Bayesian networks for Risk Assessment and postoperative deficit prediction in intraoperative neurophysiology for brain surgery.

PURPOSE: To this day there is no consensus regarding evidence of usefulness of Intraoperative Neurophysiological Monitoring (IONM). Randomized controlled trials have not been performed in the past mainly because of difficulties in recruitment control subjects. In this study, we propose the use of Bayesian Networks to assess evidence in IONM. METHODS: Single center retrospective study from January 2020 to January 2022. Patients admitted for cranial neurosurgery with intraoperative neuromonitoring were enrolled. We built a Bayesian Network with utility calculation using expert domain knowledge based on logistic regression as potential causal inference between events in surgery that could lead to central nervous system injury and postoperative neurological function. RESULTS: A total of 267 patients were included in the study: 198 (73.9%) underwent neuro-oncology surgery and 69 (26.1%) neurovascular surgery. 50.7% of patients were female while 49.3% were male. Using the Bayesian Network´s original state probabilities, we found that among patients who presented with a reversible signal change that was acted upon, 59% of patients would wake up with no new neurological deficits, 33% with a transitory deficit and 8% with a permanent deficit. If the signal change was permanent, in 16% of the patients the deficit would be transitory and in 51% it would be permanent. 33% of patients would wake up with no new postoperative deficit. Our network also shows that utility increases when corrective actions are taken to revert a signal change. CONCLUSIONS: Bayesian Networks are an effective way to audit clinical practice within IONM. We have found that IONM warnings can serve to prevent neurological deficits in patients, especially when corrective surgical action is taken to attempt to revert signals changes back to baseline properties. We show that Bayesian Networks could be used as a mathematical tool to calculate the utility of conducting IONM, which could save costs in healthcare when performed.

Surgery for Malignant Acute Ischemic Stroke: A Narrative Review of the Knowns and Unknowns.

Malignant acute ischemic stroke (AIS) is characterized by acute neurological deterioration caused by progressive space-occupying brain edema, often occurring in the first hours to days after symptom onset. Without any treatment, the result is often fatal. Despite advances in treatment for AIS, up to 80% of patients with a large hemispheric stroke or cerebellar stroke are at risk of poor outcome. Decompressive surgery can be life-saving in a subgroup of patients with malignant AIS, but uncertainties exist on patient selection, predictors of malignant infarction, perioperative management, and timing of intervention. Although survivors are left disabled, most agree with the original decision to undergo surgery and would make the same decision again. In this narrative review, we focus on the clinical and radiological predictors of malignant infarction in AIS and outline the technical aspects of decompressive surgery as well as duraplasty and cranioplasty. We discuss the current evidence and recommendations for surgery in AIS, highlighting gaps in knowledge, and suggest directions for future studies. KEY POINTS: · Acute ischemic stroke from occlusion of a proximal intracranial artery can progress quickly to malignant edema, which can be fatal in 80% of patients despite medical management.. · Decompression surgery is life-saving within 48 hours of stroke onset, but the benefits beyond this time and in the elderly are unknown.. · Decompressive surgery is associated with high morbidity, particularly in the elderly. The decision to operate must be made after considering the individual's preference and expectations of quality of life in the context of the clinical condition.. · Further studies are needed to refine surgical technique including value of duraplasty and understand the role monitoring intracranial pressure during and after decompressive surgery.. · More studies are needed on the pathophysiology of malignant cerebral edema, prediction models including imaging and biomarkers to identify which subgroup of patients will benefit from decompressive surgery.. · More research is needed on factors associated with morbidity and mortality after cranioplasty, safety and efficacy of implants, and comparisons between them.. · Further studies are needed to assess the long-term effects of physical disability and quality of life of survivors after surgery, particularly those with severe neurological deficits..

Buried island transposition flap for joint Plastic-Neurosurgical management of spinal wound dehiscence - a technical note and single Centre experience.

