Ultrasonographic measurement of caudal vena cava to aorta ratio during fluid resuscitation of dogs with spontaneous circulatory shock

OBJECTIVES

To describe the change in the caudal vena cava to aorta ratio (CVC:Ao) ratio during fluid resuscitation of circulatory shock in dogs and compare these results with those of the physical examination and blood lactate.

MATERIALS AND METHODS

Perfusion parameters and blood lactate were recorded at admission. An abdominal point-of-care ultrasound protocol was performed, during which the caudal vena cava to aorta ratio was measured on the spleno-renal view. Measurements were performed within 5 minutes before and after a 10 mL/kg crystalloid fluid bolus. Investigators were not blinded to therapeutic interventions.

RESULTS

Twenty-nine dogs with physical signs of circulatory shock were enrolled. Caudal vena cava to aorta ratios were below reference interval in 28 of 29 dogs. After bolus administration, median caudal vena cava diameter increased by 0.14 cm (0.69 to 0.83 cm) and median aorta diameter increased by 0.03 cm (0.87 to 0.90 cm) and caudal vena cava to aorta ratio returned to within reference range in 65% of dogs (13/29). Bolus administration was associated with an increase in median caudal vena cava to aorta ratio of 0.10 (95% CI:0.05 to 0.16, P=0.0005). Blood lactate did not change significantly. Heart rate and capillary refill time decreased significantly after fluid bolus (heart rate: estimate=-19 bpm, 95% CI:-30 to -8, P=0.002; capillary refill time: estimate=-1.0 s, 95% CI:-1.3 to -0.7, P < 0.0001).

CLINICAL SIGNIFICANCE

In this population of dogs with circulatory shock, the caudal vena cava to aorta ratio significantly increased after a fluid bolus. Future studies that implement blinding of the outcome assessors are warranted to confirm these findings.

A realistic evaluation approach highlighted the success factors and difficulties of an innovative and comprehensive malnutrition programme in Madagascar

AIM

Malnutrition has multiple causes, not just a lack of calories. We explored the successes and barriers of an innovative, comprehensive programme in Madagascar that educated mothers in particular about nutrition.

METHODS

The outpatient programme in Antananarivo treats 2400 malnourished children from 6 to 59 months each year. The 35-day programme comprises health checks, cooking demonstrations, the distribution of enriched flour supplements and two food-related games that are called Nutricartes and are based on boards and picture cards. In 2014, we involved 74 of the children's mothers in a realistic evaluation process, which investigates the mechanisms that produce a particular outcome in a given context.

RESULTS

The mechanisms of success were the community-based aspects of the programme, the kindness and equality displayed by the nutritional assistants and improved household budgeting and hygiene. Children ate better and improved their health, which reduced medical visits and costs. Finally, the mothers became proud of their achievements and told other mothers what they had learnt. Adherence was greatest when the women were on a minimum wage and strongly motivated.

CONCLUSION

The effect of this multifaceted programme was that the mothers received sustainable education about healthy eating and improved childhood health and nutrition.

Most children who took part in a comprehensive malnutrition programme in Madagascar reached and maintained the recovery threshold

AIM

The benefits of including nutritional education in programmes that tackle moderate and severe acute malnutrition remain poorly documented. This study in Madagascar evaluated the nutritional status of children who took part in an innovative programme that included maternal education, on completion and after a year.

METHODS

Each year, this outpatient programme admits 2400 malnourished children from six months to 59 months in the lower districts of Antananarivo, Madagascar. Children were drawn by lots, and their anthropometric data were measured. A descriptive retrospective longitudinal study was conducted on 573 children who took part between 2010 and 2013.

RESULTS

The programme lasted an average of 38 days and, on completion, 82.2% had reached the recovery threshold, and 16.2% had moved up to mild malnutrition. This was achieved with food supplements of 720 kcal per day, despite the Malagasy Public Health recommendation of 1000-1500 kcal per day. After one year, 79.1% were still above the recovery threshold, and 15% had mild malnutrition. The recovery rate was higher for children under 24 months of age (odds ratio 2.9, 95% confidence interval 1.93-4.59).

CONCLUSION

Most children who attended this malnutrition programme with maternal education in Madagascar reached the recovery threshold on completion and had maintained it after one year.

Hemorrhagic, Hemostatic, and Thromboelastometric Disorders in 35 Dogs with a Clinical Diagnosis of Leptospirosis: A Prospective Study

Background

Leptospirosis in dogs is occasionally associated with a hemorrhagic syndrome, the pathophysiology of which is not fully understood.

Hypothesis/Objectives

To characterize hematologic, hemostatic, and thromboelastometric abnormalities in dogs with leptospirosis and to study their association with hemorrhagic diatheses and outcomes.

