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Hirotaka Hasegawa, Jamie J. Van Gompel, W. Richard Marsh, Robert E. Wharen Jr., Richard S. Zimmerman, David B. Burkholder, Brian N. Lundstrom, Jeffrey W. Britton, and Fredric B. Meyer

OBJECTIVE

Surgical site infection (SSI) is a rare but significant complication after vagus nerve stimulator (VNS) placement. Treatment options range from antibiotic therapy alone to hardware removal. The optimal therapeutic strategy remains open to debate. Therefore, the authors conducted this retrospective multicenter analysis to provide insight into the optimal management of VNS-related SSI (VNS-SSI).

METHODS

Under institutional review board approval and utilizing an institutional database with 641 patients who had undergone 808 VNS-related placement surgeries and 31 patients who had undergone VNS-related hardware removal surgeries, the authors retrospectively analyzed VNS-SSI.

RESULTS

Sixteen cases of VNS-SSI were identified; 12 of them had undergone the original VNS placement procedure at the authors’ institutions. Thus, the incidence of VNS-SSI was calculated as 1.5%. The mean (± standard deviation) time from the most recent VNS-related surgeries to infection was 42 (± 27) days. Methicillin-sensitive staphylococcus was the usual causative bacteria (58%). Initial treatments included antibiotics with or without nonsurgical procedures (n = 6), nonremoval open surgeries for irrigation (n = 3), generator removal (n = 3), and total or near-total removal of hardware (n = 4). Although 2 patients were successfully treated with antibiotics alone or combined with generator removal, removal of both the generator and leads was eventually required in 14 patients. Mild swallowing difficulties and hoarseness occurred in 2 patients with eventual resolution.

CONCLUSIONS

Removal of the VNS including electrode leads combined with antibiotic administration is the definitive treatment but has a risk of causing dysphagia. If the surgeon finds dense scarring around the vagus nerve, the prudent approach is to snip the electrode close to the nerve as opposed to attempting to unwind the lead completely.

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Benjamin T. Himes, Arnoley S. Abcejo, Panagiotis Kerezoudis, Adip G. Bhargav, Katherine Trelstad-Andrist, Patrick R. Maloney, John L. D. Atkinson, Fredric B. Meyer, W. Richard Marsh, and Mohamad Bydon

OBJECTIVE

The sitting or semisitting position in neurosurgery allows for several technical advantages, including improved visualization of the surgical field. However, it has also been associated with an increased risk of venous air embolisms and positioning-related complications that limit its commonplace adoption. The authors report a large, single-center series of cervical spine procedures performed with patients in the sitting or prone position in order to assess the perceived risk of intraoperative and postoperative complications associated with the sitting position.

METHODS

Noninstrumented, single-level posterior cervical spine procedures performed with patients in the sitting/semisitting or prone position from 2000 to 2016 at a single institution were reviewed. Institutional abstraction tools (DataMart and Chart Plus) were used to collect data from the medical records. The two positions were compared with regard to preoperative factors, intraoperative variables, and postoperative outcomes. Multivariable logistic regression models were fitted for 30-day readmission, 30-day return to the operating room, and complication rates.

RESULTS

A total of 750 patients (sitting, n = 480; prone, n = 270) were analyzed. The median age was 53 years for those who underwent surgery in the prone position and 50 years for those who underwent surgery in the sitting position (IQRs 45–62 years and 43–60 years, respectively), and 35% of the patients were female. Sitting cases were associated with significantly longer anesthetic times (221 minutes [range 199–252 minutes] vs 205 minutes [range 179–254 minutes]) and operative times (126 minutes [range 101–163 minutes] vs 149 minutes [120–181 minutes]). Cardiorespiratory events in the postanesthesia care unit (PACU) were comparable between the two groups, with the exception of episodes of apnea (2.6% vs 0.6%, p = 0.041) and hypoventilation (4.4% vs 0.8%, p < 0.003), which were more frequent in the prone-position cohort. On multivariable analysis, the effect of the sitting versus the prone position was not significant for 30-day readmission (OR 0.77, 95% CI 0.34–1.71, p = 0.52) or reoperation (OR 0.71, 95% CI 0.31–1.60, p = 0.40). The sitting position was associated with lower odds of developing any complication (OR 0.31, 95% CI 0.16–0.62, p < 0.001).

CONCLUSIONS

Based on the intraoperative and postoperative complications chosen in this study, the sitting position confers a similar safety profile to the prone position. This can be explained by a more anatomic positioning accounting for reduced temporary neurological deficits and reduced PACU-associated hypoventilation noted in this series. Nevertheless, the findings may also reflect institutional familiarity, experience, and mastery of this position type, and outcomes may not reflect practices in general.

