From "mechanical" to "neuropathic" back pain concept in FBSS patients. A systematic review based on factors leading to the chronification of pain (part C)

INTRODUCTION

Beyond initial lesions, any form of spinal (re)operation can cause direct potential aggression to the nervous system by contact with neural tissue or by imprinting a morphological change on the neural tissue. The potential consequences of nerve root injury affect both peripheral and axial dermatomal distribution. The hypothesis of a possible neuropathic aspect associated with the back pain component of failed back surgery syndrome (FBSS) therefore appears to be reasonable. Its pathophysiology remains unclear due to the permanent interplay between nociceptive and neuropathic pain components, resulting in the coexistence of physiological and pathological pain at the same anatomical site. This paper is designed to extensively review the fundamental mechanisms leading to chronification of pain and to suggest considering the emerging concept of "neuropathic back pain".

METHODS

Literature searches included an exhaustive review of 643 references and 74 book chapters updated by searching the major electronic databases from 1930 to August 2013.

RESULTS

Inflammatory and neuropathic back pain could be distinguished from pure nociceptive pain as a result of an increased activity and responsiveness of sensitized receptors at the peripheral nervous system and also as a consequence of increased afferent inflow to the central nervous system, moving to a new, more excitable "wind-up" state. This can be clinically translated to an amplified response to a moderate/intense stimulus (primary hyperalgesia) or an aversive sensation provoked by the activation of low-threshold mechanoreceptors through non-noxious stimuli, which defines allodynia. Activated non-neuronal cells including microglia have been found to be cellular intermediaries in mechanical allodynia. Major changes in the spinal cord are the loss of inhibitory mechanisms, resulting in an increased activity of interneurons or projection neurons and a structural reorganization of the central projection pattern. This abnormal excitability of sensory neurons is coupled to changes in the neurotransmitter phenotype, which could induce a resistance to conventional analgesic treatments.

CONCLUSION

A clear understanding of the factors leading to the chronification of back pain should help us to move to the choice of mechanism related pain treatments to improve outcomes in FBSS chronic condition.

TruFit Plug for Repair of Osteochondral Defects-Where Is the Evidence? Systematic Review of Literature

OBJECTIVE

Treatment of osteochondral defects remains a challenge in orthopedic surgery. The TruFit plug has been investigated as a potential treatment method for osteochondral defects. This is a biphasic scaffold designed to stimulate cartilage and subchondral bone formation. The aim of this study is to investigate clinical, radiological, and histological efficacy of the TruFit plug in restoring osteochondral defects in the joint.

DESIGN

We performed a systematic search in five databases for clinical trials in which patients were treated with a TruFit plug for osteochondral defects. Studies had to report clinical, radiological, or histological outcome data. Quality of the included studies was assessed.

RESULTS

Five studies describe clinical results, all indicating improvement at follow-up of 12 months compared to preoperative status. However, two studies reporting longer follow-up show deterioration of early improvement. Radiological evaluation indicates favorable MRI findings regarding filling of the defect and incorporation with adjacent cartilage at 24 months follow-up, but conflicting evidence exists on the properties of the newly formed overlying cartilage surface. None of the included studies showed evidence for bone ingrowth. The few histological data available confirmed these results.

CONCLUSION

There are no data available that support superiority or equality of TruFit compared to conservative treatment or mosaicplasty/microfracture. Further investigation is needed to improve synthetic biphasic implants as therapy for osteochondral lesions. Randomized controlled clinical trials comparing TruFit plugs with an established treatment method are needed before further clinical use can be supported.

Anatomy, physiology and neurobiology of the nociception: a focus on low back pain (part A)

INTRODUCTION

The treatment of Failed Back Surgery Syndrome (FBSS) remains a challenge for pain medicine due to the complexity in the interactions between [1] a residual mechanical pain after surgery and, [2] a progressive transition into chronic pain involving central nervous system plasticity and molecular reorganization. The aim of this paper is to provide a fundamental overview of the pain pathway supporting the nociceptive component of the back pain.

