Circadian changes in aperiodic activity are correlated with seizure reduction in patients with mesial temporal lobe epilepsy treated with responsive neurostimulation

OBJECTIVES

Responsive neurostimulation (RNS) is an established therapy for drug-resistant epilepsy that delivers direct electrical brain stimulation in response to detected epileptiform activity. However, despite an overall reduction in seizure frequency, clinical outcomes are variable, and few patients become seizure-free. The aim of this retrospective study was to evaluate aperiodic electrophysiological activity, associated with excitation/inhibition balance, as a novel electrographic biomarker of seizure reduction to aid early prognostication of the clinical response to RNS.

METHODS

We identified patients with intractable mesial temporal lobe epilepsy who were implanted with the RNS System between 2015 and 2021 at the University of Utah. We parameterized the neural power spectra from intracranial RNS System recordings during the first 3 months following implantation into aperiodic and periodic components. We then correlated circadian changes in aperiodic and periodic parameters of baseline neural recordings with seizure reduction at the most recent follow-up.

RESULTS

Seizure reduction was correlated significantly with a patient's average change in the day/night aperiodic exponent (r = .50, p = .016, n = 23 patients) and oscillatory alpha power (r = .45, p = .042, n = 23 patients) across patients for baseline neural recordings. The aperiodic exponent reached its maximum during nighttime hours (12 a.m. to 6 a.m.) for most responders (i.e., patients with at least a 50% reduction in seizures).

SIGNIFICANCE

These findings suggest that circadian modulation of baseline broadband activity is a biomarker of response to RNS early during therapy. This marker has the potential to identify patients who are likely to respond to mesial temporal RNS. Furthermore, we propose that less day/night modulation of the aperiodic exponent may be related to dysfunction in excitation/inhibition balance and its interconnected role in epilepsy, sleep, and memory.

A novel naïve Bayes approach to identifying grooming behaviors in the force-plate actometric platform

BACKGROUND

Self-grooming behavior in rodents serves as a valuable behavioral index for investigating stereotyped and perseverative responses. Most current grooming analyses rely on video observation, which lacks standardization, efficiency, and quantitative information about force. To address these limitations, we developed an automated paradigm to analyze grooming using a force-plate actometer.

NEW METHOD

Grooming behavior is quantified by calculating ratios of relevant movement power spectral bands. These ratios are input into a naïve Bayes classifier, trained with manual video observations. The effectiveness of this method was tested using CIN-d mice, an animal model developed through early-life depletion of striatal cholinergic interneurons (CIN-d) and featuring prolonged grooming responses to acute stressors. Behavioral monitoring was simultaneously conducted on the force-place actometer and by video recording.

RESULTS

The naïve Bayes approach achieved 93.7% accurate classification and an area under the receiver operating characteristic curve of 0.894. We confirmed that male CIN-d mice displayed significantly longer grooming durations than controls. However, this elevation was not correlated with increases in grooming force. Notably, the dopaminergic antagonist haloperidol reduced grooming force and duration.

COMPARISON WITH EXISTING METHODS

In contrast to observation-based approaches, our method affords rapid, unbiased, and automated assessment of grooming duration, frequency, and force.

CONCLUSIONS

Our novel approach enables fast and accurate automated detection of grooming behaviors. This method holds promise for high-throughput assessments of grooming stereotypies in animal models of neuropsychiatric disorders.

Closed-loop stimulation in periods with less epileptiform activity drives improved epilepsy outcomes

In patients with drug-resistant epilepsy, electrical stimulation of the brain in response to epileptiform activity can make seizures less frequent and debilitating. This therapy, known as closed-loop responsive neurostimulation (RNS), aims to directly halt seizure activity via targeted stimulation of a burgeoning seizure. Rather than immediately stopping seizures as they start, many RNS implants produce slower, long-lasting changes in brain dynamics that better predict clinical outcomes. Here we hypothesize that stimulation during brain states with less epileptiform activity drives long-term changes that restore healthy brain networks. To test this, we quantified stimulation episodes during low- and high-risk brain states-that is, stimulation during periods with a lower or higher risk of generating epileptiform activity-in a cohort of 40 patients treated with RNS. More frequent stimulation in tonic low-risk states and out of rhythmic high-risk states predicted seizure reduction. Additionally, stimulation events were more likely to be phase-locked to prolonged episodes of abnormal activity for intermediate and poor responders when compared to super-responders, consistent with the hypothesis that improved outcomes are driven by stimulation during low-risk states. These results support the hypothesis that stimulation during low-risk periods might underlie the mechanisms of RNS, suggesting a relationship between temporal patterns of neuromodulation and plasticity that facilitates long-term seizure reduction.

A novel naïve Bayes approach to identifying grooming behaviors in the force-plate actometric platform

Background

Self-grooming behavior in rodents serves as a valuable model for investigating stereotyped and perseverative responses. Most current grooming analyses primarily rely on video observation, which lacks standardization, efficiency, and quantitative information about force. To address these limitations, we developed an automated paradigm to analyze grooming using a force-plate actometer.

New Method

Grooming behavior is quantified by calculating ratios of relevant movement power spectral bands. These ratios are then input into a naïve Bayes classifier, trained with manual video observations. To validate the effectiveness of this method, we applied it to the behavioral analysis of the early-life striatal cholinergic interneuron depletion (CIN-d) mouse, a model of tic pathophysiology recently developed in our laboratory, which exhibits prolonged grooming responses to acute stressors. Behavioral monitoring was simultaneously conducted on the force-place actometer and by video recording.

Results

The naïve Bayes approach achieved 93.7% accurate classification and an area under the receiver operating characteristic curve of 0.894. We confirmed that male CIN-d mice displayed significantly longer grooming durations compared to controls. However, this elevation was not correlated with increases in grooming force. Notably, haloperidol, a benchmark therapy for tic disorders, reduced both grooming force and duration.

Comparison with Existing Methods

In contrast to observation-based approaches, our method affords rapid, unbiased, and automated assessment of grooming duration, frequency, and force.

Conclusions

Our novel approach enables fast and accurate automated detection of grooming behaviors. This method holds promise for high-throughput assessments of grooming stereotypies in animal models of tic disorders and other psychiatric conditions.

