Memory functioning after hippocampal removal: Does side matter?

To address the memory functioning after medial temporal lobe (MTL) surgery for refractory epilepsy and relationships with the side of the hippocampal removal, 22 patients with pharmaco-resistant epilepsy who had undergone MTL resection (10 right/12 left) at the Salpêtrière Hospital were compared with 21 matched healthy controls. We designed a specific neuropsychological binding memory test that specifically addressed hippocampal cortex functioning, and left-right material-specific lateralization. Our results showed that both left and right mesial temporal lobe removal cause a severe memory impairment, for both verbal and visual material. The removal of left medial temporal lobe causes worse memory impairment than the right removal regardless of the stimuli type (verbal or visual) questioning the theory of the hippocampal material-specific lateralization. The present study provided new evidence for the role of both hippocampus and surrounding cortices in memory-binding whatever the material type and also suggested that a left MTL removal is more deleterious for both verbal and visual episodic memory in comparison with right MTL removal.

Fixel-Based Analysis Reveals Whole-Brain White Matter Abnormalities in Cervical Dystonia

BACKGROUND

Cervical dystonia (CD) is a form of isolated focal dystonia typically associated to abnormal head, neck, and shoulder movements and postures. The complexity of the clinical presentation limits the investigation of its pathophysiological mechanisms, and the neural networks associated to specific motor manifestations are still the object of debate.

OBJECTIVES

We investigated the morphometric properties of white matter fibers in CD and explored the networks associated with motor symptoms, while regressing out nonmotor scores.

METHODS

Nineteen patients affected by CD and 21 healthy controls underwent diffusion-weighted magnetic resonance imaging. We performed fixel-based analysis, a novel method evaluating fiber orientation within specific fiber bundles, and compared fiber morphometric properties between groups. Moreover, we correlated fiber morphometry with the severity of motor symptoms in patients.

RESULTS

Compared to controls, patients exhibited decreased white matter fibers in the right striatum. Motor symptom severity negatively correlated with white matter fibers passing through inferior parietal areas and the head representation area of the motor cortex.

CONCLUSIONS

Abnormal white matter integrity at the basal ganglia level may affect several functional networks involved, for instance, in motor preparation and execution, visuomotor coordination, and multimodal integration. This may result in progressive maladaptive plasticity, culminating in overt symptoms of dystonia. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Human periventricular nodular heterotopia shows several interictal epileptic patterns and hyperexcitability of neuronal firing

Periventricular nodular heterotopia (PNH) is a malformation of cortical development that frequently causes drug-resistant epilepsy. The epileptogenicity of ectopic neurons in PNH as well as their role in generating interictal and ictal activity is still a matter of debate. We report the first in vivo microelectrode recording of heterotopic neurons in humans. Highly consistent interictal patterns (IPs) were identified within the nodules: (1) Periodic Discharges PLUS Fast activity (PD+F), (2) Sporadic discharges PLUS Fast activity (SD+F), and (3) epileptic spikes (ES). Neuronal firing rates were significantly modulated during all IPs, suggesting that multiple IPs were generated by the same local neuronal populations. Furthermore, firing rates closely followed IP morphologies. Among the different IPs, the SD+F pattern was found only in the three nodules that were actively involved in seizure generation but was never observed in the nodule that did not take part in ictal discharges. On the contrary, PD+F and ES were identified in all nodules. Units that were modulated during the IPs were also found to participate in seizures, increasing their firing rate at seizure onset and maintaining an elevated rate during the seizures. Together, nodules in PNH are highly epileptogenic and show several IPs that provide promising pathognomonic signatures of PNH. Furthermore, our results show that PNH nodules may well initiate seizures.

Long-term deep intracerebral microelectrode recordings in patients with drug-resistant epilepsy: proposed guidelines based on 10-year experience

PURPOSE

Human neuronal activity, recorded in vivo from microelectrodes, may offer valuable insights into physiological mechanisms underlying human cognition and pathophysiological mechanisms of brain diseases, in particular epilepsy. Continuous and long-term recordings are necessary to monitor non predictable pathological and physiological activities like seizures or sleep. Because of their high impedance, microelectrodes are more sensitive to noise than macroelectrodes. Low noise levels are crucial to detect action potentials from background noise, and to further isolate single neuron activities. Therefore, long-term recordings of multi-unit activity remains a challenge. We shared here our experience with microelectrode recordings and our efforts to reduce noise levels in order to improve signal quality. We also provided detailed technical guidelines for the connection, recording, imaging and signal analysis of microelectrode recordings.

RESULTS

During the last 10 years, we implanted 122 bundles of Behnke-Fried hybrid macro-microelectrodes, in 56 patients with pharmacoresistant focal epilepsy. Microbundles were implanted in the temporal lobe (74%), as well as frontal (15%), parietal (6%) and occipital (5%) lobes. Low noise levels depended on our technical setup. The noise reduction was mainly obtained after electrical insulation of the patient's recording room and the use of a reinforced microelectrode model, reaching median root mean square values of 5.8 µV. Seventy percent of the bundles could record multi-units activities (MUA), on around 3 out of 8 wires per bundle and for an average of 12 days. Seizures were recorded by microelectrodes in 91% of patients, when recorded continuously, and MUA were recorded during seizures for 75 % of the patients after the insulation of the room. Technical guidelines are proposed for (i) electrode tails manipulation and protection during surgical bandage and connection to both clinical and research amplifiers, (ii) electrical insulation of the patient's recording room and shielding, (iii) data acquisition and storage, and (iv) single-units activities analysis.

CONCLUSIONS

We progressively improved our recording setup and are now able to record (i) microelectrode signals with low noise level up to 3 weeks duration, and (ii) MUA from an increased number of wires . We built a step by step procedure from electrode trajectory planning to recordings. All these delicate steps are essential for continuous long-term recording of units in order to advance in our understanding of both the pathophysiology of ictogenesis and the neuronal coding of cognitive and physiological functions.

Clinical Characteristics, Angioarchitecture and Management of Tectum Mesencephali Arteriovenous Malformations : A Retrospective Case Series

PURPOSE

Tectum mesencephali arteriovenous malformations (TM-AVMs) are rare lesions deeply located close to eloquent structures making them challenging to treat. We aimed to present clinical presentation, angiographic features and treatment strategies of TM-AVMs through a single center retrospective case series.

METHODS

A TM-AVMs is defined as a nidus located in the parenchyma or on the pia mater of the posterior midbrain. Records of consecutive patients admitted with TM-AVMs over a 21-year period were retrospectively analyzed. Vascular anatomy of the region is also reviewed.