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Benjamin T. Himes, Grant W. Mallory, Arnoley S. Abcejo, Jeffrey Pasternak, John L. D. Atkinson, Fredric B. Meyer, W. Richard Marsh, Michael J. Link, Michelle J. Clarke, William Perkins, and Jamie J. Van Gompel

OBJECTIVE

Historically, performing neurosurgery with the patient in the sitting position offered advantages such as improved visualization and gravity-assisted retraction. However, this position fell out of favor at many centers due to the perceived risk of venous air embolism (VAE) and other position-related complications. Some neurosurgical centers continue to perform sitting-position cases in select patients, often using modern monitoring techniques that may improve procedural safety. Therefore, this paper reports the risks associated with neurosurgical procedures performed in the sitting position in a modern series.

METHODS

The authors reviewed the anesthesia records for instances of clinically significant VAE and other complications for all neurosurgical procedures performed in the sitting position between January 1, 2000, and October 8, 2013. In addition, a prospectively maintained morbidity and mortality log of these procedures was reviewed for instances of subdural or intracerebral hemorrhage, tension pneumocephalus, and quadriplegia. Both overall and specific complication rates were calculated in relation to the specific type of procedure.

RESULTS

In a series of 1792 procedures, the overall complication rate related to the sitting position was 1.45%, which included clinically significant VAE, tension pneumocephalus, and subdural hemorrhage. The rate of any detected VAE was 4.7%, but the rate of VAE requiring clinical intervention was 1.06%. The risk of clinically significant VAE was highest in patients undergoing suboccipital craniotomy/craniectomy with a rate of 2.7% and an odds ratio (OR) of 2.8 relative to deep brain stimulator cases (95% confidence interval [CI] 1.2–70, p = 0.04). Sitting cervical spine cases had a comparatively lower complication rate of 0.7% and an OR of 0.28 as compared with all cranial procedures (95% CI 0.12–0.67, p < 0.01). Sitting cervical cases were further subdivided into extradural and intradural procedures. The rate of complications in intradural cases was significantly higher (OR 7.3, 95% CI 1.4–39, p = 0.02) than for extradural cases. The risk of VAE in intradural spine procedures did not differ significantly from sitting suboccipital craniotomy/craniectomy cases (OR 0.69, 95% CI 0.09–5.4, p = 0.7). Two cases (0.1%) had to be aborted intraoperatively due to complications. There were no instances of intraoperative deaths, although there was a single death within 30 days of surgery.

CONCLUSIONS

In this large, modern series of cases performed in the sitting position, the complication rate was low. Suboccipital craniotomy/craniectomy was associated with the highest risk of complications. When appropriately used with modern anesthesia techniques, the sitting position provides a safe means of surgical access.

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Jamie J. Van Gompel, Kelly K. Koeller, Fredric B. Meyer, W. Richard Marsh, Peter C. Burger, Federico Roncaroli, Gregory A. Worrell, and Caterina Giannini

Object

Supratentorial cortical ependymomas (CE) are rare, with 7 cases reported. The lesions, typically occurring in the superficial cortex in young adults and associated with a history of seizures, are not fully characterized. Furthermore, their relationship with the recently described angiocentric glioma (AG) is still being debated. This study was undertaken to summarize the authors' experience with CEs.

Methods

Between 1997 and 2009, 202 cases of ependymoma were surgically treated at the Mayo Clinic, 49 of which were supratentorial. Among these, 9 CE cases were retrospectively identified. Clinical, imaging, and pathological features of each case were reviewed.

Results

Tumors arose from the frontal (5 cases), parietal (3), and occipital (1) lobes. No tumor occurred in the temporal lobe, despite its reported association with seizures. The mean age at presentation was 27 ± 19 years (± SD) and age at resection was 36 ± 16 years. The mean size of the lesion was 16 ± 14 cm3. Seizures were the presenting symptom in 78%. Cross-sectional imaging in 8 cases was characterized by a heterogeneous mass with multiple cystlike areas and enhancement of the soft-tissue component. Gross-total resection was achieved in 8 of 9 tumors. Pathologically, 6 were low-grade (WHO Grade II) and 3 were anaplastic (WHO Grade III) ependymomas. All tumors exhibited the focal presence of perivascular pseudorosettes, but only 1 (11%) exhibited the focal presence of a true rosette. A bipolar spindle cell component resembling AG was present in 3 (33%) and “Schwannian-like” nodules in 2 (22%). Subpial aggregation and peripheral infiltration were present in 4 cases (44%). With a mean postsurgery follow-up of 62 ± 38 months, only 2 lesions recurred locally after imaging-confirmed gross-total resection, both being Grade III. In 5 (71%) of 7 patients presenting with seizures an Engel Class I outcome was achieved.

