Peripartum haemorrhage from an intramedullary conus medullaris cavernous malformation: a rare but serious complication

Cavernous malformations (CMs) represent about 5% of all spinal intramedullary lesions in adults. There is growing evidence to suggest that pregnancy may increase the risk of haemorrhage from CMs. We report the case of a 28-year-old woman who presented with bilateral lower limb paraparesis following an intramedullary haemorrhage from conus medullaris CM during the peripartum period. To the best of our knowledge, this is the first such case. We also review a handful of other reported cases of peripartum symptomatic spinal intramedullary CMs from the literature highlighting the pathogenesis of such cases and the best timing for intervention.

P16.03.A Epithelioid gliobastoma requires rapid treatment and BRAF inhibitors should be made readily available for their treatment

Background

Epithelioid glioblastoma is a rare subtype of Glioblastoma. We examine two cases who presented acutely with symptoms of headache, neck stiffness and an eye squint. The purpose of this case review is to look at their management, the spread of the disease and propose the availability of BRAF inhibiting agents be made readily available for this subtype.

Material and Methods

The clinical records including pathology and surgical reports, multi-disciplinary team meeting documents, oncology plans and inpatient notes have all been reviewed alongside the literature on epithelioid GBM and BRAF V600e mutations and inhibitors.

Results

Patients were females aged 25 and 32 presenting with acute onset headache and neck stiffness to emergency Department. The 25 year old had developed a right eye squint within seven days of the other symptoms, her tumour was right frontal with midline shift. The 32 year old had symptoms for 10 days prior to presentation, the tumour was right temporal. They both underwent craniotomies. The frontal tumour was totally resected, while the temporal lobe tumour was haemorrhagic in nature and minimally de-bulked. Pre-operative stealth imaging showed that there had been an increase in the size of the temporal lesion in the fourteen days since presentation. Histology proved these to be epithelioid GBM’s with BRAF V600e mutations, IDH wild-type and TERT promoter mutant. Full pathology reports with molecular markers were available within ten days. The frontal lobe patient began chemo-radiation sixteen days from her surgical date. On day two she was admitted with severe headache and nausea. She became agitated, confused, and transferred back to the neurosurgery unit for management of hydrocephalus. She was diagnosed with PRES and simultaneously treated for this and hydrocephalus. Clinically she suffered storming, passing away exactly eight weeks from presentation. Seven days after surgery the temporal lobe tumour patient suffered a seizure and admitted for symptom management and expedite oncology treatment. She passed away six days later suffering continual neurological deterioration and the tumour progression with leptomeningeal spread. This was exactly four weeks from initial presentation.

Conclusion

The prognosis for epithelioid Glioblastoma is limited to weeks to short months. Extent of resection in these case studies demonstrates benefit in delaying progression though it is clear that time is of the essence from presentation, to surgery, to adjuvant treatment. Neither of these tumours were methylated meaning the standard treatment for glioblastoma is likely to lack efficacy. BRAF inhibitors should be made readily available for this rare sub-type to commence treatment expediently. Both patients suffered distressing neurological symptoms in their final days which require expert management and are best managed in a neurosurgical centre.

P11.06.A benefits of carbohydrate loading drinks pre-operatively for patients with a presumed high-grade glioma planned for an awake craniotomy

Background

As part of enhanced recovery after surgery in neuro oncology, carbohydrate loading drinks were reviewed to see if there were any benefits in administering this pre operatively, in particularly for patients for awake craniotomy electively. This method is currently used in colorectal and spinal teams within the trust. Carbohydrate loading drinks are clear, and can be consumed up to 2 hours before induction of anaesthesia. Currently reviewed for patients for awake craniotomy with the vision to implement for all patients planned for craniotomy, both asleep and awake. The concept of this drink, is that it helps with post-operative nausea and vomiting , insulin resistance, helps with energy boost which is helpful during awake craniotomies and potentially during their engagement with therapists post operatively and wound healing (Hausel J et al, 2005). This could essentially lead to safer discharge, reduced risk of wound infection and reduced length of stay.

