Anatomic Characteristics of Intrapetrous Carotid Artery: A 3-Dimensional Segmentation Study on Head Computed Tomography Scan

World Neurosurg. (2019) 121:e419-e425

The intrapetrous carotid artery (IPCA) is one of the most unexplored anatomic regions, and its 3-dimensional reconstruction in living subjects is still missing. This study aims to describe the IPCA on 3D models extracted from head computed tomography (CT) scans.

METHODS: The intrapetrous carotid artery was manually segmented on head CT scans of 100 healthy patients free from vascular and neurologic pathologies (50 men and 50 women; age range, 18e91 years). Angles of the posterior and anterior genu, diameter and length of the horizontal portion, and volume of the entire canal were calculated through 3D analysis software. Statistically significant differences according to sex and side were assessed through 2-way analysis of variance (P < 0.05). Correlation of each measurement with age was calculated as well.

RESULTS: On average, the angles of the posterior and anterior genu were 120.1±2.4 and 118.0±10.0 in men and 119.5±9.2 and 117.6±10.3 in women, respectively, without statistically significant differences according to sex or side (P > 0.05). The average length and diameter of the horizontal part were, respectively, 25.5±2.9 and 5.8±0.8 mm in men and 24.0±2.3 and 5.3±0.8 mm in women. The volume of the IPCA was 0.941±0.215 cm3 in men and 0.752±0.159 cm3 in women. The length and diameter of the horizontal portion and the volume of the IPCA showed statistically significant differences according to sex (P < 0.05). No correlation with age was found.

CONCLUSIONS: This study provides data concerning not only linear and angular measurements, but also volumes of the IPCA, which are useful in planning surgical interventions of the cranial base.

Functional Balance Testing in Cervical Spondylotic Myelopathy Patients

Spine 2019;44:103–109

Study Design. A prospective cohort study.

Objective. The aim of this study was to quantify the amount of sway associated with maintaining a balanced posture in a group of untreated cervical spondylotic myelopathy (CSM) patients.

Summary of Background Data. Balance is defined as the ability of the human body to maintain its center of mass (COM) within the base of support with minimal postural sway. Sway is the movement of the COM in the horizontal plane when a person is standing in a static position. CSM patients have impaired body balance and proprioceptive loss.

Methods. Thirty-two CSM patients performed a series of functional balance tests a week before surgery. Sixteen healthy controls (HCs) performed a similar balance test. Patients are instructed to stand erect with feet together and eyes opened in their self-perceived balanced and natural position for a full minute. All test subjects were fitted to a full-body reflective markers set and surface electromyography (EMG).

Results. CSM patients had more COM sway in the anteriorposterior (CSM: 2.87cm vs. C: 0.74 cm; P¼0.023), right-left (CSM: 5.16cm vs. C: 2.51 cm; P¼0.003) directions as well as head sway (anterior-posterior – CSM: 2.17cm vs. C: 0.82 cm; P ¼0.010 and right-left – CSM: 3.66 cm vs. C: 1.69cm; P¼0.044), more COM (CSM: 44.72 cm vs. HC: 19.26 cm, p¼0.001), and head (Pre: 37.87cm vs. C: 19.93 cm, P¼0.001) total sway in comparison to controls. CSM patients utilized significantly more muscle activity to maintain static standing, evidenced by the increased trunk and lower extremity muscle activity (multifidus, erector spinae, rectus femoris, and tibialis anterior, P<0.050) during 1-minute standing.

Conclusion. In symptomatic CSM patients, COM and head total sway were significantly greater than controls. Individuals with CSM exhibit more trunk and lower extremity muscle activity, and thus expend more neuromuscular energy to maintain a balanced, static standing posture. This study is the first effort to evaluate global balance as a dynamic process in this patient population.

Level of Evidence: 3

Anterior clinoidectomy using an extradural and intradural 2-step hybrid technique

J Neurosurg 130:238–247, 2019

Anterior clinoidectomy is a difficult yet essential technique in skull base surgery. Two main techniques (extradural and intradural) with multiple modifications have been proposed to increase efficiency and avoid complications.