RESULTS

In this study 13 patients (1.63% of the complete cohort; 10 males), mean age 48 years, were included. All patients presented with intracranial hemorrhage and two patients (15%) died after an early recurrent bleeding. Mean size of the TM-AVMs was 10.1 ± 5 mm. Multiple arterial feeders were noted in every cases. Of the patients 11 underwent an exclusion treatment, 8 via embolization (6 via arterial access and 2 via venous access) and 4 via stereotactic radiosurgery (SRS) (1 patient received both). Overall success treatment rate was 7/11 patients (64% overall; 63% in the embolization group, 25% in the SRS group). Two hemorrhagic events led to a worsened outcome, one during embolization and one several years after SRS. All other patients remained clinically stable or improved.

CONCLUSION

The TM-AVMs are rare but stereotypic lesions found in a hemorrhagic context. Multiple arterial feeders are always present. Endovascular treatment seems to be an effective technique with relatively low morbidity; SRS had a low success rate but was only use in a limited number of patients.

Conscious and unconscious expectancy effects: A behavioral, scalp and intracranial electroencephalography study

OBJECTIVE

The scope of unconscious cognition stretched its limits dramatically during the last 40 years, yet most unconscious processes and representations that have been described so far are fleeting and very short-lived, whereas conscious representations can be actively maintained in working memory for a virtually unlimited period. In the present work we aimed at exploring conscious and unconscious lasting (>1 second) expectancy effects.

METHODS

In a series of four experiments we engaged participants in the foreperiod paradigm while using both unmasked and masked cues that were informative about the presence/absence of an upcoming target. We recorded behavioral responses, high-density scalp EEG (Exp. 2a), and intra-cranial EEG (Exp. 2b).

RESULTS

While conscious expectancy was associated with a large behavioral effect (~150 ms), unconscious expectancy effect was significant but much smaller (4 ms). Both conscious and unconscious expectancy Contingent Negative Variations (CNVs) originated from temporal cortices, but only the late component of conscious CNV originated from an additional source located in the vicinity of mesio-frontal areas and supplementary motor areas. Finally, only conscious expectancy was accessible to introspection.

CONCLUSIONS

Both unmasked and masked cues had an impact on response times and on brain activity.

SIGNIFICANCE

These results support a two-stage model of the underlying mechanisms of expectancy.

Resting-State Neural Firing Rate Is Linked to Cardiac-Cycle Duration in the Human Cingulate and Parahippocampal Cortices

Stimulation and functional imaging studies have revealed the existence of a large network of cortical regions involved in the regulation of heart rate. However, very little is known about the link between cortical neural firing and cardiac-cycle duration (CCD). Here, we analyze single-unit and multiunit data obtained in humans at rest, and show that firing rate covaries with CCD in 16.7% of the sample (25 of 150). The link between firing rate and CCD was most prevalent in the anterior medial temporal lobe (entorhinal and perirhinal cortices, anterior hippocampus, and amygdala), where 36% (18 of 50) of the units show the effect, and to a lesser extent in the mid-to-anterior cingulate cortex (11.1%, 5 of 45). The variance in firing rate explained by CCD ranged from 0.5 to 11%. Several lines of analysis indicate that neural firing influences CCD, rather than the other way around, and that neural firing affects CCD through vagally mediated mechanisms in most cases. These results show that part of the spontaneous fluctuations in firing rate can be attributed to the cortical control of the cardiac cycle. The fine tuning of the regulation of CCD represents a novel physiological factor accounting for spontaneous variance in firing rate. It remains to be determined whether the "noise" introduced in firing rate by the regulation of CCD is detrimental or beneficial to the cognitive information processing carried out in the parahippocampal and cingulate regions.SIGNIFICANCE STATEMENT Fluctuations in heart rate are known to be under the control of cortical structures, but spontaneous fluctuations in cortical firing rate, or "noise," have seldom been related to heart rate. Here, we analyze unit activity in humans at rest and show that spontaneous fluctuations in neural firing in the medial temporal lobe, as well as in the mid-to-anterior cingulate cortex, influence heart rate. This phenomenon was particularly pronounced in the entorhinal and perirhinal cortices, where it could be observed in one of three neurons. Our results show that part of spontaneous firing rate variability in regions best known for their cognitive role in spatial navigation and memory corresponds to precise physiological regulations.

Intracranial Recordings and Computational Modeling of Music Reveal the Time Course of Prediction Error Signaling in Frontal and Temporal Cortices

Prediction is held to be a fundamental process underpinning perception, action, and cognition. To examine the time course of prediction error signaling, we recorded intracranial EEG activity from nine presurgical epileptic patients while they listened to melodies whose information theoretical predictability had been characterized using a computational model. We examined oscillatory activity in the superior temporal gyrus (STG), the middle temporal gyrus (MTG), and the pars orbitalis of the inferior frontal gyrus, lateral cortical areas previously implicated in auditory predictive processing. We also examined activity in anterior cingulate gyrus (ACG), insula, and amygdala to determine whether signatures of prediction error signaling may also be observable in these subcortical areas. Our results demonstrate that the information content (a measure of unexpectedness) of musical notes modulates the amplitude of low-frequency oscillatory activity (theta to beta power) in bilateral STG and right MTG from within 100 and 200 msec of note onset, respectively. Our results also show this cortical activity to be accompanied by low-frequency oscillatory modulation in ACG and insula-areas previously associated with mediating physiological arousal. Finally, we showed that modulation of low-frequency activity is followed by that of high-frequency (gamma) power from approximately 200 msec in the STG, between 300 and 400 msec in the left insula, and between 400 and 500 msec in the ACG. We discuss these results with respect to models of neural processing that emphasize gamma activity as an index of prediction error signaling and highlight the usefulness of musical stimuli in revealing the wide-reaching neural consequences of predictive processing.

Practical contouring guidelines with an MR-based atlas of brainstem structures involved in radiation-induced nausea and vomiting

BACKGROUND AND PURPOSE

The objective of this project was to define consensus guidelines for delineating brainstem substructures (dorsal vagal complex, including the area postrema) involved in radiation-induced nausea and vomiting (RINV). The three parts of the brainstem are rarely delineated, so this study was also an opportunity to find a consensus on this subject.

MATERIALS AND METHODS

The dorsal vagal complex (DVC) was identified on autopsy sections and endoscopic descriptions. Anatomic landmarks and boundaries were used to establish radio-anatomic correlations on CT and Magnetic Resonance Imaging (MRI). Additionally, delineation of RINV structures was performed on MRI images and reported on CT scans. Next, guidelines were provided to eight radiation oncologists for delineation guidance of these RINV-related structures on DICOM-RT images of two patients being treated for a nasopharyngeal carcinoma. Interobserver variability was computed.

