To Örebro University

BACKGROUND/OBJECTIVES: Hypoglossal nerve palsy (HNP) is a rare complication after cervical spine surgery and is reported after both anterior and posterior approaches. It often presents with dysarthria, dysphagia, and hoarseness. We present a systematic review of the literature and two cases of patients presenting with confirmed HNP after anterior cervical spine surgery.

METHODS: Two retrospective case reports and a systematic review of the literature were presented. The electronic databases PubMed and Web of Science were systematically searched from inception.

RESULTS: In total, 17 cases of HNP were reported in the literature, including the two hereby presented. Ten cases involved the anterior approach and seven the posterior approach. The reported risk of HNP following cervical spine surgery varied between 0.01% and 2.5% depending on the procedure. The main etiology was mechanical compression of the nerve. Most of the cases recovered within a few months with conservative treatment. In some cases, permanent hypoglossal injury with persistent symptoms was reported. In both of the current cases, the symptoms gradually improved and completely resolved after a few months.

CONCLUSIONS: HNP is a rare complication after cervical spine surgery. The causes of hypoglossal palsy are multifactorial, but mechanical injury is the most common. A thorough understanding of the nerve's anatomy is essential to minimize the risk of injury during anesthesia, patient positioning, and surgery. Understanding the underlying mechanisms contributing to HNP post-cervical spine surgery enables the implementation of preventive measures to mitigate its occurrence.

OBJECTIVE: To evaluate if intraoperative cone-beam CT (CBCT) provides equivalent image quality to postoperative multidetector CT (MDCT) in spine surgery, potentially eliminating unnecessary imaging and cumulative radiation exposure.

METHODS: Twenty-seven patients (16 men, 11 women; median age 39 years) treated with spinal fixation surgery were evaluated using intraoperative CBCT and postoperative MDCT. The images were independently evaluated by four neuroradiologists, utilizing a five-step Likert scale and visual grading characteristics (VGC) analysis. The area under the VGC curve (AUCVGC) quantified preferences between modalities. Intra- and inter-observer variability was evaluated using intraclass correlation coefficients (ICC). Image quality was objectively evaluated by contrast and signal-to-noise measurements (CNR, SNR).

RESULTS: In image quality, CBCT was the preferred modality in thoracolumbar spine (AUCVGC = 0.58, p < 0.001). Conversely, MDCT was preferred in cervical spine (AUCVGC = 0.38, p < 0.004). The agreement was good for inter-observer and moderate in intra-observer (ICC 0.76-0.77 vs 0.60-0.71), p < 0.001. SNR and CNR were comparable in thoracolumbar imaging, while MDCT provided superior and more consistent image quality in the cervical spine, p < 0.001.

CONCLUSION: In spine surgery, CBCT provides superior image quality for thoracolumbar imaging, while MDCT performs better for cervical imaging. Intraoperative CBCT could potentially replace postoperative MDCT in thoracolumbar spine procedures, while postoperative MDCT remains essential for cervical spine assessment.

KEY POINTS: Subjective assessment demonstrated that CBCT was the preferred modality for thoracolumbar spine imaging, while MDCT was favored for cervical spine imaging. Agreement between readers was good, while individual readings showed moderate consistency in repeated assessments. Objective assessment of image clarity and detail showed both modalities performed equally well in the thoracolumbar spine, while MDCT performed better in the cervical spine. Intraoperative CBCT proves superior to postoperative MDCT for thoracolumbar spine imaging, potentially eliminating redundant scans, and improving workflow. Postoperative MDCT remains essential for cervical spine procedures.

BACKGROUND: Dysphonia is one of the more common complications following anterior cervical discectomy and fusion (ACDF). ACDF is the gold standard for treating degenerative cervical spine disorders, and identifying high-risk patients is therefore crucial. PURPOSE: This study aimed to evaluate different machine learning models to predict persistent dysphonia after ACDF.

STUDY DESIGN: A retrospective review of the nationwide Swedish spine registry (Swespine) PATIENT SAMPLE: All adults in the Swespine registry who underwent elective ACDF between 2006 and 2020.

OUTCOME MEASURES: The primary outcome was self-reported dysphonia lasting at least one month after surgery. Predictive performance was assessed using discrimination and calibration metrics.

METHODS: Patients with missing dysphonia data at the one-year follow-up were excluded. Data preprocessing involved one-hot encoding categorical variables, scaling continuous variables, and imputing missing values. Four machine learning models (logistic regression, random forest (RF), gradient boosting, K-nearest neighbor) were employed. The models were trained and tested using an 80:20 data split and 5-fold cross-validation, with performance metrics guiding the selection of the best model for predicting persistent dysphonia.

RESULTS: In total, 2,708 were included in the study. Twelve key predictors were identified. Four machine learning models were tested, with the RF model achieving the best performance (AUC = 0.794). The most significant predictors across models included preoperative NDI, EQ5Dindex, preoperative neurology, number of operated levels, and use of a fusion cage. The RF model, chosen for its superior performance, showed high sensitivity and consistent accuracy, but a low specificity and positive predictive value.