In this study, the authors sought to develop a hybrid technique based on localization of the optic strut (OS) to combine the advantages and avoid the disadvantages of both techniques. Ten cadaveric specimens were prepared for surgical simulation. After a standard pterional craniotomy, the anterior clinoid process (ACP) was resected in 2 steps. The segment anterior to the OS was resected extradurally, while the segment posterior to the OS was resected intradurally. The proposed technique was performed in 6 clinical cases to evaluate its safety and efficiency.

Anterior clinoidectomy was successfully performed in all cadaveric specimens and all 6 patients by using the proposed technique. The extradural phase enabled early decompression of the optic nerve while avoiding the adjacent internal carotid artery. The OS was drilled intradurally under direct visualization of the adjacent neurovascular structures. The described landmarks were easily identifiable and applicable in the surgically treated patients. No operative complication was encountered.

A proposed 2-step hybrid technique combines the advantages of the extradural and intradural techniques while avoiding their disadvantages. This technique allows reduced intradural drilling and subarachnoid bone dust deposition. Moreover, the most critical part of the clinoidectomy—that is, drilling of the OS and removal of the body of the ACP—is left for the intradural phase, when critical neurovascular structures can be directly viewed.


Fivefold higher rate of pseudarthrosis with polyetheretherketone interbody device than with structural allograft used for 1-level anterior cervical discectomy and fusion

J Neurosurg Spine 30:46–51, 2019

Common interbody graft options for anterior cervical discectomy and fusion (ACDF) include structural allograft and polyetheretherketone (PEEK). PEEK has gained popularity due to its radiolucency and its elastic modulus, which is similar to that of bone. The authors sought to compare the rates of pseudarthrosis, a lack of solid bone growth across the disc space, and the need for revision surgery with the use of grafts made of allogenic bone versus PEEK.

METHODS The authors retrospectively reviewed 127 cases in which patients had undergone a 1-level ACDF followed by at least 1 year of radiographic follow-up. Data on age, sex, body mass index, tobacco use, pseudarthrosis, and the reoperation rate for pseudarthrosis were collected. These data were analyzed by performing a Pearson’s chi-square test.

RESULTS Of 127 patients, 56 had received PEEK implants and 71 had received allografts. Forty-six of the PEEK implants (82%) were stand-alone devices. There were no significant differences between the 2 treatment groups with respect to patient age, sex, or body mass index. Twenty-nine (52%) of 56 patients with PEEK implants demonstrated radiographic evidence of pseudarthrosis, compared to 7 (10%) of 71 patients with structural allografts (p < 0.001, OR 9.82; 95% CI 3.836–25.139). Seven patients with PEEK implants required reoperation for pseudarthrosis, compared to 1 patient with an allograft (p = 0.01, OR 10.00; 95% CI 1.192–83.884). There was no significant difference in tobacco use between the PEEK and allograft groups (p = 0.586).

CONCLUSIONS The results of this study demonstrate that the use of PEEK devices in 1-level ACDF is associated with a significantly higher rate of radiographically demonstrated pseudarthrosis and need for revision surgery compared with the use of allografts. Surgeons should be aware of this when deciding on interbody graft options, and reimbursement policies should reflect these discrepancies.

The Aalborg Bolt-Connected Drain (ABCD) study: a prospective comparison of tunnelled and bolt-connected external ventricular drains

Acta Neurochirurgica (2019) 161:33–39

Acutely increased intracranial pressure (ICP) is frequently managed by external ventricular drainage (EVD). This procedure is life-saving but marred by a high incidence of complications. It has recently been indicated that bolt-connected external ventricular drainage (BC-EVD) compared to the standard technique of tunnelled EVD (T-EVD) may result in less complications.

Aim To prospectively sample and compare two cohorts by consecutive allocation to either BC-EVD or T-EVD from the introduction of the BC-EVD technique in our department and 12 months onward.

