Carlos Ciraolo

A New Classification of Complications in Neurosurgery

OBJECTIVE To define and grade neurosurgical and spinal postoperative complications based on their need for treatment. METHODS Complications were defined as any deviation from the normal postoperative course occurring within 30 days of surgery. A four-grade scale was proposed based on the therapy used to treat the complications: grade I, any non-life-threatening complications treated without invasive procedures; grade II, complications requiring invasive management such as surgical, endoscopic, and endovascular procedures; grade III, life-threatening adverse events requiring treatment in an intensive care unit (ICU); and grade IV, deaths as a result of complications. Each grade was classified as a surgical or medical complication. An observational test of this system was conducted between January 2008 and December 2009 in a cohort of 1190 patients at the Hospital Italiano de Buenos Aires. RESULTS Of 167 complications, 129 (10.84%) were classified as surgical, and 38 (3.19%) were classified as medical complications. Grade I (mild) complications accounted for 31.73%, grade II (moderate) complications accounted for 25.74%, and grade III (severe) complications accounted for 34.13%. The overall mortality rate was 1.17%; 0.84% of deaths were directly related to surgical procedures. CONCLUSIONS The authors present a simple, practical, and easy to reproduce way to report negative outcomes based on the therapy administered to treat a complication. The main advantages of this classification are the ability to compare surgical results among different centers and times, the ability to compare medical and surgical complications, and the ability to perform future meta-analyses.

Jugular venous oxygen saturation or arteriovenous difference of lactate content and outcome in children with severe traumatic brain injury.

Objective To assess the association between neurologic outcome and the alterations of jugular venous oxygen saturation (Sjvo2) or the increase in arteriovenous difference of lactate content (AVDL) in children with severe traumatic brain injury. Design Observational prospective cohort study. Setting Multidisciplinary pediatric intensive care unit of a university hospital. Patients A total of 27 pediatric patients with severe traumatic brain injury, with a Glasgow Coma Scale after resuscitation of <9, who were admitted to the pediatric intensive care unit within 36 hrs after injury. Interventions Intermittent measurement of Sjvo2 and AVDL. Measurements and Main Results Sjvo2 and AVDL were assessed simultaneously every 6 hrs. The primary dependent variable measured was assessed independently 3 months after trauma according to the Pediatric Cerebral Performance Category. Patients were classified into two groups: group 1 (favorable outcome, Pediatric Cerebral Performance Category 1–3) and group 2 (unfavorable outcome, Pediatric Cerebral Performance Category 4–6); 81% were included in group 1 and 19% in group 2. A total of 354 measurements of Sjvo2 and AVDL were made, with a mean of 13.1 ± 7.9 per patient. The number of abnormal measurements of Sjvo2 and increased AVDL used to predict the neurologic outcome was selected according to the area under the receiver operating characteristic curve. Mortality was 15% (four patients). The strongest association was found between a poor neurologic outcome and two or more pathologic AVDL measurements (higher than −0.37 mmol/L; relative risk, 17.6; 95% confidence interval, 2.5–112.5;p = .001). The presence of two or more measurements of Sjvo2 of ≤55% was significantly associated with a poor neurologic outcome (relative risk, 6.6; 95% confidence interval, 1.5–29.7;p = .003). The frequency of measurements of Sjvo2 of ≥75% was not different between groups 1 and 2. Conclusion In children with severe traumatic brain injury, two or more measurements of Sjvo2 of ≤55% or two or more pathologic AVDL measurements were associated with a poor neurologic outcome. Further studies are needed to recommend the use of these variables as a guideline to optimize treatment.

Auditory Feedback Differentially Modulates Behavioral and Neural Markers of Objective and Subjective Performance When Tapping to Your Heartbeat

Interoception, the perception of our body internal signals, plays a key role in maintaining homeostasis and guiding our behavior. Sometimes, we become aware of our body signals and use them in planning and strategic thinking. Here, we show behavioral and neural dissociations between learning to follow ones own heartbeat and metacognitive awareness of ones performance, in a heartbeat-tapping task performed before and after auditory feedback. The electroencephalography amplitude of the heartbeat-evoked potential in interoceptive learners, that is, participants whose accuracy of tapping to their heartbeat improved after auditory feedback, was higher compared with non-learners. However, an increase in gamma phase synchrony (30–45 Hz) after the heartbeat auditory feedback was present only in those participants showing agreement between objective interoceptive performance and metacognitive awareness. Source localization in a group of participants and direct cortical recordings in a single patient identified a network hub for interoceptive learning in the insular cortex. In summary, interoceptive learning may be mediated by the right insular response to the heartbeat, whereas metacognitive awareness of learning may be mediated by widespread cortical synchronization patterns.

