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John W. Rutland, Javin Schefflein, Annie E. Arrighi-Allisan, Daniel Ranti, Travis R. Ladner, Akila Pai, Joshua Loewenstern, Hung-Mo Lin, James Chelnis, Bradley N. Delman, Raj K. Shrivastava and Priti Balchandani

OBJECTIVE

Predicting vision recovery following surgical decompression of the optic chiasm in pituitary adenoma patients remains a clinical challenge, as there is significant variability in postoperative visual function that remains unreliably explained by current prognostic factors. Available literature inadequately characterizes alterations in adenoma patients involving the lateral geniculate nucleus (LGN). This study examined the association of LGN degeneration with chiasmatic compression as well as with the retinal nerve fiber layer (RNFL), pattern standard deviation (PSD), mean deviation (MD), and postoperative vision recovery. PSD is the degree of difference between the measured visual field pattern and the normal pattern (“hill”) of vision, and MD is the average of the difference from the age-adjusted normal value.

METHODS

A prospective study of 27 pituitary adenoma patients and 27 matched healthy controls was conducted. Participants were scanned on a 7T ultra–high field MRI scanner, and 3 independent readers measured the LGN at its maximum cross-sectional area on coronal T1-weighted MPRAGE imaging. Readers were blinded to diagnosis and to each other’s measurements. Neuro-ophthalmological data, including RNFL thickness, MD, and PSD, were acquired for 12 patients, and postoperative visual function data were collected on patients who underwent surgical chiasmal decompression. LGN areas were compared using two-tailed t-tests.

RESULTS

The average LGN cross-sectional area of adenoma patients was significantly smaller than that of controls (13.8 vs 19.2 mm2, p < 0.0001). The average LGN cross-sectional area correlated with MD (r = 0.67, p = 0.04), PSD (r = −0.62, p = 0.02), and RNFL thickness (r = 0.75, p = 0.02). The LGN cross-sectional area in adenoma patients with chiasm compression was 26.6% smaller than in patients without compression (p = 0.009). The average tumor volume was 7902.7 mm3. Patients with preoperative vision impairment showed 29.4% smaller LGN cross-sectional areas than patients without deficits (p = 0.003). Patients who experienced improved postoperative vision had LGN cross-sectional areas that were 40.8% larger than those of patients without postoperative improvement (p = 0.007).

CONCLUSIONS

The authors demonstrate novel in vivo evidence of LGN volume loss in pituitary adenoma patients and correlate imaging results with neuro-ophthalmology findings and postoperative vision recovery. Morphometric changes to the LGN may reflect anterograde transsynaptic degeneration. These findings indicate that LGN degeneration may be a marker of optic apparatus injury from chiasm compression, and measurement of LGN volume loss may be useful in predicting vision recovery following adenoma resection.

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Kazuya Motomura, Lushun Chalise, Fumiharu Ohka, Kosuke Aoki, Kuniaki Tanahashi, Masaki Hirano, Tomohide Nishikawa, Junya Yamaguchi, Hiroyuki Shimizu, Toshihiko Wakabayashi and Atsushi Natsume

OBJECTIVE

Lower-grade gliomas (LGGs) are often observed within eloquent regions, which indicates that tumor resection in these areas carries a potential risk for neurological disturbances, such as motor deficit, language disorder, and/or neurocognitive impairments. Some patients with frontal tumors exhibit severe impairments of neurocognitive function, including working memory and spatial awareness, after tumor removal. The aim of this study was to investigate neurocognitive and functional outcomes of frontal LGGs in both the dominant and nondominant hemispheres after awake brain mapping.

METHODS

Data from 50 consecutive patients with diffuse frontal LGGs in the dominant and nondominant hemispheres who underwent awake brain surgery between December 2012 and September 2018 were retrospectively analyzed. The goal was to map neurocognitive functions such as working memory by using working memory tasks, including digit span testing and N-back tasks.