Conclusions

Cortical ependymomas represent a rare type of ependymoma occurring superficially in the cortex. Morphologically, these tumors are protean, varying from classic to epithelioid, clear cell, and tanycytic. Some also exhibited features typical of AG. Most tumors were low grade and cured with resection. Anaplastic tumors occur and may recur locally despite provision of radiation therapy. Cortical ependymomas frequently, but not always, present with seizures, but despite their high association with epilepsy, none occurred in the temporal lobe in any of the authors' 9 patients. Overall, CEs appear to have a relatively favorable prognosis compared with other supratentorial ependymomas.

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Jamie J. Van Gompel, W. Richard Marsh, Fredric B. Meyer, and Gregory A. Worrell

Object

Microsurgical resection of supratentorial cavernomas associated with intractable epilepsy is performed frequently. Despite its common occurrence, little is known about patient perceptions of microsurgical resection for cavernomas. This survey study was performed to investigate patient perceived outcome after surgery for cavernomas associated with intractable epilepsy.

Methods

The authors' surgical database was searched for cavernoma resection performed between 1971 and July of 2006. Of the initial 173 patients identified, 102 met criteria for medically intractable seizures. These 102 patients were then mailed a survey to determine follow-up and patient satisfaction. Thirty-nine surveys were returned as undeliverable, and 30 (48%) of the remaining 63 patients responded.

Results

The average age at surgery for patients responding to this survey was 40 ± 16 years compared with 35 ± 15 years for all 102 patients. At prolonged follow-up, 87% of patients reported being seizure-free. Of those with seizures, 2 (7%) reported being nearly seizure-free (rare disabling seizures), 2 (7%) believed they had a worthwhile improvement in seizure frequency, and no patient (0%) in this series believed they did not have a worthwhile improvement in seizure frequency. Ninety percent of responders stated they definitely, and 10% probably, would have surgery again. No patient responded that they probably or definitely would not have epilepsy surgery. Mean clinical follow-up was 36 ± 8 months and survey follow-up was 97 ± 13 months for these 30 patients. Use of the mail-in survey increased follow-up length 2.7 times longer compared with clinical follow-up.

Conclusions

It is clear from this select group of survey responders that patients undergoing surgery for cavernomas associated with medically intractable epilepsy are happy they underwent surgery (100%) and had excellent surgical outcomes (87% seizure-free) at prolonged follow-up of 97 ± 13 months. These survey results support that microsurgical resection for cavernomas is highly effective and significantly improves these patients' quality of life.

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Jamie J. Van Gompel, Fredric B. Meyer, W. Richard Marsh, Kendall H. Lee, and Gregory A. Worrell

Object

Intracranial monitoring for temporal lobe seizure localization to differentiate neocortical from mesial temporal onset seizures requires both neocortical subdural grids and hippocampal depth electrode implantation. There are 2 basic techniques for hippocampal depth electrode implantation. This first technique uses a stereotactically guided 8-contact depth electrode directed along the long axis of the hippocampus to the amygdala via an occipital bur hole. The second technique involves direct placement of 2 or 3 4-contact depth electrodes perpendicular to the temporal lobe through the middle temporal gyrus and overlying subdural grid. The purpose of this study was to determine whether one technique was superior to the other by examining monitoring success and complications.

Methods

Between 1997 and 2005, 41 patients underwent invasive seizure monitoring with both temporal subdural grids and depth electrodes placed in 2 ways. Patients in Group A underwent the first technique, and patients in Group B underwent the second technique.

Results

Group A consisted of 26 patients and Group B 15 patients. There were no statistically significant differences between Groups A and B regarding demographics, monitoring duration, seizure localization, or outcome (Engel classification). There was a statistically significant difference at the point in time at which these techniques were used: Group A represented more patients earlier in the series than Group B (p < 0.05). The complication rate attributable to the grids and depth electrodes was 0% in each group. It was more likely that the depth electrodes were placed through the grid if there was a prior resection and the patient was undergoing a new evaluation (p < 0.05). Furthermore, Group A procedures took significantly longer than Group B procedures.

Conclusions

In this patient series, there was no difference in efficacy of monitoring, complications, or outcome between hippocampal depth electrodes placed laterally through temporal grids or using an occipital bur hole stereotactic approach. Placement of the depth electrodes perpendicularly through the grids and middle temporal gyrus is technically more practical because multiple head positions and redraping are unnecessary, resulting in shorter operative times with comparable results.

