Drop metastasis from the extradural to the intradural space in spinal Ewing's sarcoma - a novel case report.

Spinal Ewing's Sarcoma is a rare tumour predominantly affecting children and adolescents. We describe the case of an 18-year-old male patient who first presented with a primary extradural cervical Ewing's sarcoma tumour, and 5 years later had a recurrence with thoracolumbar and lumbosacral intradural extramedullary Ewing's sarcoma tumours. Both presentations were successfully treated by surgical resection and adjuvant chemo- and radiotherapy, and he remains disease-free at 12 months follow-up. This is the first reported case of seeding of tumour from an extradural primary Ewing's sarcoma to intradural metastases. Total surgical resection of his initial cervical tumour, performed at another centre, was complicated by a dural tear and CSF leak. Thus, we propose that isolated drop metastasis via CSF fistula is the most likely mechanism for tumour spread in this case. Thus, clinicians may wish to counsel patients on the possibility of such spread if a CSF leak is encountered, and potentially increase the frequency of imaging surveillance of the whole spine in this context.

ICP during head movement: significance of the venous system.

BACKGROUND: It is thought that the internal jugular veins (IJV) are the primary route for cranial venous outflow in supine position and the vertebral venous plexus when upright. Previous studies have noted a greater increase in intracranial pressure (ICP) when subjects turn their head in one direction compared to the other, but no clear cause had been investigated. We hypothesised that in the supine position, head turning and consequently obstructing the IJV draining the dominant transverse sinus (TVS) would lead to a greater rise in ICP compared to turning to the non-dominant side. METHODS: A prospective study in a large-volume neurosurgical centre. Patients undergoing continuous ICP monitoring as part of their standard clinical management were recruited. Immediate ICP was measured in different head positions (neutral, rotated to the right and left) when supine, seated, and standing. TVS dominance was established by consultant radiologist report on venous imaging. RESULTS: Twenty patients were included in the study, with a median age of 44 years. Venous system measurements revealed 85% right-sided vs 15% left-sided dominance. Immediate ICP rose more when head turning from neutral to the dominant TVS (21.93mmHg ± 4.39) vs non-dominant side (16.66mmHg ± 2.71) (p= <0.0001). There was no significant relationship in the sitting (6.08mmHg ± 3.86 vs 4.79mmHg ± 3.81, p = 0.13) or standing positions (8.74mmHg ± 4.30 vs 6.76mmHg ± 4.14, p =0.07). CONCLUSION: This study has provided further evidence that the transverse venous sinus to internal jugular system pathway is the likely primary venous drainage when supine; and quantified its effect when head turning on ICP. It may guide patient-specific nursing care and advice.

Optimising trajectory planning for stereotactic brain tumour biopsy using artificial intelligence: a systematic review of the literature.

PURPOSE: Despite advances in technology, stereotactic brain tumour biopsy remains challenging due to the risk of injury to critical structures. Indeed, choosing the correct trajectory remains essential to patient safety. Artificial intelligence can be used to perform automated trajectory planning. We present a systematic review of automated trajectory planning algorithms for stereotactic brain tumour biopsies. METHODS: A PRISMA adherent systematic review was conducted. Databases were searched using keyword combinations of 'artificial intelligence', 'trajectory planning' and 'brain tumours'. Studies reporting applications of artificial intelligence (AI) to trajectory planning for brain tumour biopsy were included. RESULTS: All eight studies were in the earliest stage of the IDEAL-D development framework. Trajectory plans were compared through a variety of surrogate markers of safety, of which the minimum distance to blood vessels was the most common. Five studies compared manual to automated planning strategies and favoured automation in all cases. However, this comes with a significant risk of bias. CONCLUSIONS: This systematic review reveals the need for IDEAL-D Stage 1 research into automated trajectory planning for brain tumour biopsy. Future studies should establish the congruence between expected risk of algorithms and the ground truth through comparisons to real world outcomes.

Dopamine signals encode internally determined subjective value regardless of externally indicated reward attributes.