Methods Patients undergoing ventriculostomy between the 1st of March 2017 and the 28th of February 2018 were considered for inclusion. The neurosurgeon on-call sovereignly set the indication and decided on EVD type (BC-EVD or T-EVD), consequently resulting in two cohorts as 3/7 senior neurosurgeons on call were open to the use of BC-EVD, while 4/7 were reluctant to use this technique. Data was continuously collected using patient records, including results of cerebrospinal fluid (CSF) culturing and available CT/MRI-scans. Recorded complications included CSF leakage, accidental discontinuation, placement-related intracranial haemorrhage, malfunction, migration, infection and revision.

Results Forty-nine EVDs (32 T-EVDs/17 BC-EVDs) were included; 19/32 (59.4%) T-EVDs and 3/17 (17.6%) BC-EVDs were found to have complications (p = 0.007). The relative risk of complications when using T-EVD was 3.4 times that of BC-EVD.

Conclusion Ventriculostomy by BC-EVD compared to T-EVD reduces incidence and risk of complications and should be the first choice in EVD placement. That said, T-EVD has a role in paediatric patients and for intraoperatively and occipitally placed EVDs.

Potential of Human Nucleus Pulposus-Like Cells Derived From Umbilical Cord to Treat Degenerative Disc Disease

Neurosurgery 84:272–283, 2019

Degenerative disc disease (DDD) is a common spinal disorder that manifests with neck and lower back pain caused by the degeneration of intervertebral discs (IVDs). Currently, there is no treatment to cure this debilitating ailment.

OBJECTIVE: To investigate the potential of nucleus pulposus (NP)-like cells (NPCs) derived from human umbilical cord mesenchymal stem cells (MSCs) to restore degenerated IVDs using a rabbit DDD model.

METHODS: NPCs differentiated from MSC swere characterized using quantitative real-time reverse transcription polymerase chain reaction and immunocytochemical analysis. MSCs and NPCs were labeled with fluorescent dye, PKH26, and transplanted into degenerated IVDs of a rabbit model of DDD (n = 9 each). Magnetic resonance imaging of the IVDs was performed before and after IVD degeneration, and following cell transplantation. IVDs were extracted 8 wk post-transplantation and analyzed by various biochemical, immunohistological, and molecular techniques.

RESULTS: NPC derivatives of MSCs expressed known NP-specific genes, SOX9, ACAN, COL2, FOXF1, and KRT19. Transplanted cells survived, dispersed, and integrated into the degenerated IVDs. IVDs augmented with NPCs showed significant improvement in the histology, cellularity, sulfated glycosaminoglycan andwater contents of the NP. In addition, expression of human genes, SOX9, ACAN, COL2, FOXF1, KRT19, PAX6, CA12, and COMP, aswell as proteins, SOX9, ACAN, COL2, and FOXF1, suggest NP biosynthesis due to transplantation of NPCs. Based on these results, a molecular mechanism for NP regeneration was proposed.

CONCLUSION: The findings of this study demonstrating feasibility and efficacy of NPCs to regenerate NP should spur interest for clinical studies to treat DDD using cell therapy.

Older Patients Have Better Pain Outcomes Following Microvascular Decompression for Trigeminal Neuralgia

Neurosurgery 84:116–122, 2019

Trigeminal neuralgia (TN) increases in prevalence with age. Although microvascular decompression (MVD) is the most effective long-term operative treatment for TN, its use in older patient populations has been debated due to its invasive nature. Recent studies have demonstrated safety of MVD in older patients; however, efficacy data are more limited.

OBJECTIVE: To determine the relationship between age and pain outcomes following MVD for TN.

METHODS: Subjects underwent MVD for TN at our institution between 1/1/2004 and 12/31/2013, had typical TN, and demonstrated neurovascular compression on preoperative imaging.We performed a retrospective case series study by reviewing the electronic medical records and performing phone interviews to determine long-term outcomes. We divided patients into 2 groups for analysis, under 60 and 60 yr of age and older.