Chronic intracranial recordings after resection for epilepsy reveal a "running down" of epileptiform activity

We describe an electrical "running down" phenomenon and also a consistent spectral change (in the aperiodic component of the power spectrum) derived from chronic interictal electrocorticography (ECoG) after surgery in a patient with drug-resistant epilepsy. These data were recorded using a closed-loop neurostimulation system that was implanted after resection. The patient has been seizure-free for 2.5 years since resection without requiring the neurostimulator to be turned on to stimulate. Concurrently, there was an exponential decrease in the number of epileptiform electrographic detections recorded by the device, particularly over the first 26 weeks, indicative of an electrical running down phenomenon as the brain adapted to an extended period of seizure freedom. We also find that the aperiodic exponent of the power spectrum gradually decreases over time. The aperiodic component of intracranial ECoG may represent a novel marker of epileptogenicity, independent of seizures.

Subsets of cortico-cortical evoked potentials propagate as traveling waves

Emerging evidence suggests that the temporal dynamics of cortico-cortical evoked potentials (CCEPs) may be used to characterize the patterns of information flow between and within brain networks. At present, however, the spatiotemporal dynamics of CCEP propagation cortically and subcortically are incompletely understood. We hypothesized that CCEPs propagate as an evoked traveling wave emanating from the site of stimulation. To elicit CCEPs, we applied single-pulse stimulation to stereoelectroencephalography (SEEG) electrodes implanted in 21 adult patients with intractable epilepsy. For each robust CCEP, we measured the timing of the maximal descent in evoked local field potentials and broadband high-gamma power (70-150 Hz) envelopes relative to the distance between the recording and stimulation contacts using three different metrics (i.e., Euclidean distance, path length, geodesic distance), representing direct, subcortical, and transcortical propagation, respectively. Many evoked responses to single-pulse electrical stimulation appear to propagate as traveling waves (~17-30%), even in the sparsely sampled, three-dimensional SEEG space. These results provide new insights into the spatiotemporal dynamics of CCEP propagation.

Patient-specific structural connectivity informs outcomes of responsive neurostimulation for temporal lobe epilepsy

OBJECTIVE

Responsive neurostimulation is an effective therapy for patients with refractory mesial temporal lobe epilepsy. However, clinical outcomes are variable, few patients become seizure-free, and the optimal stimulation location is currently undefined. The aim of this study was to quantify responsive neurostimulation in the mesial temporal lobe, identify stimulation-dependent networks associated with seizure reduction, and determine if stimulation location or stimulation-dependent networks inform outcomes.

METHODS

We modeled patient-specific volumes of tissue activated and created probabilistic stimulation maps of local regions of stimulation across a retrospective cohort of 22 patients with mesial temporal lobe epilepsy. We then mapped the network stimulation effects by seeding tractography from the volume of tissue activated with both patient-specific and normative diffusion-weighted imaging. We identified networks associated with seizure reduction across patients using the patient-specific tractography maps and then predicted seizure reduction across the cohort.

RESULTS

Patient-specific stimulation-dependent connectivity was correlated with responsive neurostimulation effectiveness after cross-validation (p = .03); however, normative connectivity derived from healthy subjects was not (p = .44). Increased connectivity from the volume of tissue activated to the medial prefrontal cortex, cingulate cortex, and precuneus was associated with greater seizure reduction.

SIGNIFICANCE

Overall, our results suggest that the therapeutic effect of responsive neurostimulation may be mediated by specific networks connected to the volume of tissue activated. In addition, patient-specific tractography was required to identify structural networks correlated with outcomes. It is therefore likely that altered connectivity in patients with epilepsy may be associated with the therapeutic effect and that utilizing patient-specific imaging could be important for future studies. The structural networks identified here may be utilized to target stimulation in the mesial temporal lobe and to improve seizure reduction for patients treated with responsive neurostimulation.

LeGUI: A Fast and Accurate Graphical User Interface for Automated Detection and Anatomical Localization of Intracranial Electrodes

Accurate anatomical localization of intracranial electrodes is important for identifying the seizure foci in patients with epilepsy and for interpreting effects from cognitive studies employing intracranial electroencephalography. Localization is typically performed by coregistering postimplant computed tomography (CT) with preoperative magnetic resonance imaging (MRI). Electrodes are then detected in the CT, and the corresponding brain region is identified using the MRI. Many existing software packages for electrode localization chain together separate preexisting programs or rely on command line instructions to perform the various localization steps, making them difficult to install and operate for a typical user. Further, many packages provide solutions for some, but not all, of the steps needed for confident localization. We have developed software, Locate electrodes Graphical User Interface (LeGUI), that consists of a single interface to perform all steps needed to localize both surface and depth/penetrating intracranial electrodes, including coregistration of the CT to MRI, normalization of the MRI to the Montreal Neurological Institute template, automated electrode detection for multiple types of electrodes, electrode spacing correction and projection to the brain surface, electrode labeling, and anatomical targeting. The software is written in MATLAB, core image processing is performed using the Statistical Parametric Mapping toolbox, and standalone executable binaries are available for Windows, Mac, and Linux platforms. LeGUI was tested and validated on 51 datasets from two universities. The total user and computational time required to process a single dataset was approximately 1 h. Automatic electrode detection correctly identified 4362 of 4695 surface and depth electrodes with only 71 false positives. Anatomical targeting was verified by comparing electrode locations from LeGUI to locations that were assigned by an experienced neuroanatomist. LeGUI showed a 94% match with the 482 neuroanatomist-assigned locations. LeGUI combines all the features needed for fast and accurate anatomical localization of intracranial electrodes into a single interface, making it a valuable tool for intracranial electrophysiology research.

Probabilistic comparison of gray and white matter coverage between depth and surface intracranial electrodes in epilepsy

In this study, we quantified the coverage of gray and white matter during intracranial electroencephalography in a cohort of epilepsy patients with surface and depth electrodes. We included 65 patients with strip electrodes (n = 12), strip and grid electrodes (n = 24), strip, grid, and depth electrodes (n = 7), or depth electrodes only (n = 22). Patient-specific imaging was used to generate probabilistic gray and white matter maps and atlas segmentations. Gray and white matter coverage was quantified using spherical volumes centered on electrode centroids, with radii ranging from 1 to 15 mm, along with detailed finite element models of local electric fields. Gray matter coverage was highly dependent on the chosen radius of influence (RoI). Using a 2.5 mm RoI, depth electrodes covered more gray matter than surface electrodes; however, surface electrodes covered more gray matter at RoI larger than 4 mm. White matter coverage and amygdala and hippocampal coverage was greatest for depth electrodes at all RoIs. This study provides the first probabilistic analysis to quantify coverage for different intracranial recording configurations. Depth electrodes offer increased coverage of gray matter over other recording strategies if the desired signals are local, while subdural grids and strips sample more gray matter if the desired signals are diffuse.