Attention, in and Out: Scalp-Level and Intracranial EEG Correlates of Interoception and Exteroception

Interoception, the monitoring of visceral signals, is often presumed to engage attentional mechanisms specifically devoted to inner bodily sensing. In fact, most standardized interoceptive tasks require directing attention to internal signals. However, most studies in the field have failed to compare attentional modulations between internally- and externally-driven processes, thus probing blind to the specificity of the former. Here we address this issue through a multidimensional approach combining behavioral measures, analyses of event-related potentials and functional connectivity via high-density electroencephalography, and intracranial recordings. In Study 1, 50 healthy volunteers performed a heartbeat detection task as we recorded modulations of the heartbeat-evoked potential (HEP) in three conditions: exteroception, basal interoception (also termed interoceptive accuracy), and post-feedback interoception (sometimes called interoceptive learning). In Study 2, to evaluate whether key interoceptive areas (posterior insula, inferior frontal gyrus, amygdala, and somatosensory cortex) were differentially modulated by externally- and internally-driven processes, we analyzed human intracranial recordings with depth electrodes in these regions. This unique technique provides a very fine grained spatio-temporal resolution compared to other techniques, such as EEG or fMRI. We found that both interoceptive conditions in Study 1 yielded greater HEP amplitudes than the exteroceptive one. In addition, connectivity analysis showed that post-feedback interoception, relative to basal interoception, involved enhanced long-distance connections linking frontal and posterior regions. Moreover, results from Study 2 showed a differentiation between oscillations during basal interoception (broadband: 35–110 Hz) and exteroception (1–35 Hz) in the insula, the amygdala, the somatosensory cortex, and the inferior frontal gyrus. In sum, this work provides convergent evidence for the specificity and dynamics of attentional mechanisms involved in interoception.

Massive subarachnoid pneumocephalus after a stereotactic brain biopsy

Sir, Image-guided stereotactic brain biopsy (SBB) is a common and generally safe procedure with a morbidity of 3-5% and a mortality of 0-7%.[1] The most frequent complications include hemorrhage and infection. Pneumocephalus is a common consequence of craniotomies in neurosurgical practice[2] but not following SBB. We could not find a case of tension pneumocephalus (TP) following SBB in the review of English literature.

Integration And Differentiation Of Neural Information Dissociate Between Conscious Percepts

At any given moment, we experience a perceptual scene as a single whole and yet we may distinguish a variety of objects within it. This phenomenon instantiates two properties of conscious perception: integration and differentiation. Integration to experience a collection of objects as a unitary percept, and differentiation to experience these objects as distinct from each other. Here we evaluated the neural information dynamics underlying integration and differentiation of perceptual contents during bistable perception. Participants listened to a sequence of tones (auditory bistable stimuli) experienced either as a single stream (perceptual integration) or as two parallel streams (perceptual differentiation) of sounds. We computed neurophysiological indices of information integration and information differentiation with electroencephalographic and intracranial recordings. When perceptual alternations were endogenously driven, the integrated percept was associated with an increase in neural information-integration and a decrease in neural differentiation across frontoparietal regions, whereas the opposite pattern was observed for the differentiated percept. However, when perception was exogenously driven by a change in the sound stream (no bistability) neural oscillatory power distinguished between percepts but information measures did not. We demonstrate that perceptual integration and differentiation can be mapped to theoretically-motivated neural information signatures, suggesting a direct relationship between phenomenology and neurophysiology.At any given moment, we experience a perceptual scene as a single whole and yet we may distinguish a variety of objects within it. This characteristic of perception instantiates two general properties of phenomenological experience: integration and differentiation. While integration is the property of experiencing a collection of objects as a unitary percept, differentiation is the property of experiencing these objects as different percepts. Little is known about how these two phenomenological properties are dynamically indexed by the brain in terms of information processing. Here we evaluated the dynamics of neural information underlying phenomenological integration and differentiation in bistable perception. Participants listened to auditory bistable stimuli, a sequence of tones experienced either as a (single) integrated percept (phenomenological integration) or as two (parallel) differentiated percepts (phenomenological differentiation). We computed neurophysiological indices of information integration and information differentiation with electroencephalographic and direct cortical recordings in human participants. We focused specifically on the gamma-band dynamics within the frontoparietal network, commonly implicated in conscious processing. In electrical recordings at the scalp and intracranially, the phenomenologically integrated percept generated an increase in neural information integration and a decrease in differentiation between frontal and parietal regions, whereas the opposite pattern was observed for the phenomenologically differentiated percept. This effect was not observed in the auditory control task. Furthermore, this dissociation was not observed when computing traditional measures of neural oscillatory integration (phase synchronization) within the same frontoparietal network and frequency range. However, this frontoparietal phase synchrony was able to distinguish between a stable perceptual window and the transitional period between the two percepts. These theoretically-motivated neural indices of information dynamics dissociated phenomenological integration and differentiation that indices of oscillatory dynamics did not. By incorporating theoretically motivated measures of information theory in the characterization of perceptual content, we contribute to the construction of a testable framework to investigate the neuroscience of conscious experience.