METHODS

Literature searches included an exhaustive review of 643 references and 74 book chapters updated by searching the major electronic databases from 1930 to August 2013.

RESULTS

Pain input is gathered by the peripheral fibre from the innervated tissue's environment and relayed by two contiguous central axons to the brain, via the spinal cord. At this level, it is possible to characterize physical pain and emotional pain. These are supported by two different pathways, encoding two dimensions of pain perception: In Neo-spino-thalamic pathway, the wide dynamic range neuron system is able to provide the information needed for mapping the "sensory-discriminative" dimension of pain. The second projection system (Paleo-spino-thalamic pathway) also involves the ventromedial thalamus but projects to the amygdala, the insula and the anterior cingulate cortex. These areas are associated with emotionality and affect.

CONCLUSION

The mechanical component of FBSS cannot be understood unless the functioning of the pain system is known. But ultimately, the highly variable nature of back pain expression among individuals would require a careful pathophysiological dissection of the potential generators of back pain to guide pain management strategies.

Pathophysiological characterisation of back pain generators in failed back surgery syndrome (part B)

INTRODUCTION

Low back surgery, including as many type of spine procedures as the multitude of failed back surgery syndrome (FBSS) etiologies, is not always the answer for patients with chronic low back pain. Paradoxically, although a patient is considered to present FBSS because he has already undergone spinal surgery, any new symptom in the back or deterioration of back pain must not be immediately attributed to FBSS, but could be related to another cause independently of the initial mechanical problem. The aim of this paper is to extensively review the potential back pain generators in FBSS patients and to discuss their respective roles and interactions in back pain pathophysiology.

METHODS

Literature searches included an exhaustive review of 643 references and 74 book chapters updated by searching the major electronic databases from 1930 to August 2013.

RESULTS

Nociceptive fibres innervating any of the back anatomical structures can all play a part in the pathogenesis of the low back pain component in FBSS. The main spinal pain generators are not only myofascial syndrome or muscle spasm but also the facets, the disc complex or a sagittal imbalance and should therefore be carefully reviewed. Only after these steps and appropriate imaging, would it be justified to irremediably diagnose the patient with a refractory chronic condition, requiring no further spine surgery and to propose "palliative" pain treatment options.

CONCLUSION

Clinical investigations of the low back pain component in FBSS patients should be based on meticulous dissection of all potential triggers that could be a source of the nociceptive pain characteristics and possibly amenable to further aetiological treatment. Clinicians should therefore refine pain management strategies to ensure that the chronic nature of the pain becomes the guiding principle for multidisciplinary assessment.

Multicolumn spinal cord stimulation for significant low back pain in failed back surgery syndrome: design of a national, multicentre, randomized, controlled health economics trial (ESTIMET Study)

BACKGROUND

Many studies have demonstrated the efficacy of spinal cord stimulation (SCS) for chronic neuropathic radicular pain over recent decades, but despite global favourable outcomes in failed back surgery syndrome (FBSS) with leg pain, the back pain component remains poorly controlled by neurostimulation. Technological and scientific progress has led to the development of new SCS leads, comprising a multicolumn design and a greater number of contacts. The efficacy of multicolumn SCS lead configurations for the treatment of the back pain component of FBSS has recently been suggested by pilot studies. However, a randomized controlled trial must be conducted to confirm the efficacy of new generation multicolumn SCS. Évaluation médico-économique de la STImulation MEdullaire mulTi-colonnes (ESTIMET) is a multicentre, randomized study designed to compare the clinical efficacy and health economics aspects of mono- vs. multicolumn SCS lead programming in FBSS patients with radicular pain and significant back pain.

MATERIALS AND METHODS

FBSS patients with a radicular pain VAS score≥50mm, associated with a significant back pain component were recruited in 14 centres in France and implanted with multicolumn SCS. Before the lead implantation procedure, they were 1:1 randomized to monocolumn SCS (group 1) or multicolumn SCS (group 2). Programming was performed using only one column for group 1 and full use of the 3 columns for group 2. Outcome assessment was performed at baseline (pre-implantation), and 1, 3, 6 and 12months post-implantation. The primary outcome measure was a reduction of the severity of low back pain (bVAS reduction≥50%) at the 6-month visit. Additional outcome measures were changes in global pain, leg pain, paraesthesia coverage mapping, functional capacities, quality of life, neuropsychological aspects, patient satisfaction and healthcare resource consumption.