INTRODUCTION: Spinal surgical wound infection can lead to tissue voids between the spine and skin that can be difficult to reconstruct. Previously described techniques include myocutaneous flaps or perforator based fasciocutaneous flaps. However, these procedures can be time-consuming and surgically challenging. AIMS: This study aimed to assess the effectiveness of a novel technique employing a buried island transposition (BIT) flap, for the repair of non-irradiated dehisced spinal wounds. METHODS: Fifteen patients with failed conservative management of infected midline posterior spinal wounds, underwent wound repair using a local buried islanded de-epithelialized double-breasted fasciocutaneous transposition flap, performed by joint input from the neurosurgical and plastic surgical teams. RESULTS: Mean age was 58 years (range, 31-76 years) with male-to-female ratio of 8:7. The BIT flap was used to repair four wounds in the cervical spine with underlying fixation; four wounds in the thoracic spine with underlying fixation; and seven wounds in the lumbar-sacral spine, of which three had underlying fixation. Pre-operatively, each of the wounds were either dehiscent with exposed hardware, or had large defects unsuitable for primary closure following debridement. There was no procedure-related mortality. All patients demonstrated good wound healing with no subsequent repeat surgery or removal of spinal fixation at mean 24-month follow-up. CONCLUSION: We successfully used a novel buried island transposition flap that has not previously been described in repair of spinal wounds. This technique, which led in all cases to good wound healing and prevented removal of metalwork, has comparable efficacy but increased ease of use compared to traditional techniques. It requires redundant skin at the wound site.

Dural arteriovenous fistula causing reversible cognitive impairment.

A previously independent 82-year-old woman presented with 5 months of worsening confusion, mobility and cognitive decline, with deficits in orientation, language and executive function. A cerebral dural arteriovenous fistula was identified and successfully embolised, after which her cognitive ability and independence dramatically improved. Although rare, a dural arteriovenous fistula may mimic a rapidly progressive dementia, but its early recognition and treatment can completely reverse the dementia.

Medial-tonsillar telovelar approach for resection of a superior medullary velum cerebral cavernous malformation: anatomical and tractography study of the surgical approach and functional implications.

BACKGROUND: Superior medullary velum cerebral cavernous malformations pose a challenge in terms of appropriate microsurgical approach. Safe access to this deep location as well as preservation of surrounding anatomical structures, in particular the superior cerebellar peduncle just lateral to the superior medullary velum and the dentate nuclei, is paramount to achieve a good functional outcome. METHODS: Cadaveric dissections provide useful knowledge of the normal anatomy while tractography allows a better understanding of the individual anatomy in the presence of a lesion. The medial-tonsillar telovelar approach provides a feasible corridor for accessing superior velum cerebral cavernous malformations without compromising the fibres contained in the superior cerebellar peduncle. The major cerebellar efferents-cerebello-rubral, cerebello-thalamic and cerebello-vestibular tracts-and afferents, anterior spinocerebellar, tectocerebellar and trigeminocerebellar tracts, within the superior cerebellar peduncle are preserved, and the dentate nuclei are not affected. RESULTS AND CONCLUSION: A retraction-free exposure through this natural posterior fossa corridor allows the patient with the anatomical and functional subtract to make a good functional recovery by minimizing the risk of a superior cerebellar syndrome, ataxia, tremor and dysmetria; decomposition of movement in the ipsilateral extremities, nystagmus and hypotonia; or akinetic mutism, reduced or absent speech with onset within the first post-operative week.

Neurosurgery and coronavirus: impact and challenges-lessons learnt from the first wave of a global pandemic.