Animals

Thirty‐five client‐owned dogs.

Methods

A prospective observational single cohort study was conducted. Results from the CBC, coagulation tests (prothrombin, activated partial thromboplastin and thrombin times, fibrinogen, fibrin(ogen) degradation products, and D‐dimer concentrations), rotational thromboelastometry (TEM), signalment, hemorrhagic diatheses, occurrence of disseminated intravascular coagulation (DIC) at admission, and survival to discharge were recorded.

Results

The most common hematologic and hemostatic abnormalities were anemia (30/35), thrombocytopenia (21/35), and hyperfibrinogenemia (15/35). Eight dogs were diagnosed with DIC. A normal TEM profile was found in 14 dogs, a hypercoagulable profile in 14 dogs, and a hypocoagulable profile in 7 dogs. The 8 dogs with hemorrhagic diatheses at admission had significantly decreased platelet counts (P = .037) and increased D‐dimer concentrations (P = .015) compared with other dogs. Dogs with a hypocoagulable profile exhibited more hemorrhagic diatheses compared with the dogs that had normal and hypercoagulable profiles (P = .049). The mortality rate was lower in dogs with a hypercoagulable profile than in those with a hypocoagulable profile (21% vs 57%; P = .043). Disseminated intravascular coagulation was not a significant prognostic factor.

Conclusions and Clinical Importance

Thromboelastometric parameters were altered in dogs with both hypercoagulable and hypocoagulable profiles. A hypocoagulable profile was significantly correlated with hemorrhagic diathesis and higher mortality rate.

Phosphorus utilization in finishing broiler chickens: effects of dietary calcium and microbial phytase

A decrease in dietary P, especially in finishing broilers (21 to 38 d old), is a crucial issue in poultry production from an environmental and economic point of view. Nevertheless, P must be considered together with other dietary components such as Ca and microbial phytase. Different corn and soybean meal-based diets varying in Ca [low (LCa) 0.37, medium (MCa) 0.57, and high (HCa) 0.77%], and nonphytate P [nPP; low (LnPP) 0.18 and high (HnPP) 0.32%] content were tested with and without microbial phytase [0 or 500 phytase units (FTU)/kg]. Feed intake, BW gain, bone mineralization, and mineral retention were examined in 144 Ross PM3 broilers (22 to 38 d old) reared in individual cages. Growth performance was not significantly affected by the treatments. Nevertheless, a numerical decrease of ADG and ADFI was observed in HCa-LnPP and LCa-HnPP associated with an increase of feed conversion ratio. Decreased dietary Ca reduced tibia ash content (Ca, linear: P < 0.001; quadratic: P = 0.034) and tibia ash weight for the highest level of nPP (Ca × nPP; P = 0.035). In parallel, increasing dietary Ca reduced the flow of retained P (P = 0.022) but also tibia ash weight in LnPP diets (Ca × nPP; P = 0.035). The responses of the animals in terms of tibia ash content and P retention were improved by the addition of microbial phytase especially for the lowest P diets (nPP × phytase, P = 0.021 and P = 0.009; respectively). Phytase increased dry tibia weight, bone breaking strength, and tibia diameter in broilers fed the highest Ca diets (Ca × phytase; P < 0.05). We conclude that is possible to decrease P levels in finishing broilers, if the Ca content is appropriate. Nevertheless, decreasing the dietary P and Ca cannot allow a maximization of bone mineralization, but the optimal threshold remains to be determined.

How the pain of others enhances our pain: searching the cerebral correlates of 'compassional hyperalgesia'

Observing other people's pain increases our own reports to painful stimuli, a phenomenon that can be defined as 'compassional hyperalgesia' (CH). This functional magnetic resonance imaging study examined the neural correlates of CH, and whether CH could emerge when exposure to the driving stimulus was subliminal. Subjects received electric somatosensory stimuli while observing images of people undergoing painful or enjoyable somatic sensations, presented during a period allowing or not allowing conscious perception. The intensity attributed to painful stimuli increased significantly when these were delivered close to images showing human pain, but only when such images were consciously perceived. The basic core of the Pain Matrix (SI, SII, insula, mid-anterior cingulate) was activated by painful stimuli, but its activation magnitude did not increase during CH. Compassional hyperalgesia was associated with increased activity in polymodal areas involved in emotional tuning (anterior prefrontal, pregenual cingulated) and areas involved in multisensory integration and short-term memory (dorsolateral prefrontal, temporo-parieto-occipital junction). CH appears as a high-order phenomenon needing conscious appraisal of the eliciting visual stimulus, and supported by polymodal areas distinct from the basic Pain Matrix. This suggests that compassion to pain does not result from a mere 'sensory resonance' in pain networks, but rather from an interaction between the output of a first-line processing in the Pain Matrix, and the activity of a high-order network involving multisensory integration (temporo-parietal), encoding of internal states (mid-prefrontal) and short-time memory encoding (dorsolateral prefrontal). The Pain Matrix cannot be considered as an 'objective' correlate of the pain experience in all situations.