TRIAL STATUS

Trial recruitment started in May 2012. As of September 2013, all 14 study centres have been initiated and 112/115 patients have been enrolled. Preliminary results are expected to be published in 2015.

TRIAL REGISTRATION

Clinical trial registration information-URL: www.clinicaltrials.gov. Unique identifier NCT01628237.

Is pineal melatonin released in the third ventricle in humans? A study in movement disorders

In order to determine sources and metabolism of melatonin in human cerebrospinal fluid (CSF), melatonin and 6-sulfatoxymelatonin (aMT6S) concentrations were measured in CSF sampled during neurosurgery in both lateral and third ventricles in patients displaying movement disorder (Parkinson's disease, essential tremor, dystonia or dyskinesia) and compared with their plasma levels. Previous determinations in nocturnal urine had showed that the patients displayed melatonin excretion in the normal range, compared with healthy controls matched according to age. A significant difference in melatonin concentration was observed between lateral and third ventricles, with the highest levels in the third ventricle (8.75±2.75pg/mL vs. 3.20±0.33pg/mL, P=0.01). CSF aMT6s levels were similar in both ventricles and of low magnitude, less than 5pg/mL. They were not correlated with melatonin levels or influenced by the area of sampling. Melatonin levels were significantly higher in third ventricle than in the plasma, whereas there was no difference between plasma and lateral ventricle levels. These findings show that melatonin may enter directly the CSF through the pineal recess in humans. The physiological meaning of these data remains to be elucidated.

Anatomy of the pineal region applied to its surgical approach

INTRODUCTION

The pineal region is situated in the posterior part of the incisural space. This region includes the pineal body inside the quadrigeminal arachnoidal cistern. This article reviews the anatomic features of this region, with particular emphasis on those aspects of importance for surgical access to the pineal region.

MATERIAL & METHODS

Five cadaver heads fixed in 10% formalin and injected with colored latex were used for anatomic dissection (five other specimens were also prepared and dissected to illustrate the articles on surgical techniques and approaches presented elsewhere in this issue).

RESULTS

The pineal body is surrounded by several important structures such as: posterior part of the third ventricle, tectum, the complex of the great cerebral vein of Galen, pulvinar nuclei of the thalamus and splenium of corpus callosum.

CONCLUSION

The surgical approach of the pineal body, whatever the route or the technique used (microsurgical, endoscopic or stereotactic), creates a great challenge for the neurosurgeons due to its location in the deep part of the brain and its close relationships with complex surrounded vascular structures.

Does the rectus femoris nerve block improve knee recurvatum in adult stroke patients? A kinematic and electromyographic study

Knee recurvatum (KR) during gait is common in hemiplegic patients. Quadriceps spasticity has been postulated as a cause of KR in this population. The aim of this study was to assess the role of rectus femoris spasticity in KR by using selective motor nerve blocks of the rectus femoris nerve in hemiparetic stroke patients. The data from six adult, post-stroke hemiplegic patients who underwent a rectus femoris nerve block for a stiff-knee gait were retrospectively analyzed. An extensive clinical and functional evaluation was performed and gait was assessed by motion analysis (kinematic, kinetic and electromyographic parameters) before and during the block realized using 2% lidocaine injected under a neurostimulation and ultrasonographic targeting procedure. The main outcome measures were the peak knee extension in stance and peak knee extensor moment obtained during gait analysis. No serious adverse effect of the nerve block was observed. The block allowed a reduction of rectus femoris overactivity in all patients. Peak knee extension and extensor moment in stance did not improve in any patient, but peak knee flexion during the swing phase was significantly higher after block (mean: 31.2° post, 26.4 pre, p < 0.05). Our results provide arguments against the hypothesis that the spasticity of the rectus femoris contributes to KR.