Material and Methods

In a single centre, data for patients who have undergone awake craniotomies this year were abstracted. Patients planned for an awake surgery were prescribed carb-loading drinks. Due to the start date of this study, there were already a number of patients who have had their awake craniotomies without having carb-loading drinks prescribed. The data for both cohorts enabled comparison on engagement during and after awake craniotomies with therapists and length of stay.

Results

The current data collected has found that the average length of stay in the group who were not prescribed carbohydrate loading drinks pre operatively, had an average length of stay 7.2 days in total, 50% had experienced nausea and vomiting post operatively, which led therapists unable to perform assessments. 66% of patients in this group were found to have some form of difficulties engaging with the therapists during the awake phase of their craniotomies. Compared with patients who were prescribed the carbohydrate loading drink, the average length of stay was 4.6 days, with no post operative nausea and vomiting, no difficulties engaging with therapists post operatively.

Conclusion

Though the current data is of a small volume, carbohydrate loading pre-operatively can help patients for elective awake craniotomies and reduce length of stay in hospital, optimising their recovery in a fast yet safe manner to ensure they are in the best performance status prior to commencing oncology treatment. With further analysis into the use of carb-loading drinks pre-operatively, this can be used widely within neuro-oncology surgeries.

Hausel J, Nygren J, Thorell A et al Randomized clinical trial of the effects of oral preoperative carbohydrates on postoperative nausea and vomiting after laparoscopic cholecystectomy. Br J Surg 2005; : 415-421. [PubMed] [Google Scholar]

OS07.2.A Evaluation of Intraoperative Surgical Adjuncts and Resection of Glioblastoma (ELISAR GB): A UK and Ireland multicentre, prospective observational cohort study

Background

Despite operative and adjuvant therapies, glioblastoma remains incurable, with the extent of resection being one of few treatments that can improve survival. To improve resection, operative adjuncts are used, with neuronavigation and 5-aminolevulinic acid (5-ALA) recommended as a standard of care in those aimed for maximal safe resection. Despite the standards, meta-analysis concluded that the impact of 5-ALA on the extent of surgical resection is of low quality due to bias in reporting tumour location and additional image guidance used, factors impacting on extent of resection as well as short-term neurological outcomes being uncertain. Therefore we aimed to evaluate the availability and use of 5-ALA and other adjuncts and compare surgical outcomes of 5-ALA-guided versus non-5-ALA-guided resections.

Material and Methods

A multicenter prospective observational cohort study was conducted across 27 out of 31 available centres in the UK and Ireland from 6 January until 19 March 2020. Inclusion criteria included adults with first diagnosis, supratentorial glioblastoma undergoing resection. Primary outcomes included: i) the availability and use of surgical adjuncts and ii) complete resection of enhancing tissue (CRET). Secondary outcomes included adverse events, new onset of postoperative neurological deficit and post-operative neurological function. Descriptive and inferential statistics were used for analysis with a p-value <0.05 deemed significant.

Results

232 consecutive cases were identified. 142/232 cases were aimed for maximal safe resection subsequently divided into 5-ALA-guided (n=92) versus non-5-ALA-guided (n=50) resections. 5-ALA and neuronavigation were available across all centres. Neuronavigation and 5-ALA were used in 91% (n=129/142) and 65% (n=92/142) of cases aimed for maximal safe resection whereas 83% (n=75/90) and 49% (n=44/90) for debulk surgery. 35 unique combinations of surgical adjuncts were used in 232 operations. 5-ALA-guided resection yielded a higher percentage of CRET than without (55% versus 28%, p < 0.01). The two groups showed no difference in adverse events (p=0.98), new onset of neurological deficit (p=0.88) nor neurological function (p=0.7). A logistic regression analysis showed that 5-ALA was an important predictor of CRET regardless of additional adjuncts used (OR 2.4, CI 0.96-5.97, P = 0.05), tumour location and molecular characterisation (OR 3.48, CI 1.61-7.51, P <0.01).

Conclusion

Firstly, we showed that 5-ALA is not always used for glioblastoma aimed for CRET. Secondly, we report a great heterogeneity of adjuncts used for resection, possibly explained by a lack of high-quality evidence and surgeon training. Thirdly we demonstrate that 5-ALA-guided resection leads to higher percentage of CRET regardless of other adjuncts used, tumour location and molecular characterisation.

