COVID-19 nasopharyngeal swab and cribriform fracture

Since the start of the pandemic, over 400 million COVID-19 swab tests have been conducted in the UK with a non-trivial number associated with skull base injury. Given the continuing use of nasopharyngeal swabs, further cases of swab-associated skull base injury are anticipated. We describe a 54-year-old woman presenting with persistent colourless nasal discharge for 2 weeks following a traumatic COVID-19 nasopharyngeal swab. A β2-transferrin test confirmed cerebrospinal fluid (CSF) rhinorrhoea and a high-resolution sinus computed tomography (CT) scan demonstrated a cribriform plate defect. Magnetic resonance imaging showed radiological features of idiopathic intracranial hypertension (IIH): a Yuh grade V empty sella and thinned anterior skull base. Twenty-four hour intracranial pressure (ICP) monitoring confirmed raised pressures, prompting insertion of a ventriculoperitoneal shunt. The patient underwent CT cisternography and endoscopic transnasal repair of the skull base defect using a fluorescein adjuvant, without complications. A systematic search was performed to identify cases of COVID-19 swab-related injury. Eight cases were obtained, of which three presented with a history of IIH. Two cases were complicated by meningitis and were managed conservatively, whereas six required endoscopic skull base repair and one had a ventriculoperitoneal shunt inserted. A low threshold for high-resolution CT scanning is suggested for patients presenting with rhinorrhoea following a nasopharyngeal swab. The literature review suggests an underlying association between IIH, CSF rhinorrhoea and swab-related skull base injury. We highlight a comprehensive management pathway for these patients, including high-resolution CT with cisternography, ICP monitoring, shunt and fluorescein-based endoscopic repair to achieve the best standard of care.

Historical and future trends in emergency pituitary referrals: a machine learning analysis

PURPOSE

Acute pituitary referrals to neurosurgical services frequently necessitate emergency care. Yet, a detailed characterisation of pituitary emergency referral patterns, including how they may change prospectively is lacking. This study aims to evaluate historical and current pituitary referral patterns and utilise state-of-the-art machine learning tools to predict future service use.

METHODS

A data-driven analysis was performed using all available electronic neurosurgical referrals (2014-2021) to the busiest U.K. pituitary centre. Pituitary referrals were characterised and volumes were predicted using an auto-regressive moving average model with a preceding seasonal and trend decomposition using Loess step (STL-ARIMA), compared against a Convolutional Neural Network-Long Short-Term Memory (CNN-LSTM) algorithm, Prophet and two standard baseline forecasting models. Median absolute, and median percentage error scoring metrics with cross-validation were employed to evaluate algorithm performance.

RESULTS

462 of 36,224 emergency referrals were included (referring centres = 48; mean patient age = 56.7 years, female:male = 0.49:0.51). Emergency medicine and endocrinology accounted for the majority of referrals (67%). The most common presentations were headache (47%) and visual field deficits (32%). Lesions mainly comprised tumours or haemorrhage (85%) and involved the pituitary gland or fossa (70%). The STL-ARIMA pipeline outperformed CNN-LSTM, Prophet and baseline algorithms across scoring metrics, with standard accuracy being achieved for yearly predictions. Referral volumes significantly increased from the start of data collection with future projected increases (p < 0.001) and did not significantly reduce during the COVID-19 pandemic.

CONCLUSION

This work is the first to employ large-scale data and machine learning to describe and predict acute pituitary referral volumes, estimate future service demands, explore the impact of system stressors (e.g. COVID pandemic), and highlight areas for service improvement.

Microsurgery for intracranial aneurysms: A qualitative survey on technical challenges and technological solutions

Introduction

Microsurgery for the clipping of intracranial aneurysms remains a technically challenging and high-risk area of neurosurgery. We aimed to describe the technical challenges of aneurysm surgery, and the scope for technological innovations to overcome these barriers from the perspective of practising neurovascular surgeons.

Materials and Methods

Consultant neurovascular surgeons and members of the British Neurovascular Group (BNVG) were electronically invited to participate in an online survey regarding surgery for both ruptured and unruptured aneurysms. The free text survey asked three questions: what do they consider to be the principal technical barriers to aneurysm clipping? What technological advances have previously contributed to improving the safety and efficacy of aneurysm clipping? What technological advances do they anticipate improving the safety and efficacy of aneurysm clipping in the future? A qualitative synthesis of responses was performed using multi-rater emergent thematic analysis.