Computational investigation of the impact of deep brain stimulation contact size and shape on neural selectivity

Background.Understanding neural selectivity is essential for optimizing medical applications of deep brain stimulation (DBS). We previously showed that modulation of the DBS waveform can induce changes in orientation-based selectivity, and that lengthening of DBS pulses or directional segmentation can reduce preferential selectivity for large axons. In this work, we sought to investigate a simple, but important question from a generalized perspective: how do the size and shape of the contact influence neural selectivity?Methods.We created multicompartment neuron models for several axon diameters and used finite element modeling with standard-sized cylindrical leads to determine the effects on changing contact size and shape on axon activation profiles and volumes of tissue activated. Contacts ranged in size from 0.04 to 16 mm2, compared with a standard size of 6 mm2.Results.We found that changes in contact size are predicted to induce substantial changes in orientation-based selectivity in the context of a cylindrical lead, and changes in contact width or height can alter this selectivity. Smaller contact sizes were more effective in constraining neural activation to small, nearby axons. However, micro-scale contacts enable only limited spread of neural activation before exceeding standard charge density limitations; further, energetic efficiency is optimized by somewhat larger contacts.Interpretations.Small-scale contacts may be optimal for constraining stimulation in nearby grey matter and avoiding orientation-selective activation. However, given charge density limitations and energy inefficiency of micro-scale contacts, we predict that contacts sized similarly to or slightly smaller than segmented clinical leads may optimize energy efficiency while avoiding charge density limitations.

Structural connectivity predicts clinical outcomes of deep brain stimulation for Tourette syndrome

Deep brain stimulation may be an effective therapy for select cases of severe, treatment-refractory Tourette syndrome; however, patient responses are variable, and there are no reliable methods to predict clinical outcomes. The objectives of this retrospective study were to identify the stimulation-dependent structural networks associated with improvements in tics and comorbid obsessive-compulsive behaviour, compare the networks across surgical targets, and determine if connectivity could be used to predict clinical outcomes. Volumes of tissue activated for a large multisite cohort of patients (n = 66) implanted bilaterally in globus pallidus internus (n = 34) or centromedial thalamus (n = 32) were used to generate probabilistic tractography to form a normative structural connectome. The tractography maps were used to identify networks that were correlated with improvement in tics or comorbid obsessive-compulsive behaviour and to predict clinical outcomes across the cohort. The correlated networks were then used to generate 'reverse' tractography to parcellate the total volume of stimulation across all patients to identify local regions to target or avoid. The results showed that for globus pallidus internus, connectivity to limbic networks, associative networks, caudate, thalamus, and cerebellum was positively correlated with improvement in tics; the model predicted clinical improvement scores (P = 0.003) and was robust to cross-validation. Regions near the anteromedial pallidum exhibited higher connectivity to the positively correlated networks than posteroventral pallidum, and volume of tissue activated overlap with this map was significantly correlated with tic improvement (P < 0.017). For centromedial thalamus, connectivity to sensorimotor networks, parietal-temporal-occipital networks, putamen, and cerebellum was positively correlated with tic improvement; the model predicted clinical improvement scores (P = 0.012) and was robust to cross-validation. Regions in the anterior/lateral centromedial thalamus exhibited higher connectivity to the positively correlated networks, but volume of tissue activated overlap with this map did not predict improvement (P > 0.23). For obsessive-compulsive behaviour, both targets showed that connectivity to the prefrontal cortex, orbitofrontal cortex, and cingulate cortex was positively correlated with improvement; however, only the centromedial thalamus maps predicted clinical outcomes across the cohort (P = 0.034), but the model was not robust to cross-validation. Collectively, the results demonstrate that the structural connectivity of the site of stimulation are likely important for mediating symptom improvement, and the networks involved in tic improvement may differ across surgical targets. These networks provide important insight on potential mechanisms and could be used to guide lead placement and stimulation parameter selection, as well as refine targets for neuromodulation therapies for Tourette syndrome.

Neural selectivity, efficiency, and dose equivalence in deep brain stimulation through pulse width tuning and segmented electrodes

BACKGROUND

Achieving deep brain stimulation (DBS) dose equivalence is challenging, especially with pulse width tuning and directional contacts. Further, the precise effects of pulse width tuning are unknown, and recent reports of the effects of pulse width tuning on neural selectivity are at odds with classic biophysical studies.

METHODS

We created multicompartment neuron models for two axon diameters and used finite element modeling to determine extracellular influence from standard and segmented electrodes. We analyzed axon activation profiles and calculated volumes of tissue activated.

RESULTS

We find that long pulse widths focus the stimulation effect on small, nearby fibers, suppressing distant white matter tract activation (responsible for some DBS side effects) and improving battery utilization when equivalent activation is maintained for small axons. Directional leads enable similar benefits to a greater degree. Reexamining previous reports of short pulse stimulation reducing side effects, we explore a possible alternate explanation: non-dose equivalent stimulation may have resulted in reduced spread of neural activation. Finally, using internal capsule avoidance as an example in the context of subthalamic stimulation, we present a patient-specific model to show how long pulse widths could help increase the biophysical therapeutic window.

DISCUSSION

We find agreement with classic studies and predict that long pulse widths may focus the stimulation effect on small, nearby fibers and improve power consumption. While future pre-clinical and clinical work is necessary regarding pulse width tuning, it is clear that future studies must ensure dose equivalence, noting that energy- and charge-equivalent amplitudes do not result in equivalent spread of neural activation when changing pulse width.

Activation robustness with directional leads and multi-lead configurations in deep brain stimulation

OBJECTIVE

Clinical outcomes from deep brain stimulation (DBS) can be highly variable, and two critical factors underlying this variability are the location and type of stimulation. In this study we quantified how robustly DBS activates a target region when taking into account a range of different lead designs and realistic variations in placement. The objective of the study is to assess the likelihood of achieving target activation.

APPROACH

We performed finite element computational modeling and established a metric of performance robustness to evaluate the ability of directional and multi-lead configurations to activate target fiber pathways while taking into account location variability. A more robust lead configuration produces less variability in activation across all stimulation locations around the target.

MAIN RESULTS

Directional leads demonstrated higher overall performance robustness compared to axisymmetric leads, primarily 1-2 mm outside of the target. Multi-lead configurations demonstrated higher levels of robustness compared to any single lead due to distribution of electrodes in a broader region around the target.