INTRODUCTION AND OBJECTIVES: The novel severe acute respiratory syndrome coronavirus 2 (COVID-19) pandemic has had drastic effects on global healthcare with the UK amongst the countries most severely impacted. The aim of this study was to examine how COVID-19 challenged the neurosurgical delivery of care in a busy tertiary unit serving a socio-economically diverse population. METHODS: A prospective single-centre cohort study including all patients referred to the acute neurosurgical service or the subspecialty multidisciplinary teams (MDT) as well as all emergency and elective admissions during COVID-19 (18th March 2020-15th May 2020) compared to pre-COVID-19 (18th of January 2020-17th March 2020). Data on demographics, diagnosis, operation, and treatment recommendation/outcome were collected and analysed. RESULTS: Overall, there was a reduction in neurosurgical emergency referrals by 33.6% and operations by 55.6% during the course of COVID-19. There was a significant increase in the proportion of emergency operations performed during COVID-19 (75.2% of total, n=155) when compared to pre-COVID-19 (n = 198, 43.7% of total, p < 0.00001). In contrast to other published series, the 30-day perioperative mortality remained low (2.0%) with the majority of post-operative COVID-19-infected patients (n = 13) having underlying medical co-morbidities and/or suffering from post-operative complications. CONCLUSION: The capacity to safely treat patients requiring urgent or emergency neurosurgical care was maintained at all times. Strategies adopted to enable this included proactively approaching the referrers to maintain lines of communications, incorporating modern technology to run clinics and MDTs, restructuring patient pathways/facilities, and initiating the delivery of NHS care within private sector hospitals. Through this multi-modal approach we were able to minimize service disruptions, the complications, and mortality.

Which factors influence the decision to transfer patients with traumatic brain injury to a neurosurgery unit in a major trauma network?

Objectives: Within the pan London Major Trauma System many patients with minor or non-life threatening traumatic brain injury (TBI) remain at their local hospital and are not transferred to a major trauma centre (MTC). Our aim was to identify factors that influence the decision to transfer patients with TBI to a neurosurgical centre.Methods: This is a single centre prospective cohort study of all patients with TBI referred to our neurosurgery unit from regional acute hospitals over a 4-month period (Sept 2016-Jan 2017). Our primary outcome was transferred to a neurosurgical centre. We identified the following factors that may predict decision to transfer: patient demographics, transfer distance, antithrombotic therapy and severity of TBI based on initial Glasgow Coma Scale (GCS) and Marshall CT score. A multivariable logistic regression analysis was performed.Results: A total of 339 patients were referred from regional hospitals with TBI and of these, 53 (15.6%) were transferred to our hospital. The mean age of patients referred was 70.6 years, 62.5% were men and 43% on antithrombotic drugs. Eighty-six percent of patients had mild TBI (GCS 13-15) on initial assessment and 79% had a Marshall CT score of 2. The adjusted analysis revealed only higher age, higher Marshall Score, the presence of chronic subdural haematoma (CSDH), the presence of contusion(s) and fracture(s) predicted transfer (p<.05). Subgroup analysis consistently showed a higher Marshall score predicted transfer (p<.05).Conclusions: In our cohort higher Marshall score consistently predicted transfer to our neurosurgical centre. Presenting GCS, transfer distance and antithrombotic therapy did not influence decision to transfer.

Encephaloduroateriosynangiosis (EDAS) in the management of Moyamoya syndrome in children with sickle cell disease.

BACKGROUND: Encephalo-duro-arterio-synangiosis (EDAS) in Moyamoya syndrome (MMS) treatment has been well described in the literature, however in MMS caused by sickle cell anaemia (SCA), EDAS use remains controversial with poor long-term follow-up. We present a case-series of SCA patients who have undergone EDAS for SCA-related MMS and describe their post-operative course as well as provide a literature review of the role of EDAS in the treatment of sickle cell anaemia. METHODS: A retrospective review of all the paediatric EDAS procedures conducted in our institution for SCA from 2007 to 2015. Two patients underwent behavioural screening. RESULTS: A total of eight patients with MMS secondary to SCA underwent EDAS. Unilateral EDAS was performed without complication in seven patients. One patient underwent bilateral EDAS but with a two-year gap in between procedures. Follow-up magnetic resonance angiography demonstrated no progression of Moyamoya collaterals or further ischaemic events with regression of collaterals clearly visible in one patient. All patients have demonstrated a return to normal school activities. CONCLUSIONS: EDAS is a well-tolerated revascularisation procedure for children with MMS. The prevention of further infarcts in our group with sickle cell disease has allowed these children to resume normal school activities.

Recurrent sampling and ventriculostomy-associated infections: a case-control study.