RESULTS

The DVC and the three parts of the brainstem were defined with a concise description of their main anatomic boundaries. The interobserver analysis showed that the DVC, the midbrain, the pons, and the medulla oblongata delineations were reproducible with KI = 0.72, 0.84, 0.94 and 0.89, respectively. The Supplemental Material section provides an atlas of the consensus guidelines projected on 1-mm MR axial slices.

CONCLUSIONS

This RINV-atlas was feasible and reproducible for the delineation of RINV structures on planning CT using fused MRI. It may be used to prospectively assess dose-volume relationship for RINV structures and occurrence of nausea vomiting during intracranial or head and neck irradiation.

Single-unit activities during the transition to seizures in deep mesial structures

Focal seizures are assumed to arise from a hypersynchronous activity affecting a circumscribed brain region. Using microelectrodes in seizure-generating deep mesial regions of 9 patients, we investigated the firing of hundreds of single neurons before, during, and after ictal electroencephalogram (EEG) discharges. Neuronal spiking activity at seizure initiation was highly heterogeneous and not hypersynchronous. Furthermore, groups of neurons showed significant changes in activity minutes before the seizure with no concomitant changes in the corresponding macroscopic EEG recordings. Altogether, our findings suggest that only limited subsets of neurons in epileptic depth regions initiate the seizure-onset and that ictogenic mechanisms operate in submillimeter-scale microdomains. Ann Neurol 2017 Ann Neurol 2017;82:1022-1028.

Cognitive dissonance resolution depends on episodic memory

The notion that past choices affect preferences is one of the most influential concepts of social psychology since its first report in the 50 s, and its theorization within the cognitive dissonance framework. In the free-choice paradigm (FCP) after choosing between two similarly rated items, subjects reevaluate chosen items as more attractive and rejected items as less attractive. However the relations prevailing between episodic memory and choice-induced preference change (CIPC) remain highly debated: is this phenomenon dependent or independent from memory of past choices? We solve this theoretical debate by demonstrating that CIPC occurs exclusively for items which were correctly remembered as chosen or rejected during the choice stage. We used a combination of fMRI and intra-cranial electrophysiological recordings to reveal a modulation of left hippocampus activity, a hub of episodic memory retrieval, immediately before the occurrence of CIPC during item reevaluation. Finally, we show that contrarily to a previous influential report flawed by a statistical artifact, this phenomenon is absent in amnesic patients for forgotten items. These results demonstrate the dependence of cognitive dissonance on conscious episodic memory. This link between current preferences and previous choices suggests a homeostatic function of this regulative process, aiming at preserving subjective coherence.

Voluntary control of intracortical oscillations for reconfiguration of network activity

Voluntary control of oscillatory activity represents a key target in the self-regulation of brain function. Using a real-time closed-loop paradigm and simultaneous macro- and micro-electrode recordings, we studied the effects of self-induced intracortical oscillatory activity (4–8 Hz) in seven neurosurgical patients. Subjects learned to robustly and specifically induce oscillations in the target frequency, confirmed by increased oscillatory event density. We have found that the session-to-session variability in performance was explained by the functional long-range decoupling of the target area suggesting a training-induced network reorganization. Downstream effects on more local activities included progressive cross-frequency-coupling with gamma oscillations (30–120 Hz), and the dynamic modulation of neuronal firing rates and spike timing, indicating an improved temporal coordination of local circuits. These findings suggest that effects of voluntary control of intracortical oscillations can be exploited to specifically target plasticity processes to reconfigure network activity, with a particular relevance for memory function or skill acquisition.

Is the cardiac monitoring function related to the self in both the default network and right anterior insula?

The self has been proposed to be rooted in the neural monitoring of internal bodily signals and might thus involve interoceptive areas, notably the right anterior insula (rAI). However, studies on the self consistently showed the involvement of midline default network (DN) nodes, without referring to visceral monitoring. Here, we investigate this apparent discrepancy. We previously showed that neural responses to heartbeats in the DN encode two different self-dimensions, the agentive ‘I’ and the introspective ‘Me’, in a whole-brain analysis of magnetoencephalography (MEG) data. Here, we confirm and anatomically refine this result with intracranial recordings (intracranial electroencephalography, iEEG). In two patients, we show a parametric modulation of neural responses to heartbeats by the self-relatedness of thoughts, at the single trial level. A region-of-interest analysis of the insula reveals that MEG responses to heartbeats in the rAI encode the ‘I’ self-dimension. The effect in rAI was weaker than in the DN and was replicated in iEEG data in one patient out of two. We propose that a common mechanism, the neural monitoring of cardiac signals, underlies the self in both the DN and rAI. This might reconcile studies on the self highlighting the DN, with studies on interoception focusing on the insula.

This article is part of the themed issue ‘Interoception beyond homeostasis: affect, cognition and mental health’.

Predictors of Trigeminal Neuropathy After Radiosurgery for Vestibular Schwannomas

PURPOSE

To analyze the relationship between dosimetric characteristics and symptoms related to trigeminal neuropathy (TN) observed after radiosurgery (RS) for vestibular schwannomas (VS); to propose guidelines to optimize planification in VS RS regarding TN preservation; and to detail the mechanism of TN impairment after VS RS.

METHODS AND MATERIALS

One hundred seventy-nine patients treated between 2011 and 2013 for VS RS and without trigeminal impairment before RS were included in a retrospective study. Univariate and multivariate analyses were performed to determine predictors of TN among characteristics of the patients, the dosimetry, and the VS.

RESULTS

There were 20 Koos grade 1, 99 grade 2, 57 grade 3, and 3 grade 4. Fourteen patients (7.8%) presented a transitory or permanent TN. Between the patients with and without TN after VS RS, there was no significant difference regarding dosimetry or VS volume itself. Significant differences (univariate analysis P<.05, Mann-Whitney test) were found for parameters related to the cisternal portion of the trigeminal nerve: total integrated dose, maximum dose, mean dose, volume of the Vth nerve (Volv), and volume of the Vth nerve receiving at least 11 Gy (VolVcist>11Gy), but also for maximal dose to the Vth nerve nucleus and intra-axial portion (Dose maxVax). After multivariate analysis, the best model predicting TN included VolVcist>11Gy (P=.0045), Dose maxVax (P=.0006), and Volv (P=.0058). The negative predictive value of this model was 97%.

CONCLUSIONS

The parameters VolVcist>11Gy, Dose maxVax, and Volv should be checked when designing dosimetry for VS RS.