SIGNIFICANCE

Robustness measures can be used to evaluate the performance of existing DBS lead designs and aid in the development of novel lead designs to better accommodate known variability in lead location and orientation. This type of analysis may also be useful to understand how DBS clinical outcome variability is influenced by lead location among groups of patients.

Evaluation of methodologies for computing the deep brain stimulation volume of tissue activated

Objective.

Computational models are a popular tool for predicting the effects of deep brain stimulation (DBS) on neural tissue. One commonly used model, the volume of tissue activated (VTA), is computed using multiple methodologies. We quantified differences in the VTAs generated by five methodologies: the traditional axon model method, the electric field norm, and three activating function based approaches—the activating function at each grid point in the tangential direction (AF-Tan) or in the maximally activating direction (AF-3D), and the maximum activating function along the entire length of a tangential fiber (AF-Max).

Approach.

We computed the VTA using each method across multiple stimulation settings. The resulting volumes were compared for similarity, and the methodologies were analyzed for their differences in behavior.

Main results.

Activation threshold values for both the electric field norm and the activating function varied with regards to electrode configuration, pulse width, and frequency. All methods produced highly similar volumes for monopolar stimulation. For bipolar electrode configurations, only the maximum activating function along the tangential axon method, AF-Max, produced similar volumes to those produced by the axon model method. Further analysis revealed that both of these methods are biased by their exclusive use of tangential fiber orientations. In contrast, the activating function in the maximally activating direction method, AF-3D, produces a VTA that is free of axon orientation and projection bias.

Significance.

Simulating tangentially oriented axons, the standard approach of computing the VTA, is too computationally expensive for widespread implementation and yields results biased by the assumption of tangential fiber orientation. In this work, we show that a computationally efficient method based on the activating function, AF-Max, reliably reproduces the VTAs generated by direct axon modeling. Further, we propose another method, AF-3D as a potentially superior model for representing generic neural tissue activation.

The μDBS: Multiresolution, Directional Deep Brain Stimulation for Improved Targeting of Small Diameter Fibers

Directional deep brain stimulation (DBS) leads have recently been approved and used in patients, and growing evidence suggests that directional contacts can increase the therapeutic window by redirecting stimulation to the target region while avoiding side-effect-inducing regions. We outline the design, fabrication, and testing of a novel directional DBS lead, the μDBS, which utilizes microscale contacts to increase the spatial resolution of stimulation steering and improve the selectivity in targeting small diameter fibers. We outline the steps of fabrication of the μDBS, from an integrated circuit design to post-processing and validation testing. We tested the onboard digital circuitry for programming fidelity, characterized impedance for a variety of electrode sizes, and demonstrated functionality in a saline bath. In a computational experiment, we determined that reduced electrode sizes focus the stimulation effect on small, nearby fibers. Smaller electrode sizes allow for a relative decrease in small-diameter axon thresholds compared to thresholds of large-diameter fibers, demonstrating a focusing of the stimulation effect within small, and possibly therapeutic, fibers. This principle of selectivity could be useful in further widening the window of therapy. The μDBS offers a unique, multiresolution design in which any combination of microscale contacts can be used together to function as electrodes of various shapes and sizes. Multiscale electrodes could be useful in selective neural targeting for established neurological targets and in exploring novel treatment targets for new neurological indications.

Optimized programming algorithm for cylindrical and directional deep brain stimulation electrodes

OBJECTIVE

Deep brain stimulation (DBS) is a growing treatment option for movement and psychiatric disorders. As DBS technology moves toward directional leads with increased numbers of smaller electrode contacts, trial-and-error methods of manual DBS programming are becoming too time-consuming for clinical feasibility. We propose an algorithm to automate DBS programming in near real-time for a wide range of DBS lead designs.

APPROACH

Magnetic resonance imaging and diffusion tensor imaging are used to build finite element models that include anisotropic conductivity. The algorithm maximizes activation of target tissue and utilizes the Hessian matrix of the electric potential to approximate activation of neurons in all directions. We demonstrate our algorithm's ability in an example programming case that targets the subthalamic nucleus (STN) for the treatment of Parkinson's disease for three lead designs: the Medtronic 3389 (four cylindrical contacts), the direct STNAcute (two cylindrical contacts, six directional contacts), and the Medtronic-Sapiens lead (40 directional contacts).

MAIN RESULTS

The optimization algorithm returns patient-specific contact configurations in near real-time-less than 10 s for even the most complex leads. When the lead was placed centrally in the target STN, the directional leads were able to activate over 50% of the region, whereas the Medtronic 3389 could activate only 40%. When the lead was placed 2 mm lateral to the target, the directional leads performed as well as they did in the central position, but the Medtronic 3389 activated only 2.9% of the STN.

SIGNIFICANCE

This DBS programming algorithm can be applied to cylindrical electrodes as well as novel directional leads that are too complex with modern technology to be manually programmed. This algorithm may reduce clinical programming time and encourage the use of directional leads, since they activate a larger volume of the target area than cylindrical electrodes in central and off-target lead placements.

Abstract PD4-07: PET imaging of PARP-1 expression in breast cancer

18F-FluorThanatrace ([18F]-FTT) is a novel radiotracer shown to quantify Poly [ADP-ribose] polymerase 1 (PARP-1) expression in vitro and in vivo through a receptor-ligand interaction. A recent study at the University of Pennsylvania in women with ovarian cancer demonstrated in vivo visualization of PARP-1 expression in tumors using this radiotracer that closely correlated with an in vitro assay of PARP-1 in tumor tissue (Makvandi, M. J. Clin. Invest. 128:2116, 2018). A radioligand with PARP-1 specificity, [125I]-KX1, was also developed as a companion tool for ex vivo evaluation of PARP-1 expression and PARP inhibitor (PARPi) drug occupancy by radioligand binding assay (Makvandi, M. Cancer Res. 76:4516, 2016). As the first step in validating this biomarker in breast cancer, we performed a prospective clinical trial comparing in vivo [18F]-FTTuptake and ex vivo PARP-1 expression in women with primary breast cancer.

Methods: 24 patients with Stage I-IV primary breast cancer were imaged with [18F]-FTT prior to any therapy including surgery. We correlated in vivo uptake with ex vivo immunohistochemistry (IHC) for PARP-1 and [125I]-KX1 autoradiography in untreated surgical specimens. Tumors were analyzed for alterations in DNA repair genes, copy number-based as well as mutational signatures indicative of homologous recombination deficiency (HRD) and mutational burden, using our established protocol (Maxwell, KN, Nature Commun. 8:319, 2017).