OS08.6.A Glioblastoma treatment response machine learning monitoring biomarkers: a systematic review and meta-analysis

BACKGROUND

The aim of the systematic review was to assess recently published studies on diagnostic test accuracy of glioblastoma treatment response monitoring biomarkers in adults, developed through machine learning (ML).

MATERIAL AND METHODS

PRISMA methodology was followed. Articles published 09/2018-01/2021 (since previous reviews) were searched for using MEDLINE, EMBASE, and the Cochrane Register by two reviewers independently. Included study participants were adult patients with high grade glioma who had undergone standard treatment (maximal resection, radiotherapy with concomitant and adjuvant temozolomide) and subsequently underwent follow-up imaging to determine treatment response status (specifically, distinguishing progression/recurrence from progression/recurrence mimics - the target condition). Risk of bias and applicability was assessed with QUADAS 2. A third reviewer arbitrated any discrepancy. Contingency tables were created for hold-out test sets and recall, specificity, precision, F1-score, balanced accuracy calculated. A meta-analysis was performed using a bivariate model for recall, false positive rate and area-under the receiver operator characteristic curve (AUC).

RESULTS

Eighteen studies were included with 1335 patients in training sets and 384 in test sets. To determine whether there was progression or a mimic, the reference standard combination of follow-up imaging and histopathology at re-operation was applied in 67% (13/18) of studies. The small numbers of patient included in studies, the high risk of bias and concerns of applicability in the study designs (particularly in relation to the reference standard and patient selection due to confounding), and the low level of evidence, suggest that limited conclusions can be drawn from the data. Ten studies (10/18, 56%) had internal or external hold-out test set data that could be included in a meta-analysis of monitoring biomarker studies. The pooled sensitivity was 0.77 (0.65–0.86). The pooled false positive rate (1-specificity) was 0.35 (0.25–0.47). The summary point estimate for the AUC was 0.77.

CONCLUSION

There is likely good diagnostic performance of machine learning models that use MRI features to distinguish between progression and mimics. The diagnostic performance of ML using implicit features did not appear to be superior to ML using explicit features. There are a range of ML-based solutions poised to become treatment response monitoring biomarkers for glioblastoma. To achieve this, the development and validation of ML models require large, well-annotated datasets where the potential for confounding in the study design has been carefully considered. Therefore, multidisciplinary efforts and multicentre collaborations are necessary.

Machine learning and glioma imaging biomarkers

AIM

To review how machine learning (ML) is applied to imaging biomarkers in neuro-oncology, in particular for diagnosis, prognosis, and treatment response monitoring.

MATERIALS AND METHODS

The PubMed and MEDLINE databases were searched for articles published before September 2018 using relevant search terms. The search strategy focused on articles applying ML to high-grade glioma biomarkers for treatment response monitoring, prognosis, and prediction.

RESULTS

Magnetic resonance imaging (MRI) is typically used throughout the patient pathway because routine structural imaging provides detailed anatomical and pathological information and advanced techniques provide additional physiological detail. Using carefully chosen image features, ML is frequently used to allow accurate classification in a variety of scenarios. Rather than being chosen by human selection, ML also enables image features to be identified by an algorithm. Much research is applied to determining molecular profiles, histological tumour grade, and prognosis using MRI images acquired at the time that patients first present with a brain tumour. Differentiating a treatment response from a post-treatment-related effect using imaging is clinically important and also an area of active study (described here in one of two Special Issue publications dedicated to the application of ML in glioma imaging).

CONCLUSION

Although pioneering, most of the evidence is of a low level, having been obtained retrospectively and in single centres. Studies applying ML to build neuro-oncology monitoring biomarker models have yet to show an overall advantage over those using traditional statistical methods. Development and validation of ML models applied to neuro-oncology require large, well-annotated datasets, and therefore multidisciplinary and multi-centre collaborations are necessary.