Effect of reduced dietary calcium concentration and phytase supplementation on calcium and phosphorus utilization in weanling pigs with modified mineral status

The present study was conducted to assess the effect of 2 dietary Ca concentrations on P and Ca digestive and metabolic utilization in weanling pigs fed diets providing practical concentrations of P, with or without phytase. The responses of pigs fed diets adequate or moderately deficient in Ca and P postweaning were compared. A total of 60 pigs weaned at 28 d of age were used. Two groups of 30 pigs with differing mineral status resulted from a 10-d depletion period, during which the animals received depletion diets (DD) that consisted of corn-soybean meal with either 1.42% Ca and 0.80% P (DD+) or 0.67% Ca and 0.43% P (DD-), designed to achieve the same Ca:digestible P ratio. At the end of the depletion period, a plasma sample was taken from each pig and 12 pigs (6 from each group) were slaughtered for bone assessment to establish the baseline mineral status. The animals fed the DD- diet had signs of P deficiency with reduced plasma P (13%; P < 0.01) and femur ash concentration (8%; P < 0.05), and increased plasma Ca (9%; P < 0.05) and alkaline phosphatase activity (31%; P < 0.01). For the subsequent 25-d period, the remaining 24 pigs from each group were fed 1 of 4 repletion diets: 1) 0.56% P, 1.06% Ca; 2) 0.56% P, 0.67% Ca; 3) diet 1 + 1,000 phytase units (FTU) of Natuphos phytase/kg; and 4) diet 2 + 1,000 FTU of Natuphos phytase/kg. Total feces and urine were collected from d 5 to 11, and a blood sample was taken from each pig at d 11 and 25. The initial moderate P deficiency (DD-) stimulated Ca absorption (5%; P < 0.01), irrespective of the repletion diet, and stimulated P absorption (5%; DD x phytase, P < 0.05), only when the diets contained phytase. At the end of the repletion period, because of these compensatory phenomena, the depleted pigs achieved full recovery of femur DM and ash weight when they received phytase, whereas ash concentration tended to remain reduced by 3% (P = 0.08). Phosphorus digestibility was improved in the diets supplemented with phytase (73.0 vs. 56.0%; P < 0.001), whereas an increase in dietary Ca decreased P digestibility (65.6 vs. 63.4%; P < 0.05). Those 2 effects were independent, indicating that dietary Ca reduced equally P digestibility with and without phytase and did not influence the efficiency of phytase in releasing P in the digestive tract. In pigs fed diets with phytase, however, the reduction of Ca (Ca:P from 1.9 to 1.3) increased urinary P losses 5-fold. Those extra losses were due to a lack of Ca for skeleton ash deposition, resulting in a 4% reduction in femur ash concentration. In the end, reducing the dietary Ca:P from 1.9 to 1.3 in a practical diet containing 0.56% P did not improve the efficiency of phytase in releasing P. Moreover, the reduction in dietary Ca (Ca:P) caused an imbalance between Ca and P that impaired bone mineralization.

Cross-modal plasticity in the human thalamus: evidence from intraoperative macrostimulations

During stereotactic functional neurosurgery, stimulation procedure to control for proper target localization provides a unique opportunity to investigate pathophysiological phenomena that cannot be addressed in experimental setups. Here we report on the distribution of response modalities to 487 intraoperative thalamic stimulations performed in 24 neurogenic pain (NP), 17 parkinsonian (PD) and 10 neuropsychiatric (Npsy) patients. Threshold responses were subdivided into somatosensory, motor and affective, and compared between medial (central lateral nucleus) and lateral (ventral anterior, ventral lateral and ventral medial) thalamic nuclei and between patients groups. Major findings were as follows: in the medial thalamus, evoked responses were for a large majority (95%) somatosensory in NP patients, 47% were motor in PD patients, and 54% affective in Npsy patients. In the lateral thalamus, a much higher proportion of somatosensory (83%) than motor responses (5%) was evoked in NP patients, while the proportion was reversed in PD patients (69% motor vs. 21% somatosensory). These results provide the first evidence for functional cross-modal changes in lateral and medial thalamic nuclei in response to intraoperative stimulations in different functional disorders. This extensive functional reorganization sheds new light on wide-range plasticity in the adult human thalamocortical system.

Motor cortex stimulation for pain control induces changes in the endogenous opioid system

BACKGROUND

Motor cortex stimulation (MCS) for neuropathic pain control induces focal cerebral blood flow changes involving regions with high density of opioid receptors. We studied the possible contribution of the endogenous opioid system to MCS-related pain relief.