RESULTS: One hundred twenty-four subjects were included in the study, 82 under 60, and 42 60 yr of age and older. The average length of follow-up was 42.4 mo. Patients in the older age group had average pain score of 1.57 at most recent follow-up, while for the younger age group it was 2.18 (P = .0084). Multiple regression analysis found that older age, male gender, and preoperative medication responsiveness were significantly correlated with lower long-term pain scores, while V2 dermatome involvement was correlated with higher long-term pain scores.

CONCLUSION: Patients 60 yr of age and older have significantly better long-term pain outcomes following MVD than younger patients.

Prognostic Importance of Age, Tumor Location, and Tumor Grade in Grade II Astrocytomas

World Neurosurg. (2019) 121:e411-e418

Previous work in anaplastic astrocytoma (AA) demonstrated that the survival benefit from gross total resection (GTR) is modified by age and tumor location. Here, we determined the influence of age and tumor location on survival benefit from GTR in diffuse astrocytoma (DA).

METHODS: We used the Surveillance, Epidemiology, and End Results (SEER) database (1999-2010). We used Kaplan- Meier curves and Cox survival models to determine the survival benefit from GTR in populations stratified by age and tumor location. We determined the prevalence of the mutated isocitrate dehydrogenase (mIDH) using The Cancer Genome Atlas (TCGA).

RESULTS: We identified 1980 patients with DA. For frontal DAs, GTR resulted in improved survival relative to subtotal resection in all ages (age ≤50 years hazard ratio [HR], 0.56; P [ 0.002; age >50 years HR, 0.41; P < 0.001). For nonfrontal DAs, only patients ≤50 years experienced improved survival with GTR (age ≤50 years HR, 0.55; P [ 0.002; age >50 years HR, 0.78; P [ 0.114). For patients ≤50 years with frontal tumors, survival was comparable between DA and AA after GTR (75% survival DA: 80 months, AA: 89 months, P [ 0.973). In TCGA, these tumors were nearly uniformly mIDH (DA: 98%; AA: 90%, P [ 0.11). However, for patients ≤50 years with nonfrontal tumors, there was a survival difference after GTR (75% survival DA: 80 months, AA: 30 months, P [ 0.001) despite comparable mIDH prevalence (DA: 82%, AA: 75%, P [ 0.49).

CONCLUSIONS: Age and tumor location modify the survival benefit derived from GTR in DA. Survival patterns in SEER imperfectly correlated with mIDH prevalence in TCGA, suggesting that tumor grade and mIDH status convey nonredundant prognostic information in select clinical contexts

Prospective Tractography-Based Targeting for Improved Safety of Focused Ultrasound Thalamotomy

Neurosurgery 84:160–168, 2019

Focused ultrasound thalamotomy (FUS-T) was recently approved for the treatment of refractory essential tremor (ET). Despite its noninvasive approach, FUS-T reinitiated concerns about the adverse effects and long-term efficacy after lesioning.

OBJECTIVE: To prospectively assess the outcomes of FUS-T in 10 ET patients using tractography-based targeting of the ventral intermediate nucleus (VIM).

METHODS: VIM was identified at the intercommissural plane based on its neighboring tracts: the pyramidal tract and medial lemniscus. FUS-T was performed at the center of tractography-defined VIM. Tremor outcomes, at baseline and 3 mo, were assessed independently by the Tremor Research Group.We analyzed targeting coordinates, clinical outcomes, and adverse events. The FUS-T lesion location was analyzed in relation to unbiased thalamic parcellation using probabilisitic tractography. Quantitative diffusionweighted imaging changes were also studied in fiber tracts of interest.

RESULTS: The tractography coordinates were more anterior than the standard. Intraoperatively, therapeutic sonications at the tractography target improved tremor (>50% improvement) without motor or sensory side effects. Sustained improvement in tremor was observed at 3mo(tremor score: 18.3±6.9 vs 8.1±4.4, P=.001).Nomotorweakness and sensory deficits after FUS-T were observed during 6-mo follow-up. Ataxia was observed in 3 patients. FUS-T lesions overlapped with the VIM parcellated with probablisitic tractography. Significant microstructural changes were observed in the white matter connecting VIM with cerebellum and motor cortex.