P11.49 An electrophysiological signature of glioma infiltration in the ex vivo human brain

BACKGROUND

Invading glioma cells affect the physiological function of the peritumoural cortex. This may manifest clinically as seizures. Here, we investigate the effect the invading glioma cells on the electrophysiological signalling of the peritumoral cortex using living human brain tissue donated by people having a craniotomy for glioma resection (REC approval, 18/SW/002).

MATERIAL AND METHODS

The brain tissue was cut into thin slices, which preserved the architecture of the glioma and the adjacent healthy brain. The brain slices were incubated in 5-aminolevulinic acid to make the glioma cells fluorescent. We observed 5-ALA induced fluorescence in both low-grade and high-grade gliomas. This enabled us to make electrophysiological recordings of brain activity across the boundary between glioma and brain.

RESULTS

We recorded from brain slices of 5 participants with glioblastoma and 4 participants with oligodendroglioma (WHO grade II - III). Spontaneous “seizure-like” discharges were recorded in brain slices from 5/8 participants (3 GBM, 2 oligodendroglioma) who reported seizures and from one participant (GBM) who had not had any clinical seizures. Further analysis of the electrical discharges revealed that they could be subdivided into two distinct types based on the major frequencies in the discharge.

CONCLUSION

We concluded that human brain slices from people with either a low-grade or a high-grade glioma can generate spontaneous seizure-like discharges. This electrophysiological signature will be compared to infiltration and grade of the glioma cells in the donated sample. The living human brain tissue preparation gives us a platform to study the mechanisms of tumour-associated seizures and how abnormal neural activity affects glioma growth.

ATRX immunohistochemistry can help refine 'not elsewhere classified' categorisation for grade II/III gliomas

Purpose: The 2016 WHO tumour classification highlights the role of IDH1/2 gene mutation and 1p/19q co-deletion in classifying grade II/III gliomas. A recent cIMPACT-NOW update proposes the use of the term 'Not Elsewhere Classified' (NEC) for IDH-mutant, non co-deleted tumours. Here we show how the incorporation of ATRX immunohistochemistry can be used to better delineate the NEC group. Methods: Clinical data was collected for 112 patients (59% male) treated at our unit. Mutations in IDH1/2 genes were detected by pyrosequencing or immunohistochemistry, 1p/19q co-deletion was assessed with fluorescence in situ hybridisation and ATRX status was determined using immunohistochemical techniques. Tumours were grouped on the basis of molecular markers and outcomes compared. Results: The mean age of diagnosis was 42.6 years (20-73 years). There were 88 oligodendrogliomas (II = 47, III = 41), 18 diffuse astrocytomas (II = 9, III = 9) and 6 oligoastrocytomas (II = 4, III = 2). The majority of gliomas (87.5%) had mutations in IDH1/2. 1p/19q co-deletion was significantly associated with oligodendroglial morphology (p = < 0.001) and was mutually exclusive with ATRX mutation. Classification on the basis of molecular information showed a significant different in survival between the groups. Conclusions: ATRX immunohistochemisty is a useful adjunct which can be used with IDH mutation status, 1p/19q co-deletion and histological findings to further define tumour groups. More work is needed to understand the molecular profiles and prognostic implications for non co-deletion, ATRX preserved cases.

P6 The use of 5-ALA fluorescence in excision of supratentorial endodermal cyst

Objectives

The first documented use of 5-ALA in the excision of an intraparenchymal endodermal cyst.

Design

Case review.

Subjects

52 year old female presented with headaches, progressive right sided hemiparesis and anomic aphasia. She had a large cystic frontal lesion, adjacent of the frontal horn of the lateral ventricles cyst which did not show any nodular or solid component, and did not enhance with gadolinium.

Methods

Case report and review of the literature.

Results

5-ALA assisted, image guided fenestration of the cystic lesion and insertion of a ventricular catheter connected to an Ommaya reservoir was performed. The cyst wall was observed under the microscope and it fluoresced with 5-ALA. Multiple biopsies were obtained from this tissue, which confirmed diagnosis of endodermal cyst. The patient had improvement in clinical symptoms and size of the cyst radiologically in both the immediate post-operative period and the 6 months follow up.