METHODS

Changes in opioid receptor availability induced by MCS were studied with PET scan and [(11)C]diprenorphine in eight patients with refractory neuropathic pain. Each patient underwent two preoperative (test-retest) PET scans and one postoperative PET scan acquired after 7 months of chronic MCS.

RESULTS

The two preoperative scans, performed at 2 weeks interval, did not show significant differences. Conversely, postoperative compared with preoperative PET scans revealed significant decreases of [(11)C]diprenorphine binding in the anterior middle cingulate cortex (aMCC), periaqueductal gray (PAG), prefrontal cortex, and cerebellum. Binding changes in aMCC and PAG were significantly correlated with pain relief.

CONCLUSION

The decrease in binding of the exogenous ligand was most likely explained by receptor occupancy due to enhanced secretion of endogenous opioids. Motor cortex stimulation (MCS) may thus induce release of endogenous opioids in brain structures involved in the processing of acute and chronic pain. Correlation of this effect with pain relief in at least two of these structures supports the role of the endogenous opioid system in pain control induced by MCS.

Subthalamic nucleus stimulation in Parkinson’s disease

OBJECTIVES

1 - To assess the anatomical localization of the active contacts of deep brain stimulation targeted to the subthalamic nucleus (STN) in Parkinson's disease patients. 2 - To analyze the stereotactic spatial distribution of the active contacts in relation to the dorsal and the ventral electrophysiologically-defined borders of the STN and the stereotactic theoretical target.

METHODS

Twenty-eight patients underwent bilateral high-frequency stimulation of the STN (HFS-STN). An indirect anatomical method based on ventriculography coupled to electrophysiological techniques were used to localize the STN. Clinical improvement was evaluated by Unified Parkinson's Disease Rating Scale motor score (UPDRS III). The normalized stereotactic coordinates of the active contact centres, dorsal and ventral electrophysiologically-defined borders of the STN were obtained from intraoperative X-rays images. These coordinates were represented in a three-dimensional stereotactic space and in the digitalized atlas of the human basal ganglia.

RESULTS

HFS-STN resulted in significant improvement of motor function (62.8%) in off-medication state and levodopa-equivalent dose reduction of 68.7% (p < 0.05). Most of the active contacts (78.6%) were situated close to (+/- 1.6 mm) the dorsal border of the STN (STN-DB), while 16% were dorsal and 5.4% were ventral to it. Similar distribution was observed in the atlas. The euclidean distance between the STN-DB distribution center and the active contacts distribution center was 0.31 mm, while the distance between the active contacts distribution center and the stereotactic theoretical target was 2.15 mm. Most of the space defined by the active contacts distribution (53%) was inside that defined by the STN-DB distribution.

CONCLUSION

In our series, most of the active electrodes were situated near the STN-DB. This suggests that HFS-STN could influence not only STN but also the dorsal adjacent structures (zona incerta and/or Fields of Forel).

Vers une théorie unifiée des symptômes positifs

Defined more than one century ago, the concept of positive symptoms has become obsolete, except in the psychiatric domain. However, its relevance remains intact today when considering such pathophysiologies as neuropathic (phantom) pain, movement disorders, tinnitus, epilepsy, and psychiatric disorders. Beside their very different clinical characteristics, all these symptoms arise from a lesion in the nervous system. Furthermore, they are paradoxical in the sense that they correspond to a spontaneous hyperactivity of the injured functional system, concomitant to the usual deficits resulting from the lesion. Could these similarities reflect the existence of some common pathophysiological process? A peculiar electrophysiological property of thalamic cells is likely to be compatible with this hypothesis. A thalamic cell produces action potentials when depolarised by excitatory inputs. Conversely, its ability to produce action potentials is decreased or even completely suppressed when the same cell is hyperpolarized by inhibitory influences. However, depending on its level of hyperpolarization, this cell can also produce rhythmic paradoxical bursts of activity at low frequency (3-4 Hz). In this context, a lesion involving, for example, the somatosensory excitatory fibres gives rise to hyperpolarization of the corresponding thalamic cells, which may produce such rhythmic bursting activity. This causes an increase of low frequency thalamo-cortical activity, which, through reduction of collateral cortico-cortical inhibition, induces high frequency activity in neighbouring thalamo-cortical loops ("edge effect"). This leads to the appearance of the clinical symptoms, in this case, pain. Electrophysiological recordings performed in patients suffering from sensory or motor positive symptoms have shown the presence of such deleterious sequence of events. Furthermore, the efficiency of neurosurgical treatments that are used against some positive symptoms can be explained on the basis of such a dynamic process. Both considerations support the validity of the proposed hypothesis and open avenues for the control of other positive symptoms.