Incomplete Hippocampal Inversion: A Comprehensive MRI Study of Over 2000 Subjects

The incomplete-hippocampal-inversion (IHI), also known as malrotation, is an atypical anatomical pattern of the hippocampus, which has been reported in healthy subjects in different studies. However, extensive characterization of IHI in a large sample has not yet been performed. Furthermore, it is unclear whether IHI are restricted to the medial-temporal lobe or are associated with more extensive anatomical changes. Here, we studied the characteristics of IHI in a community-based sample of 2008 subjects of the IMAGEN database and their association with extra-hippocampal anatomical variations. The presence of IHI was assessed on T1-weighted anatomical magnetic resonance imaging (MRI) using visual criteria. We assessed the association of IHI with other anatomical changes throughout the brain using automatic morphometry of cortical sulci. We found that IHI were much more frequent in the left hippocampus (left: 17%, right: 6%, χ(2)-test, p < 10(-28)). Compared to subjects without IHI, subjects with IHI displayed morphological changes in several sulci located mainly in the limbic lobe. Our results demonstrate that IHI are a common left-sided phenomenon in normal subjects and that they are associated with morphological changes outside the medial temporal lobe.

Intracranial markers of emotional valence processing and judgments in music

The involvement of the amygdala and orbitofrontal cortex in the processing of valenced stimuli is well established. However, less is known about the extent to which activity in these regions reflects a stimulus' physical properties, the individual subjective experience it evokes, or both. We recorded cortical electrical activity from five epileptic patients implanted with depth electrodes for presurgical evaluation while they rated "consonant" and "dissonant" musical chords using a "pleasantness" scale. We compared the pattern of responses in the amygdala and orbitofrontal cortex when trials were sorted by pleasantness judgments relative to when they were sorted by the acoustic properties known to influence emotional reactions to musical chords. This revealed earlier differential activity in the amygdala in the physical properties-based, relative to in the judgment-based, analyses. Thus, our results demonstrate that the amygdala has, first and foremost, a high initial sensitivity to the physical properties of valenced stimuli. The finding that differentiations in the amygdala based on pleasantness ratings had a longer latency suggests that in this structure, mediation of emotional judgment follows accumulation of sensory information. This is in contrast to the orbitofrontal cortex where sensitivity to sensory information did not precede differentiation based on affective judgments.

Detection of volume loss in hippocampal layers in Alzheimer's disease using 7 T MRI: a feasibility study

In Alzheimer's disease (AD), the hippocampus is an early site of tau pathology and neurodegeneration. Histological studies have shown that lesions are not uniformly distributed within the hippocampus. Moreover, alterations of different hippocampal layers may reflect distinct pathological processes. 7 T MRI dramatically improves the visualization of hippocampal subregions and layers. In this study, we aimed to assess whether 7 T MRI can detect volumetric changes in hippocampal layers in vivo in patients with AD. We studied four AD patients and seven control subjects. MR images were acquired using a whole-body 7 T scanner with an eight channel transmit–receive coil. Hippocampal subregions were manually segmented from coronal T2*-weighted gradient echo images with 0.3 × 0.3 × 1.2 mm³ resolution using a protocol that distinguishes between layers richer or poorer in neuronal bodies. Five subregions were segmented in the region of the hippocampal body: alveus, strata radiatum, lacunosum and moleculare (SRLM) of the cornu Ammonis (CA), hilum, stratum pyramidale of CA and stratum pyramidale of the subiculum. We found strong bilateral reductions in the SRLM of the cornu Ammonis and in the stratum pyramidale of the subiculum (p < 0.05), with average cross-sectional area reductions ranging from −29% to −49%. These results show that it is possible to detect volume loss in distinct hippocampal layers using segmentation of 7 T MRI. 7 T MRI-based segmentation is a promising tool for AD research.

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Manual segmentation of hippocampal layers is feasible in-vivo at 7T in patients with Alzheimer’s disease (AD)

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It allows distinguishing layers richer and poorer in neuronal bodies

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In AD patients, strong atrophy is found in the stratum pyramidale of the subiculum and the strata radiatum, lacunosum and moleculare of Ammon’s horn

Event-Related Potential, Time-frequency, and Functional Connectivity Facets of Local and Global Auditory Novelty Processing: An Intracranial Study in Humans

Auditory novelty detection has been associated with different cognitive processes. Bekinschtein et al. (2009) developed an experimental paradigm to dissociate these processes, using local and global novelty, which were associated, respectively, with automatic versus strategic perceptual processing. They have mostly been studied using event-related potentials (ERPs), but local spiking activity as indexed by gamma (60-120 Hz) power and interactions between brain regions as indexed by modulations in beta-band (13-25 Hz) power and functional connectivity have not been explored. We thus recorded 9 epileptic patients with intracranial electrodes to compare the precise dynamics of the responses to local and global novelty. Local novelty triggered an early response observed as an intracranial mismatch negativity (MMN) contemporary with a strong power increase in the gamma band and an increase in connectivity in the beta band. Importantly, all these responses were strictly confined to the temporal auditory cortex. In contrast, global novelty gave rise to a late ERP response distributed across brain areas, contemporary with a sustained power decrease in the beta band (13-25 Hz) and an increase in connectivity in the alpha band (8-13 Hz) within the frontal lobe. We discuss these multi-facet signatures in terms of conscious access to perceptual information.

An Intracranial EEG Study of the Neural Dynamics of Musical Valence Processing

The processing of valence is known to recruit the amygdala, orbitofrontal cortex, and relevant sensory areas. However, how these regions interact remains unclear. We recorded cortical electrical activity from 7 epileptic patients implanted with depth electrodes for presurgical evaluation while they listened to positively and negatively valenced musical chords. Time-frequency analysis suggested a specific role of the orbitofrontal cortex in the processing of positively valenced stimuli while, most importantly, Granger causality analysis revealed that the amygdala tends to drive both the orbitofrontal cortex and the auditory cortex in theta and alpha frequency bands, during the processing of valenced stimuli. Results from the current study show the amygdala to be a critical hub in the emotion processing network: specifically one that influences not only the higher order areas involved in the evaluation of a stimulus's emotional value but also the sensory cortical areas involved in the processing of its low-level acoustic features.