BACKGROUND: External ventricular drain (EVD) insertion is a common neurosurgical procedure with a significant risk of ventriculostomy-associated infections (VAIs), other morbidities and mortality. Several risk factors have been identified but their effect is unclear. OBJECTIVE: Our primary objective was to assess whether recurrent EVD sampling increased the risk of VAIs. The secondary objective was to explore the effect of sampling frequency, duration of EVD stay, presence of cerebrospinal fluid leak and concurrent infections. METHODS: Ours was a retrospective, single-centre, age-matched, case control study of 83 patients and 249 controls who underwent EVD insertion between 1 January 2010 - 31 December 2016. Patients with primary CNS infections, age under 1 year and death within 5 days of EVD insertion were excluded. Blinded abstractors collected all patient data through the electronic patient record system and regression analysis was used to compare the two groups. RESULTS: Sampling the EVD more than once did not increase the risk of infection (OR 0.47, 95% CI 0.27-0.83, p = 0.01). Risk factors significantly associated with VAI included CSF leak (OR 2.06, 95% CI 1.16-3.67, p = 0.01), concurrent infection (OR 1.85, 95% CI 1.09-3.16, p = 0.02), and an EVD duration of >10 days (OR 2.28, 95% CI 1.24-4.18, p = 0.01). CONCLUSION: Our findings do not support the notion that increased sampling of EVDs is associated with a higher risk of VAI. CSF leaks, concurrent infection and long-term EVDs are also statistically significant risk factors for infection.

Outcome study of the pipeline embolization device for treatment of intracranial aneurysms at a single UK institution.

BACKGROUND: The introduction of flow-diverting stents in the last decade provides an alternative endovascular treatment choice in selected intracranial aneurysms. This retrospective analysis of a UK centre's experience provides insight into clinical and radiographic outcomes. METHODS: Electronic patient records, diagnostic and procedural images and written procedural records for patients treated with the PED between August 2009 and April 2014 were reviewed. Follow-up TOF MRA was performed after treatment. Clinical and radiographic outcomes were analyzed and compared with other PED studies. RESULTS: Twenty-nine patients with 30 attempted PED treatments were reviewed representing 3.5% of the treated aneurysm patient cohort. 63.6% (21/33) of the aneurysms were wide-necked (>4 mm), 60.6% (20/33) were large or giant (≥10 mm). The mean aneurysm sac diameter was 12.0 mm; the mean neck width was 4.5 mm. Mortality and morbidity rates were 3.3% and 10.0%, respectively. The total adequate occlusion rate was 78.1% (25/32) at 18 months. The neck width of aneurysms with residual sac filling and complete occlusion differed significantly (p = 0.04). CONCLUSIONS: Highly selected aneurysms treated with a PED in a UK centre have similar occlusion and complication rates when compared to non-UK studies. Again, it appeared that delayed aneurysm rupture remained a risk for PED treatment in large or giant aneurysms. Follow-up with TOF MRA gave similar occlusion results compared to those obtained with DSA in other studies. The influence of neck size on occlusion rate should be examined in future PED studies.

Intracranial Aneurysms in Sickle-Cell Disease Are Associated With the Hemoglobin SS Genotype But Not With Moyamoya Syndrome.

BACKGROUND AND PURPOSE: Intracranial aneurysms and aneurysmal subarachnoid hemorrhage may occur more frequently in sickle-cell disease (SCD), and this could be related to the sickle genotype and moyamoya syndrome seen in SCD. METHODS: Records from a total of 1002 patients with SCD attending 2 specialized adult hematologic services were retrospectively reviewed. We analyzed data of a cohort of 767 patients attending 1 SCD clinic between 2002 and 2013 and of 235 patients from the other clinic who have had neurovascular imaging between 2007 and 2014. RESULTS: We identified 4 patients in the cohort who had an aneurysmal subarachnoid hemorrhage during 9063 patient-years. The highest incidence rate was seen among women in the age group 30 to 39 years with the hemoglobin SS (HbSS) genotype (440 per 100 000 patient-years). Unruptured intracranial aneurysms were found in 20 of the 324 patients, who had imaging data; the prevalence was significantly higher in patients with HbSS genotype compared with other sickle genotypes with the highest prevalence (15%) observed in women in the age group 30 to 39 years. Fifty-one HbSS patients had a moyamoya vasculopathy, but only 3 of these had concomitant intracranial aneurysms. CONCLUSIONS: Intracranial aneurysms are common in HbSS SCD. There was also a trend toward more common occurrence of aneurysmal subarachnoid hemorrhage in HbSS; women in the age group 30 to 39 years were most at risk. There was no correlation between the occurrence of intracranial aneurysms and moyamoya syndrome.