Hippocampal-orbitofrontal connectivity in human: an electrical stimulation study

OBJECTIVE

The identification of the pathways involved in seizure propagation remains poorly understood in humans. For instance, the respective role of the orbitofrontal cortex (OFC) and of the commissural pathways in the interhemispheric propagation of mesial temporal lobe seizures (mTLS) is a matter of debate. In order to address this issue, we have directly tested the functional connectivity between the hippocampus and the OFC in 3 epileptic patients undergoing an intra-cranial stereotactic EEG investigation.

METHODS

Bipolar electrical stimulations, consisting of two series of 25 pulses of 1 ms duration, 0.2 Hz frequency, and 3 mA intensity, were delivered in the hippocampus. Evoked potentials (EPs) were analysed for each series, separately. Grand average of reproducible EPs was then used to calculate latency of the first peak of each individual potential.

RESULTS

Hippocampal stimulations evoked reproducible responses in the OFC in all 3 patients, with a mean latency of the first peak of 222 ms (range: 185-258 ms).

CONCLUSIONS

Our data confirm a functional connectivity between the hippocampus and the OFC in human.

SIGNIFICANCE

This connectivity supports the potential role of the OFC in the propagation of mTLS.

Neuropsychiatric thalamocortical dysrhythmia: surgical implications

Clearly, more clinical experience must be amassed to define in detail the possibilities of this surgical approach in disabling neuropsychiatric disorders. We propose, however, that the evidence for benign and efficient surgical intervention against the neuropsychiatric TCD syndrome is already compelling. The potential appearance of strong postoperative reactive manifestations requires a close association between surgery and psychotherapy, with the latter providing support for the integration of the new situation as well as the resolution of old unresolved issues.

Microelectrode recording and macrostimulation in thalamic and subthalamic MRI guided stereotactic surgery

Stereotactic neurosurgery aims at placing therapeutic lesions or chronic stimulating electrodes at very precise locations within the brain. Microelectrode recording and macrostimulation are used in addition to anatomoradiological techniques to optimize targeting. Recently, the usefulness of electrophysiological procedures has been questioned. Based on more than 500 therapeutic stereotactic lesions in the last 10 years at the thalamic and subthalamic levels, we evaluate here retrospectively the utility of the two electrophysiological procedures. In two of the three stereotactic targets considered in this study, intraoperative electrophysiological confirmation is mandatory because of the target size with respect to interindividual anatomical variations and of the more or less close vicinity of eloquent structures.

Effects of medial thalamotomy and pallido-thalamic tractotomy on sleep and waking EEG in pain and Parkinsonian patients

OBJECTIVES

Investigation of sleep and sleep EEG before and after stereotactic neurosurgery.

METHODS

All-night polysomnographic recordings were obtained in 3 neurogenic pain patients and 3 parkinsonian patients. One subject of each group was recorded in addition 3 months after surgery. Stereotactic operations were performed in the medial thalamus and on the pallido-thalamic tract to relieve neurogenic pain and parkinsonian symptoms, respectively.

RESULTS

Sleep efficiency was little affected by the surgical intervention in neurogenic pain patients and a dramatic reduction in REM sleep occurred, which had recovered in the subject recorded after 3 months. After the surgery parkinsonian patients showed an increase in total sleep time and in sleep efficiency, and a decrease in REM sleep latency. Sleep efficiency remained elevated in the 3 months follow-up. Medial thalamotomy abolished spindle frequency activity (SFA) in the power and coherence spectra in non-REM sleep stage 2 systematically. Pallido-thalamic tractotomy attenuated SFA only to varying degrees. After 3 months SFA had reemerged. The alpha peak of the waking EEG was shifted to lower frequencies after surgery in 5 of 6 patients and had reverted to the original frequency 3 months later.

CONCLUSIONS

Medial thalamotomy or pallido-thalamic tractotomy had acute and reversible effects on the EEG and long-term deleterious side effects of stereotactic surgery on sleep and sleep EEG are improbable. The results provide further evidence for the involvement of the human thalamus in the generation of sleep spindles.

