[When diagnostic imaging is misleading: a case of subacute liver failure]. / LE CAS CLINIQUE DU MOIS. Quand l'imagerie nous induit en erreur: à propos d'un cas d'insuffisance hépatique subaiguë.

We report the case of a 67 year old woman presenting with a mixed alteration of liver function tests. Despite normal results of tomodensitometry and positon emission tomography, a liver biopsy was performed due to the development of acute liver failure: it showed a diffuse infiltration of liver sinusoids by a breast adenocarcinoma, unfortunately fatal for the patient. The tumour infiltration was responsible for portal hypertension and hepatic perfusion disorders leading to liver failure.

Neural correlates of consciousness during general anesthesia using functional magnetic resonance imaging (fMRI).

This paper reviews the current knowledge about the mechanisms of anesthesia-induced alteration of consciousness. It is now evident that hypnotic anesthetic agents have specific brain targets whose function is hierarchically altered in a dose-dependent manner. Higher order networks, thought to be involved in mental content generation, as well as sub-cortical networks involved in thalamic activity regulation seems to be affected first by increasing concentrations of hypnotic agents that enhance inhibitory neurotransmission. Lower order sensory networks are preserved, including thalamo-cortical connectivity into those networks, even at concentrations that suppress responsiveness, but cross-modal sensory interactions are inhibited. Thalamo-cortical connectivity into the consciousness networks decreases with increasing concentrations of those agents, and is transformed into an anti-correlated activity between the thalamus and the cortex for the deepest levels of sedation, when the subject is non responsive. Future will tell us whether these brain function alterations are also observed with hypnotic agents that mainly inhibit excitatory neurotransmission. The link between the observations made using fMRI and the identified biochemical targets of hypnotic anesthetic agents still remains to be identified.

Linking sleep and general anesthesia mechanisms: this is no walkover.

This review aims at defining the link between physiological sleep and general anesthesia. Despite common behavioral and electrophysiological characteristics between both states, current literature suggests that the transition process between waking and sleep or anesthesia-induced alteration of consciousness is not driven by the same sequence of events. On the one hand, sleep originates in sub-cortical structures with subsequent repercussions on thalamo-cortical interactions and cortical activity. On the other hand, anesthesia seems to primarily affect the cortex with subsequent repercussions on the activity of sub-cortical networks. This discrepancy has yet to be confirmed by further functional brain imaging and electrophysiological experiments. The relationship between the observed functional modifications of brain activity during anesthesia and the known biochemical targets of hypnotic anesthetic agents also remains to be determined.

Surgical resection of a sphenoid wing meningioma in a patient with Glanzmann thrombasthenia.

Glanzmann thrombasthenia (GT) is a rare autosomal recessive disorder characterized by a deficiency or functional defect of platelet glycoprotein (GP) IIb/IIIa. Physiologically, this platelet receptor mediates aggregation of activated platelets by binding the adhesive proteins, fibrinogen, von Willebrand factor (VWF) and fibronectin. This facilitates attachment and aggregation of platelets at sites of vascular injury. We reported the management of a pterional meningioma resection in a patient with Glanzmann thrombasthenia, with recombinant factor VIIa (rFVIIa - NovoSeven) as haemostatic agent. A 48-year-old woman suffering from Glanzmann thrombasthenia was scheduled for spheno-orbital meningioma en plaque surgery. Because of repeated platelet transfusions, this patient developed isoantibodies against missing GPIIbIIIa and alloantibodies against Human Leukocyte Antigen (HLA) leading to refractoriness to platelet transfusions. We observed that Novoseven offered sufficient haemostasis conditions. Therefore, we noticed a deep vein thrombosis. This imposed us to use low weight molecular heparin despite recent surgery.

Bispectral index correlates with regional cerebral blood flow during sleep in distinct cortical and subcortical structures in humans.

The relationship between the Bispectral Index (BIS), an EEG-based monitor of anesthesia, and brain activity is still unclear. This study aimed at investigating the relationship between changes in BIS values during natural sleep and regional cerebral blood flow (rCBF) variations, as measured by Positron Emission Tomography (PET). Data were obtained from six young, healthy, right-handed, male volunteers (20-30 years old) using the H2(15)O infusion method. PET scans were performed both during waking and various stages of sleep. BIS values were monitored continuously and recorded during each PET scan. Positive correlations were detected between BIS and rCBF values in dorsolateral prefontal, parietal, anterior and posterior cingulate, precuneal, mesiofrontal, mesiotemporal and insular cortices. These areas belong to a frontoparietal network known to be related to awareness of self conscious sensory perception, attention and memory. BIS values also positively correlated with activity in brainstem and thalami, both structures known to be involved in arousal and wakefulness. These results show that BIS changes associated with physiological sleep depth co-vary with the activity of specific cortical and subcortical areas. The latter are known to modulate arousal, which in turn allows sustained thalamo-cortical enhancement of activity in a specific frontoparietal network known to be related to the content of consciousness. Thus, although mainly derived from frontal EEG, BIS could represent a wider index of cerebral activity.

Functional connectivity in the default network during resting state is preserved in a vegetative but not in a brain dead patient.