Moyamoya angiopathy - Is there a Western phenotype?

Moyamoya disease (MMD) is a chronic cerebrovascular disease involving progressive bilateral stenosis of the intracranial segments of the internal carotid arteries. It results in the development of a rich, but friable collateral supply, prone to rupture. The disease is well described in Japanese literature and was originally thought to be a predozminantly Eastern disease. However, the recent literature describes a Western phenotype that may present with a different clinical course. This review aims to describe the variations in the epidemiology of the MMD between Eastern and Western populations, the possible reasons for them and highlight their implications for clinical practise and future research.

Detection of spreading depolarization with intraparenchymal electrodes in the injured human brain.

BACKGROUND: Spreading depolarization events following ischemic and traumatic brain injury are associated with poor patient outcome. Currently, monitoring these events is limited to patients in whom subdural electrodes can be placed at open craniotomy. This study examined whether these events can be detected using intra-cortical electrodes, opening the way for electrode insertion via burr hole. METHODS: Animal work was carried out on adult Sprague-Dawley rats in a laboratory setting to investigate the feasibility of recording depolarization events. Subsequently, 8 human patients requiring craniotomy for traumatic brain injury or aneurysmal subarachnoid hemorrhage were monitored for depolarization events in an intensive care setting with concurrent strip (subdural) and depth (intra-parenchymal) electrode recordings. RESULTS: (1) Depolarization events can be reliably detected from intra-cortically placed electrodes. (2) A reproducible slow potential change (SPC) waveform morphology was identified from intra-cortical electrodes on the depth array. (3) The depression of cortical activity known to follow depolarization events was identified consistently from both intra-cortical and sub-cortical electrodes on the depth array. CONCLUSIONS: Intra-parenchymally sited electrodes can be used to consistently identify depolarization events in humans. This technique greatly extends the capability of monitoring for spreading depolarization events in injured patients, as electrodes can be sited without the need for craniotomy. The method provides a new investigative tool for the evaluation of the contribution of these events to secondary brain injury in human patients.

Intraoperative indocyanine green video-angiography as an aid to the microsurgical treatment of spinal vascular malformations.

AIMS AND OBJECTIVES. Intra-operative Indocyanine Green (ICG) video-angiography (ICG-VA) has become an established aid to cerebrovascular surgery. We describe our experience using this technique to define angio-architecture intraoperatively in a range of spinal vascular malformations. METHODS. A retrospective review of notes and imaging was carried out from a prospectively maintained database. Our series comprises 27 patients who underwent surgical treatment between September 2007 and August 2012. We carried out a retrospective review of data from a prospectively maintained database. RESULTS. For slow-flow Type 1 fistulae the ICG videoangiogram demonstrated conclusively that the arteriovenous shunt was obliterated. This is a consideration on the rare occasions where a second fistula is present, an example of which is included in this series. ICG-VA also helps to demonstrate normal vascular anatomy and distinguish these vessels from pathology. For Type II lesions it allowed orientation to the vascular anatomy as demonstrated by the pre-operative angiogram. In one of two cases in this series it ensured to the complete extirpation of a large arteriovenous malformation (AVM). However a second Type II case demonstrated its limitations, as a diffuse intramedullary component could not be identified. Two cases were explored where digital subtraction spinal angiography was not possible and incomplete understanding of the angio-architectures of the lesions were available from Time Resolved dynamic magnetic resonance angiography and/or multi-detector CT angiography. ICG-VA provided invaluable information on alterations in arterio-venous flow that allowed diagnosis and obliteration of the arteriovenous shunts in each case. DISCUSSION. ICG video-angiography is a time-efficient and safe alternative to intra-operative spinal angiography. It provided useful information on haemodynamic changes intraoperatively and completeness of treatment. We discuss its limitations and role in the management of these lesions.