Single-unit analysis of the pallidum, thalamus and subthalamic nucleus in parkinsonian patients

Microelectrode-guided stereotactic operations performed in 29 parkinsonian patients allowed the recording of 86 cells located in the globus pallidus and 563 in thalamic nuclei. In the globus pallidus, the average firing rate was significantly higher in the internal (91+/-52 Hz) than in the external (60+/-21 Hz) subdivision. This difference was further accentuated when the average firing rate in the external subdivision was compared with that of the internal part of the internal subdivision (114+/-30 Hz). A rhythmic modulation in globus pallidus activities was observed in 19.7% of the cells, and this only during rest tremor episodes. In these cases, modulation frequency of unit activities was not statistically different from the rest tremor frequency (average: 4.6+/-0.5 vs 4. 4+/-0.4 Hz, respectively). In the medial thalamus, four types of unit activities could be defined. A sporadic type was mainly found in the parvocellular division of the mediodorsal nucleus (96.8% of the cells recorded) and in the centre median-parafascicular complex (74.2%). Two other types of activities characterized by random or rhythmic bursts fulfilling the extracellular criteria of low-threshold calcium spike bursts were concentrated in the central lateral nucleus (62.3%) and the paralamellar division of the mediodorsal nucleus (34.1%). These activities could be recorded independently of the presence of a rest tremor. When a tremor episode occurred, the rhythmic low-threshold calcium spike bursts had an interburst frequency similar to rest tremor frequency, although they were not synchronized with it. The fourth type, the so-called tremor locked, was also characterized by rhythmic bursts which, however, did not display low-threshold calcium spike burst properties. These bursts occurred only when a rest tremor was present and was in-phase with the electromyographic bursts. All tremor-locked cells were located in the centre median-parafascicular complex. In the lateral thalamus, cells exhibiting random or rhythmic low-threshold calcium spike bursts were found preponderantly in the ventral anterior nucleus (53.4%) and in the ventral lateral anterior nucleus (52.7%). Tremor-locked units were confined to the ventral division of the ventral lateral posterior nucleus (35.4%). None of the random or rhythmic low-threshold calcium spike bursting units responded to somatosensory stimuli or voluntary movements, either in the medial or in the lateral thalamus. The presence of low-threshold calcium spike bursts at the thalamic level, together with the paucity (8%) of responses to voluntary movements compared to what is found in normal non-human primates, demonstrate a pathological state of inhibition due to the overactivity of the internal subdivision of the globus pallidus units. Activities of the thalamic cells producing low-threshold calcium spike bursts are not synchronized with each other or with the tremor. However, this does not exclude a causal role of these activities in the generation of tremor. Indeed, it has been demonstrated that even random electrical stimulations of the rolandic cortex in parkinsonian patients induce tremor episodes, probably due to the triggering of rhythmic, low-threshold calcium spike-dependent, thalamocortical activities. Similarly, low-threshold calcium spike bursts could be at the origin of rigidity and dystonia through an activation of the supplementary motor area and of akinesia when reaching the pre-supplementary motor area. We conclude that the intrinsic oscillatory properties of individual neurons, combined with the dynamic properties of the thalamocortical circuitry, are responsible for the three cardinal parkinsonian symptoms.

Accuracy of MRI-guided stereotactic thalamic functional neurosurgery

Our goal was to evaluate the accuracy of stereotactic technique using MRI in thalamic functional neurosurgery. A phantom study was designed to estimate errors due to MRI distortion. Stereotactic mechanical accuracy was assessed with the Suetens-Gybels-Vandermeulen (SGV) angiographic localiser. Three-dimensional MRI reconstructions of 86 therapeutic lesions were performed. Their co-ordinates were corrected from adjustments based on peroperative electrophysiological data and compared to those planned. MR image distortion (maximum: 1 mm) and chemical shift of petroleum oil-filled localiser rods (2.2 mm) induced an anterior target displacement of 2.6 mm (at a field strength of 1.5 T, frequency encoding bandwidth of 187.7 kHz, on T1-weighted images). The average absolute error of the stereotactic material was 0.7 mm for anteroposterior (AP), 0.5 mm for mediolateral (ML) and 0.8 mm for dorsoventral (DV) co-ordinates (maximal absolute errors: 1.6 mm, 2.2 mm and 1.7 mm, respectively; mean euclidean error: 1 mm). Three-dimensional MRI reconstructions showed an average absolute error of 0.8 mm, 0.9 mm and 1.9 mm in AP, ML and DV co-ordinates, respectively (maximal absolute errors: 2.4 mm, 2.7 mm and 5.7 mm, respectively; mean euclidean error: 2.3 mm). MRI distortion and chemical-shift errors must be determined by a phantom study and then compensated for. The most likely explanation for an average absolute error of 1.9 mm in the DV plane is displacement of the brain under the pressure of the penetrating electrode. When this displacement is corrected for by microelectrode recordings and stimulation data, MRI offers a high degree of accuracy and reliability for thalamic stereotaxy.