RESULTS

Due to awake language mapping, the frontal aslant tract was frequently identified as a functional boundary in patients with left superior frontal gyrus tumors (76.5%). Furthermore, functional boundaries were identified while evaluating verbal and spatial working memory function by stimulating the dorsolateral prefrontal cortex using the digit span and visual N-back tasks in patients with right superior frontal gyrus tumors (7.1%). Comparing the preoperative and postoperative neuropsychological assessments from the Wechsler Adult Intelligence Scale–Third Edition (WAIS-III) and Wechsler Memory Scale–Revised (WMS-R), significant improvement following awake surgery was observed in mean Perceptual Organization (Z = −2.09, p = 0.04) in WAIS-III scores. Postoperative mean WMS-R scores for Visual Memory (Z = −2.12, p = 0.03) and Delayed Recall (Z = −1.98, p = 0.04) were significantly improved compared with preoperative values for every test after awake surgery. No significant deterioration was noted with regard to neurocognitive functions in a comprehensive neuropsychological test battery. In the postoperative course, early transient speech and motor disturbances were observed in 30.0% and 28.0% of patients, respectively. In contrast, late permanent speech and motor disturbances were observed in 0% and 4.0%, respectively.

CONCLUSIONS

It is noteworthy that no significant postoperative deterioration was identified compared with preoperative status in a comprehensive neuropsychological assessment. The results demonstrated that awake functional mapping enabled favorable neurocognitive and functional outcomes after surgery in patients with diffuse frontal LGGs.

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Stephanie D. C. van de Beeten, Martijn J. Cornelissen, Renee M. van Seeters, Marie-Lise C. van Veelen, Sarah L. Versnel, Sjoukje E. Loudon and Irene M. J. Mathijssen

OBJECTIVE

Unicoronal synostosis results in frontal plagiocephaly and is preferably treated before the patient is 1 year of age to prevent intracranial hypertension (ICH). However, data on the prevalence of ICH in these patients is currently lacking. This study aimed to establish the prevalence of preoperative and postoperative signs of ICH in a large cohort of patients with unicoronal synostosis and to test whether there is a correlation between papilledema and occipitofrontal head circumference (OFC) curve stagnation in unicoronal synostosis.

METHODS

The authors included all patients with unicoronal synostosis treated before 2 years of age at a single center between 2003 and 2013. The presence of ICH was evaluated by routine fundoscopy. The OFC growth curve was analyzed for deflection and in relationship to signs of ICH.

RESULTS

In total, 104 patients were included in this study, 84 (81%) of whom were considered to have nonsyndromic unicoronal synostosis. Preoperatively, none of the patients had papilledema as determined by fundoscopy (mean age at surgery 11 months). Postoperatively, 5% of patients with syndromic synostosis and 3% of those with nonsyndromic synostosis had papilledema, and this was confirmed by optical coherence tomography. Raised intracranial pressure was confirmed in 1 patient with syndromic unicoronal synostosis. Six of 78 patients had OFC stagnation, which was not significantly correlated to papilledema (p = 0.22). One child with syndromic unicoronal synostosis required repeated surgery for ICH (0.96%).

CONCLUSIONS

Papilledema was not found in patients with unicoronal synostosis when they underwent surgery before the age of 1 year and was also very rare during follow-up. There was no relationship between papilledema and OFC stagnation.

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Sameer Kitab, Ghaith Habboub, Salam B. Abdulkareem, Muthanna B. Alimidhatti and Edward Benzel

OBJECTIVE

Age is commonly thought to be a risk factor in defining lumbar spinal stenosis (LSS) degenerative or developmental subtypes. This article is a follow-up to a previous article (“Redefining Lumbar Spinal Stenosis as a Developmental Syndrome: An MRI-Based Multivariate Analysis of Findings in 709 Patients Throughout the 16- to 82-Year Age Spectrum”) that describes the radiological differences between developmental and degenerative types of LSS. MRI-based analysis of “degeneration” variables and spinal canal morphometric characteristics of LSS segments have been thought to correlate with age at presentation.

METHODS

The authors performed a re-analysis of data from their previously reported prospective MRI-based study, stratifying data from the 709 cases into 3 age categories of equal size (instead of the original < 60 vs ≥ 60 years). Relative spinal canal dimensions, as well as radiological degenerative variables from L1 to S1, were analyzed across age groups in a multivariate mode. The total degenerative scale score (TDSS) for each lumbar segment from L1 to S1 was calculated for each patient. The relationships between age and qualitative stenosis grades, TDSS, disc degeneration, and facet degeneration were analyzed using Pearson’s product-moment correlation and multiple regression.