Motor cortex stimulation does not improve dystonia secondary to a focal basal ganglia lesion

OBJECTIVE

To assess the efficacy of epidural motor cortex stimulation (MCS) on dystonia, spasticity, pain, and quality of life in patients with dystonia secondary to a focal basal ganglia (BG) lesion.

METHODS

In this double-blind, crossover, multicenter study, 5 patients with dystonia secondary to a focal BG lesion were included. Two quadripolar leads were implanted epidurally over the primary motor (M1) and premotor cortices, contralateral to the most dystonic side. The leads were placed parallel to the central sulcus. Only the posterior lead over M1 was activated in this study. The most lateral or medial contact of the lead (depending on whether the dystonia predominated in the upper or lower limb) was selected as the anode, and the other 3 as cathodes. One month postoperatively, patients were randomly assigned to on- or off-stimulation for 3 months each, with a 1-month washout between the 2 conditions. Voltage, frequency, and pulse width were fixed at 3.8 V, 40 Hz, and 60 μs, respectively. Evaluations of dystonia (Burke-Fahn-Marsden Scale), spasticity (Ashworth score), pain intensity (visual analog scale), and quality of life (36-Item Short Form Health Survey) were performed before surgery and after each period of stimulation.

RESULTS

Burke-Fahn-Marsden Scale, Ashworth score, pain intensity, and quality of life were not statistically significantly modified by MCS.

CONCLUSIONS

Bipolar epidural MCS failed to improve any clinical feature in dystonia secondary to a focal BG lesion.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that bipolar epidural MCS with the anode placed over the motor representation of the most affected limb failed to improve any clinical feature in dystonia secondary to a focal BG lesion.

Deep-brain stimulation for dystonia: current indications and future orientations

ABSTRACT: Deep-brain stimulation of the internal globus pallidus is a therapeutic option for dystonia. However, the available data are heterogeneous, ranging from single case reports to a few controlled studies. The outcomes are also largely heterogeneous, depending mostly on the etiology of the dystonia. Except for some well-established good indications, such as primary generalized dystonia and tardive dyskinesia, the efficacy of globus pallidus stimulation remains debated for several forms of dystonia. In addition, many issues are still unsolved, such as the best target of stimulation and the interest of simultaneously combining multiple targets of stimulation or not. Finally the efficacy of new strategies of treatment, such as cortical stimulation, remains to be determined. The aim of this review is to cover these different aspects and give an overview of the current indications and future orientations.

Is Life better after motor cortex stimulation for pain control? Results at long-term and their prediction by preoperative rTMS

BACKGROUND

A positive effect of motor cortex stimulation (MCS) (defined as subjective estimations of pain relief ≥ 30%) has been reported in 55 - 64% of patients. Repetitive magnetic cortical stimulation (rTMS) is considered a predictor of MCS effect. These figures are, however, mostly based on subjective reports of pain intensity, and have not been confirmed in the long-term.

OBJECTIVES

This study assessed long-term pain relief (2 - 9 years) after epidural motor cortex stimulation and its pre-operative prediction by rTMS, using both intensity and Quality of Life (QoL) scales.

STUDY DESIGN

Analysis of the long-term evolution of pain patients treated by epidural motor cortex stimulation, and predictive value of preoperative response to rTMS.

SETTING

University Neurological Hospital Pain Center.

PATIENTS

Twenty patients suffering chronic pharmaco-resistant neuropathic pain.

INTERVENTION

All patients received first randomized sham vs. active 20 Hz-rTMS, before being submitted to MCS surgery.

MEASUREMENT

Postoperative pain relief was evaluated at 6 months and then up to 9 years post-MCS (average 6.1 ± 2.6 y) using (i) pain numerical rating scores (NRS); (ii) a combined assessment (CPA) including NRS, drug intake, and subjective quality of life; and (iii) a short questionnaire (HowRu) exploring discomfort, distress, disability, and dependence.