Resting state networks' corticotopy: the dual intertwined rings architecture

How does the brain integrate multiple sources of information to support normal sensorimotor and cognitive functions? To investigate this question we present an overall brain architecture (called "the dual intertwined rings architecture") that relates the functional specialization of cortical networks to their spatial distribution over the cerebral cortex (or "corticotopy"). Recent results suggest that the resting state networks (RSNs) are organized into two large families: 1) a sensorimotor family that includes visual, somatic, and auditory areas and 2) a large association family that comprises parietal, temporal, and frontal regions and also includes the default mode network. We used two large databases of resting state fMRI data, from which we extracted 32 robust RSNs. We estimated: (1) the RSN functional roles by using a projection of the results on task based networks (TBNs) as referenced in large databases of fMRI activation studies; and (2) relationship of the RSNs with the Brodmann Areas. In both classifications, the 32 RSNs are organized into a remarkable architecture of two intertwined rings per hemisphere and so four rings linked by homotopic connections. The first ring forms a continuous ensemble and includes visual, somatic, and auditory cortices, with interspersed bimodal cortices (auditory-visual, visual-somatic and auditory-somatic, abbreviated as VSA ring). The second ring integrates distant parietal, temporal and frontal regions (PTF ring) through a network of association fiber tracts which closes the ring anatomically and ensures a functional continuity within the ring. The PTF ring relates association cortices specialized in attention, language and working memory, to the networks involved in motivation and biological regulation and rhythms. This "dual intertwined architecture" suggests a dual integrative process: the VSA ring performs fast real-time multimodal integration of sensorimotor information whereas the PTF ring performs multi-temporal integration (i.e., relates past, present, and future representations at different temporal scales).

Human gamma oscillations during slow wave sleep

Neocortical local field potentials have shown that gamma oscillations occur spontaneously during slow-wave sleep (SWS). At the macroscopic EEG level in the human brain, no evidences were reported so far. In this study, by using simultaneous scalp and intracranial EEG recordings in 20 epileptic subjects, we examined gamma oscillations in cerebral cortex during SWS. We report that gamma oscillations in low (30-50 Hz) and high (60-120 Hz) frequency bands recurrently emerged in all investigated regions and their amplitudes coincided with specific phases of the cortical slow wave. In most of the cases, multiple oscillatory bursts in different frequency bands from 30 to 120 Hz were correlated with positive peaks of scalp slow waves ("IN-phase" pattern), confirming previous animal findings. In addition, we report another gamma pattern that appears preferentially during the negative phase of the slow wave ("ANTI-phase" pattern). This new pattern presented dominant peaks in the high gamma range and was preferentially expressed in the temporal cortex. Finally, we found that the spatial coherence between cortical sites exhibiting gamma activities was local and fell off quickly when computed between distant sites. Overall, these results provide the first human evidences that gamma oscillations can be observed in macroscopic EEG recordings during sleep. They support the concept that these high-frequency activities might be associated with phasic increases of neural activity during slow oscillations. Such patterned activity in the sleeping brain could play a role in off-line processing of cortical networks.

[Epilepsy surgery: when thinking about? Who are the good candidates?]

Epilepsy surgery concerns any patient with pharmacoresistant partial epilepsy, responsible for disability. Children and adult patients can be candidates for epilepsy surgery. A presurgical evaluation, adapted to each patient, must identify the most precisely the cortical area, where the seizures originate, using converging data: the clinical and electroencephalographic semiology of the seizures, the structural and sometimes functional brain imagings, and evaluate if the removal of the epileptogenic focus may induce a neurological or cognitive deficit, using neuropsychological tests and sometimes functional brain imagings. Such therapeutical strategy should be evoked as soon as possible in patients for whom the epilepsy becomes pharmacoresistant, and these patients should be oriented in specialized centres. The results of epilepsy surgery vary according to the lobar origin of the epileptogenic focus and to the existence of a visible lesion on brain MRI. A multidisciplinary evaluation of the benefits and risks should be presented to the patient. Results of the surgery are usually excellent when a focus is clearly identified and the neuropsychological tests did not predict a deficit.

Mapping interictal oscillations greater than 200 Hz recorded with intracranial macroelectrodes in human epilepsy

Interictal high-frequency oscillations over 200 Hz have been recorded with microelectrodes in the seizure onset zone of epileptic patients suffering from mesial temporal lobe epilepsy. Recent work suggests that similar high-frequency oscillations can be detected in the seizure onset zone using standard diagnostic macroelectrodes. However, only a few channels were examined in these studies, so little information is available on the spatial extent of high-frequency oscillations. Here, we present data on high-frequency oscillations recorded from a larger number of intracerebral contacts spatial (mean 38) in 16 patients. Data were obtained from 1 h of interictal recording sampled at 1024 Hz and was analysed using a new semi-automatic detection procedure based on a wavelet decomposition. A detailed frequency analysis permitted a rapid and reliable discrimination of high-frequency oscillations from other high-frequency events. A total of 1932 high-frequency oscillations were detected with an average frequency of 261 +/- 53 Hz, amplitude of 11.9 +/- 6.7 microV and duration of 22.7 +/- 11.6 ms. Records from a patient often showed several different high-frequency oscillation patterns. We classified 24 patterns from 11 patients. Usually (20/24 patterns) high-frequency oscillations were nested in an epileptic paroxysm, such as a spike or a sharp wave, and typically high-frequency oscillations (19/24) were recorded from just one recording contact. Unexpectedly in other cases, high-frequency oscillations (5/24) were detected simultaneously on two or three contacts, sometimes separated by large distances. This large spatial extent suggests that high-frequency oscillations may sometimes result from a neuronal synchrony manifest on a scale of centimetres. High-frequency oscillations were almost always recorded in seizure-generating structures of patients suffering from mesial (9/9) or polar (1/3) temporal lobe epilepsy. They were never found in the epileptic or healthy basal, lateral temporal or extra temporal neocortex nor in the healthy amygdalo-hippocampal complex. These findings confirm that the generation of oscillations at frequencies higher that 200 Hz is, at this scale, a specific, intrinsic property of seizure-generating networks in medial and polar temporal lobes, which have a common archaic phylogenetic origin. We show that this activity can be detected and its spatial extent determined with conventional intracranial electroencephalography electrodes in records from patients with temporal lobe epilepsy. It is a reliable marker of the seizure onset zone that should be considered in decisions on surgical treatment.