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Nicholas M. Wetjen, W. Richard Marsh, Fredric B. Meyer, Gregory D. Cascino, Elson So, Jeffrey W. Britton, S. Matthew Stead, and Gregory A. Worrell

Object

Patients with normal MR imaging (nonlesional) findings and medically refractory extratemporal epilepsy make up a disproportionate number of nonexcellent outcomes after epilepsy surgery. In this paper, the authors investigated the usefulness of intracranial electroencephalography (iEEG) in the identification of surgical candidates.

Methods

Between 1992 and 2002, 51 consecutive patients with normal MR imaging findings and extratemporal epilepsy underwent intracranial electrode monitoring. The implantation of intracranial electrodes was determined by seizure semiology, interictal and ictal scalp EEG, SPECT, and in some patients PET studies. The demographics of patients at the time of surgery, lobar localization of electrode implantation, duration of follow-up, and Engel outcome score were abstracted from the Mayo Rochester Epilepsy Surgery Database. A blinded independent review of the iEEG records was conducted for this study.

Results

Thirty-one (61%) of the 51 patients who underwent iEEG ultimately underwent resection for their epilepsy. For 28 (90.3%) of the 31 patients who had epilepsy surgery, adequate information regarding follow-up (> 1 year), seizure frequency, and iEEG recordings was available. Twenty-six (92.9%) of 28 patients had frontal lobe resections, and 2 had parietal lobe resections. The most common iEEG pattern at seizure onset in the surgically treated group was a focal high-frequency discharge (in 15 [53.6%] of 28 patients). Ten (35.7%) of the 28 surgically treated patients were seizure free. Fourteen (50%) had Engel Class I outcomes, and overall, 17 (60.7%) had significant improvement (Engel Class I and IIAB with ≥80% seizure reduction). Focal high-frequency oscillation at seizure onset was associated with Engel Class I surgical outcome (12 [85.7%] of 14 patients, p = 0.02), and it was uncommon in the nonexcellent outcome group (3 [21.4%] of 14 patients).

Conclusions

A focal high-frequency oscillation (> 20 Hz) at seizure onset on iEEG may identify patients with nonlesional extratemporal epilepsy who are likely to have an Engel Class I outcome after epilepsy surgery. The prospect of excellent outcome in nonlesional extratemporal lobe epilepsy prior to intracranial monitoring is poor (14 [27.5%] of 51 patients). However, iEEG can further stratify patients and help identify those with a greater likelihood of Engel Class I outcome after surgery.

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Jamie J. Van Gompel, S. Matthew Stead, Caterina Giannini, Fredric B. Meyer, W. Richard Marsh, Todd Fountain, Elson So, Aaron Cohen-Gadol, Kendall H. Lee, and Gregory A. Worrell

Object

Cerebral cortex electrophysiology is poorly sampled using standard, low spatial resolution clinical intracranial electrodes. Adding microelectrode arrays to the standard clinical macroelectrode arrays increases the spatial resolution and may ultimately improve the clinical utility of intracranial electroencephalography (iEEG). However, the safety of hybrid electrode systems containing standard clinical macroelectrode and microelectrode arrays is not yet known. The authors report on their preliminary experience in 24 patients who underwent implantation of hybrid electrodes.

Methods

In this study, 24 consecutive patients underwent long-term iEEG monitoring with implanted hybrid depth and subdural grid and strip electrodes; both clinical macroelectrodes and research microelectrodes were used. The patients included 18 women and 6 men with an average age of 35 ± 12 years (range 21–65). The mean hospital stay was 11 ± 4 days (range 5–20), with mean duration of implantation 7.0 ± 3.2 days (range 3–15). Data from the 198 consecutive craniotomies for standard clinical subdural grid insertion (prior to surgery in the 24 patients described here) were used for comparison to investigate the relative risk of complications.

Results

Focal seizure identification and subsequent resection was performed in 20 patients. One patient underwent a subsequent operation after neurological deterioration secondary to cerebral swelling and a 5-mm subdural hematoma. There were no infections. The overall complication rate was 4.2% (only 1 patient had a complication), which did not significantly differ from the complication rate previously reported by the authors of 6.6% when standard subdural and depth intracranial electrodes were used. There were no deaths or permanent neurological deficits related to electrode implantation.