RESULTS

Pain scores were significantly reduced by active (but not sham) rTMS and by subsequent MCS. Ten out of 20 patients kept a long-term benefit from MCS, both on raw pain scores and on CPA. The CPA results were strictly comparable when obtained by the surgeon or by a third-party on telephonic survey (r = 0.9). CPA scores following rTMS and long-term MCS were significantly associated (Fisher P = 0.02), with 90% positive predictive value and 67% negative predictive value of preoperative rTMS over long-term MCS results. On the HowRu questionnaire, long-term MCS-related improvement concerned "discomfort" (physical pain) and "dependence" (autonomy for daily activities), whereas "disability" (work, home, and leisure activities) and "distress" (anxiety, stress, depression) did not significantly improve.

LIMITATIONS

Limited cohort of patients with inhomogeneous pain etiology. Subjectivity of the reported items by the patient after a variable and long delay after surgery. Predictive evaluation based on a single rTMS session compared to chronic MCS.

CONCLUSIONS

Half of the patients still retain a significant benefit after 2 - 9 years of continuous MCS, and this can be reasonably predicted by preoperative rTMS. Adding drug intake and QoL estimates to raw pain scores allows a more realistic assessment of long-term benefits and enhance the rTMS predictive value. The aims of this study and its design were approved by the local ethics committee (University Hospitals St Etienne and Lyon, France).

What is the dorsal median sulcus of the spinal cord? Interest for surgical approach of intramedullary tumors

PURPOSE

For intramedullary tumor (IMT) surgery, a balance has to be found between aggressively resecting the tumor and respecting all the sensory and motor pathways. The most common surgical approach is through the dorsal median sulcus (DMS) of the spinal cord. However, the precise organization of the meningeal sheats in the DMS remains obscure in the otherwise well-described anatomy of the spinal cord. A better understanding of this architecture may be of benefit to IMT surgeon to spare the spinal cord.

METHODS

Three spinal cords were studied. The organization of the spinal cord meninges in the DMS was described via macroscopic, microsurgical and optical microscopic views. A micro dissection of the DMS was also performed.

RESULTS

No macroscopic morphological abnormalities were observed. With the operative magnifying lens, the dura was opened, the arachnoid was removed and the pia mater was cut to access the DMS. The histological study showed that the DMS was composed of a thin rim of capillary-carrying connective tissue extending from the pia mater and covering the entire DMS. There was no true space between the dorsal columns, no arachnoid or crossing axons either.

CONCLUSION

Our work indicates that the DMS is not a sulcus but a thin blade of collagen extending from the pia mater. Its location is given by tiny vessels coming from the surface towards the deep. Thus, the surgical corridor has to follow the DMS as closely as possible to prevent damage to the spinal cord during midline IMT removal.

Definition of a stereotactic 3-dimensional magnetic resonance imaging template of the human insula

BACKGROUND

This study proposes a 3-dimensional (3-D) template of the insula in the bicommissural reference system with posterior commissure (PC) as the center of coordinates.

OBJECTIVE

Using the bicommissural anterior commissure (AC)-PC reference system, this study aimed to define a template and design a method for the 3-D reconstruction of the human insula that may be used at an individual level during stereotactic surgery.

METHODS

Magnetic resonance imaging (MRI)-based morphometric analysis was performed on 100 cerebral cortices with normal insulae based on a 3-step procedure: Step 1: AC-PC reference system-based reconstruction of the insula from the 1-mm thick 3-D T1-weighted MRI slices. Step 2: Digitalization and superposition of the data obtained in the 3 spatial planes. Step 3: Representation of pixels as colors on a scale corresponding to the probability of localization of each insular anatomic component.

RESULTS

The morphometric analysis of the insula confirmed our previously reported findings of a more complex shape delimited by 4 peri-insular sulci. A very significant correlation between the coordinates of the main insular structures and the length of AC-PC was demonstrated. This close correlation allowed us to develop a method that allows the 3-D reconstruction of the insula from MRI slices and only requires the localization of AC and PC. This process defines an area deemed to contain insula with 100% probability.