Results: [18F]-FTT uptake was visualized above background in all primary breast tumors and known metastases. Two areas of unexpected uptake revealed an unknown contralateral breast cancer and an ovarian carcinoid, respectively. We expected that uptake might be highest in triple negative breast cancer (TNBC), where PARPi have been most heavily studied. However, a range of tracer uptake was observed in tumors independent of breast cancer subtype (hormone receptor positive/HER2 negative, TNBC, HER2+) and BRCA status. Uptake ratios (SUVmax tumor/SUV max opposite breast) ranged from 1.2-10.5 with a median 4.0. Ex vivo[125I]-KX1 autoradiography was performed on a subset of untreated primary tumors (n=5) and compared with IHC staining for PARP-1 on sequential sections. This revealed a close spatial correspondence between elevated PARP-1 expression by IHC and regions of elevated [125I]-KX1 binding radiographically. There was also a strong positive correlation between in vivo [18F]-FTT uptake and ex vivo quantitative [125I]-KX1 autoradiography (r=0.78). Genomic analysis of HRD in all tumors is pending and will be reported.

Conclusion: Initial analyses support the ability of [18F]-FTT to visualize and measure PARP-1 expression in breast cancer. This is the first step toward developing an imaging companion diagnostic to help guide PARP inhibitor treatment in breast cancer. Ongoing studies are expanding upon these results, testing the extent to which expression of PARP-1 by [18F]-FTT can predict response to PARP inhibitors and measure target engagement during therapy.

Citation Format: McDonald ES, Carlin S, Maxwell KN, Nayak A, Doot RK, Pantel AR, Farwell MD, Pryma DA, Clark AS, Shah P, DeMichele AM, Ziober A, Schubert EK, Palmer K, Lee HS, Matro J, de la Cruz L, Tchou J, Anderson DN, Feldman MD, Sheffer RE, Knollman H, Schnall MD, Makvandi M, Domchek S, Hubbard RA, Mach RH, Mankoff DA. PET imaging of PARP-1 expression in breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD4-07.

Anodic stimulation misunderstood: preferential activation of fiber orientations with anodic waveforms in deep brain stimulation

OBJECTIVE

During deep brain stimulation (DBS), it is well understood that extracellular cathodic stimulation can cause activation of passing axons. Activation can be predicted from the second derivative of the electric potential along an axon, which depends on axonal orientation with respect to the stimulation source. We hypothesize that fiber orientation influences activation thresholds and that fiber orientations can be selectively targeted with DBS waveforms.

APPROACH

We used bioelectric field and multicompartment NEURON models to explore preferential activation based on fiber orientation during monopolar or bipolar stimulation. Preferential fiber orientation was extracted from the principal eigenvectors and eigenvalues of the Hessian matrix of the electric potential. We tested cathodic, anodic, and charge-balanced pulses to target neurons based on fiber orientation in general and clinical scenarios.

MAIN RESULTS

Axons passing the DBS lead have positive second derivatives around a cathode, whereas orthogonal axons have positive second derivatives around an anode, as indicated by the Hessian. Multicompartment NEURON models confirm that passing fibers are activated by cathodic stimulation, and orthogonal fibers are activated by anodic stimulation. Additionally, orthogonal axons have lower thresholds compared to passing axons. In a clinical scenario, fiber pathways associated with therapeutic benefit can be targeted with anodic stimulation at 50% lower stimulation amplitudes.

SIGNIFICANCE

Fiber orientations can be selectively targeted with simple changes to the stimulus waveform. Anodic stimulation preferentially activates orthogonal fibers, approaching or leaving the electrode, at lower thresholds for similar therapeutic benefit in DBS with decreased power consumption.

Subthalamic deep brain stimulation reduces pathological information transmission to the thalamus in a rat model of parkinsonism

The degeneration of dopaminergic neurons in the substantia nigra pars compacta leads to parkinsonian motor symptoms via changes in electrophysiological activity throughout the basal ganglia. High-frequency deep brain stimulation (DBS) partially treats these symptoms, but the mechanisms are unclear. We hypothesize that motor symptoms of Parkinson’s disease (PD) are associated with increased information transmission from basal ganglia output neurons to motor thalamus input neurons and that therapeutic DBS of the subthalamic nucleus (STN) treats these symptoms by reducing this extraneous information transmission. We tested these hypotheses in a unilateral, 6-hydroxydopamine-lesioned rodent model of hemiparkinsonism. Information transfer between basal ganglia output neurons and motor thalamus input neurons increased in both the orthodromic and antidromic directions with hemiparkinsonian (hPD) onset, and these changes were reversed by behaviorally therapeutic STN-DBS. Omnidirectional information increases in the parkinsonian state underscore the detrimental nature of that pathological information and suggest a loss of information channel independence. Therapeutic STN-DBS reduced that pathological information, suggesting an effective increase in the number of independent information channels. We interpret these data with a model in which pathological information and fewer information channels diminishes the scope of possible motor activities, driving parkinsonian symptoms. In this model, STN-DBS restores information-channel independence by eliminating or masking the parkinsonism-associated information, and thus enlarges the scope of possible motor activities, alleviating parkinsonian symptoms.

Chicken or the leg: Sigmoid colon perforation by ingested poultry fibula proximal to an occult malignancy

INTRODUCTION

Colonic perforation by ingested foreign bodies is exceedingly rare, with the diagnosis made more challenging by patients infrequently recalling any inadvertent ingestion and the poor sensitivity of plain radiography.

PRESENTATION OF CASE

The presented case demonstrates that bony perforation of the large bowel might occur immediately proximal to an otherwise occult colonic malignancy.

DISCUSSION

Ingestion of foreign bodies is common and rarely results in colonic perforation. However, bony ingestion is not usually remembered and can be missed even with cross-sectional imaging. If present, consideration should be given to the presence of an adjacent concealed colon cancer.

CONCLUSION

The co-existence of separate pathology should be carefully assessed in these patients, since this has important implications for relevant investigations and appropriate surgical management.

Preoperative conditioning with oral carbohydrate loading and oral nutritional supplements can be combined with mechanical bowel preparation prior to elective colorectal resection

OBJECTIVE

Preoperative conditioning with oral fluid and carbohydrate (CHO) loading allows the patient to undergo surgery in the fed state and is associated with reduced postoperative insulin resistance. Further benefit may accrue from oral nutritional supplements (ONS) to counteract the fasting associated with mechanical bowel preparation (MBP). In this study we assess the ability to prescribe, dispense and have patients comply with a protocol combining preoperative ONS and CHO/fluid loading during MBP.