RESULTS

Multivariate analysis of TDSS and spinal canal dimensions revealed highly significant differences across the 3 age groups at L2–3 and L3–4 and a weaker, but still significant, association with changes at L5–S1. Age helped to explain only 9.6% and 12.2% of the variance in TDSS at L1–2 and L2–3, respectively, with a moderate positive correlation, and 7.8%, 1.2%, and 1.9% of the variance in TDSS at L3–4, L4–5, and L5–S1, respectively, with weak positive correlation. Age explained 24%, 26%, and 18.4% of the variance in lumbar intervertebral disc (LID) degeneration at L1–2, L2–3, and L3–4, respectively, while it explained only 6.2% and 7.2% of the variance of LID degeneration at L4–5 and L5–S1, respectively. Age explained only 2.5%, 4.0%, 1.2%, 0.8%, and 0.8% of the variance in facet degeneration at L1–2, L2–3, L3–4, L4–5, and L5–S1, respectively.

CONCLUSIONS

Age at presentation correlated weakly with degeneration variables and spinal canal morphometries in LSS segments. Age correlated with upper lumbar segment (L1–4) degeneration more than with lower segment (L4–S1) degeneration. The actual chronological age of the patients did not significantly correlate with the extent of degenerative pathology of the lumbar stenosis segments. These study results lend support for a developmental contribution to LSS.

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Benjamin A. Plog, Nanhong Lou, Clifford A. Pierre, Alex Cove, H. Mark Kenney, Emi Hitomi, Hongyi Kang, Jeffrey J. Iliff, Douglas M. Zeppenfeld, Maiken Nedergaard and G. Edward Vates

OBJECTIVE

Cranial neurosurgical procedures can cause changes in brain function. There are many potential explanations, but the effect of simply opening the skull has not been addressed, except for research into syndrome of the trephined. The glymphatic circulation, by which CSF and interstitial fluid circulate through periarterial spaces, brain parenchyma, and perivenous spaces, depends on arterial pulsations to provide the driving force for bulk flow; opening the cranial cavity could dampen this force. The authors hypothesized that a craniectomy, without any other pathological insult, is sufficient to alter brain function due to reduced arterial pulsatility and decreased glymphatic flow. Furthermore, they postulated that glymphatic impairment would produce activation of astrocytes and microglia; with the reestablishment of a closed cranial compartment, the glymphatic impairment, astrocytic/microglial activation, and neurobehavioral decline caused by opening the cranial compartment might be reversed.

METHODS

Using two-photon in vivo microscopy, the pulsatility index of cortical vessels was quantified through a thinned murine skull and then again after craniectomy. Glymphatic influx was determined with ex vivo fluorescence microscopy of mice 0, 14, 28, and 56 days following craniectomy or cranioplasty; brain sections were immunohistochemically labeled for GFAP and CD68. Motor and cognitive performance was quantified with rotarod and novel object recognition tests at baseline and 14, 21, and 28 days following craniectomy or cranioplasty.

RESULTS

Penetrating arterial pulsatility decreased significantly and bilaterally following unilateral craniectomy, producing immediate and chronic impairment of glymphatic CSF influx in the ipsilateral and contralateral brain parenchyma. Craniectomy-related glymphatic dysfunction was associated with an astrocytic and microglial inflammatory response, as well as with the development of motor and cognitive deficits. Recovery of glymphatic flow preceded reduced gliosis and return of normal neurological function, and cranioplasty accelerated this recovery.

CONCLUSIONS

Craniectomy causes glymphatic dysfunction, gliosis, and changes in neurological function in this murine model of syndrome of the trephined.

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Ryan M. Jones, Shona Kamps, Yuexi Huang, Nadia Scantlebury, Nir Lipsman, Michael L. Schwartz and Kullervo Hynynen

OBJECTIVE

The object of this study was to correlate lesion size with accumulated thermal dose (ATD) in transcranial MRI-guided focused ultrasound (MRgFUS) treatments of essential tremor with focal temperatures limited to 50°C–54°C.

METHODS

Seventy-five patients with medically refractory essential tremor underwent MRgFUS thalamotomy at the authors’ institution. Intraoperative MR thermometry was performed to measure the induced temperature and thermal dose distributions (proton resonance frequency shift coefficient = −0.00909 ppm/°C). In 19 patients, it was not possible to raise the focal temperature above 54°C because of unfavorable skull characteristics and/or the pain associated with cranial heating. In this patient subset, sonications with focal temperatures between 50°C and 54°C were repeated (5.1 ± 1.5, mean ± standard deviation) to accumulate a sufficient thermal dose for lesion formation. The ATD profile sizes (17, 40, 100, 200, and 240 cumulative equivalent minutes at 43°C [CEM43]) calculated by combining axial MR thermometry data from individual sonications were correlated with the corresponding lesion sizes measured on axial T1-weighted (T1w) and T2-weighted (T2w) MR images acquired 1 day posttreatment. Manual corrections were applied to the MR thermometry data prior to thermal dose accumulation to compensate for off-resonance–induced spatial-shifting artifacts.