CONCLUSION

This 3-D reconstruction of the insula should be useful to improve its localization and other cortical areas and allow the differentiation of insular cortex from opercular cortex.

Parkinsonian apathy responds to dopaminergic stimulation of D2/D3 receptors with piribedil

Apathy is one of the most common symptoms encountered in Parkinson's disease, and is defined as a lack of motivation accompanied by reduced goal-directed cognition, behaviour and emotional involvement. In a previous study we have described a delayed withdrawal syndrome after successful motor improvement related to subthalamic stimulation allowing for a major decrease in dopaminergic treatment. This withdrawal syndrome correlated with a diffuse mesolimbic dopaminergic denervation. To confirm our hypothesis of parkinsonian apathy being related to mesolimbic dopaminergic denervation, we performed a randomized controlled study using piribedil, a relatively selective D2/D3 dopamine agonist to treat parkinsonian apathy, using the model of postoperative apathy. A 12-week prospective, placebo-controlled, randomized, double-blinded trial was conducted in 37 patients with Parkinson's disease presenting with apathy (Starkstein Apathy Scale score > 14) following subthalamic nucleus stimulation. Patients received either piribedil up to 300 mg per day (n = 19) or placebo (n = 18) for 12 weeks. The primary end point was the improvement of apathy under treatment, as assessed by the reduction of the Starkstein Apathy Scale score in both treatment groups. Secondary end points included alleviation in depression (Beck Depression Inventory), anxiety (Beck Anxiety Inventory), improvement of quality of life (PDQ39) and anhedonia (Snaith-Hamilton Pleasure Scale). Exploratory endpoints consisted in changes of the Robert Inventory score and Hamilton depression scales. An intention to treat analysis of covariance analysis was performed to compare treatment effects (P < 0.05). The number of premature study dropouts was seven in the placebo and five in the piribedil groups, mostly related to intolerance to hypodopaminergic symptoms. At follow-up evaluation, the apathy score was reduced by 34.6% on piribedil versus 3.2% on placebo (P = 0.015). With piribedil, modifications in the Beck depression and anxiety scores were -19.8% and -22.8%, respectively versus +1.4% and -8.3% with placebo, without reaching significance level. Piribedil led to a trend towards improvement in quality of life (-16.2% versus +6.7% on placebo; P = 0.08) and anhedonia (-49% versus -5.6% on the placebo; P = 0.08). Apathy, assessed by the Robert Inventory score, improved by 46.6% on piribedil and worsened by 2.3% on placebo (P = 0.005). Depression, measured by the Hamilton score, improved in the piribedil group (P = 0.05). No significant side effects were observed. The present study provides a class II evidence of the efficacy of the dopamine agonist piribedil in the treatment of apathy in Parkinson's disease.

Neurostimulation for Parkinson's disease with early motor complications

BACKGROUND

Subthalamic stimulation reduces motor disability and improves quality of life in patients with advanced Parkinson's disease who have severe levodopa-induced motor complications. We hypothesized that neurostimulation would be beneficial at an earlier stage of Parkinson's disease.

METHODS

In this 2-year trial, we randomly assigned 251 patients with Parkinson's disease and early motor complications (mean age, 52 years; mean duration of disease, 7.5 years) to undergo neurostimulation plus medical therapy or medical therapy alone. The primary end point was quality of life, as assessed with the use of the Parkinson's Disease Questionnaire (PDQ-39) summary index (with scores ranging from 0 to 100 and higher scores indicating worse function). Major secondary outcomes included parkinsonian motor disability, activities of daily living, levodopa-induced motor complications (as assessed with the use of the Unified Parkinson's Disease Rating Scale, parts III, II, and IV, respectively), and time with good mobility and no dyskinesia.