Application of Fibrin Rich in Leukocytes and Platelets in the Reconstruction of Endoscopic Approaches to the Skull Base

BACKGROUND The objective of this work is to report the feasibility and results of an institutional protocol for the application of an innovative biologically active hemoderivative autologous material, denominated leukocyte- and platelet-rich fibrin (L-PRF), in the reconstruction of endoscopic approaches to the sellar region. METHODS L-PRF membranes were produced from centrifuged autologous venous blood. They were used for the reconstruction of transsphenoidal endoscopic approaches to the sellar region in 12 patients. The trophism of the mucosa was monitored during the first 30 days by means of fiberoptic endoscopic controls on the second and seventh postoperative days. Follow-up was performed to rule out complications up to 30 postoperatively days. RESULTS The product obtained bore the characteristics of the original descriptions of L-PRF. Standardized preparation of L-PRF membranes promoted early regeneration of the sphenoid sinus mucosa to close endoscopic approaches to the sellar region. No complications within the first 30 postsurgical days were reported. CONCLUSIONS L-PRF membranes offer characteristics that are superior to other techniques and products, mainly because of their role as biological promoters of tissue regeneration, their low economic cost, and immediate availability. However, it would be necessary to confirm these results in studies involving more patients.

Intracranial high-γ connectivity distinguishes wakefulness from sleep

ABSTRACT Neural synchrony in the &ggr;‐band is considered a fundamental process in cortical computation and communication and it has also been proposed as a crucial correlate of consciousness. However, the latter claim remains inconclusive, mainly due to methodological limitations, such as the spectral constraints of scalp‐level electroencephalographic recordings or volume‐conduction confounds. Here, we circumvented these caveats by comparing &ggr;‐band connectivity between two global states of consciousness via intracranial electroencephalography (iEEG), which provides the most reliable measurements of high‐frequency activity in the human brain. Non‐REM Sleep recordings were compared to passive‐wakefulness recordings of the same duration in three subjects with surgically implanted electrodes. Signals were analyzed through the weighted Phase Lag Index connectivity measure and relevant graph theory metrics. We found that connectivity in the high‐&ggr; range (90–120 Hz), as well as relevant graph theory properties, were higher during wakefulness than during sleep and discriminated between conditions better than any other canonical frequency band. Our results constitute the first report of iEEG differences between wakefulness and sleep in the high‐&ggr; range at both local and distant sites, highlighting the utility of this technique in the search for the neural correlates of global states of consciousness. HighlightsIEEG recordings overcome the methodological limitations of other techniques.IEEG high‐&ggr; connectivity is higher during wakefulness than during sleep.It distinguishes between states better than any other canonical frequency band.Connectivity differences are present at both local and distant sites.

Cirugía de la epilepsia de la región posterior: pronóstico y estrategias en dos centros de Argentina

Resumen Introduccion Las epilepsias de la region posterior (ERP) comprenden las que comprometen los lobulos occipitales, la region parietal por detras del surco poscentral y los limites temporales posteriores, y corresponden a menos del 10% de epilepsias focales. La cirugia de este tipo de epilepsias es poco frecuente, debido principalmente a la alta proporcion de areas elocuentes de esta region. Objetivo Evaluar los resultados y estrategias de la cirugia en ERP en nuestro medio. Material y metodos Se analizaron retrospectivamente pacientes con epilepsia refractaria sometidos a cirugia de la ERP entre los anos 2005 y 2008. La evaluacion prequirurgica fue realizada mediante la semiologia ictal, IRM de alta resolucion, EEG interictal, V-EEG ictal, evaluacion neuropsicologica, EEG invasivo y mapeo funcional por estimulacion electrica. El pronostico de crisis fue evaluado con escala de Engel, con un seguimiento minimo de un ano. Resultados Seis pacientes fueron incluidos, con un seguimiento medio de 2 anos (1 a 3 anos). La edad promedio fue de 23 anos (1 a 33 anos), con una duracion media de la epilepsia de 18 anos (0 a 33 anos). Las etiologias fueron: tumores de bajo grado (2 pacientes), displasias corticales focales (2) y gliosis (2). Durante el seguimiento, 3 pacientes se encontraban libres de crisis, uno continua con auras y 2 presentaron una reduccion mayor del 50% de las crisis. Dos pacientes presentaron exacerbacion de un deficit neurologico previo (hemianopsia). Conclusion La cirugia de la ERP es posible realizarla en nuestro medio, presenta un buen pronostico de crisis y el deficit posquirurgico es aceptable.