Results

The most significant reported historical advances in aneurysm surgery fell into five themes: (1) optimising clip placement, (2) minimising brain retraction, (3) tissue handling, (4) visualisation and orientation, and (5) management of intraoperative rupture. The most frequently reported innovation by far was indocyanine green angiography (84% of respondents). The three most commonly cited future advances were hybrid surgical and endovascular techniques, advances in intraoperative imaging, and patient-specific simulation and planning.

Conclusions

While some surgeons perceive that the rate of innovation in aneurysm clipping has been dwarfed in recent years by endovascular techniques, surgeons surveyed highlighted a broad range of future technologies that have the potential to continue to improve the safety of aneurysm surgery in the future.

795 Trends in Cerebrospinal Fluid Leak Rates Following the Extended Endoscopic Endonasal Approach for Anterior Skull Base Meningioma: A Meta-Analysis Over the Last 20 Years

Introduction

The extended endoscopic approach (EEA) provides direct access for resection of tuberculum sellae (TSM) and olfactory groove meningiomas (OGM) but is associated with cerebrospinal fluid (CSF) leak in up to 25% of patients. To evaluate the impact of improved skull base reconstructive techniques, we assessed published CSF leak percentages in EEA over the last two decades.

Method

Random-effects meta-analyses were performed for studies published between 2004-2020. Outcomes assessed were CSF leak, gross total resection, visual improvement, intraoperative arterial injury and 30-day mortality. For the main analyses, publications were pragmatically grouped based on publication year in three categories: 2004-2010, 2011-2015, and 2016-2020.

Results

We included 29 studies describing 540 TSM and 115 OGM patients. CSF leak incidence dropped over time from 22% (95% CI: 6-43%) in studies published between 2004 and 2010, to 16% (95% CI: 11-23%) between 2011 and 2015, and 4% (95% CI: 1-9%) between 2016 and 2020. Outcomes of gross total resection, visual improvement, intraoperative arterial injury, and 30-day mortality remained stable over time

Conclusions

We report a noticeable decrease in CSF leak over time, which might be attributed to the development of reconstructive techniques (e.g., hadad bassagasteguy flap, and gasket seal), refined multilayer repair protocols, and selected lumbar drain usage.

926 CSF Rhinorrhoea After Endonasal Intervention to The Skull Base (CRANIAL): Multicentre Pilot Study

Introduction

CRANIAL (CSF Rhinorrhoea After Endonasal Intervention to the Skull Base) is a prospective, multicentre observational study seeking to determine: the scope of skull base repair methods used, and the corresponding rates of postoperative CSF rhinorrhoea in endonasal transsphenoidal (TSA) expanded endonasal approaches (EEA) for skull base tumours.

Method

A prospective, observational cohort pilot study was carried out at eleven neurosurgical units, via NANSIG and BNTRC collaboratives.

Results

192 cases were included – 167 TSA (87%), 25 EEA (13%). The most common (MC) pathologies included: pituitary adenomas (n = 150/192), craniopharyngiomas (n = 7/192) and meningiomas (n = 4/192). The MC skull base repair techniques used were tissue glues (n = 135/192, MC Tisseel®), grafts (n = 94/192, MC fat or Spongostan™) and vascularised flap (52/192, MC nasoseptal). These repairs were most frequently supported by nasal packs (n = 127/192) and lumbar drains (n = 23/197). Biochemically confirmed CSF rhinorrhoea occurred in 10/167 (6%) TSA and 4/25 (16%) EEA. 5 cases required operative management for CSF rhinorrhoea (CSF diversion or direct repair). Qualitative feedback was largely positive (e.g., user-friendly data collection), demonstrating acceptability.

Conclusions

Our pilot experience highlights the acceptability and feasibility of CRANIAL. There is clear precedent for multicentre dissemination of this project, in order to establish a benchmark of contemporary skull base neurosurgery practice.

Second surgery for progressive glioblastoma: a multi-centre questionnaire and cohort-based review of clinical decision-making and patient outcomes in current practice

PURPOSE

Glioblastoma prognosis is poor. Treatment options are limited at progression. Surgery may benefit, but no quality guidelines exist to inform patient selection. We sought to describe variations in surgical management at progression, highlight where further evidence is needed, and build towards a consensus strategy.

METHODS

Current practice in selection of patients with progressive GBM for second surgery was surveyed online amongst specialists in the UK and Europe. We complemented this with an assessment of practice in a retrospective cohort study from six United Kingdom neurosurgical units. We used descriptive statistics to analyse the data.