CONCLUSIONS: In this study, machine learning models were employed to identify predictors of persistent dysphonia following ACDF. Among the models tested, the RF classifier demonstrated superior performance, with an AUC value of 0.790. The RF model identified NDI, EQ5Dindex, and number of fused vertebrae as key variables. These findings underscore the potential of machine learning models in identifying patients at increased risk for dysphonia persisting for more than one month after surgery.

BACKGROUND AND OBJECTIVES: Vertebral artery injury (VAI) because of traumatic subaxial cervical spine injury is a rare but potentially devastating condition as it could lead to stroke. The aim of this study was to examine the incidence, risk factors, outcomes, and radiographic predictors of VAI in patients surgically treated for subaxial cervical spine injuries at a tertiary care trauma center.

METHODS: This is a retrospective population-based cohort study, including all patients surgically treated for traumatic subaxial cervical spine injuries at the study center between 2006 and 2018. Primary outcomes included mortality and morbidity after the injury. Propensity score matching, survival, univariable, and multivariable analyses were used to study the outcomes of interest.

RESULTS: Traumatic VAI primarily occurred after high-energy traumas such as motor vehicle accidents and falls from heights. The median age was 64.4 years (47.4-69.1), and 69% were male. In the cohort of patients with subaxial cervical injury, 54% had a spinal cord injury (SCI). In the subgroup with VAI, the frequency of SCI was 66% and a concomitant SCI and VAI were associated with a more severe American Spinal Cord Injury Association Impairment Scale grade (P = .015). However, after accounting for age, sex, and associated injuries, VAI did not affect postoperative complications, short- or long-term outcomes, or mortality rates. Facet joint dislocation was a unique radiographic predictor of VAI (odds ratio 3.8 [CI 1.42-10.7], P = .009).

CONCLUSION: The findings suggest that clinical outcomes of patients with traumatic cervical spine injuries were not negatively affected by the presence of a VAI. Several radiographic factors were associated with VAI; however, only facet joint dislocation remained as an independent predictor of this injury.

External ventricular drain (EVD) insertion using the freehand technique is often associated with misplacements resulting in unfavorable outcomes. Augmented Reality (AR) has been increasingly used to complement conventional neuronavigation. The accuracy of AR guided EVD insertion has been investigated in several studies, on anthropomorphic phantoms, cadavers, and patients. This review aimed to assess the current knowledge and discuss potential benefits and challenges associated with AR guidance in EVD insertion. MEDLINE, EMBASE, and Web of Science were searched from inception to August 2023 for studies evaluating the accuracy of AR guidance for EVD insertion. Studies were screened for eligibility and accuracy data was extracted. The risk of bias was assessed using the Cochrane Risk of Bias Tool and the quality of evidence was assessed using the Newcastle-Ottawa-Scale. Accuracy was reported either as the average deviation from target or according to the Kakarla grading system. Of the 497 studies retrieved, 14 were included for analysis. All included studies were prospectively designed. Insertions were performed on anthropomorphic phantoms, cadavers, or patients, using several different AR devices and interfaces. Deviation from target ranged between 0.7 and 11.9 mm. Accuracy according to the Kakarla grading scale ranged between 82 and 96%. Accuracy was higher for AR compared to the freehand technique in all studies that had control groups. Current evidence demonstrates that AR is more accurate than free-hand technique for EVD insertion. However, studies are few, the technology developing, and there is a need for further studies on patients in relevant clinical settings.

INTRODUCTION: Peripheral nerve sheath tumors are the most common tumor of the peripheral nerves. In general, surgery has a favorable outcome and is the treatment of choice. However, postoperative neurologic deficits are not uncommon, and predictors of outcome are poorly defined.

OBJECTIVE: To evaluate clinical outcomes after surgical treatment of benign peripheral nerve sheath tumors and identify outcome predictors that may affect preoperative decision making and improve surgical outcomes.

METHOD: In this single center retrospective study, all patients surgically treated for a benign peripheral nerve sheath tumor between 2005 and 2020 were eligible for inclusion. Medical records and imaging data were reviewed. Studied outcomes were changes in neurological symptoms, pain, and tumor recurrence. Logistic regression was performed to identify possible outcome predictors.

RESULTS: In total, 81 patients undergoing 85 separate surgeries for benign peripheral nerve sheath tumors were included. The most common preoperative symptoms were local pain (90%) followed by a noticeable mass (78%), radiating pain (72%), sensory deficit (18%) and motor deficit (16%). A postoperative improvement of symptoms was seen in 94% of those with pain, 48% of those with sensory deficits and 78% of those with motor deficits. However, 35% and 9% developed new postoperative sensory and motor deficits, respectively. Multivariable analysis showed complete tumor removal as a predictor of reduced pain (p = 0.033), and younger age and larger tumors were risk factors for persistent or increased sensory deficits (p = 0.002 and p = 0.005, respectively). There were no significant predictors of motor deficits. Neurocutaneous syndromes were associated with increased odds of tumor recurrence on univariable analysis (p = 0.008).

