

Materials and methods

We treated 94 patients with 99 aneurysms with intracranial stenting (with or without coiling). Patients were either pretreated with DAPM daily for ≥3 days before stenting (pretreatment group) or received an abciximab bolus during or immediately after stent placement followed by postoperative DAPM (abciximab group), at the treating physician's discretion. Twenty patients underwent immediate postoperative MRI. Demographic, clinical, and radiological information and periprocedural complications were recorded.

Results

There were 52 procedures in the pretreatment group and 47 in the abciximab group. More flow-diverting stents were placed in the pretreatment group than in the abciximab group (45 vs 23, p<0.001), and the aneurysm diameter was larger (11.2±6.7 vs 8.3±4.7 mm, p=0.01). There were 11 thrombotic and 7 access site complications, with no significant difference between the groups (p>0.99 and p=0.12, respectively). There were no intracranial hemorrhages. In patients with postoperative MRI, there was no difference in the presence of diffusion-restricted lesions between groups (p=0.20). Multivariate analysis of a composite of any complication did not show significant associations with aneurysm or patient variables in either group.

Conclusions

Standalone intraprocedural abciximab bolus was not associated with an increased rate of complications compared with pretreatment with DAPM for unruptured intracranial aneurysm stenting.

Venous sinus stenting for idiopathic intracranial hypertension is not associated with cortical venous occlusion

Background

The effect of dural venous sinus stenting has been investigated for the treatment of idiopathic intracranial hypertension (IIH) but the effect of stenting on the long-term patency of the cortical draining veins, especially the vein of Labbé (VOL), remains unknown.

Methods

We reviewed our database of 38 patients with IIH with 41 stented dural venous sinuses between October 2006 and December 2014. Demographic, clinical, and radiological data were reviewed. Follow-up catheter angiographic data were included when available.

Results

Stent placement spanned the ostium of the VOL in 35 patients (92.1%), with no immediate effect on the drainage of the VOL. Follow-up angiography (mean 35.1 months, range 1.7–80.7 months) was available in 24 patients, 21 of whom had stents spanning the VOL ostium. The VOL remained patent without occlusion or drainage alteration in all 21 patients. There were no immediate or long-term intracranial complications.

Conclusions

Dural venous sinus stenting for patients with IIH does not affect the immediate or long-term patency of the VOL and is not associated with intracranial complications.

Intraspinal primitive neuroectodermal tumor in a man with neurofibromatosis type 1: Case report and review of the literature

BACKGROUND

The occurrence of primitive neuroectodermal tumors (PNET) in patients with neurofibromatosis type 1 (NF1) has only been reported in two other cases in English-Language literature. Owing to the rarity of intraspinal PNET and the extremely high gene mutation variability in NF1, there is currently no conclusive evidence to suggest that PNET is associated with NF1. Here, we report a case of intradural PNET in a patient with NF1.

CASE DESCRIPTION

A 27-year-old male underwent a C1-C3 laminectomy for resection of an intramedullary mass. Histopathology and immunohistopathology analysis was performed. Microscopic examination and immunohistochemical staining indicated the mass was a primitive neuroectodermal tumor. Within 1 month after tumor resection, the patient developed leptomeningeal carcinomatosis. The patient was not a candidate for radiation therapy but underwent palliative systemic chemotherapy. He subsequently developed neutropenia and died 3 months after tumor resection.

CONCLUSION

To our knowledge, this is the first reported intraspinal PNET associated with NF1. Genetic analysis of CNS PNETs suggests a possible correlation, but larger case series are needed to support this theory.

The International Tethered Cord Partnership: Beginnings, process, and status

Background:

Spina bifida presents a significant cause of childhood morbidity in lower- and middle-income nations. Unfortunately, there is a paucity of literature examining outcomes among children with spina bifida in these countries. The goal of the International Tethered Cord Parternship is twofold: (1) to establish an international surveillance database to examine the correlation between time of repair and clinical outcomes in children with spina bifida and tethered cord; and (2) to foster collaboration among international institutions around pediatric neurosurgical concerns.

Methods:

Twelve institutions in 7 countries committed to participating in the International Tethered Cord Partnership. A neurosurgeon at each institution will evaluate all children presenting with spina bifida and/or tethered cord using the survey instrument after appropriate consent is obtained. The instrument was developed collaboratively and based on previous measures of motor and sensory function, ambulation, and continence. All institutions who have begun collecting data received appropriate Institutional Review Board approval. All data will be entered into a Health Insurance Portability and Accountability Act (HIPAA) compliant database. In addition, a participant restricted internet forum was created to foster communication and includes non–project-specific communications, such as case and journal article discussion.

Results:

From October 2010 to December 2010, 82 patients were entered from the various study sites.

Conclusion:

To our knowledge this is the first international pediatric neurosurgical database focused on clinical outcomes and predictors of disease progression. The collaborative nature of the project will not only increase knowledge of spina bifida and tethered cord, but also foster discussion and further collaboration between neurosurgeons internationally.