RESULTS

234 questionnaire responses were received. Maintaining or improving patient quality of life was key to decision making, with variation as to whether patient age, performance status or intended extent of resection was relevant. MGMT methylation status was not important. Half considered no minimum time after first surgery. 288 patients were reported in the cohort analysis. Median time to second surgery from first surgery 390 days. Median overall survival 815 days, with no association between time to second surgery and time to death (p = 0.874).

CONCLUSIONS

This is the most wide-ranging examination of contemporaneous practice in management of GBM progression. Without evidence-based guidelines, the variation is unsurprising. We propose consensus guidelines for consideration, to reduce heterogeneity in decision making, support data collection and analysis of factors influencing outcomes, and to inform clinical trials to establish whether second surgery improves patient outcomes, or simply selects to patients already performing well.

Implementation of duty of candour within neurosurgery: a national survey and framework for improved application in clinical practice

INTRODUCTION

Statutory duty of candour was introduced in November 2014 for NHS bodies in England. Contained within the regulation were definitions regarding the threshold for what constitutes a notifiable patient safety incident. However, it can be difficult to determine when the process should be implemented. The aim of this survey was to evaluate the interpretation of these definitions by British neurosurgeons.

MATERIALS AND METHODS

All full (consultant) members of the Society of British Neurological Surgeons were electronically invited to participate in an online survey. Surgeons were presented with 15 cases and asked to decide in the case of each one whether they would trigger the process of duty of candour. Cases were stratified according to their likelihood and severity.

RESULTS

In all, 106/357 (29.7%) members participated in the survey. Responses varied widely, with almost no members triggering the process of duty of candour in cases where adverse events were common (greater than 10% likelihood) and required only outpatient follow-up (7/106; 6.6%), and almost all members doing so in cases where adverse events were rare (less than 0.1% likelihood) and resulted in death (102/106; 96.2%). However, there was clear equipoise in triggering the process of duty of candour in cases where adverse events were uncommon (0.1-10% likelihood) and resulted in moderate harm (38/106; 35.8%), severe harm (57/106; 53.8%) or death (49/106; 46.2%).

CONCLUSION

There is considerable nationwide variation in the interpretation of definitions regarding the threshold for duty of candour. To this end, we propose a framework for the improved application of duty of candour in clinical practice.

FP1-2 Implementation of duty of candor regulation within neurosurgery: a national cross-sectional survey

Objectives

Statutory Duty of Candor was introduced in 2014 for NHS bodies in England. Contained within the regulation were definitions regarding the threshold for what constitutes a notifiable patient safety incident. The aim of this survey was to evaluate the interpretation of these definitions by British neurosurgeons.

Methods

Full members of the SBNS were electronically invited to participate in an online survey. Surgeons were presented with 15 cases and asked to decide in each one whether they would trigger the process of Duty of Candor. Cases were stratified according to their likelihood and severity.

Results

In all, 106/357 (29.7%) members participated in the survey. Responses varied widely with almost no members triggering the process of Duty of Candor in cases where adverse events were likely (>10% likelihood) and required only outpatient follow up (7/106; 6.6%), and almost all members doing so in cases where adverse events were rare (<0.1% likelihood) and resulted in death (102/106; 96.2%). However, there was clear equipoise in triggering the process of Duty of Candor in cases where adverse events were unlikely (0.1%–10% likelihood) and resulted in moderate harm (38/106; 35.8%), severe harm (57/106; 53.8%), or death (49/106; 46.2%).

Conclusions

There is considerable nationwide variation in the interpretation of definitions regarding the threshold for Duty of Candor; this has important implications with some providers at risk of penalties, and others unduly burdened by the associated administrative processes.

TP1-9 Vestibular dysfunction in acute traumatic brain injury

Objectives

Vestibular dysfunction following traumatic brain injury (TBI) is a major cause of morbidity and unemployment and has impact on the patient’s ability to rehabilitate. Chronically, up to a quarter of TBI cases have cryptogenic dizziness and imbalance, possibly due to chronic brain adaptation that masks the diagnosis. Establishing the spectrum of vestibular diagnoses in acute TBI – when they may be more obvious – may aid diagnosis in chronic TBI cases.

Design

Prospective audit of referrals to specialist neuro-otology team.

Subjects

Consecutive Major Trauma Ward TBI in-patients admitted between June 2014 and May 2015.

Methods

All cases were screened by the therapists for vestibular symptoms and/or signs and referred for specialist neuro-otology review.