Multiarchitectonic and stereotactic atlas of the human thalamus

To improve anatomical definition and stereotactic precision of thalamic targets in neurosurgical treatments of chronic functional disorders, a new atlas of the human thalamus has been developed. This atlas is based on multiarchitectonic parcellation in sections parallel or perpendicular to the standard intercommissural reference plane. The calcium-binding proteins parvalbumin (PV), calbindin D-28K (CB), and calretinin (CR) were used as neurochemical markers to further characterize thalamic nuclei and delimit subterritories of functional significance for stereotactic explorations. Their overall distribution reveals a subcompartmentalization of thalamic nuclei into several groups. Predominant PV immunostaining characterizes primary somatosensory, visual and auditory nuclei, the ventral lateral posterior nucleus, reticular nucleus (R), and to a lesser degree also, lateral part of the centre median nucleus, and anterior, lateral, and inferior divisions of the pulvinar complex. In contrast, CB immunoreactivity is prevalent in medial thalamic nuclei (intralaminar and midline), the posterior complex, ventral posterior inferior nucleus, the ventral lateral anterior nucleus, ventral anterior, and ventral medial nuclei. The complementary distributions of PV and CB appear to correlate with distinct lemniscal and spinothalamic somatosensory pathways and to cerebellar and pallidal motor territories, respectively. Calretinin, while overlapping with CB in medial thalamic territories, is also expressed in R and limbic associated anterior group nuclei that contain little or no CB. Preliminary analysis indicates that interindividual nuclear variations cannot easily be taken into account by standardization procedures. Nevertheless, some corrections in antero-posterior coordinates in relation to different intercommissural distances are proposed.

Multiarchitectonic and stereotactic atlas of the human thalamus

To improve anatomical definition and stereotactic precision of thalamic targets in neurosurgical treatments of chronic functional disorders, a new atlas of the human thalamus has been developed. This atlas is based on multiarchitectonic parcellation in sections parallel or perpendicular to the standard intercommissural reference plane. The calcium-binding proteins parvalbumin (PV), calbindin D-28K (CB), and calretinin (CR) were used as neurochemical markers to further characterize thalamic nuclei and delimit subterritories of functional significance for stereotactic explorations. Their overall distribution reveals a subcompartmentalization of thalamic nuclei into several groups. Predominant PV immunostaining characterizes primary somatosensory, visual and auditory nuclei, the ventral lateral posterior nucleus, reticular nucleus (R), and to a lesser degree also, lateral part of the centre median nucleus, and anterior, lateral, and inferior divisions of the pulvinar complex. In contrast, CB immunoreactivity is prevalent in medial thalamic nuclei (intralaminar and midline), the posterior complex, ventral posterior inferior nucleus, the ventral lateral anterior nucleus, ventral anterior, and ventral medial nuclei. The complementary distributions of PV and CB appear to correlate with distinct lemniscal and spinothalamic somatosensory pathways and to cerebellar and pallidal motor territories, respectively. Calretinin, while overlapping with CB in medial thalamic territories, is also expressed in R and limbic associated anterior group nuclei that contain little or no CB. Preliminary analysis indicates that interindividual nuclear variations cannot easily be taken into account by standardization procedures. Nevertheless, some corrections in antero-posterior coordinates in relation to different intercommissural distances are proposed.

Spontaneous anterior and lateral tibial compartment syndrome in a type I diabetic patient: case report

We report the case of a 46-year-old man with type I diabetes who spontaneously developed compartment syndrome of the anterior and lateral compartment of the left leg. The patient was treated with two compartment fasciotomies.

Novel animal model for studying the molecular mechanisms of bacterial adhesion to bone-implanted metallic devices: role of fibronectin in Staphylococcus aureus adhesion

Infection around metallic implants is a rare but severe complication of orthopaedic surgery. A novel animal model mimicking conditions of internal fixation devices was developed to evaluate the role of host proteins adsorbed on metallic devices in promoting adhesion and colonization of the material surfaces by Staphylococcus aureus. Small plates made of pure titanium were either fixed (three screws per plate) onto the iliac bones of guinea pigs or implanted into their subcutaneous space as controls. Five to 6 weeks after surgery, the plates and screws were removed from the previously killed animals, carefully rinsed in buffer, and tested in an in vitro assay of S. aureus adhesion to metallic surfaces. To evaluate the role of fibronectin in staphylococcal adhesion to explanted plates and screws, a mutant of S. aureus that is specifically defictive in fibronectin adhesion due to decreased expression of the fibronectin adhesin was compared with its isogenic parental strain. A significant reduction in adhesion of the fibronectin adhesin-defective mutant compared with the parental strain occurred on both the subcutaneously implanted and bone-implanted metallic plates. The results of this specific biological assay suggest that fibronectin is present on bone-implanted metallic devices and promotes attachment of S. aureus to their surfaces. This novel experimental model should help, to characterize several parameters of bacterial adhesion to metallic orthopaedic devices and to develop novel anti-adhesive strategies for preventing such infections.