Conclusions

Previous reports described the use of 5-ALA to identify tumour cells within the solid component of cystic haemangioblastomas as well as in cystic ependymomas where the cystic component does not fluoresce. In our patient, the homogeneous fluorescence of the wall suggested that this was indeed a different entity from a haemangioblastoma or an ependymoma because of the different pattern of fluorescence observed. 5-ALA-assisted resection of cystic lesions should be considered when a tumoral origin is uncertain.

WP1-17 Risk factors and patterns of progression in a surgical cohort of low grade glioma patients

Objectives

To understand the risk factors for and patterns of progression of low grade glioma (LGG).

Design

Single centre retrospective cohort study.

Subjects

Patients undergoing at least two neurosurgical procedures for LGG, the first being for diffuse LGG (WHO 2). 22 patients included (14M; 8F); mean age at time of first operation 37.7±2.7 years. 20 patients had a Performance Status (PS) 0–1 and 2 patients had a PS 2.

Methods

All patients with LGG diagnosed in between 2009–2018 were retrospectively evaluated. Variables of interest included demographics, staging, performance status, time to re-operation (TTR), extent of resection, molecular genetics (1p19q co-deletion, IDH status). Tumour volumes were estimated from MRI images by the validated ABC/2 equation. Statistical analyses were performed by Stata13.0.

Results

The tumour progressed in WHO grade in 18 patients (WHO grade 3 (n=15); WHO grade 4 (n=3). Mean time to re-operation after the first surgery was 7.0±1.2 years following gross total resection (GTR) and 3.2±0.7 years following subtotal resection (STR). Non-adjusted analysis of risk factors for time to re-operation (TTR) showed absence of 1p19q co-deletion as a risk factor (p=0.021). Adjusted analysis revealed that GTR, 1p19q mutation, PS 0 at 1 st surgery and tumour volumetric change decrease the risk for re-intervention (p<0.05). Chemo-radiotherapy was not associated with TTR.

Conclusions

In our cohort, TTR in LGG was influenced by the amount of initial resection, 1p19q deletion, PS and post-operative volumetric change.

WP1-18 Risk factors and patterns of recurrence of low grade glioma: a systematic review

Objectives

To review the risk factors and patterns of progression/recurrence of low grade glioma (LGG).

Design

Systematic review of the published literature.

Subjects

Inclusion criteria were peer reviewed publications of cohort studies of recurrent/progressive LGG. Studies of wider populations were included if relevant LGG data could be analysed separately.

Methods

Medline and Cochrane databases were searched using MeSH and non-MeSH terms, including ‘glioma’, ‘astrocytoma’, ‘oligoastrocytoma’, ‘diffuse glioma’, ‘oligodendroglioma’, ‘low grade’ and ‘disease recurrence’ by two independent reviewers.

Results

Overall, 917 studies were screened, of which 57 studies met the inclusion criteria. The most frequently described risk factor for recurrent LGG was suboptimal extent of resection (EOR) of the initial tumour (in 20 studies); recurrence was also associated with the patient’s age (2), tumour location (4), neurological status (3), tumour volume (6), bihemispherical tumour (3) and astrocytic histology (6). IDH mutation was associated with recurrence in 1 out of 3 studies, but TP53 mutation (2 of 4) and MGMT methylation status (4) were not. Malignant transformation was associated with TP53 mutations (3), IDH mutation (1) and EOR (1). Favourable progression free survival (PFS) and/or overall survival (OS) were associated with greater EOR (16), oligodendroglioma histology (2 of 4), initial KPS (3) and the use of adjuvant therapies (9 of 14). IDH mutation was associated with improved PFS and OS (3 of 4). TP53 mutation improved PFS in 1 of 3 studies. MGMT methylation and 1 p/19q codeletion may predict treatment response but their effects on survival are unclear.

Conclusions

Astrocytoma histology, IDH and TP53 mutation statuses and surgical treatment (EOR) are essential in determining the time to recurrence or progression in LGG.

FP1-6 Factors influencing clinician’s participation in neurosurgical research – a multicentre cross-sectional study

Objectives

Research remains a foundation in advancing the field of neurosurgery. We explore attitudes and perceived barriers to conducting research in neurosurgery globally.