RESULTS

Mean lesion sizes measured on T2w MRI (5.0 ± 1.4 mm) were, on average, 28% larger than those measured on T1w MRI (3.9 ± 1.4 mm). The ATD thresholds found to provide the best correlation with lesion sizes measured on T2w and T1w MRI were 100 CEM43 (regression slope = 0.97, R2 = 0.66) and 200 CEM43 (regression slope = 0.98, R2 = 0.89), respectively, consistent with data from a previous study of MRgFUS thalamotomy via repeated sonications at higher focal temperatures (≥ 55°C). Two-way linear mixed-effects analysis revealed that dominant tremor subscores on the Fahn-Tolosa-Marin Clinical Rating Scale for Tremor (CRST) were statistically different from baseline at 3 months and 1 year posttreatment in both low-temperature (50°C–54°C) and high-temperature (≥ 55°C) patient cohorts. No significant fixed effect on the dominant tremor scores was found for the temperature cohort factor.

CONCLUSIONS

In transcranial MRgFUS thalamotomy for essential tremor, repeated sonications with focal temperatures between 50°C and 54°C can accumulate a sufficient thermal dose to generate lesions for clinically relevant tremor suppression up to 1 year posttreatment, and the ATD can be used to predict the size of the resulting ablation zones measured on MRI. These data will serve to guide future clinical MRgFUS brain procedures, particularly those in which focal temperatures are limited to below 55°C.

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Robert A. Scranton, Kushal Shah and Aaron A. Cohen-Gadol

OBJECTIVE

Trigeminal neuralgia is a debilitating disease that can be treated effectively by a number of modalities. Percutaneous balloon compression rhizotomy of the gasserian ganglion is an important technique that can be offered as a primary or secondary strategy after failure of medical therapy. However, the commercial kit for this procedure was discontinued in the United States in early 2016 and therefore is not currently available. The authors describe a low-cost, effective solution for continuing to offer this procedure using equipment already available in most hospitals.

METHODS

The authors provide a detailed equipment list with step-by-step instructions on how to prepare all the necessary items and perform a percutaneous balloon compression rhizotomy.

RESULTS

The custom “homemade” kit and technique described have been utilized successfully since June 2016 in 34 patients. The kit is a low-cost alternative, and its application does not add any operative time beyond that required for the previously commercially available kit.

CONCLUSIONS

Percutaneous balloon compression rhizotomy of the gasserian ganglion is an important technique that should be readily available to patients who are not medically fit for microvascular decompression and need immediate relief of their pain. The alternative kit described here can be assembled easily using equipment that is readily available in most hospitals.

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Mehmet Sabri Gürbüz, Adnan Dağçınar, Yaşar Bayri, Aşkın Şeker and Hasan Güçlü

OBJECTIVE

The authors sought to develop a set of parameters that reliably predict the clinical success of endoscopic third ventriculostomy (ETV) when assessed before and after the operation, and to establish a plan for MRI follow-up after this procedure.

METHODS

This retrospective study involved 77 patients who had undergone 78 ETV procedures for obstructive hydrocephalus between 2010 and 2015. Constructive interference in steady-state (CISS) MRI evaluations before and after ETV were reviewed, and 4 parameters were measured. Two well-known standard parameters, fronto-occipital horn ratio (FOHR) and third ventricular index (TVI), and 2 newly defined parameters, infundibulochiasmatic (IC) angle and anterior third ventricular height (TVH), were measured in this study. Associations between preoperative measurements of and postoperative changes in the 4 variables and the clinical success of ETV were analyzed.