METHOD

One hundred and forty-seven patients undergoing elective left colonic or rectal resection were recruited to an Enhanced Recovery after Surgery (ERAS) programme. All patients were prescribed MBP (2 sachets Picolax). On the daytime prior to surgery, eligible patients were prescribed 2 x 200 ml of ONS (Fortijuice, Nutricia) and in the evening 800 ml oral CHO/fluid loading (Preop(R), Nutricia,). Patients were prescribed a further 400 ml of oral/CHO/fluid on the morning of surgery 2 h prior to induction of anaesthesia. Protocol compliance was audited prospectively.

RESULTS

One hundred and forty-seven patients received MBP. Twenty-three patients were ineligible for oral CHO/fluid loading [diabetes (n = 22), allergy to lemon flavoured drinks (n = 1)]. Fourteen patients did not receive the preoperative CHO drinks due to failure to prescribe (n = 8) or dispense (n = 6). One hundred and ten patients were dispensed the combined ONS and CHO/fluid loading regimen, compliance rates were 83% with ONS, 80% with CHO/fluid loading and 74% with both.

CONCLUSION

Approximately 74% of patients undergoing MBP can comply with preoperative conditioning with ONS and CHO/fluid loading. Prescription and dispensing requires close attention to detail.

Basic Surgical Training in the Era of the European Working Time Directive: What are the Problems and Solutions?

Background and Aims

Imposed reductions in working hours will impact significantly on the ability of surgical trainees to achieve competency. The objective of this study was to obtain the opinions of Scottish surgical trainees concerning the training they receive, in order to inform and guide the development of future, high-standard training programmes.

Methods

An anonymous questionnaire was sent to basic surgical trainees on the Edinburgh, Aberdeen and Dundee Basic Surgical Rotations commencing after August 2002.

Results

Thirty six questionnaire responses were analysed. Very few of the returned comments were complimentary to the existing training structure; indeed, most comments demonstrated significant trainee disappointment. Despite “regular” exposure to operative sessions, training tutorials and named consultant trainers, the most common concern was a perceived lack of high-quality, structured, operative exposure and responsibility. Textbooks and journals remain the most frequently utilised learning tools, with high-tech systems such as teleconferencing, videos, CD-ROMS, and DVDs being poorly exploited.

Conclusions

Current surgical training is not meeting the expectation of the majority of its trainees. To solve this problem will require extensive revision of attitudes and current educational format. A greater emphasis on the integration of 21st century learning tools in the training programme may help bridge this gap.

Paraileostomy recontouring by collagen sealant injection: a novel approach to one aspect of ileostomy morbidity. Report of a case

INTRODUCTION

Poorly fitting stoma appliances, resulting in stomal leakage and subsequent skin excoriation, remain a significant cause of ileostomy-related morbidity. One cause of ill-fitting stoma bags is the presence of parastomal dermal contour defects/irregularities. These may occur after surgical complications or change in patient weight and body habitus.

METHODS

We report the case of a 29-year-old man who, after panproctocolectomy and formation of ileostomy for ulcerative colitis, experienced significant problems with stoma bag application because of dermal contour defects. As a result, he suffered from significant stomal leakage and skin excoriation. After a single treatment of cutaneous parastomal infiltration of porcine collagen (Permacol Injection), applied stoma bags achieved a watertight seal, and the patient experienced complete and sustained resolution of his symptoms.

CONCLUSIONS

Porcine collagen is a safe, versatile, and relatively easy method of restoring irregular skin defects surrounding abdominal stomas, thus resolving the significant patient morbidity associated with ill-fitting stomal appliances. Such a technique avoids the need for surgical stoma refashioning, which may be associated with significant morbidity and unsatisfactory outcomes.

Secondary perineal hernia following open abdominoperineal excision of the rectum: report of a case and review of the literature

This is a case report of a 46-year-old man who presented with a painful perineal lump four months after abdominoperineal excision of the rectum (APER) with pre-operative radiotherapy and adjuvant chemotherapy. Perineal hernia (suspected clinically) was confirmed by magnetic resonance imaging, and the patient underwent open Permacol mesh repair via a perineal approach. Symptomatic perineal herniation after surgical resection is a rare phenomenon, and the approach to management remains challenging. Several different surgical approaches and techniques of repair have been described. In this report, we review the literature surrounding the presentation, aetiology and repair of this unusual post-operative complication. Furthermore, our case confirms that closure of the hernial orifice with mesh via a perineal approach is a satisfactory technique.

Red herring: a rare cause of small bowel obstruction

This is a case report of a 73-year-old man with a small bowel obstruction secondary to an incarcerated paracaecal hernia. His large right inguinal hernia, initially suspected as a potential source of obstruction, turned out to be a red herring. Congenital internal hernias are a very rare cause of bowel obstruction. In this report we review the literature and embryology behind these uncommon occurrences.

Duodenal webs--no age limit

BACKGROUND

Duodenal webs usually give rise to symptoms of gastric outlet obstruction in infancy, but they occasionally present in adulthood.

CASE OUTLINE

We report an 82-year-old woman with an unusual cause of gastric outlet obstruction. Peptic ulcer stricture or carcinoma were suspected, but a CT scan and upper gastrointestinal endoscopy revealed that her symptoms were the result of duodenal webs. The webs were successfully dilated at endoscopy.

DISCUSSION

Duodenal webs may rarely account for gastric outlet obstruction in adults. Failure to visualise the second and third parts of the duodenum at endoscopy means that the diagnosis may be missed. Diclofenac and slow-release potassium tablets may have played an aetiological role in the formation of the webs in this patient.

Domiciliary clinics I: effects on non-attendance

OBJECTIVE

To compare the rate of non-attendance for new referrals to a hospital based clinic versus home assessment.

SETTING

Two old age psychiatry services in an urban area.

METHOD

A four year prospective study comparing rates of non-attendance for new referrals to a hospital based clinic versus assessment at home in two parallel old age psychiatry services.

RESULTS

The rate of non-attendance for new referrals seen at home was considerably lower (1.7%) than the hospital based clinic (21.2%).

CONCLUSIONS

Assessing new outpatient referrals to old age psychiatry services at home reduces non-attendance. This improves efficient use of medical time in a small geographical catchment area but may not apply to rural or larger areas.