Unconscious contextual memory affects early responses in the anterior temporal lobe

Memory and perception are two tightly interrelated cognitive processes, but the neural level of their interaction remains a matter of debate. Proponents of a late interaction emphasize feedback memory effects on visual processing, whereas others suggest that feed forward processing is affected by memory. In the visual domain, unconscious memory for stable relations among objects is known to influence visually-guided behavior. Recent evidence suggest an early interaction between this form of unconscious memory and visually-driven neural activity: the brain dissociates stable and unstable spatial relations at surprisingly early latencies, within the first 100 ms of sensory processing. The anatomical localization of this early effect however was still uncertain. In this study, we estimated the sources of the early effect in magnetoencephalographic (MEG) recordings, and analyzed intracranial electroencephalographic (iEEG) signal from seven epileptic patients in the modified version of the contextual cueing paradigm we recently developed. In spite of a lack of behavioral effect in the patient population, the striking agreement between the two electrophysiological datasets suggests that memory for spatial relations leads to differential responses in the anterior temporal lobe before 100 ms. The intracranial data further revealed orbitofrontal and more posterior temporal memory related activities around 100 ms. Altogether, the data point toward an early interaction between contextual memories and perceptual processing. The anterior temporal cortex, in particular appears to play a critical role in merging sensory processing with unconscious memory as soon as it gets activated.

Converging intracranial markers of conscious access

We compared conscious and nonconscious processing of briefly flashed words using a visual masking procedure while recording intracranial electroencephalogram (iEEG) in ten patients. Nonconscious processing of masked words was observed in multiple cortical areas, mostly within an early time window (<300 ms), accompanied by induced gamma-band activity, but without coherent long-distance neural activity, suggesting a quickly dissipating feedforward wave. In contrast, conscious processing of unmasked words was characterized by the convergence of four distinct neurophysiological markers: sustained voltage changes, particularly in prefrontal cortex, large increases in spectral power in the gamma band, increases in long-distance phase synchrony in the beta range, and increases in long-range Granger causality. We argue that all of those measures provide distinct windows into the same distributed state of conscious processing. These results have a direct impact on current theoretical discussions concerning the neural correlates of conscious access.

[The neuropathology of sleep in human neurodegenerative diseases]

The neuropathology of human sleep remains an ill-defined issue. The data concerning the main structures of human brain areas involved, or supposed to be implicated, in sleep organisation are reviewed. Five levels of organisation can be schematically recognized: (i) the ascending arousal system, (ii) the non REM and REM systems (iii) regulated by hypothalamic areas, (iv) and the biological clock, (v) modulated by a number of "allostatic" influences. These are briefly described, with emphasis on the location of structures involved in humans, and on the recently revised concepts. Current knowledge on the topography of lesions associated with the main sleep disorders in degenerative diseases is recalled, including REM sleep behavior disorders, restless legs syndrome and periodic leg movements, sleep apneas, insomnia, excessive daily sleepiness, secondary narcolepsy and disturbed sleep-wake rhythms. The lesions of sleep related structures observed in early and late stages of four degenerative diseases are then reviewed. Two synucleinopathies (Lewy lesions associated disorders, including Parkinson's disease and Dementia with Lewy bodies, and Multiple System Atrophy) and two tauopathies (Progressive Supranuclear Palsy and Alzheimer's disease) are dealt with. The distribution of lesions usually found in affected patients fit with that expected from the prevalence of different sleep disorders in these diseases. This confirms the current opinion that these disorders depend on the distribution of lesions rather than on their biochemical nature. Further studies might throw insight on the mechanism of normal and pathological sleep in humans, counterpart of the increasing knowledge provided by animal models. Specially designed prospective clinicopathological studies including peculiar attention to sleep are urgently needed.

Autobiographical memory after temporal lobe resection: neuropsychological and MRI volumetric findings

This study examined the contribution of medial temporal lobe (MTL) structures in autobiographical memory. While some investigators have reported a temporal gradient in memory performance, characterized by retrieval difficulties limited to recent periods of life [Squire and Alvarez (Retrograde amnesia and memory consolidation: a neurobiological perspective. Curr Opin Neurobiol 1995; 5: 169-77)], others have suggested that this impairment involves all life-time periods [Nadel and Moscovitch (Memory consolidation, retrograde amnesia and the hippocampal complex. Curr Opin Neurobiol 1997; 7: 217-27)]. In this study, autobiographical memory was assessed in 22 patients who had undergone a left (n = 12) or a right (n = 10) MTL resection for the relief of epileptic seizures and in 22 normal control participants. For this purpose, we used an autobiographical memory task (TEMPau, Piolino et al., 2003) across four time periods covering the subjects' entire lifespan. For each period, an overall autobiographical memory score (AM score) was obtained, from which a strictly episodic score (SE score), characterized by specificity and richness of details, was computed. For all events recalled, Remember responses justified by specificity of factual, spatial and temporal contents (jR responses) were measured using the Remember/Know paradigm. MRI volumetric analyses performed on the medial (i.e. hippocampus, temporopolar, entorhinal, perirhinal and parahippocampal cortices) and lateral temporal (i.e. superior, middle and inferior temporal gyri) lobe structures stated that the resection mainly included MTL structures. AM and SE scores were impaired in patients with right and left MTL resections as compared to normal controls across all time periods, reflecting the patients' particular difficulty in producing specific and detailed memories across all periods. This impairment was associated with poor autonoetic consciousness, revealed by the small number of jR responses across all periods. Results of correlation analysis between MRI volume measures of temporal lobe structures and autobiographical memory scores suggest that the right MTL structures are particularly responsive in reliving the encoding context regardless of remoteness. Our results support the bilateral MTL contribution to episodic autobiographical memory covering the entire lifespan, which is consistent with the multiple trace theory of MTL function [Moscovitch et al. (Functional neuroanatomy of remote episodic, semantic and spatial memory: a unified account based on multiple trace theory. J Anat 2005; 207: 35-66.)].

Subliminal words durably affect neuronal activity

Unconscious mental representations elicited by subliminal stimuli are marked by their fleeting lifetimes, usually below 1 s. Can such evanescent subliminal stimuli, nevertheless, lead to long-lasting learning? To date, evidence suggesting a long-term influence of briefly perceived stimuli on behaviour or brain activity is scarce and questionable. In this study, we used intracranial recordings to provide the first direct demonstration that unconsciously perceived subliminal words could exert long-lasting effects on neuronal signals. When repeating subliminal words over long interstimulus intervals, we observed electrophysiological repetition effects. These unconscious repetition effects suggest that the single presentation of a masked word can durably affect neural architecture.

Role of the medial temporal lobe in time estimation in the range of minutes

This study examined the role of medial temporal lobe structures in verbal estimation and production of time intervals. Left medial temporal lobe lesions produced deficits in both tasks, whereas right medial temporal lobe lesions only disturbed time production. Although both tasks require adequate use of chronometric units, they seem to be subserved by distinct cognitive processing and to depend on different neural substrates. Verbal estimation of intervals in retrospect seems to depend mainly on contextual memory, and production of intervals depends more specifically on the mental load devoted to time. These findings, documenting for the first time the role of each temporal lobe in duration estimation within the range of minutes, are discussed in light of memory-based and attentional models of time.