RESULTS

Of the 78 ETV procedures, 70 (89.7%) were successful and 8 (10.3%) failed. On the preoperative MR images, the mean IC angle and anterior TVH were significantly larger in the successful procedures. On the 24-hour postoperative MR images of the successful procedures, the mean IC angle declined significantly from 114.2° to 94.6° (p < 0.05) and the mean anterior TVH declined significantly from 15 to 11.2 mm (p < 0.05). The mean percentage reduction of the IC angle was 17.1%, and that of the anterior TVH was 25.5% (both p < 0.05). On the 1-month MR images of the successful procedures, the mean IC angle declined significantly from 94.6° to 84.2° (p < 0.05) and the mean anterior TVH declined significantly from 11.2 to 9.3 mm (p < 0.05). The mean percentage reductions in IC angle (11%) and anterior TVH (16.9%) remained significant at this time point but were smaller than those observed at 24 hours. The 6-month and 1-year postoperative MR images of the successful group showed no significant changes in mean IC angle or mean anterior TVH. Regarding the unsuccessful procedures, there were no significant changes observed in IC angle or anterior TVH at any of the time points studied. Reduction of IC angle and reduction of anterior TVH on 24-hour postoperative MR images were significantly associated with successful ETV. However, no clinically significant association was found between FOHR, TVI, and ETV success.

CONCLUSIONS

Assessing the IC angle and anterior TVH on preoperative and 24-hour postoperative MR images is useful for predicting the clinical success of ETV. These 2 measurements could also be valuable as radiological follow-up parameters.

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Seung-Bo Lee, Hakseung Kim, Young-Tak Kim, Frederick A. Zeiler, Peter Smielewski, Marek Czosnyka and Dong-Joo Kim

OBJECTIVE

Monitoring intracranial and arterial blood pressure (ICP and ABP, respectively) provides crucial information regarding the neurological status of patients with traumatic brain injury (TBI). However, these signals are often heavily affected by artifacts, which may significantly reduce the reliability of the clinical determinations derived from the signals. The goal of this work was to eliminate signal artifacts from continuous ICP and ABP monitoring via deep learning techniques and to assess the changes in the prognostic capacities of clinical parameters after artifact elimination.

METHODS

The first 24 hours of monitoring ICP and ABP in a total of 309 patients with TBI was retrospectively analyzed. An artifact elimination model for ICP and ABP was constructed via a stacked convolutional autoencoder (SCAE) and convolutional neural network (CNN) with 10-fold cross-validation tests. The prevalence and prognostic capacity of ICP- and ABP-related clinical events were compared before and after artifact elimination.

RESULTS

The proposed SCAE-CNN model exhibited reliable accuracy in eliminating ABP and ICP artifacts (net prediction rates of 97% and 94%, respectively). The prevalence of ICP- and ABP-related clinical events (i.e., systemic hypotension, intracranial hypertension, cerebral hypoperfusion, and poor cerebrovascular reactivity) all decreased significantly after artifact removal.

CONCLUSIONS

The SCAE-CNN model can be reliably used to eliminate artifacts, which significantly improves the reliability and efficacy of ICP- and ABP-derived clinical parameters for prognostic determinations after TBI.

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

OBJECTIVE

Minimally invasive transforaminal interbody fusion techniques vary among surgeons. One decision point is whether to perform a unilateral facetectomy (UF), a unilateral facetectomy plus partial contralateral facetectomy (UF/PF), or a complete bilateral facetectomy (CBF). The authors therefore compared the biomechanical benefits of all 3 types of facetectomies to determine which approach produces improved biomechanical outcomes.

METHODS

Seven human cadaveric specimens (L3–S1) were potted and prepped for UF, with full facet removal, hemilaminectomy, discectomy, and pedicle screw placement. After distraction, a fixed interbody spacer was placed, and compression was performed. A final fixation configuration was performed by locking the rods across the screws posteriorly with bilateral compression. Final lordosis angle and change and foraminal height were measured, and standard nondestructive flexibility tests were performed to assess intervertebral range of motion (ROM) and compressive stiffness. The same procedure was followed for UF/PF and CBF in all 7 specimens.

RESULTS

All 3 conditions demonstrated similar ROM and compressive stiffness. No statistically significant differences occurred with distraction, but CBF demonstrated significantly greater change than UF in mean foraminal height after bilateral posterior compression (1.90 ± 0.62 vs 1.00 ± 0.45 mm, respectively, p = 0.04). With compression, the CBF demonstrated significantly greater mean ROM than the UF (2.82° ± 0.83° vs 2.170° ± 1.10°, p = 0.007). The final lordosis angle was greatest with CBF (3.74° ± 0.70°) and lowest with UF (2.68° ± 1.28°). This finding was statistically significant across all 3 conditions (p ≤ 0.04).

CONCLUSIONS

Although UF/PF and CBF may require slightly more time and effort and incur more risk than UF, the potential improvement in sagittal balance may be worthwhile for select patients.