Low-threshold calcium spike bursts in the human thalamus. Common physiopathology for sensory, motor and limbic positive symptoms

Positive symptoms arise after lesions of the nervous system. They include neurogenic pain, tinnitus, abnormal movements, epilepsy and certain neuropsychiatric disorders. Stereotactic medial thalamotomies were performed on 104 patients with chronic therapy-resistant positive symptoms. Peroperative recordings of 2012 single units revealed an overwhelming unresponsiveness (99%) to sensory stimuli or motor activation. Among these unresponsive cells, 45.1% presented a rhythmic or random bursting activity. Rhythmic bursting activities had an average interburst interval of 263 +/- 46 ms corresponding to a frequency of 3.8 +/- 0.7 Hz. Frequency variations among the different symptoms were not statistically different. Intraburst characteristics such as the highest frequency encountered in the burst (480 +/- 80 Hz) or the mean frequency of the burst (206 +/- 44 Hz) were also similar in all patients. All bursts, rhythmic or random, fulfilled the extracellular criteria of low-threshold calcium spike (LTS) bursts. After medial thalamotomy and depending on the symptom, 43-67% of the patients reached a 50-100% relief, with sparing of all neurological functions. On the basis of these electrophysiological and clinical results, we propose a unified concept for all positive symptoms centred on a self-perpetuating thalamic cell membrane hyperpolarization, similar to the one seen in slow-wave sleep.

Chronic neurogenic pain and the medial thalamotomy

69 patients suffering from chronic therapy-resistant neurogenic pain of peripheral and/or central origin underwent a stereotactic medial thalamotomy. Medial thalamic unit recordings were performed peroperatively, allowing the physiological confirmation of the electrode location and the recognition of a specific physiopathology. Thanks to these recordings, a concept was developed, based on the presence of an imbalance between medial (nucleus centralis lateralis mainly) and lateral (nucleus ventroposterior) thalamic nuclei, resulting in an over-inhibition of both by the reticular thalamic nucleus, and then in a paradoxical activation of pain-related cortical areas. The medial thalamotomy, re-actualized by new technical, anatomical and physiological data, offers a 50-100% relief to 67% of all patients with peripheral as well as central neurogenic pain, on all body localizations, without producing neurological deficits and without risk for the development of iatrogenic pain.

Neuroanatomical pathways linking vision and olfaction in mammals

Retinal projections to several telencephalic structures have been demonstrated in a wide range of mammalian species following intraocular injections of tritiated amino acids and cholera toxin subunit-B conjugated to horseradish peroxidase. Since these regions are also innervated by olfactory fibers, we investigated the distribution of convergent projections using simultaneous injections of different anterograde tracers in the eye and olfactory bulbs. Convergent projections from the retina and from the olfactory bulbs were observed in the piriform cortex, olfactory tubercle, the cortical region of the medial amygdala, lateral hypothalamus, and the bed nucleus of the stria terminalis. A few retinal fibers also invade the nucleus of the lateral olfactory tract, the bed nucleus of the accessory olfactory bulb and the diagonal band of Broca. Injections of retrograde tracers in the medial amygdala, the bed nucleus or the lateral hypothalamus shows that the visuo-olfactory convergence mainly involves projections originating from the accessory olfactory bulb, and to a lesser extent from the ventromedial region of the main olfactory bulb. Fewer than 20 retinotelencephalic ganglion cells were identified in the retina, mainly located contralateral to the injection site. Ganglion cells were medium sized and possessed two long slender opposing dendrites. These retinal and olfactory projections could provide an anatomical substrate for the modulation of gonadotropin hormone levels and the olfactory influence on light mediated rhythms related to reproductive physiology.

Anatomical segregation of different adaptative processes within the vestibulocerebellum of the cat

Bilateral surgical lesions of the flocculus or the nodulo-uvular lobes were performed in the cat. Effects of these lesions on optokinetic and optokinetic afternystagmus OKAN), vestibulo-ocular reflex (VOR), visual suppression, and adaptation and habituation of VOR were studied using an identical experimental protocol. After flocculectomy, all these functions were impaired, except for habituation. Long-term postoperative recordings only revealed a recovery of the suppression of VOR, suggesting a limited contribution of the flocculus to this function. After nodulo-uvulectomy, only habituation and OKAN were modified. When the lesion was restricted to part of the uvula, OKAN duration was decreased. For other lesions involving the uvula together with the nodulus and/or the lobules VII-VIII,OKAN duration was increased. Habituation was lost after destruction of the nodulo-uvular lobes. When this latter structure was damaged, the retention component of habituation was selectively impaired, sparing the acquisition. Additional lesions outside the vestibulocerebellum appeared necessary to suppress the two components. Comparison of results obtained after flocculectomy and after nodulouvulectomy confirms and extends to non-primate species the concept of a "differential control" of adaptation and habituation by distinct vestibulocerebellar structures.