Anatomically constrained region deformation for the automated segmentation of the hippocampus and the amygdala: Method and validation on controls and patients with Alzheimer's disease

We describe a new algorithm for the automated segmentation of the hippocampus (Hc) and the amygdala (Am) in clinical Magnetic Resonance Imaging (MRI) scans. Based on homotopically deforming regions, our iterative approach allows the simultaneous extraction of both structures, by means of dual competitive growth. One of the most original features of our approach is the deformation constraint based on prior knowledge of anatomical features that are automatically retrieved from the MRI data. The only manual intervention consists of the definition of a bounding box and positioning of two seeds; total execution time for the two structures is between 5 and 7 min including initialisation. The method is evaluated on 16 young healthy subjects and 8 patients with Alzheimer's disease (AD) for whom the atrophy ranged from limited to severe. Three aspects of the performances are characterised for validating the method: accuracy (automated vs. manual segmentations), reproducibility of the automated segmentation and reproducibility of the manual segmentation. For 16 young healthy subjects, accuracy is characterised by mean relative volume error/overlap/maximal boundary distance of 7%/84%/4.5 mm for Hc and 12%/81%/3.9 mm for Am; for 8 Alzheimer's disease patients, it is 9%/84%/6.5 mm for Hc and 15%/76%/4.5 mm for Am. We conclude that the performance of this new approach in data from healthy and diseased subjects in terms of segmentation quality, reproducibility and time efficiency compares favourably with that of previously published manual and automated segmentation methods. The proposed approach provides a new framework for further developments in quantitative analyses of the pathological hippocampus and amygdala in MRI scans.

Emotional responses to unpleasant music correlates with damage to the parahippocampal cortex

Music is typically a pleasurable experience. But under certain circumstances, music can also be unpleasant, for example, when a young child randomly hits piano keys. Such unpleasant musical experiences have been shown to activate a network of brain structures involved in emotion, mostly located in the medial temporal lobe: the parahippocampal gyrus, amygdala, hippocampus and temporal pole. However, the differential roles of these regions remain largely unknown. In this study, pleasant and unpleasant music was presented to 17 patients with variable excisions of the medial temporal lobe, as well as to 19 matched controls. The pleasant music corresponded to happy and sad selections taken from the classical instrumental repertoire; the unpleasant music was the dissonant arrangement of the same selections. Only patients with substantial resections of the left or right parahippocampal cortex (PHC) gave highly abnormal judgements to dissonant music; they rated dissonant music as slightly pleasant while controls found it unpleasant. This indifference to dissonance was correlated with the remaining volume in the PHC, but was unrelated to the volume of the surrounding structures. The impairment was specific: the same patients judged consonant music to be pleasant, and were able to judge music as happy or sad. Furthermore, this lack of responsiveness to unpleasantness was not due to a perceptual disorder, because all patients were able to detect intentional errors in the musical excerpts. Moreover, the impairment differed from that induced by amygdala damage alone. These findings are consistent with a two-dimensional model of defensive responses to aversive stimuli, in which the PHC and the amygdala subserve different roles.

A volumetric MRI study of the hippocampus and the parahippocampal region after unilateral medial temporal lobe resection

Segmentation guidelines on high-resolution MRI designed to assess remaining volumes of the hippocampus and the parahippocampal cortices after medial temporal lobe (MTL) surgery could provide a useful tool to investigate the involvement of these anatomical regions in surgical outcomes and in human memory. For this purpose, we implemented an MRI volumetric analysis, already applied to healthy population or epileptic patient before surgery, to quantify the volume of the hippocampus, the temporopolar cortex and the regions of the parahippocampal gyrus (perirhinal, entorhinal and parahippocampal cortices) spared after unilateral MTL resection carried out to treat medically uncontrolled temporal lobe epilepsy (TLE). Based on the locations of remaining anatomical landmarks, we quantified the volume of these regions in 24 patients after MTL resection and in 16 control participants. Our results show that (1) mean volumes of these regions contralateral to the epileptic focus were similar to those of normal subjects, (2) volumetric measures obtained from the resected side were much smaller than those from the non-resected side or from normal values and (3) the extent of MTL resection was comparable in right or left MTL surgery. Individual analysis of patients showed that the parahippocampal cortex, as opposed to the other regions, was not systematically removed across patients. As a post-operative MRI-based method, it therefore proves valuable to assess group data as well as to explore differences between individual patients.

Direct intracranial, FMRI, and lesion evidence for the causal role of left inferotemporal cortex in reading

Models of the "visual word form system" postulate that a left occipitotemporal region implements the automatic visual word recognition required for efficient reading. This theory was assessed in a patient in whom reading was explored with behavioral measures, fMRI, and intracranial local field potentials. Prior to surgery, when reading was normal, fMRI revealed a normal mosaic of ventral visual selectivity for words, faces, houses, and tools. Intracranial recordings demonstrated that the left occipitotemporal cortex responded with a short latency to conscious but also to subliminal words. Surgery removed a small portion of word-responsive occipitotemporal cortex overlapping with the word-specific fMRI activation. The patient developed a marked reading deficit, while recognition of other visual categories remained intact. Furthermore, in the post-surgery fMRI map of visual cortex, only word-specific activations disappeared. Altogether, these results provide direct evidence for the causal role of the left occipitotemporal cortex in the recognition of visual words.

Chordomas of the base of the skull and upper cervical spine. One hundred patients irradiated by a 3D conformal technique combining photon and proton beams

To define the prognostic factors for local control and overall survival among 100 consecutive patients with chordoma of the base of skull or upper cervical spine treated by fractionated irradiation combining proton and photon beams. Between December 1993 and August 2002, 100 patients (median age: 53 years [8 - 85], M/F sex ratio: 3/2) were treated by a combination of high-energy photons and protons. The proton component was delivered at the Centre de Protonthérapie d'Orsay (CPO) by a 201 MeV beam. The median total dose delivered to the tumor volume was 67 GyECo. With a median follow-up of 31 months [range: 0 - 87], 25 tumours relapsed locally. The 2- and 4-year local control rates were 86.3% (+/-3.9%) and 53.8% (+/-7.5%), respectively. According to multivariate analysis, at least 95% of the tumor volume encompassed by the 95% isodose (p = 0.048; RR: 3.4 95%CI [1.01 - 11.8]) and a minimal dose delivered into the tumor volume <56 GyECo (p = 0.042; RR: 2.3 95%CI [1.03 - 5.2]) were independent prognostic factors of local control. Ten patients died. The 2- and 5-year overall survival rates were 94.3% (+/-2.5%) and 80.5% (+/-7.2%), respectively. According to multivariate analysis, local tumor control (p = 0.005; RR: 21 95%CI [2.2 - 200]) was a prognostic factor of overall survival. For chordomas of the base of the skull and upper cervical spine treated by surgery and irradiation combining photons and protons, the quality of irradiation, reflected by homogeneity of the dose into the tumor volume, is a major factor of local control. Close attention must be paid to minimize the underdosed areas close to critical organs. The role of surgical resection remains paramount, and a trial of dose escalation would have to consider an increase in the dose to critical organs, especially as current results indicate the low toxicity of this treatment.