Design

A 29-item questionnaire, consisting of multiple-choice questions, Likert scales and short answers.

Subjects

Clinicians at various stages of the Neurosurgical career.

Methods

The questionnaire was distributed through the Society of British Neurological Surgeons (SBNS) and European Association of Neurosurgical Societies (EANS).

Results

A total of 324 responses from 29 countries consisted of Clinical Fellows (n=26), Junior Trainees (n=48), Senior Trainees (n=46), Sub-specialty Fellows (n=18), Consultants (n=128) and Professors of Neurosurgery (n=58). Whilst 83% of participants believe research is a crucial aspect of a neurosurgeons’ career, only a third (33%) believed that neurosurgery as a speciality fosters a culture that promotes research. The top three perceived barriers to conducting research were lack of time (78%), insufficient access to funding (58%) and lack of mentorship (49%). Despite these, more than 87% of participants are interested in formal academic roles with 58% willing to interrupt clinical training to pursue research opportunities. The region of clinical practice had no correlation with respondents’ research output or their perceptions towards research barriers.

Conclusions

This study identified important barriers to research, elucidating which, allows the neurosurgical community to improve integration of research into clinical practice.

FM2-7 Paediatric robot-assisted DBS surgery: electrode problems and revision techniques

Objectives

We review our cases of hardware problems requiring revision surgery and consider the technical aspects of revising the electrodes, including a frameless technique using the Renishaw Guide tubes.

Design

Retrospective Review.

Subjects

Children (≤18 years old) who presented with hardware problems following implantation of a DBS for dystonia at King’s College Hospital between May 2005 and April 2018.

Methods

Information was obtained from a prospectively kept database.

Results

Of 166 paediatric patients with DBS, 25 patients had hardware problems, and of these 21 (13%) patients had specifically electrode problems requiring replacement/revision of one or more electrodes. 7 patients had high impedances requiring revision, without obvious lead migration of fracture. 7 patients had lead migration and a further 7 patients had a lead fracture with or without lead migration. 15 patients had original DBS insertion with the Leksell Stereotactic System utilising the Medtronic Stimlock for lead fixation. 6 patients had DBS inserted with the Renishaw Sterotactic Robot and utilised the Renishaw Guide Tubes, in these patients who required lead replacement it was possible to revise the electrode without using stereotactic apparatus. As the guide tubes are implanted in the correct trajectory it is possible to measure the distance required to advance/implant the lead within this to target without the need for full stereotactic reimplantation.

Conclusions

Electrode dysfunction is relatively common in children with DBS and a systematic approach is required to identify the cause. When an electrode requires repositioning or replacement, the procedure can be performed in the conventional manner with a stereotactic frame, or freehand without a frame if a Renishaw Guide tube is used at time of first insertion.

Surgery in space

Background

There has been renewed public interest in manned space exploration owing to novel initiatives by private and governmental bodies. Long-term goals include manned missions to, and potential colonization of, nearby planets. Travel distances and mission length required for these would render Earth-based treatment and telemedical solutions unfeasible. These issues present an anticipatory challenge to planners, and novel or adaptive medical technologies must therefore be devised to diagnose and treat the range of medical issues that future space travellers will encounter.

Methods

The aim was to conduct a search of the literature pertaining to human physiology, pathology, trauma and surgery in space.

Results

Known physiological alterations include fluid redistribution, cardiovascular changes, bone and muscle atrophy, and effects of ionizing radiation. Potential pathological mechanisms identified include trauma, cancer and common surgical conditions, such as appendicitis.

Conclusion

Potential surgical treatment modalities must consist of self-sufficient and adaptive technology, especially in the face of uncertain pathophysiological mechanisms and logistical concerns.