CONCLUSION: This is the first report of prospective VIM targeting with tractography for FUS-T. These results suggest that tractography-guided targeting is safe and has satisfactory short-term clinical outcomes.

Prerupture Intracranial Aneurysm Morphology in Predicting Risk of Rupture

Neurosurgery 84:132–140, 2019

Maximal size and other morphological parameters of intracranial aneurysms (IAs) are used when deciding if an IA should be treated prophylactically. These parameters are derived from postrupture morphology. As time and rupture may alter the aneurysm geometry, possiblemorphological predictors of a rupture should be established in prerupture aneurysms.

OBJECTIVE: To identify morphological parameters of unruptured IAs associated with later rupture.

METHODS: Nationwide matched case-control study. Twelve IAs that later ruptured were matched 1:2 with 24 control IAs that remained unruptured during a median follow-up time of 4.5 (interquartile range, 3.7-8.2) yr. Morphological parameters were automatically measured on 3-dimensional models constructed from angiograms obtained at time of diagnosis. Cases and controls were matched by aneurysm location and size, patient age and sex, and the PHASES (population, hypertension, age, size of aneurysm, earlier subarachnoid hemorrhage from another aneurysm, and site of aneurysm) score did not differ between the 2 groups.

RESULTS: Only inflow angle was significantly different in cases vs controls in univariate analysis (P = .045), and remained significant in multivariable analysis. Maximal size correlated with size ratio in both cases and controls (P = .015 and <.001, respectively). However, maximal size and inflow angle were correlated in cases but not in controls (P = .004. and .87, respectively).

CONCLUSION: A straighter inflow angle may predispose an aneurysm to changes that further increase risk of rupture. Traditional parameters of aneurysm morphology may be of limited value in predicting IA rupture.



Trigeminal Nerve Compression Without Trigeminal Neuralgia: Intraoperative vs Imaging Evidence

Neurosurgery 84:60–65, 2019

While high-resolution imaging is increasingly used in guiding decisions about surgical interventions for the treatment of trigeminal neuralgia, direct assessment of the extent of vascular contact of the trigeminal nerve is still considered the gold standard for the determination of whether nerve decompression is warranted.

OBJECTIVE: To compare intraoperative and magnetic resonance imaging (MRI) findings of the prevalence and severity of vascular compression of the trigeminal nerve in patients without classical trigeminal neuralgia.

METHODS: We prospectively recruited 27 patients without facial pain who were undergoing microvascular decompression for hemifacial spasm and had undergone highresolution preoperative MRI. Neurovascular contact/compression (NVC/C) by artery or vein was assessed both intraoperatively and by MRI, and was stratified into 3 types: simple contact, compression (indentation of the surface of the nerve), and deformity (deviation or distortion of the nerve).

RESULTS: Intraoperative evidence of NVC/C was detected in 23 patients. MRI evidence of NVC/Cwas detected in 18 patients, all ofwhomhad intraoperative evidence ofNVC/C. Thus, there were 5, or 28% more patients in whom NVC/C was detected intraoperatively than with MRI (Kappa = 0.52); contact was observed in 4 of these patients and compression in 1 patient. In patients where NVC/C was observed by both methods, there was agreement regarding the severity of contact/compression in 83% (15/18) of patients (Kappa=0.47). No patients exhibited deformity of the nerve by imaging or intraoperatively.

CONCLUSION: There was moderate agreement between imaging and operative findings with respect to both the presence and severity of NVC/C.


Lateral Lumbar Interbody Fusion Revisited: Complication Avoidance and Outcomes with the Mini-Open Approach

World Neurosurg. (2019) 121:e647-e653

OBJECTIVE: To discuss lessons learned from an initial lateral lumbar interbody fusion (LLIF) experience with a focus on evolving surgical technique, complication avoidance, and new motor and sensory outcomes after implementation of a modified surgical approach.

METHODS: A retrospective analysis of a prospectively collected series of all patients undergoing LLIF by the senior author (A.D.L.) from January 2010 to January 2018 after implementation of a modified surgical mini-open technique, compared with previously reported institutional results with the originally recommended percutaneous technique. LLIF-specific complications examined included groin/thigh sensory dysfunction, flank bulge/pseudohernia, psoas-pattern weakness, and femoral nerve injury.