Treating depression in old age: the reasons to be positive

Depression affects 10-15% of people over 65 living at home in the United Kingdom. It is the commonest and the most reversible mental health problem in old age. Depression is associated with physical illness and disability, life events, social isolation and loneliness. Depression in old age carries an increased risk of suicide and natural mortality. Recognition and simple intervention can reduce morbidity, demand on health and social services and the cost of community care. Despite a favourable response to treatment, depression remains largely undetected and untreated.

Onycholysis as a complication of systemic chemotherapy: report of five cases associated with prolonged weekly paclitaxel therapy and review of the literature

BACKGROUND

Onycholysis has been reported in association with the use of several noncytotoxic drugs and with chemotherapy in 135 patients. Onycholysis may be precipitated by exposure to ultraviolet radiation.

METHODS

The authors studied 91 patients who received paclitaxel and 187 patients who received doxorubicin.

RESULTS

Onycholysis occurred in 5 of 21 patients who received > 6 courses of weekly paclitaxel, developing in the summer months in all 5 patients. It did not occur in patients who received fewer weekly paclitaxel courses or those who were treated every 3 weeks. Onycholysis did not occur in 187 patients who received doxorubicin. Review of the literature revealed that onycholysis is nearly exclusively associated with anthracycline and taxane therapy.

CONCLUSIONS

Prolonged weekly paclitaxel, other taxanes, and anthracyclines cause onycholysis in some patients, which may be precipitated by exposure to sunlight. Patients receiving these drugs should protect their nails from sunlight.

Colonic perforation following prolonged hypovolaemia in a major burns injury

Perforation of the lower gastrointestinal tract is rare in burns patients. A 41-year-old male, who sustained 40% total body surface area burns and subsequently developed an acute abdomen on day 15 postburn, is presented. Emergency management included a subtotal colectomy and ileostomy formation performed to repair a perforated transverse colon found at laparotomy. The burns were debrided and grafted and the patient required cardiac, renal and respiratory support initially in the ITU setting before making a complete recovery. It is suggested that ischaemia caused the perforated transverse colon due to a prolonged low flow state. This was not detected until invasive cardiovascular catheterisation was performed and revealed a hypovolaemic state, which was corrected by fluids and noradrenaline. Both the previous cardiac history of the patient (Fallot's Tetralogy repair) and the noradrenaline may have exacerbated the low flow state within the mesenteric circulation leading to ultimate perforation. This case highlights the difficulties that may arise in resuscitating a patient who has previously had a cardiac defect repaired. Despite repair, abnormal physiology may persist resulting in misleading observations that produce undetected hypovolaemia with subsequent adverse events, as in this case. In such patients, early invasive cardiovascular monitoring should be considered.

The role of pterins and related factors in the biology of early postpartum depression

Plasma tryptophan and other putative amino acids, cortisol, folate and vitamin B12 and urinary biopterin (B) and neopterins (N) were measured in three groups of women: 62 women in the early postpartum period, 23 pregnant and 38 non-gravid controls. Sixty-two postpartum women were screened for depression by the Edinburgh postnatal depression scale (EPDS) on day 7 after delivery. Postpartum women had significantly lower tryptophan, vitamin B12 and significantly greater levels of cortisol, folate, neopterins and biopterins than controls. Comparisons between women who were classified on the EPDS as cases and non-cases revealed only a statistically significant difference for lower N:B (P<0.01) and lower folate (P<0.01) ratio in cases than non-cases. Multiple regression analysis showed a significant contribution for low tryptophan to increased EPDS which also showed significant correlations with low methionine, low tyrosine, low N:B ratio and high vitamin B12.

Vesico-colic fistulae in the Grampian region: presentation, assessment, management and outcome

Over a 12-year period, 67 patients presented with a vesico-colic fistula. The mean age was 69 years (range 19-96 years), with symptoms predominantly referred to the urinary tract. Cystoscopy and barium enema confirmed the presence of a fistula in 60 and 44% of patients respectively. A computerized tomography (CT) scan, used in only seven patients, revealed the fistula in each case. The underlying pathology included diverticular disease (62%), carcinoma (27%) and inflammatory bowel disease (6%). Fifty-one patients proceeded to surgery, of whom 32 (63%) had a sigmoid/recto sigmoid resection with primary anastomosis, and 13 (25%) a Hartmann's procedure. A diverting colostomy alone was employed to palliate cases of widespread carcinoma. No patient subsequently had the Hartmann's reversed. In addition to colonic resection, 48 (92%) patients had a simultaneous bladder procedure, varying from simple oversew in 32 (70%) patients to cystectomy and ileal conduit in three (6%). Wedge excision with primary bladder closure was practised in 12 (24%). Fistula recurrence occurred in seven (14%) patients, and the 30-day mortality was 10%. Surgery for vesico-colic fistula has an appreciable morbidity and mortality, yet if offers the only hope of achieving permanent symptomatic control.

Diverticular disease in patients under 50 years of age

Sigmoid diverticular disease, when it occurs in a young age group, may follow a more aggressive course with a higher incidence of complications than in elderly. The mode of presentation and management in 77 patients under 50 years of age presenting with sigmoid diverticular disease over a 6-year period is described. Surgery for complications (peritonitis, abscess, bowel obstruction, fistula and haemorrhage) was performed in 18 (23%) individuals. Colonic resection was carried out in 14 (78%) of the operated group with primary anastomosis in six patients and Hartmann's procedure in eight patients. The mortality (30 day) was zero. Nineteen (25%) of the entire group, and 12 (67%) of those undergoing surgery had been previously hospitalized with a complication of diverticular disease. The recurrent nature and frequency of serious complications in this group, suggests that elective surgery should be considered if an acute infective episode is successfully managed conservatively.

Maintenance electroconvulsive therapy and cognitive function

BACKGROUND

ECT is rarely used as a prophylactic treatment. A 74-year-old woman with unstable bipolar affective disorder receiving maintenance ECT presented a unique opportunity to measure the cognitive effects of continuing ECT.

METHOD

A single case report with serial psychometric testing during over 400 ECT treatments as a single maintenance treatment.

RESULTS

Serial testing did not demonstrate progressive cognitive deterioration, but consistent cognitive deficits typical of acute treatment were evident. The degree of cognitive difficulty may be related to the frequency of treatment.

CONCLUSIONS

Maintenance ECT can be an effective prophylactic treatment for selected patients. Cognitive effects would appear to be no greater than with acute treatment and seem to be non-progressive.

