Challenges with segmenting intraoperative ultrasound for brain tumours.

Objective - Addressing the challenges that come with identifying and delineating brain tumours in intraoperative ultrasound. Our goal is to both qualitatively and quantitatively assess the interobserver variation, amongst experienced neuro-oncological intraoperative ultrasound users (neurosurgeons and neuroradiologists), in detecting and segmenting brain tumours on ultrasound. We then propose that, due to the inherent challenges of this task, annotation by localisation of the entire tumour mass with a bounding box could serve as an ancillary solution to segmentation for clinical training, encompassing margin uncertainty and the curation of large datasets. Methods - 30 ultrasound images of brain lesions in 30 patients were annotated by 4 annotators - 1 neuroradiologist and 3 neurosurgeons. The annotation variation of the 3 neurosurgeons was first measured, and then the annotations of each neurosurgeon were individually compared to the neuroradiologist's, which served as a reference standard as their segmentations were further refined by cross-reference to the preoperative magnetic resonance imaging (MRI). The following statistical metrics were used: Intersection Over Union (IoU), Sørensen-Dice Similarity Coefficient (DSC) and Hausdorff Distance (HD). These annotations were then converted into bounding boxes for the same evaluation. Results - There was a moderate level of interobserver variance between the neurosurgeons [ I o U : 0.789 , D S C : 0.876 , H D : 103.227 ] and a larger level of variance when compared against the MRI-informed reference standard annotations by the neuroradiologist, mean across annotators [ I o U : 0.723 , D S C : 0.813 , H D : 115.675 ] . After converting the segments to bounding boxes, all metrics improve, most significantly, the interquartile range drops by [ I o U : 37 % , D S C : 41 % , H D : 54 % ] . Conclusion - This study highlights the current challenges with detecting and defining tumour boundaries in neuro-oncological intraoperative brain ultrasound. We then show that bounding box annotation could serve as a useful complementary approach for both clinical and technical reasons.

Illusions of Self-Motion during Magnetic Resonance-Guided Focused Ultrasound Thalamotomy for Tremor.

OBJECTIVE: Brain networks mediating vestibular perception of self-motion overlap with those mediating balance. A systematic mapping of vestibular perceptual pathways in the thalamus may reveal new brain modulation targets for improving balance in neurological conditions. METHODS: Here, we systematically report how magnetic resonance-guided focused ultrasound surgery of the nucleus ventralis intermedius of the thalamus commonly evokes transient patient-reported illusions of self-motion. In 46 consecutive patients, we linked the descriptions of self-motion to sonication power and 3-dimensional (3D) coordinates of sonication targets. Target coordinates were normalized using a standard atlas, and a 3D model of the nucleus ventralis intermedius and adjacent structures was created to link sonication target to the illusion. RESULTS: A total of 63% of patients reported illusions of self-motion, which were more likely with increased sonication power and with targets located more inferiorly along the rostrocaudal axis. Higher power and more inferiorly targeted sonications increased the likelihood of experiencing illusions of self-motion by 4 and 2 times, respectively (odds ratios = 4.03 for power, 2.098 for location). INTERPRETATION: The phenomenon of magnetic vestibular stimulation is the most plausible explanation for these illusions of self-motion. Temporary unilateral modulation of vestibular pathways (via magnetic resonance-guided focused ultrasound) unveils the central adaptation to the magnetic field-induced peripheral vestibular bias, leading to an explicable illusion of motion. Consequently, systematic mapping of vestibular perceptual pathways via magnetic resonance-guided focused ultrasound may reveal new intracerebral targets for improving balance in neurological conditions. ANN NEUROL 2024;96:121-132.

The cost-effectiveness of unilateral magnetic resonance-guided focused ultrasound in comparison with unilateral deep brain stimulation for the treatment of medically refractory essential tremor in England.