Relationships between deep brain stimulation and impulse control disorders in Parkinson's disease, with a literature review

Impulse control disorders (ICDs) are behavioural/neuropsychiatric complications of the pharmacological treatment of Parkinson's disease. Long term motor complications of PD can be effectively treated using deep brain stimulation (DBS) of subcortical nuclei. The relationships between ICDs and DBS treatment of the motor complications of Parkinson's disease remain unclear. We describe 50 consecutive patients in whom detailed neuropsychiatric assessments were performed as part of our routine pre-operative assessment. Eight had current or past ICDs during pre-operative assessment. These patients were more likely to be male and were younger than those without ICDs. Other psychosocial variables did not predict the presence of ICDs. Detailed neuropsychological examination failed to show any between-group differences. Our prevalence rate of 16% helps raise awareness of ICDs in this specialised clinic population and may reflect common denominators between significant motor fluctuations and dopaminergic drug - related behavioural disturbances. Four patients were deemed suitable for surgery after multi-disciplinary assessment. One had re-emergence of his ICD 18 months post-operatively, the ICD having resolved in the first 18 months. We also review published literature and the evidence regarding post-operative outcomes. We recommend the routine pre-operative examination of patients for psychopathology and emphasize the importance of post-operative psychiatric surveillance.

Deep brain stimulation can suppress pathological synchronisation in parkinsonian patients

BACKGROUND

Although deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a highly effective therapeutic intervention in severe Parkinson's disease, its mechanism of action remains unclear. One possibility is that DBS suppresses local pathologically synchronised oscillatory activity.

METHODS

To explore this, the authors recorded from DBS electrodes implanted in the STN of 16 patients with Parkinson's disease during simultaneous stimulation (pulse width 60 μs; frequency 130 Hz) of the same target using a specially designed amplifier. The authors analysed data from 25 sides.

RESULTS

The authors found that DBS progressively suppressed peaks in local field potential activity at frequencies between 11 and 30 Hz as voltage was increased beyond a stimulation threshold of 1.5 V. Median peak power had fallen to 54% of baseline values by a stimulation intensity of 3.0 V.

CONCLUSION

The findings suggest that DBS can suppress pathological 11-30 Hz activity in the vicinity of stimulation in patients with Parkinson's disease. This suppression occurs at stimulation voltages that are clinically effective.

Deep brain stimulation of the subthalamic nucleus in Parkinson's Disease 1993 – 2003: where are we 10 years on?

Since its advent in 1993, high frequency stimulation (HFS) of the subthalamic nucleus (STN) has rapidly developed into the most commonly practiced surgical procedure for the treatment of Parkinson's Disease (PD). Although its exact mechanism of action, be it through an inhibitory depolarization block, desynchronization of neuronal circuits or other means, is not clear, the efficacy and safety of the technique are now well established. HFS of the STN improves the motor function by at least 60%, drastically reduces the levodopa requirement and significantly improves the quality of life in PD. This review updates the recent concepts on the pathophysiology of PD and analyses the basic science principles underlying the clinical practice of the STN HFS. The evolution of the surgical technique and long-term patients' outcome are further discussed.

Meningeal melanocytoma: clinical features and review of the literature

A case of meningeal melanocytoma in the posterior fossa of a 16-year-old male is reported. Computed tomographic and magnetic resonance imaging features are presented. Pathological investigation including light and electron microscopy, and immunohistochemical staining are discussed. Current literature is reviewed and differentiating criteria from meningioma and other pigmented tumours of the nervous system are discussed.

Evolution in practice: how has British neurosurgery changed in the last 10 years?

INTRODUCTION

Neurosurgery is a fast-evolving surgical subspecialty driven by technological advances, socio-economic factors and patient expectations. In this study, we have compared the work-load volume in a single institution in the years of 1994 and 2004 and commented on the possible reasons for the changes and the impacts they may have for the future.

PATIENTS AND METHODS

A retrospective, log-book review of all operations performed in the years 1994 and 2004 in a single, tertiary, neurosurgical centre was performed.

RESULTS

Neurosurgical practice has evolved over this period. Current practice has moved away from clipping of aneurysms and towards coil embolisation performed by interventional radiologists. Electrode stimulation of deep brain regions for movement disorders is the current practice, whereas 10 years ago the same disorders were dealt with by lesioning of the relevant regions. In spinal neurosurgery, instrumentation is increasingly favoured currently. In the field of neuro-oncology, current practice favours minimal access to the target area by the use of stereotactic localisation.