Results

Of 111 patients screened, 96 had features of vestibular dysfunction. Of 96 cases, SYMPTOMS (i.e. subjective report) included: – imbalance (58.3%) – headache (50%) -dizziness (40%) Of 96 cases, SIGNS (i.e. examination) included: – gait ataxia (75.5%) – broken smooth pursuit (61.2%) – positive Hallpike (51%) – positive head impulse test (18%). The data indicate that BPPV affects 49% and headache with migraine-like features affect 40.8%. Acute peripheral unilateral vestibular loss affects 18% TBI cases.

Conclusions

Vestibular dysfunction in TBI is common, typically involving peripheral and central structures, often in the same case, and requires specialist neuro-otological management.

TM1-3 Improved prediction of surgical resectability in patients with glioblastoma multiforme using an artificial neural network

Objectives

In managing a patient with glioblastoma multiforme (GBM), a surgeon must weigh up whether sufficient tumour can be removed so that the patient can enjoy the benefits of decompression and cytoreduction, without impacting on the patient’s neurological status. In a previous study we identified the five most important anatomical features on a pre-operative MRI that are predictive of surgical resectability and used them to develop a grading system. The aim of this study was to apply an artificial neural network (ANN) to improve the prediction of surgical resectability.

Methods

A prospectively maintained database was searched between February and August 2017 to identify all adult patients with supratentorial GBM that underwent resection. Pre-operative MRI scans were scored using the aforementioned grading system and post-operative scans assessed to determine the extent of resection. Performance of the standard grading system and ANN were then evaluated by analysing their Receiver Operator Characteristic curves; Area Under Curve (AUC) and accuracy were calculated and compared using the t-­test with a value of p<0.05 considered significant.

Results

In all, 47 patients were included, of which 18 (38.3%) were found to have complete excision. The AUC and accuracy were significantly greater using the ANN compared to the standard grading system (0.87 vs. 0.79 and 0.81 vs. 0.77 respectively; p<0.01 in both cases).

Conclusions

An ANN allows for improved prediction of surgical resectability in patients with GBM.

WP1-15 Computer-assisted versus manual planning for stereotactic brain biopsy: retrospective comparative pilot study

Objectives

Stereotactic brain biopsy is among the most common neurosurgical procedures. Planning a safe surgical trajectory requires careful attention to a number of features including:

traversing the skull perpendicularly;

avoiding critical neurovascular structures; and

minimising trajectory length.

The aim of this study was to develop a platform, SurgiNav, for automated trajectory planning in stereotactic brain biopsy.

Methods

A prospectively maintained database was searched between February and August 2017 to identify all adult patients that underwent stereotactic brain biopsy in whom post-operative imaging was available. In each case, the standard pre-operative T1-weighted gadolinium-enhanced MRI was used to generate models of the cortex and vasculature. A surgical trajectory was then generated using automated computer-assisted planning (CAP) and metrics compared to the trajectory of the implemented manual plan (MP) using the paired T-test.

Results

15 consecutive patients were identified; who had a diagnostic biopsy and there were no immediate complications. Feasible trajectories were generated using CAP in 12 patients, and in these the mean trajectory length using CAP was comparable to MP (31.7 mm vs. 37.1 mm; p=0.3), and mean angle was similarly perpendicular from orthogonal (9.3° vs. 15.3° p=0.1), but the risk-metric was significantly lower (0.16 vs. 0.48; p=0.03).

Conclusions

Computer-assisted planning for stereotactic brain biopsy appears feasible in most cases and may be safer in selected cases.

Bedside saccadometry as an objective and quantitative measure of hemisphere-specific neurological function in patients undergoing cranial surgery

Cranial surgery continues to carry a significant risk of neurological complications. New bedside tools that can objectively and quantitatively evaluate cerebral function may allow for earlier detection of such complications, more rapid initiation of therapy, and improved patient outcomes. We assessed the potential of saccadic eye movements as a measure of cerebral function in patients undergoing cranial surgery peri-operatively. Visually evoked saccades were measured in 20 patients before (-12 hours) and after (+2 and +5 days) undergoing cranial surgery. Hemisphere specific saccadic latencies were measured using a simple step-task and saccadic latency distributions were compared using the Kolmogorov-Smirnov test. Saccadic latency values were incorporated into an empirically validated mathematical model (Linear Approach to Threshold with Ergodic Rate [LATER] model) for further analysis (using Wilcoxon signed rank test). Thirteen males and seven females took part in our study (mean age 55 ± 4.9 years). Following cranial surgery, saccades initiated by the cerebral hemisphere on the operated side demonstrated significant deteriorations in function after 2 days (p < 0.01) that normalised after 5 days. Analysis using the LATER model confirmed these findings, highlighting decreased cerebral information processing as a potential mechanism for noted changes (p < 0.05). No patients suffered clinical complications after surgery. To conclude, bedside saccadometry can demonstrate hemisphere-specific changes after surgery in the absence of clinical symptoms. The LATER model confirms these findings and offers a mechanistic explanation for this change. Further work will be necessary to assess the practical validity of these changes in relation to clinical complications after surgery.