OBJECTIVES: This study aims to ascertain the cost-effectiveness of magnetic resonance-guided focused ultrasound (MRgFUS) for the treatment of medically refractory Essential Tremor (mrET) in England. Essential Tremor (ET) is the most common movement disorder affecting approximately 1 million in the UK causing considerable societal impact affecting patients, carers and the wider healthservice. Medical treatment has mixed efficacy, with approximately 25-55% of ET medication refractory. Deep brain stimulation (DBS) is a proven neurosurgical treatment; however, the risks of surgery and anaesthesia mean some patients are ineligible. MRgFUS is an emerging noninvasive technique that causes tremor suppression by thermal ablation of tremor-sensitive brain tissue. Several international clinical trials have demonstrated MRgFUS is safe and clinically effective; however, to-date no cost-effectiveness study has been performed in Europe. METHODS: A Markov model was used to assess two subpopulations of mrET - those eligible and those ineligible for neurosurgery - in the context specific to England and its healthcare system. For those eligible for neurosurgery, MRgFUS was compared to DBS, the current standard treatment. For those ineligible for neurosurgery, MRgFUS was compared to treatment with medication alone. The model calculated the Incremental cost-effectiveness ratio (ICER) with appropriate sensitivity and scenario analyses. RESULTS: For those eligible for neurosurgery: In the model base case, the MRgFUS was economically dominant compared to DBS; MRgFUS was less costly (£19,779 vs £62,348) and more effective generating 0.03 additional quality-adjusted life-years (QALYs) per patient (3.71 vs 3.68) over the 5-year time horizon.For those ineligible for neurosurgery: In the model base case, MRgFUS cost over £16,000 per patient more than medication alone (£19,779 vs £62,348) but yielded 0.77 additional QALYs per patient(3.71 vs 2.95), producing an incremental cost-effectiveness ratio (ICER) of £20,851 per QALY. This ICER of £20,851 per QALY falls within the National Institute for Clinical Excellence's (NICE) willingness to pay threshold (WTP) of 20,000-30,000 demonstrating the cost-effectiveness profile of MRgFUS. CONCLUSION: This study demonstrates the favourable cost-effectiveness profile of MRgFUS for the treatment of mrET in England; in both patients suitable and not suitable for neurosurgery. ADVANCES IN KNOWLEDGE: The introduction of MRgFUS as a widely available ET treatment in UK is currently undergoing the necessary stages of regulatory approval. As the first European study, these favourable cost-effectiveness outcomes (notably the model base case ICER falling within NICE's WTP) can provide a basis for future commissioning of brain MRgFUS treatments in the UK, Europe and globally.

The predictive value of DESH for shunt responsiveness in idiopathic normal pressure hydrocephalus.

OBJECTIVE: Selecting probable idiopathic normal pressure hydrocephalus (INPH) patients for shunt insertion presents a challenge because of coexisting comorbidities and other conditions that could mimic NPH. The characteristic appearance of DESH (Disproportionately Enlarged Subarachnoid Space Hydrocephalus) on brain imaging has been shown to have a high positive predictive value in identifying shunt responsive INPH patients (SINPHONI trial). However, the negative predictive value of this radiological sign was not clearly demonstrated. The aim of the present study was to calculate the negative predictive value of the DESH sign. METHODS: A single centre study of probable INPH patients, who underwent ventriculoperitoneal (VP) shunt insertion. Shunt responsive INPH patients were identified as those having improvement in their walking speed, neuropsychological assessment and continence one year post operatively. Preoperative images were reviewed for DESH sign. Negative and Positive Predictive Values (NPV and PPV) of DESH sign were determined post analysis. RESULTS: A total of 103 probable INPH patients were included (31 were DESH positive (30%) and 72 were DESH negative (70%)). A total of 78 patients showed measurable improvement one year post shunt insertion (76%); 24 (31%) of these patients were DESH positive and 54 (69%) were DESH negative (p=<0.001). Therefore, the DESH sign had an estimated PPV of 77% and NPV of 25%. CONCLUSION: DESH sign demonstrates a low negative predictive value. We conclude that DESH negative patients should still undergo prognostic tests for iNPH, such as an extended lumbar drainage protocol, and should not be excluded from shunt insertion.

Prokineticin 2 is a hypothalamic neuropeptide that potently inhibits food intake.