CONCLUSIONS

Changes were most pronounced in the subspecialties of vascular, functional and spinal neurosurgery within this 10-year period. Knowledge of such dynamics is valuable in health resource management as well as planning for neurosurgical training programmes.

Effect of electrode contact location on clinical efficacy of pallidal deep brain stimulation in primary generalised dystonia

OBJECTIVES

To determine the effect of electrode contact location on efficacy of bilateral globus pallidus internus (GPi) deep brain stimulation (DBS) for primary generalised dystonia (PGD).

SUBJECTS AND METHODS

A consecutive series of 15 patients with PGD (10 females, mean age 42 years, seven DYT1) who underwent bilateral GPi DBS, were assessed using the Burke-Fahn-Marsden (BFM) dystonia scale before and 6 months after surgery. The position of the stimulated electrode contact(s) was determined from the postoperative stereotactic MRI. Contralateral limb and total axial BFM subscores were compared with the location of the stimulated contact(s) within the GPi.

RESULTS

The mean total BFM score decreased from 38.9 preoperatively to 11.9 at 6 months, an improvement of 69.5% (p<0.00001). Cluster analysis of the stimulated contact coordinates identified two groups, distributed along an anterodorsal to posteroventral axis. Clinical improvement was greater for posteroventral than anterodorsal stimulation for the arm (86% vs 52%; p<0.05) and trunk (96% vs 65%; p<0.05) and inversely correlated with the y coordinate. For the leg, posteroventral and anterodorsal stimulation were of equivalent efficacy. Overall clinical improvement was maximal with posteroventral stimulation (89% vs 67%; p<0.05) and inversely correlated with the y (A-P) coordinate (r = -0.62, p<0.05).

CONCLUSION

GPi DBS is effective for PGD but outcome is dependent on contact location. Posteroventral GPi stimulation provides the best overall effect and is superior for the arm and trunk. These results may be explained by the functional anatomy of GPi and its outflow tracts.

Variability of the subthalamic nucleus: the case for direct MRI guided targeting

Because of concerns about direct visualization of the subthalamic nucleus (STN) on magnetic resonance imaging (MRI), many functional neurosurgeons continue to rely on atlas-based coordinates to reach this target. T2-weighted MRI does allow direct visualisation of the STN. In order to compare the coordinates of the target point within the visualised STN with those obtained from standard brain atlases, the preoperative stereotactic T2-weighted MRI used to implant 55 deep brain stimulation electrodes in the visualised STN of 29 consecutive patients with Parkinson's disease treated in two European centres were studied. The coordinates of the directly visualised STN were significantly different from those of the atlas target. Variability of the position of the STN may render direct visualisation a more accurate means of targeting this nucleus.

Unusual cervical nerve root arrangement exposed during surgery: case report and review of the literature

Anatomical variations of neural structures in the cervical spine are rare and are not necessarily visible on pre-operative imaging. The authors report an unusual arrangement of neural structures identified during cervical foraminotomy. Anatomical variations of the cervical nerve roots are reviewed and their importance in neurosurgical practice is discussed.

A comparison of magnetic resonance imaging and neurophysiological studies in the assessment of cervical radiculopathy

Neurophysiological studies (NPS) are often used by both neurosurgeons and neurologists to supplement neuroimaging findings in the diagnosis of cervical radiculopathy and in operative decision-making. The aim of this study was to assess whether nerve conduction and electromyographic studies added significant information to that obtained from high resolution MRI to warrant routine use. Over the 10-year period (1991-2001), we identified 48 patients who underwent both preoperative NPS and MRI for cervical radiculopathy. Sensitivity of MRI and NPS for diagnosing cervical radiculopathy was 93 and 42%, respectively. Whilst the positive predictive values for MRI and NPS were similar (91% versus 86%), the former had a higher negative predictive value (25% versus 7%). In only one case was the decision to operate based on NPS despite a negative MRI. We therefore suggest that in patients with clinical and MRI evidence of cervical radiculopathy, NPS has limited additional diagnostic value.

Cystic meningioma: challenges in the diagnosis

A patient with an unusual cystic meningioma is described. The pathophysiology of cyst formation is discussed.