The dopamine reward prediction error signal is known to be subjective but has so far only been related to explicit external stimuli and rewards. However, personal choices are based on private internal values of the rewards at stake. Without indications of an agent's private internal value, we do not know whether dopamine neurons, or any reward neurons, encode the internal value. The well-established Becker-DeGroot-Marschak (BDM) auction-like mechanism allows participants to place bids for freely stating their private internal value for a good. BDM bids are known to reflect the agent's true internal valuation, as inaccurate bidding results in suboptimal reward ('incentive compatibility'). In our experiment rhesus monkeys placed BDM bids for juice rewards without specific external constraints. Their bids for physically identical rewards varied trial by trial and increased overall for larger rewards. Responses of midbrain dopamine neurons followed the trial-by-trial variation of bids despite constant, explicitly predicted reward amounts; correspondingly, the dopamine responses were similar when the animal placed similar bids for different reward amounts. Support Vector Regression demonstrated accurate prediction of the animal's bids by as few as twenty dopamine neurons, demonstrating the validity of the dopamine code for internal reward value. Thus, dopamine responses reflect the instantaneous internal subjective reward value rather than the value imposed by external stimuli.

Cerebral cavernous malformation: Management, outcomes, and surveillance strategies - A single centre retrospective cohort study.

BACKGROUND: Cerebral cavernous malformations (CCM) may undergo a period of clinical and/or radiographical surveillance that precedes or follows definitive treatment. There are no international guidelines on the optimal surveillance strategy. This study describes the surveillance strategies at our centre and explore the related clinical outcomes. METHODS: We performed a retrospective study of adult patients with CCMs referred to a neurovascular service over an 8-year period, to determine the frequency and type of surveillance, intervention, and explore the associated outcomes. We report our findings adhering to STROBE guidelines. RESULTS: 133 patients (Male:Female 73:60; men age 42 years; range 12-82) were included. CCMs were identified in patients first presenting with symptomatic intracerebral haemorrhage (42.11%); headache, focal neurological deficit, or seizure without haemorrhage (41.35%); or, as an incidental finding (16.54%). The most common CCM location was supratentorial (59.40%), followed by brain stem (21.80%), cerebellum (10.53%) and basal ganglia (6.02%). Of the 133 patients, 77 patients (57.89%) were managed conservatively, 49 patients (36.84%) were managed by surgical resection alone, and seven patients (5.26%) were managed with stereotactic radiosurgery (SRS). Patients follow-up had a mean duration of 65.94 months, and varied widely (SD = 52.59; range 0-265), for a total of 730.83 person-years of follow up. During surveillance, 16 patients suffered an ICH equating to a bleeding rate of 2.19 per 100 patient years. CCMs that increased in size had a higher bleeding rate (p = 8.58 ×10-4). There were 8 (6.02%) cases where routine clinic review or MRI resulted in a change in management. CONCLUSIONS: Our single centre retrospective study supports existing literature relating to presentation and sequalae of CCM, with an increase in CCM size being associated with higher rates of detected bleeding. There remains heterogeneity, even within a single centre, on the frequency and modality of surveillance. Further, there are no international guidelines or high-quality data that recommends the optimal duration and frequency of surveillance, and its effect on clinical outcomes. This is a future research direction.

Reward Value Revealed by Auction in Rhesus Monkeys.

Economic choice is thought to involve the elicitation of the subjective values of the choice options. Thus far, value estimation in animals has relied on stochastic choices between multiple options presented in repeated trials and expressed from averages of dozens of trials. However, subjective reward valuations are made moment-to-moment and do not always require alternative options; their consequences are usually felt immediately. Here, we describe a Becker-DeGroot-Marschak (BDM) auction-like mechanism that provides more direct and simple valuations with immediate consequences. The BDM encourages agents to truthfully reveal their true subjective value in individual choices ("incentive compatibility"). Male monkeys reliably placed well-ranked BDM bids for up to five juice volumes while paying from a water budget. The bids closely approximated the average subjective values estimated with conventional binary choices (BCs), thus demonstrating procedural invariance and aligning with the wealth of knowledge acquired with these less direct estimation methods. The feasibility of BDM bidding in monkeys paves the way for an analysis of subjective neuronal value signals in single trials rather than from averages; the feasibility also bridges the gap to the increasingly used BDM method in human neuroeconomics.SIGNIFICANCE STATEMENT The subjective economic value of rewards cannot be measured directly but must be inferred from observable behavior. Until now, the estimation method in animals was rather complex and required comparison between several choice options during repeated choices; thus, such methods did not respect the imminence of the outcome from individual choices. However, human economic research has developed a simple auction-like procedure that can reveal in a direct and immediate manner the true subjective value in individual choices [Becker-DeGroot-Marschak (BDM) mechanism]. The current study implemented this mechanism in rhesus monkeys and demonstrates its usefulness for eliciting meaningful value estimates of liquid rewards. The mechanism allows future neurophysiological assessment of subjective reward value signals in single trials of controlled animal tasks.