OBJECTIVE: Prokineticin 2 (PK2) is a hypothalamic neuropeptide expressed in central nervous system areas known to be involved in food intake. We therefore hypothesized that PK2 plays a role in energy homeostasis. RESEARCH DESIGN AND METHODS: We investigated the effect of nutritional status on hypothalamic PK2 expression and effects of PK2 on the regulation of food intake by intracerebroventricular (ICV) injection of PK2 and anti-PK2 antibody. Subsequently, we investigated the potential mechanism of action by determining sites of neuronal activation after ICV injection of PK2, the hypothalamic site of action of PK2, and interaction between PK2 and other hypothalamic neuropeptides regulating energy homeostasis. To investigate PK2's potential as a therapeutic target, we investigated the effect of chronic administration in lean and obese mice. RESULTS: Hypothalamic PK2 expression was reduced by fasting. ICV administration of PK2 to rats potently inhibited food intake, whereas anti-PK2 antibody increased food intake, suggesting that PK2 is an anorectic neuropeptide. ICV administration of PK2 increased c-fos expression in proopiomelanocortin neurons of the arcuate nucleus (ARC) of the hypothalamus. In keeping with this, PK2 administration into the ARC reduced food intake and PK2 increased the release of alpha-melanocyte-stimulating hormone (alpha-MSH) from ex vivo hypothalamic explants. In addition, ICV coadministration of the alpha-MSH antagonist agouti-related peptide blocked the anorexigenic effects of PK2. Chronic peripheral administration of PK2 reduced food and body weight in lean and obese mice. CONCLUSIONS: This is the first report showing that PK2 has a role in appetite regulation and its anorectic effect is mediated partly via the melanocortin system.

Hypothalamic injection of oxyntomodulin suppresses circulating ghrelin-like immunoreactivity.

Ghrelin is a gastric peptide that regulates appetite and GH secretion. Circulating ghrelin levels are elevated by fasting and suppressed postprandially. However, the mechanisms regulating circulating ghrelin levels are unclear. Oxyntomodulin is an anorexic peptide hormone released from L cells in the gut. We investigated the effects of intracerebroventricular (icv) administration of oxyntomodulin on circulating ghrelin levels. The icv administration of 1, 3, or 10 nmol oxyntomodulin reduced circulating acylated and total (acylated and des-acylated) ghrelin 60 min after icv injection. Administration of 1 nmol oxyntomodulin directly into the arcuate nucleus of the hypothalamus significantly reduced total and acylated ghrelin levels, and administration of 3 nmol oxyntomodulin into the lateral ventricle induced c-fos mRNA expression in arcuate nucleus neurons expressing the glucagon-like peptide-1 (GLP-1) receptor. In a final study, the reduction in total ghrelin observed after icv injection of 3 nmol oxyntomodulin was blocked by coadministration of the GLP-1 receptor antagonist exendin (9-39). These studies suggest oxyntomodulin reduces peripheral ghrelin levels via GLP-1 receptor-dependent hypothalamic pathways. Postprandial release of anorexic gut hormones may thus act centrally to contribute to the postprandial reduction in circulating ghrelin.

Cholinergic modulation of intrinsic fibre-evoked excitatory transmission contains a nicotinic component in immature but not adult rat piriform cortex, in vitro.

The piriform cortex (PC) is highly prone to epileptogenesis, particularly in immature animals, where decreased muscarinic modulation of PC intrinsic fibre excitatory neurotransmission is implicated as a likely cause. However, whether higher levels of acetylcholine (ACh) release occur in immature vs. adult PC remains unclear. We investigated this using in vitro extracellular electrophysiological recording techniques. Intrinsic fibre-evoked extracellular field potentials (EFPs) were recorded from layers II to III in PC brain slices prepared from immature (P14-18) and adult (P>40) rats. Adult and immature PC EFPs were suppressed by eserine (1 microM) or neostigmine (1 microM) application, with a greater suppression in immature (approximately 40%) than adult (approximately 30%) slices. Subsequent application of atropine (1 microM) reversed EFP suppression, producing supranormal (approximately 12%) recovery in adult slices, suggesting that suppression was solely muscarinic ACh receptor-mediated and that some 'basal' cholinergic 'tone' was present. Conversely, atropine only partially reversed anticholinesterase effects in immature slices, suggesting the presence of additional non-muscarinic modulation. Accordingly, nicotine (50 microM) caused immature field suppression (approximately 30%) that was further enhanced by neostigmine, whereas it had no effect on adult EFPs. Unlike atropine, nicotinic antagonists, mecamylamine and methyllycaconitine, induced immature supranormal field recovery (approximately 20%) following anticholinesterase-induced suppression (with no effect on adult slices), confirming that basal cholinergic 'tone' was also present. We suggest that nicotinic inhibitory cholinergic modulation occurs in the immature rat PC intrinsic excitatory fibre system, possibly to complement the existing, weak muscarinic modulation, and could be another important developmentally regulated system governing immature PC susceptibility towards epileptogenesis.