Does age predict the long-term outcome of depression treated with ECT? (a prospective study of the long-term outcome of ECT-treated depression with respect to age)

Sixty-three subjects with DSM-III-R major depression with melancholia or psychosis were followed up 2-4 years after index treatment with electroconvulsive therapy. There was a twofold increase in likelihood of improved outcome with an additional 20 years of age.

Accuracy of laparoscopic ultrasonography in the staging of upper gastrointestinal malignancy

Laparoscopic ultrasonographic staging was compared prospectively with conventional computed tomography (CT) and ultrasonographic staging of 24 lower-third oesophageal tumors and 20 gastric malignancies. Following laparoscopic ultrasonography, seven patients regarded as being resectable after conventional imaging were excluded from surgical exploration because of ascites with peritoneal deposits (four patients), liver metastases (one), advanced local disease (one) and poor tolerance of general anaesthesia (one). Preoperative T and N stages were compared with the pathological staging following resection in 34 patients. Laparoscopic ultrasonography was significantly more accurate than conventional CT and ultrasonography in assessment of the primary tumour (91 versus 64 per cent, P < 0.01) and nodal status (91 versus 62 per cent, P < 0.05). The addition of laparoscopic ultrasonography to conventional procedures for staging upper gastrointestinal malignancy improved the overall accuracy of staging. Although this may have future implications for the selection of patients for multimodality treatment, management decisions are currently based on laparoscopic findings, which in this study resulted in a resection rate of 97 per cent.

Gastric lymphoma in Grampian Region: presentation, treatment and outcome

Forty cases of gastric lymphoma presenting in Grampian Region (1974-91) were reviewed to examine the effects of changing ideas in the fields of chemotherapy, gastric surgery and diagnostic techniques, as well as the impact of Helicobacter pylori. Presentation was non-specific, and the diagnosis was made pre-operatively in only 12 cases. Survival was related to tumour size, staging (Ann Arbor), and grade, with a crude 5-year survival of 49%. Helicobacter pylori was found in all specimens reviewed. Patients who underwent "potentially curative' surgery followed by adjuvant therapy had the best survival (85% at 5 years). There remains a need for larger studies to define the best treatment for this uncommon condition.

Massive intestinal bleeding in association with Crohn's disease

Five hundred and one patients with Crohn's disease, presenting to a single surgical unit during a 20-year period, were reviewed by utilizing a computerized audit system. Ten patients were identified with rectal bleeding significant enough to require a blood transfusion to maintain cardiovascular homeostasis. The site of bleeding was correctly identified pre-operatively in only one patient, and at the time of surgery in only four patients. In nine (90%) of the 10 cases, the origin of the bleeding was subsequently found to be colonic. All 10 patients were treated surgically, with seven patients requiring fashioning of a stoma, none of whom had gastro-intestinal continuity subsequently re-established. Recurrent bleeding occurred in a single patient. The early post-operative mortality was 20%. Massive rectal bleeding remains an uncommon complication of Crohn's disease, and still carries significant morbidity and mortality. Pre-operative localization of the site of bleeding is uncommon, making intra-operative identification of the bleeding area difficult.

The role of pterins in depression and the effects of antidepressive therapy

Urinary excretion of neopterins (N) and biopterins (B) was measured in 48 patients with depression before and after treatment with placebo, antidepressants, or electroconvulsive therapy (ECT), and in 26 healthy control subjects. Patients prior to and after treatment had a significantly greater neopterin/biopterin (N:B) ratio than control subjects. There was a significant correlation between N:B ratios and the severity of depression and plasma cortisol. As a raised N:B ratio implies failure to convert neopterin to biopterin, it is possible that reduced availability of tetrahydrobiopterin, the essential cofactor for the formation of noradrenaline, serotonin and dopamine, may exert rate-limiting control over the synthesis of monoamines implicated in the pathogenesis of depressive illness.

Delusional depression, hyperparathyroidism, and ECT

A woman with delusional depression and unsuspected primary hyperparathyroid disorders responded completely to electroconvulsive therapy (ECT). Hypercalcemia is a complicating factor in the treatment of delusional depression, but there is little evidence that it is causative and the use of ECT should not be delayed. The case adds to the literature confirming the efficacy and safety of ECT with physically ill patients when it may be a life-saving procedure.

5-Methyltetrahydrofolate level in the serum of depressed subjects and its relationship to the outcome of ECT

Serum 5-MeTHF levels are reported in 26 subjects, before and after completing a course of ECT, and compared to 21 healthy volunteers. 5-MeTHF levels of depressed subjects were significantly lower than controls before and after ECT. There was no difference in 5-MeTHF levels between ECT responders and non-responders but folate deficiency was related to severity of depression before ECT. Serum 5-MeTHF was not related to treatment response and values remained markedly low even after a good response to treatment.

Loop ileostomy fixation: a simple technique to minimise the risk of stomal volvulus

Turnbull's "loop" ileostomies is a routinely performed procedure in the management of a variety of colorectal problems. Mechanical and functional complications occur with both permanent and temporary ileostomies, however they are more common with the loop than with the end (Brooke) variety. With the advent of restorative proctocolectomy with pouch formation, and the documented benefit of simultaneous temporary faecal diversion, the incidence of such complications will rise. Bowel obstruction, requiring laparotomy in the interval before stoma closure, is more commonly associated with the loop ileostomy. A loop stoma is routinely brought out directly through the abdominal wall, with little or no fixation or closure of the lateral space. However, anti-mesenteric fixation, as described here, minimises the risk of volvulus by widening the attachment of the adjacent ileum to the parities, creating a broader fulcrum. Since adopting this simple technique, we report no complications in over 30 loop ileostomies, "fixed" by this technique and followed up for a minimum of 4 years. Where applicable, no difficulty was encountered with stoma closure, either by a transverse single layer serosubmucosal technique, or as a minimal resection with end to end anastomosis (sewn or stapled), following bowel mobilisation. This technique should minimise the frequency of obstructive events, and we recommend it's routine use.

Recovery from depression after electroconvulsive therapy is accompanied by evidence of increased tetrahydrobiopterin-dependent hydroxylation

Serum phenylalanine and tyrosine levels were measured in 26 patients with severe depression before and after receiving electroconvulsive therapy. The phenylalanine:tyrosine [P:T] ratio declined significantly for those responding to treatment but not for nonresponders. These findings are discussed in relation to tetrahydrobiopterin, the essential cofactor for the formation of noradrenaline, dopamine and serotonin and the hydroxylation of phenylalanine to tyrosine.