Conclusions

The authors demonstrate the use of hybrid subdural strip and grid electrodes containing high-density microwire arrays and standard clinical macroelectrodes. Hybrid electrodes provide high spatial resolution electrophysiology of the neocortex that is impossible with standard clinical iEEG. In this initial study in 24 patients, the complication rate is acceptable, and there does not appear to be increased risk associated with the use of hybrid electrodes compared with standard subdural and depth iEEG electrodes. More research is required to show whether hybrid electrode recordings will improve localization of epileptic foci and tracking the generation of neocortical seizures.

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Frederic Collignon, Nicholas M. Wetjen, Aaron A. Cohen-Gadol, Gregory D. Cascino, Joseph Parisi, Fredric B. Meyer, W. Richard Marsh, Patrick Roche, and Stephen D. Weigand

Object

The causes of epileptic events remain unclear. Much in vitro and in vivo experimental evidence suggests that gap junctions formed by connexins (Cxs) between neurons and/or astrocytes contribute to the generation and maintenance of seizures; however, few experiments have been conducted in humans, and those completed have shown controversial data. The authors designed a study to compare the level of expression of Cxs in hippocampi from epileptic and nonepileptic patients to assess whether an alteration of gap junction expression in epileptic tissue plays a role in seizure origin and propagation.

Methods

The expression of Cxs32, -36, and -43 was studied in 47 consecutive samples of hippocampi obtained from epileptic patients who had undergone an amygdalohippocampectomy for the treatment of intractable seizure. These expression levels were compared with those in hippocampi obtained in nonepileptic patients during postmortem dissection. Immunostaining was performed to create one slide for each of the three Cxs. Each slide demonstrated multiple cells from each of six regions (CA1, CA2, CA3, CA4, dentate gyrus, and subiculum). Two independent reviewers rated each Cx–region combination according to an immunoreactive score.

Across all three measures—that is, staining intensity, percentage of positively stained cells, and immunoreactive score—Cx32 appeared to be expressed at a significantly lower level in the epileptic patients compared with controls (p < 0.001 for each measure), whereas Cx43 appeared to be expressed more among the epileptic patients (p < 0.001 for each measure). There was no evidence of any differential expression of Cx36. There was, however, regional variation within each Cx subtype. For Cx36, the staining intensity was higher in the CA2 region in the epilepsy group.

Conclusions

The increase in Cx43, decrease in Cx32, and preservation of Cx36 expression in hippocampi from epileptic persons could play a role in the development of seizures in patients with temporal sclerosis. Additional studies must be completed to understand this mechanism better.

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Nicholas M. Wetjen, Gregory D. Cascino, A. James Fessler, Elson L. So, Jeffrey R. Buchhalter, Brian P. Mullan, Terence J. O’Brien, Fredric B. Meyer, and W. Richard Marsh

Object

The aim of this study was to determine whether ictal single-photon emission computed tomography (SPECT) is useful in localizing the site of seizure onset in patients in whom surgery for intractable epilepsy failed and who are being considered for repeated surgery.

Methods

Subtraction ictal SPECT coregistered to magnetic resonance imaging (SISCOM) studies were retrospectively analyzed in 58 patients who were being evaluated for possible repeated resection for intractable partial epilepsy between January 1, 1996, and October 31, 1999. All patients had persistent seizures subsequent to an initial resection and underwent another excision. The SISCOM-demonstrated abnormalities were classified as concordant, discordant, or indeterminate, compared with the localization of the epileptogenic zone revealed on video electroencephalography monitoring. The ability of SISCOM to predict operative outcome was also determined in patients who had undergone repeated surgical procedures.

The SISCOM studies revealed a localized hyperperfused alteration in 46 (79%) of 58 patients. Forty-one (89%) of these 46 patients had a SISCOM-demonstrated alteration in the hemisphere of the previous epilepsy surgery. Imaging changes in 33 (72%) of the 46 patients were at the site of the previous focal cortical resection. Eight (17%) of the 46 had SISCOM-demonstrated abnormalities remote from the lobe in which surgery had been performed but in the ipsilateral hemisphere. The hyperperfusion focus was in the contralateral hemisphere in the remaining five patients (11%). The site of the epileptogenic zone was concordant with the SISCOM focus in 32 (70%) of 46 patients. Twenty-six patients underwent repeated resection and were followed up for a mean of 44 months thereafter; 11 of these patients (42%) had a significant reduction in seizure tendency. Only five patients (19%) were seizure free. Ten (50%) of 20 patients with a concordant SISCOM focus compared with none (0%) of three patients with a discordant focus had a favorable surgical outcome (p = 0.23).

Conclusions

The SISCOM method might be useful in the evaluation of, and the surgical planning for, patients with intractable partial epilepsy in whom previous resective treatment has failed and who are being considered for reoperation.