RESULTS: The incidence (19%, n [ 98 patients) of groin/ thigh sensory dysfunction in our cohort was significantly lower than that of the historical control (60%, n [ 59) (P < 0.0001). The incidence of abdominal flank bulge/pseudohernia (2.0%, n[98 patients) in our cohort was improved but not significantly lower than that of the historical control (4.2%, n[118) (P[0.36). The incidence of psoas-patternweakness (3.1%, n[98) in our cohort was significantly lower than that of the historical control (23.7%, n [ 59) (P [ 0.0001). The incidence of femoral nerve injury (0%, n[98 patients) in our cohort was improved but was not significantly lower than that of the historical control (1.7%, n [118) (P[0.20).

CONCLUSIONS: The adoption of an exclusive mini-open muscle-splitting approach with first-look inspection of the lumbosacral plexus nerve elements may improve motor and sensory outcomes in general and the incidence of postoperative groin/thigh sensory dysfunction and psoaspattern weakness in particular.

Pterional, Pretemporal, and Orbitozygomatic Approaches: Anatomic and Comparative Study

World Neurosurg. (2019) 121:e398-e403

Although pterional craniotomy and its variants are the most used approaches in neurosurgery, few studies have evaluated their precise indications. We evaluate the pterional (PT), pretemporal (PreT), and orbitozygomatic (OZ) approaches through quantitative measurements of area, linear, and angular exposures of the major intracranial vascular structures.

METHODS: Eight fresh, adult cadavers were operated with the PT, followed by the PreT, and ending with the OZ approach. The working area, angular exposure of vascular structures and linear exposure of the basilar artery were measured. –

RESULTS: The OZ approach presented a wider area (1301.3215.9mm2)with an increase of 456.7mm2 compared with the PT and of 167.4 mm2 to the PreT (P [ 0.011). The extension from PT to PreT and OZ increases linear exposure of the basilar artery. When comparing the PreT and OZ, we found an increase in the horizontal and vertical angle to the bifurcation of the ipsilateral middle cerebral artery (P [0.005 and P [ 0.032, respectively), horizontal angle to the basilar artery tip (P [ 0.02), and horizontal angle to the contralateral ICA bifurcation (P [ 0.048). –

CONCLUSIONS: The OZ approach offered notable surgical advantages compared with the traditional PT and PreT regarding to the area of exposure and linear exposure to basilar artery. Regarding angle of attack, the orbital rim and zygomatic arch removal provided quantitatively wider exposure and increased surgical freedom. A detailed anatomic study for each patient and surgeon experience must be considered for individualized surgical approach indication.

Smartphone-assisted minimally invasive neurosurgery


J Neurosurg 130:90–98, 2019

Advances in video and fiber optics since the 1990s have led to the development of several commercially available high-definition neuroendoscopes. This technological improvement, however, has been surpassed by the smartphone revolution. With the increasing integration of smartphone technology into medical care, the introduction of these high-quality computerized communication devices with built-in digital cameras offers new possibilities in neuroendoscopy. The aim of this study was to investigate the usefulness of smartphone-endoscope integration in performing different types of minimally invasive neurosurgery.

METHODS The authors present a new surgical tool that integrates a smartphone with an endoscope by use of a specially designed adapter, thus eliminating the need for the video system customarily used for endoscopy. The authors used this novel combined system to perform minimally invasive surgery on patients with various neuropathological disorders, including cavernomas, cerebral aneurysms, hydrocephalus, subdural hematomas, contusional hematomas, and spontaneous intracerebral hematomas.

RESULTS The new endoscopic system featuring smartphone-endoscope integration was used by the authors in the minimally invasive surgical treatment of 42 patients. All procedures were successfully performed, and no complications related to the use of the new method were observed. The quality of the images obtained with the smartphone was high enough to provide adequate information to the neurosurgeons, as smartphone cameras can record images in high definition or 4K resolution. Moreover, because the smartphone screen moves along with the endoscope, surgical mobility was enhanced with the use of this method, facilitating more intuitive use. In fact, this increased mobility was identified as the greatest benefit of the use of the smartphone-endoscope system compared with the use of the neuroendoscope with the standard video set.