RESULTS

For the primary outcome of quality of life, the mean score for the neurostimulation group improved by 7.8 points, and that for the medical-therapy group worsened by 0.2 points (between-group difference in mean change from baseline to 2 years, 8.0 points; P=0.002). Neurostimulation was superior to medical therapy with respect to motor disability (P<0.001), activities of daily living (P<0.001), levodopa-induced motor complications (P<0.001), and time with good mobility and no dyskinesia (P=0.01). Serious adverse events occurred in 54.8% of the patients in the neurostimulation group and in 44.1% of those in the medical-therapy group. Serious adverse events related to surgical implantation or the neurostimulation device occurred in 17.7% of patients. An expert panel confirmed that medical therapy was consistent with practice guidelines for 96.8% of the patients in the neurostimulation group and for 94.5% of those in the medical-therapy group.

CONCLUSIONS

Subthalamic stimulation was superior to medical therapy in patients with Parkinson's disease and early motor complications. (Funded by the German Ministry of Research and others; EARLYSTIM ClinicalTrials.gov number, NCT00354133.).

Is the medicolegal issue avoidable in neurosurgery? A retrospective survey of a series of 115 medicolegal cases from public hospitals

OBJECTIVE

Since the mid-1950s, neurosurgery has benefited from the remarkable progress due to tremendous advances in neuroimaging techniques, neuroanesthesia, neurostimulation, and brain-computer interfaces, as well as breakthroughs in operating microscopes and surgical instruments. Yet, this specialty has to do with delicate human structures and is hence considered as highly risky by insurance companies. In France, although neurosurgery's casualty rate (6%) is lower than in other specialties, the number of legal prosecutions has increased since 2002 because of easier access to medicolegal procedures. In order to avoid patients' resorting to the law courts, it becomes necessary to clearly identify the risk factors.

METHODS

From the data bank of the insurer Société Hospitalière d'Assurances Mutuelles (SHAM, main insurance company for public hospitals in France), we retrospectively analyzed 115 files (34 cranial and 81 spinal surgeries) covering the period 1997-2007 for the reasons for complaints against French neurosurgeons working in public hospitals.

RESULTS

Five main causes were identified: surgical site infection (37%), technical error (22%), lack of information (14%), delayed diagnosis (11%), and lack of supervision (9%).

CONCLUSION

Some causes are definitely avoidable at no cost to the hospital. Besides basic preventive safety procedures, we reiterate the mandatory steps for a good defense when being prosecuted. The evolution of patients' attitudes toward medical institutions observed in most countries has forced surgeons to adapt their practice. In this context, a common action certified by learned societies on sustainable health care quality, patient safety, and respect of good practices appears as the golden path to maintain a favorable legal, insurance, and financial environment.

Towards an understanding and control of cavitation activity in 1 MHz ultrasound fields

Various industrial processes such as sonochemical processing and ultrasonic cleaning strongly rely on the phenomenon of acoustic cavitation. As the occurrence of acoustic cavitation is incorporating a multitude of interdependent effects, the amount of cavitation activity in a vessel is strongly depending on the ultrasonic process conditions. It is therefore crucial to quantify cavitation activity as a function of the process parameters. At 1 MHz, the active cavitation bubbles are so small that it is becoming difficult to observe them in a direct way. Hence, another metrology based on secondary effects of acoustic cavitation is more suitable to study cavitation activity. In this paper we present a detailed analysis of acoustic cavitation phenomena at 1 MHz ultrasound by means of time-resolved measurements of sonoluminescence, cavitation noise, and synchronized high-speed stroboscopic Schlieren imaging. It is shown that a correlation exists between sonoluminescence, and the ultraharmonic and broadband signals extracted from the cavitation noise spectra. The signals can be utilized to characterize different regimes of cavitation activity at different acoustic power densities. When cavitation activity sets on, the aforementioned signals correlate to fluctuations in the Schlieren contrast as well as the number of nucleated bubbles extracted from the Schlieren Images. This additionally proves that signals extracted from cavitation noise spectra truly represent a measure for cavitation activity. The cyclic behavior of cavitation activity is investigated and related to the evolution of the bubble populations in the ultrasonic tank. It is shown that cavitation activity is strongly linked to the occurrence of fast-moving bubbles. The origin of this "bubble streamers" is investigated and their role in the initialization and propagation of cavitation activity throughout the sonicated liquid is discussed. Finally, it is shown that bubble activity can be stabilized and enhanced by the use of pulsed ultrasound by conserving and recycling active bubbles between subsequent pulsing cycles.