Interictal diffusion MRI in partial epilepsies explored with intracerebral electrodes

Patients with refractory partial seizures may benefit from epilepsy surgery. However, invasive investigations are often needed to define the precise location and limits of the epileptogenic zone (EZ). In this study, we asked whether diffusion tensor imaging (DTI) might provide a non-invasive alternative to locate the EZ or at least provide insights to help place intracerebral electrodes for stereo-electroencephalography (SEEG). Whole brain DTI and voxel-based analysis (SPM99) was used to assess diffusion properties objectively in 16 epilepsy patients investigated with SEEG. Epilepsy was symptomatic in two patients and cryptogenic in the 14 remaining patients. The suspected onset of seizures was temporal in 10 patients, frontal in 2 and occipital in 4. Individual maps of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were calculated and compared to a database of 40 healthy volunteers. Thirteen of 16 patients exhibited diffusion abnormalities. ADC abnormalities were better correlated with SEEG data than FA abnormalities which were usually located at a distance or in the white matter. A significant increase in ADC (P < 0.01) was found in 11 patients and was located in the regions explored with depth electrodes in 7 of them. Surgery outcome was available in 3 of these 7 patients (2 were seizure free and 1 not). DTI specificity was better in extratemporal lobe epilepsy (83%) than in temporal lobe epilepsy (20%). When abnormalities concurred with the SEEG data, the concordance was optimal between the localization of the diffusion abnormalities and the irritative zone defined by SEEG. These encouraging, preliminary results, suggest that DTI examinations may provide accurate spatial data on the location and extent of the epileptogenic network in extratemporal lobe epilepsies.

A direct intracranial record of emotions evoked by subliminal words

A classical but still open issue in cognitive psychology concerns the depth of subliminal processing. Can the meaning of undetected words be accessed in the absence of consciousness? Subliminal priming experiments in normal subjects have revealed only small effects whose interpretation remains controversial. Here, we provide a direct demonstration of semantic access for unseen masked words. In three epileptic patients with intracranial electrodes, we recorded brain potentials from the amygdala, a neural structure that responds to fearful or threatening stimuli presented in various modalities, including written words. We show that the subliminal presentation of emotional words modulates the activity of the amygdala at a long latency (>800 ms). Our result indicates that subliminal words can trigger long-lasting cerebral processes, including semantic access to emotional valence.

Parkinson disease, brain volumes, and subthalamic nucleus stimulation

BACKGROUND

High-frequency stimulation of the subthalamic nucleus (STN) is an effective treatment for advanced Parkinson disease (PD). The clinical and preoperative predictive factors of the best postoperative outcome have been identified. Radiologic predictive factors were investigated.

METHODS

Forty patients with PD underwent surgery for bilateral STN stimulation. MRI was performed in stereotactic conditions before surgery. Brain parenchyma, caudate nucleus, putamen, pallidum, and red nucleus volumes and the surface of the mesencephalon were measured and normalized as percentages of the intracranial volume. Clinical evaluation was performed 1 month before and 6 months after surgery.

RESULTS

The normalized brain parenchyma volume was lower in patients who were older and had a longer disease duration or a lower frontal score and was not predictive of the postoperative outcome. The residual scores for activities of daily living and parkinsonian motor disability were higher in patients with a smaller normalized mesencephalon. The normalized caudate nucleus volume was predictive of the pre- and postoperative levodopa-equivalent dosage.

CONCLUSIONS

Brain atrophy is not an exclusion criterion for neurosurgery, indicating that patients' neurologic, psychiatric, and neuropsychological characteristics are the best predictive factors for neurosurgery. The fact that a smaller normalized mesencephalon surface was associated with a lower beneficial effect of the subthalamic nucleus stimulation on the parkinsonian motor disability suggests that the normalized mesencephalon surface is a predictive factor of the postoperative outcome.

Les chordomes de la base du crâne et du rachis cervical haut. À propos d'une série de 100 patients irradiés selon une technique conformationnelle 3D par une association de faisceaux de photons et de protons

OBJECTIVE

To define prognostic factors for local control and survival in 100 consecutive patients treated by fractionated photon and proton radiation for chordoma of the skull base and upper cervical spine.

PATIENTS AND METHODS

Between December 1995 and August 2002, 100 patients (median age: 53 years, range: 8-85, M/F sex-ratio: 3/2), were treated by a combination of high-energy photons and protons. The proton component was delivered by the 201 MeV proton beam of the Centre de Protonthérapie d'Orsay (CPO). The median total dose delivered to the gross tumour volume was 67 Cobalt Gray Equivalent (CGE) (range: 60-71). A complete surgery, incomplete surgery or a biopsy was performed before the radiotherapy in 16, 75 and 9 cases, respectively.

RESULTS

With a median follow-up of 31 months (range: 1-87), 25 tumours failed locally. The 2 and 4-year local control rates were 86.3% (+/-3.9%) and 53.8% (+/-7.5%), respectively. According to multivariate analysis, less than 95% of the tumour volume encompassed by the 95% isodose line (P=0.048; RR: 3.4 IC95% [1.01-11.8]) and a minimal dose less than 56 CGE (p=0.042; RR: 2.3 IC95% [1.03-5.2]) were independent prognostic factors of local control. Ten patients died. The 2 and 5-year overall survival rates were 94.3% (+/-2.5%) and 80.5% (+/-7.2%). According to multivariate analysis, a controlled tumour (P=0.005; RR: 21 IC95% [2.2-200]) was the lonely independent favourable prognostic factor for overall survival.

CONCLUSION

In chordomas of the skull base and upper cervical spine treated by surgical resection followed by high-dose photon and proton irradiation, local control is mainly dependent on the quality of radiation, especially dose-uniformity within the gross tumour volume. Special attention must be paid to minimise underdosed areas due to the close proximity of critical structures and possibly escalate dose-constraints to tumour targets in future studies, in view of the low toxicity observed to date.