CONCLUSIONS Minimally invasive approaches are the new frontier in neurosurgery, and technological innovation and integration are crucial to ongoing progress in the application of these techniques. The use of smartphones with endoscopes is a safe and efficient new method of performing endoscope-assisted neurosurgery that may increase surgeon mobility and reduce equipment costs.  

Utility of the Vidian Canal in Endoscopic Skull Base Surgery: Detailed Anatomy and Relationship to the Internal Carotid Artery

World Neurosurg. (2019) 121:e140-e146

OBJECTIVE: To investigate key anatomic features of the vidian canal that have a critical role in planning and performing endoscopic skull base surgeries.

METHODS: We reviewed skull base computed tomographic images of 640 consecutive subjects. Studies were analyzed in axial, coronal and sagittal planes. –

RESULTS: The mean (SD) length of the vidian canal was 15.4±2.0 mm in female subjects and 16.6±1.7 mm in male subjects, and the difference between genders was statistically significant (P < 0.001). The most common rostral-caudal course of the vidian canal was medial to lateral and was followed by the straight course, tortuous course, and lateral-to-medial course. The frequency of pneumatization pattern from most common to least common was types 0, III, II and I. Of 342 evaluated sides, the vidian canal was located below the level of the anterior genu of petrous ICA in 303 (89%) sides, at same level with the anterior genu of petrous ICA in twenty-five(7%) sides, and above the level of the anterior genu of petrous ICA in fourteen(4.1%) sides.

CONCLUSIONS: A variety of previously undefined features of the vidian canal that can alter the course of surgical procedure were defined. The position of the vidian canal with respect to the petrous internal carotid artery (ICA) was extensively described. From a surgical standpoint, a working room inferior and medial to the vidian canal might not always be a safe approach, because the vidian canal could be located superior to the level of the anterior genu of petrous ICA according to our findings in the present study.

Preoperative Imaging and Microscopic Navigation During Surgery Can Avoid Unnecessarily Opening the Mastoid Air Cells Through Craniotomy Using the Retrosigmoid Approach

World Neurosurg. (2019) 121:e15-e21

To analyze treatment of microvascular decompression using the retrosigmoid approach (RA) in primary trigeminal neuralgia and hemifacial spasm using preoperative images combined with intraoperative microscopic navigation to avoid unnecessarily opening the mastoid air cells (MACs).

METHODS: Ten patients with primary trigeminal neuralgia and 20 patients with hemifacial spasm (test group) were treated using RA for microvascular decompression. Preoperative head magnetic resonance angiography and temporal bone computed tomography were performed and the images registered using SPM12 and fused with MRIcron to determine the relationship between MACs and sigmoid sinuses. An O-arm was used for navigation, and the transverse sigmoid sinus was projected under a microscope to guide RA. A control group comprised 139 patients who had the same surgical procedure as the test group but without image processing or intraoperative navigation.

RESULTS: The relationship between MACs and the ipsilateral sigmoid sinus was classified as follows: I, MACs did not exceed the lateral edge of the ipsilateral sigmoid sinus (10/60); II, MACs exceeded the ipsilateral lateral edge of the sigmoid sinus but did not exceed the medial edge (42/60); and III, MACs exceeded the medial edge of the ipsilateral sigmoid sinus (8/60). Test and control groups showed significant differences in the incidences of opening MACs (P[0.003). There was no cerebrospinal fluid leakage or scalp and intracranial infection at follow-up.

CONCLUSIONS: Image processing and intraoperative microscopic navigation can avoid unnecessarily opening MACs and might reduce postoperative cerebrospinal leakage and scalp infection after RA craniotomy

A novel mesial temporal stereotactic coordinate system

J Neurosurg 130:67–75, 2019

Stereotactic laser ablation and neurostimulator placement represent an evolution in staged surgical intervention for epilepsy. As this practice evolves, optimal targeting will require standardized outcome measures that compare electrode lead or laser source with postprocedural changes in seizure frequency. The authors propose and present a novel stereotactic coordinate system based on mesial temporal anatomical landmarks to facilitate the planning and delineation of outcomes based on extent of ablation or region of stimulation within mesial temporal structures.