Psychostimulant effect of levodopa: reversing sensitisation is possible

BACKGROUND

Levodopa therapy in Parkinson's disease (PD) is associated with non-motor complications resulting from sensitisation of the ventral striatum system. Recent studies showed an improvement in non-motor complications in PD patients with subthalamic stimulation. We hypothesised that ventral striatum desensitisation might contribute to this improvement.

METHODS

Psychostimulant effects of levodopa were prospectively assessed in 36 PD patients with an acute levodopa challenge, before and 1 year after chronic subthalamic stimulation, using the Addiction Research Centre Inventory euphoria subscale. Postoperative evaluation was performed with the same dose of levodopa used in the preoperative assessment and after switching off stimulation. Preoperative and postoperative non-motor fluctuations in everyday life were investigated with the Ardouin Scale. Furthermore, in order to artificially reproduce non-motor fluctuations, a levodopa challenge keeping subthalamic stimulation on was performed to assess depression, anxiety and motivation before and after surgery under the different medication conditions.

RESULTS

After 1 year of chronic subthalamic stimulation with 60.3% reduction in dopaminergic medication, the acute psychostimulant effects of levodopa were significantly reduced compared with preoperatively, as measured by the euphoria subscale (7.22 ± 4.75 vs 4.75 ± 5.68; p = 0.0110). On chronic subthalamic stimulation and with markedly reduced dopaminergic medication, non-motor fluctuations were significantly improved. While off medication/on stimulation scores of depression and anxiety were improved, in the on medication/on stimulation condition the motivation score worsened.

CONCLUSIONS

Acute psychostimulant effects of levodopa (off stimulation) were significantly reduced 1 year after surgery. These findings are likely due to desensitisation of the ventral striatum, allowed by the reduction of dopaminergic treatment, and the replacement of pulsatile treatment with continuous subthalamic stimulation.

Enhancement of cavitation activity and particle removal with pulsed high frequency ultrasound and supersaturation

Megasonic cleaning as applied in leading edge semiconductor device manufacturing strongly relies on the phenomenon of acoustic cavitation. As the occurrence of acoustic cavitation is incorporating a multitude of interdependent effects, the amount of cavitation activity in the cleaning liquid strongly depends on the sonication conditions. It is shown that cavitation activity as measured by means of ultraharmonic cavitation noise can be significantly enhanced when pulsed sonication is applied to a gas supersaturated liquid under traveling wave conditions. It is demonstrated that this enhancement coincides with a dramatic increase in particle removal and is therefore of great interest for megasonic cleaning applications. It is demonstrated that the optimal pulse parameters are determined by the dissolution time of the active bubbles, whereas the amount of cavitation activity depends on the ratio between pulse-off and pulse-on time as well as the applied acoustic power. The optimal pulse-off time is independent of the corresponding pulse-on time but increases significantly with increasing gas concentration. We show that on the other hand, supersaturation is needed to enable acoustic cavitation at aforementioned conditions, but has to be kept below values, for which active bubbles cannot dissolve anymore and are therefore lost during subsequent pulses. For the applicable range of gas contents between 100% and 130% saturation, the optimal pulse-off time reaches values between 150 and 340 ms, respectively. Full particle removal of 78 nm-diameter silica particles at a power density of 0.67 W/cm(2) is obtained for the optimal pulse-off times. The optimal pulse-off time values are derived from the dissolution time of bubbles with a radius of 3.3 μm and verified experimentally. The bubble radius used in the calculations corresponds to the linear resonance size in a 928 kHz sound field, which demonstrates that the recycling of active bubbles is the main enhancement mechanism. The optimal choice of the pulsing conditions however is constrained by the trade-off between the effective sonication time and the desire to have a sufficient amount of active bubbles at lower powers, which might be necessary if very delicate structures have to be cleaned.