Is endoscopic third ventriculostomy superior to shunts in patients with non-communicating hydrocephalus? A systematic review and meta-analysis of the evidence

BACKGROUND

Endoscopic third ventriculostomy (ETV) and shunts are both utilized in the treatment of non-communicating hydrocephalus. The objective of this study was to review the evidence comparing the effectiveness of these two techniques.

METHODS

The Cochrane Central Register of Controlled Trials (CENTRAL) and Medline databases were searched between 1990 and August 2012. We included all studies comparing the failure rate of patients with non-communicating hydrocephalus treated with ETV and shunts. Two authors (HJM and FTR) appraised quality and extracted data independently.

RESULTS

Of 313 articles identified, 12 were selected for further review. Of these, 6 were included for qualitative analysis, and 5 for quantitative analysis (n = 504). ETV was associated with a non-statistically significant reduction in failure using the random-effects model (OR 0.58, 95 % CI 0.29-1.13).

CONCLUSIONS

Both ETV and shunts are associated with a relatively high failure rate. At present there is insufficient proof to unequivocally recommend one mode of treatment above the other. However, there is some evidence that ETV may confer long-term survival advantage over shunts in the treatment of non-communicating hydrocephalus, particularly in patients with certain aetiologies such as aqueductal stenosis. Prospective randomized controlled trials are currently underway and may provide more robust evidence to answer this important question and better guide future management.

Adult hydrocoele complicating a lumboperitoneal shunt

We report an adult patient who developed a right-sided hydrocoele following a lumboperitoneal shunt. While hydrocoeles have been described as a rare complication following ventriculo- and lumboperitoneal shunts in children, we are unaware of any previously reported cases of hydrocoeles resulting from such shunts in adults.

Graft aneurysm complicating an extracranial-intracranial bypass

We report a patient that developed an aneurysm on a grafted saphenous vein following an extracranial-intracranial (EC-IC) bypass. Although saphenous vein graft aneurysms (SVGAs) have been described as a rare complication following coronary surgery, we are unaware of any previously reported cases of SVGAs following EC-IC bypass.

Radiotherapy as an adjuvant in the management of intracranial meningiomas: are we practising evidence-based medicine?

Although increasingly used, the precise role of radiotherapy in the management of meningiomas is still disputed. The objective of this study, therefore, was to appraise the evidence for adjuvant radiotherapy in benign and atypical intracranial meningiomas, and to compare and contrast it with the current opinion and practice of neurosurgeons in the United Kingdom and the Republic of Ireland. The use of radiotherapy as a primary treatment strategy or its use in the treatment of recurrence was not considered. We performed a systematic review of the evidence for adjuvant radiotherapy in benign and atypical intracranial meningiomas, surveyed current opinion amongst neurosurgeons involved in such cases and ascertained local practice using data from the regional cancer registry. Overall, 10 cohorts were identified that fulfilled our eligibility criteria. Four studies showed significantly improved local control in patients receiving adjuvant radiotherapy for incompletely resected grade I meningiomas. Our survey demonstrated that the vast majority (98%) of neurosurgeons would not recommend adjuvant radiotherapy in grade I meningioma. In grade II meningioma, most (80%) would not advocate adjuvant radiotherapy if completely excised, but the majority (59%) would recommend radiotherapy in cases of subtotal resection. Significant variation in opinion between centres exists, however, particularly in cases of completely resected atypical meningiomas (p = 0.02). Data from the Eastern Cancer Registration and Information Centre appears to be in line with these findings: less than 10% of patients with grade I meningiomas, but almost 30% of patients with grade II meningiomas received adjuvant radiotherapy in the Eastern region. In conclusion, our study has highlighted significant variation in opinion and practice, reflecting a lack of class 1 evidence to support the use of adjuvant radiotherapy in the treatment of meningiomas. Efforts are underway to address this with a randomized multicentre trial comparing a policy of watchful waiting versus adjuvant irradiation.