METHODS The body of the hippocampus contains a natural axis, approximated by the interface of cornu ammonis area 4 and the dentate gyrus. The uncal recess of the lateral ventricle acts as a landmark to characterize the anteriorposterior extent of this axis. Several volumetric rotations are quantified for alignment with the mesial temporal coordinate system. First, the brain volume is rotated to align with standard anterior commissure–posterior commissure (AC-PC) space. Then, it is rotated through the axial and sagittal angles that the hippocampal axis makes with the AC-PC line.

RESULTS Using this coordinate system, customized MATLAB software was developed to allow for intuitive standardization of targeting and interpretation. The angle between the AC-PC line and the hippocampal axis was found to be approximately 20°–30° when viewed sagittally and approximately 5°–10° when viewed axially. Implanted electrodes can then be identified from CT in this space, and laser tip position and burn geometry can be calculated based on the intraoperative and postoperative MRI.

CONCLUSIONS With the advent of stereotactic surgery for mesial temporal targets, a mesial temporal stereotactic system is introduced that may facilitate operative planning, improve surgical outcomes, and standardize outcome assessment.


Insular glioma surgery: an evolution of thought and practice

J Neurosurg 130:9–16, 2019

The goal of this article is to review the history of surgery for low- and high-grade gliomas located within the insula with particular focus on microsurgical technique, anatomical considerations, survival, and postoperative morbidity.

METHODS The authors reviewed the literature for published reports focused on insular region anatomy, neurophysiol- ogy, surgical approaches, and outcomes for adults with World Health Organization grade II–IV gliomas.

RESULTS While originally considered to pose too great a risk, insular glioma surgery can be performed safely due to the collective efforts of many individuals. Similar to resection of gliomas located within other cortical regions, maximal resection of gliomas within the insula offers patients greater survival time and superior seizure control for both newly diagnosed and recurrent tumors in this region. The identification and the preservation of M2 perforating and lateral len- ticulostriate arteries are critical steps to preventing internal capsule stroke and hemiparesis. The transcortical approach and intraoperative mapping are useful tools to maximize safety.

CONCLUSIONS The insula’s proximity to middle cerebral and lenticulostriate arteries, primary motor areas, and perisyl- vian language areas makes accessing and resecting gliomas in this region challenging. Maximal safe resection of insular gliomas not only is possible but also is associated with excellent outcomes and should be considered for all patients with low- and high-grade gliomas in this area.

Cervical Disc Arthroplasty: Current Evidence and Real-World Application

Neurosurgery 83:1087–1106, 2018

Cervical total disc replacement (cTDR) is still considered a developing technology, with widespread clinical use beginning in the early 2000s. Despite being relatively new to the marketplace, the literature surrounding cTDR is abundant.

We conducted a thorough review of literature published in the United States (US) and outside the US to report the current global state of cTDR research and clinical use. Search criteria were restricted to publications with a clinical patient population, excluding finite element analyses, biomechanical studies, cadaver studies, surgical technique-specific papers, and case studies. US publications mostly encompass the results of the highly controlled Food and Drug Administration Investigational Device Exemption trials.

The predominantly level I evidence in the US literature supports the use of cTDR at 1 and 2 surgical levels when compared to anterior cervical discectomy and fusion. In general, the outside the US studies typically have smaller patient populations, are rarely controlled, and include broader surgical indications. Though these studies are of lower levels of evidence, they serve to advance patient indications in the use of cTDR.

Complications such as secondary surgery, heterotopic ossification, and adjacent segment degeneration also remain a focus of studies. Other external challenges facing cTDR technology include regulatory restrictions and health economics, both of which are beginning to be addressed.

Combined, the evidence for cTDR is robust supporting a variety of clinical indications.