CONCLUSION: Surgery of benign peripheral nerve sheath tumors is a safe procedure with a favorable outcome in most cases. Younger age and larger tumors were risk factors for persistent or increased sensory deficits, while complete tumor removal was associated with reduced pain. Patients with neurocutaneous syndromes had a higher rate of tumor recurrence. To further evaluate outcome predictors, we recommend future studies to focus on longer follow-up periods to assess the natural course of postoperative neurological deficits.

PURPOSE: The purpose of this study was to evaluate patient-reported outcome measures (PROMS) on dysphagia, health-related quality of life (HRQoL) and return to work after occipitocervical fixation (OCF). Postoperative radiographic measurements were evaluated to identify possible predictors of dysphagia.

METHODS: All individuals (≥ 18 years) who underwent an OCF at the study center or were registered in the Swedish spine registry (Swespine) between 2005 and 2019, and were still alive when the study was conducted, were eligible for inclusion. There was no overlap between the cohorts. Prospectively collected data on dysphagia (Dysphagia Short Questionnaire DSQ), HRQoL (EQ5D-3L) and return to work were used. Radiological and baseline patient data were retrospectively collected. In addition, HRQoL data of a matched sample of individuals was elicited from the Stockholm Public Health Survey 2006.

RESULTS: In total, 54 individuals were included. At long-term follow-up, 26 individuals (51%) had no dysphagia, and 25 (49%) reported some degree of dysphagia: 11 (22%) had mild dysphagia, and 14 (27%) had moderate to severe dysphagia. On a group level, the OCF sample scored significantly lower EQVAS and EQ-5Dindex values compared to the general population (60.0 vs. 80.0, p = 0.016; 0.43 vs. 0.80, p < 0.001). Individuals working preoperatively returned to work after surgery. Of those responding, 88% stated that they would undergo the OCF operation if it was offered today. No predictors of dysphagia based on radiographic measurements were identified.

CONCLUSION: Occipitocervical fixation results in a high frequency of long-term dysphagia. The HRQoL of OCF patients is significantly reduced compared to matched controls. However, most patients are satisfied with their surgery. No radiographic predictors of long-term dysphagia could be identified. Future prospective and systematic studies with larger samples and more objective outcome measures are needed to elucidate the causes of dysphagia in OCF.

INTRODUCTION: Nerve sheath tumours arise from both the central and peripheral nervous systems. In particular, cases of spinal or paraspinal origins are scarce and poorly covered in the literature. This systematic review aims to summarise the body of evidence regarding spinal nerve sheath tumours and assess its quality, to provide the current knowledge on epidemiology, tumour characteristics, diagnostics, treatment strategies and outcomes.

METHODS AND ANALYSIS: Databases including PubMed, Web of Science and Embase will be searched using keywords such as "spinal", "nerve sheath", "neurofibroma", "schwannoma", "neurinoma" and "neurilemoma". The search will be limited to studies published no earlier than 2000 without language restrictions. Case reports, editorials, letters and reviews will be excluded. Reference lists of identified studies will be searched to find possible additional relevant records. Identified studies will be screened for inclusion, by one reviewer at first and then two independent ones in the next step to increase the external validity. The Rayyan platform will be used for the screening and inclusion process. Data extraction within several predetermined areas of interest will proceed. Subjects of interest include epidemiology, histopathology, radiological diagnostics, surgery, complications, non-surgical treatment alternatives, disease outcomes and predictors of outcome, and recurrence rates. On satisfactory amount of homogenous data, a meta-analysis of key outcomes such as recurrence risk or postoperative neurological improvement will be performed. This systematic review will primarily serve as a reference guide to aid in diagnosis and treatment of patients with spinal schwannomas, while also spotlighting the knowledge gaps in the literature to help guide future research initiatives.

ETHICS AND DISSEMINATION: Ethics approval is not required for the protocol or review as both are based on existing publications. For dissemination, the final manuscript will be submitted to a peer-reviewed journal.

PURPOSE: This bibliometric analysis of the top 100 cited articles on extended reality (XR) in neurosurgery aimed to reveal trends in this research field. Gender differences in authorship and global distribution of the most-cited articles were also addressed.

METHODS: A Web of Science electronic database search was conducted. The top 100 most-cited articles related to the scope of this review were retrieved and analyzed for trends in publications, journal characteristics, authorship, global distribution, study design, and focus areas. After a brief description of the top 100 publications, a comparative analysis between spinal and cranial publications was performed.

RESULTS: From 2005, there was a significant increase in spinal neurosurgery publications with a focus on pedicle screw placement. Most articles were original research studies, with an emphasis on augmented reality (AR). In cranial neurosurgery, there was no notable increase in publications. There was an increase in studies assessing both AR and virtual reality (VR) research, with a notable emphasis on VR compared to AR. Education, surgical skills assessment, and surgical planning were more common themes in cranial studies compared to spinal studies. Female authorship was notably low in both groups, with no significant increase over time. The USA and Canada contributed most of the publications in the research field.

CONCLUSIONS: Research regarding the use of XR in neurosurgery increased significantly from 2005. Cranial research focused on VR and resident education while spinal research focused on AR and neuronavigation. Female authorship was underrepresented. North America provides most of the high-impact research in this area.