Recent studies on spontaneous fluctuations in the functional MRI blood oxygen level-dependent (BOLD) signal in awake healthy subjects showed the presence of coherent fluctuations among functionally defined neuroanatomical networks. However, the functional significance of these spontaneous BOLD fluctuations remains poorly understood. By means of 3 T functional MRI, we demonstrate absent cortico-thalamic BOLD functional connectivity (i.e. between posterior cingulate/precuneal cortex and medial thalamus), but preserved cortico-cortical connectivity within the default network in a case of vegetative state (VS) studied 2.5 years following cardio-respiratory arrest, as documented by extensive behavioral and paraclinical assessments. In the VS patient, as in age-matched controls, anticorrelations could also be observed between posterior cingulate/precuneus and a previously identified task-positive cortical network. Both correlations and anticorrelations were significantly reduced in VS as compared to controls. A similar approach in a brain dead patient did not show any such long-distance functional connectivity. We conclude that some slow coherent BOLD fluctuations previously identified in healthy awake human brain can be found in alive but unaware patients, and are thus unlikely to be uniquely due to ongoing modifications of conscious thoughts. Future studies are needed to give a full characterization of default network connectivity in the VS patients population.

[Contribution of functional neuroimaging studies to the understanding of the mechanisms of general anesthesia]. / Mécanismes de l'anesthésie générale: apport de l'imagerie fonctionnelle.

Since the early beginning of anesthesia, almost 2 centuries ago, ignorance has prevailed regarding the cerebral mechanisms of the loss of consciousness induced by general anesthesia. The recent contribution of functional brain imaging studies has allowed considerable progress in that domain. Similarly, the study of brain function under general anesthesia is currently a major tool for the understanding of conscious phenomena. This functional approach leads to conceptual changes about the functioning brain and may ultimately provide tracks for new treatments and practical applications. All these aspects are reviewed in this paper, at the light of the most recent literature.

[Predicting prognosis in post-anoxic coma]. / Comment prédire l'évolution du coma post-anoxique?

Most patients who remain comatose for a few hours after a period of global cerebral ischemia have a poor prognosis. Early identification of these patients is desirable to reduce uncertainty about treatment and non-treatment decisions, and to improve relationships with the family. The absence of pupillary light response and corneal reflexes, absent or stereotyped extension motor response to noxious stimulation (3 days after insult); myoclonus status epilepticus; absence of cortical N20 response on somatosensory evoked potential studies; generalised suppression or burst-suppression EEG and serum neuron-specific enolase above 33 microg/L (sampled 1-3 days after insult) have been shown to predict poor outcome. We here propose an algorithm to help intensive care physicians' clinical decision making in post-anoxic coma.

[Hypnosis and pain perception]. / Hypnose et perception de la douleur.

Improvement in functional neuroimaging allows researchers to disentangle the brain mechanisms involved in the pain modulation encountered during hypnosis. It has been shown that the anterior cingulate and prefrontal cortices are important in the modulation of incoming sensory and noxious input. Moreover, clinical studies in certain types of surgery (eg thyroidectomy, mastectomy and plastic surgery) have demonstrated that hypnosis may avoid general anesthesia.

[Pain assessment in non-communicative patients]. / Mesurer la douleur chez le patient non communicant.

Pain is a subjective experience. Its assessment is based on the subject's direct verbal report. This method of assessment is, however, impossible in patients who cannot communicate their feelings. In this context, indirect measurements such as behavioral observations or physiological measurements are needed. To facilitate the assessment of pain in non-communicative patients, numerous standardized behavioral scales have been developed. The aim of this review is to discuss the main validated pain scales employed in end-stage dementia, newborn and preverbal children, and severely brain damaged patients with a disorder of consciousness such as coma, the vegetative state or the minimally conscious state.

[Near-death experiences: fact and fancy]. / Expériences de mort imminente: phénomènes paranormaux ou neurologiques?

Seeing a bright light at the end of a tunnel or having a sense of being out of the physical body are phenomena that some patients report after having been close to death. Some spiritual and psychological theories have been developed in order to explain these near-death-experiences. Clinical studies have aimed to determine their frequency and to assess their precipitating factors. Recent neuroimaging studies, however, have shown the involvement of the temporo-parietal cortex in the generation of out-of-body experiences and are offering a physiological, neurological account for the phenomenon, rebuffing dualistic, non-physical explanations.

[Life with Locked-In syndrome]. / Quelle vie après le Locked-In syndrome?

The Locked-In Syndrome (LIS) is classically caused by an anterior pontine vascular lesion and characterized by quadriplegia and anarthria with preserved consciousness and intellectual functioning. We here review the definition, etiologies, diagnosis and prognosis of LIS patients and briefly discuss the few studies on their quality of life and the challenging end-of-life decisions that can be encountered. Some clinicians may consider that LIS is worse than being in a vegetative or in a minimally conscious state. However, preliminary data from chronic LIS survivors show a surprisingly preserved self-scored quality of life and requests of treatment withdrawal or euthanasia, though not absent, are infrequent.

[Behavioural assessment and functional neuro-imaing in vegetative state patients]. / Evaluation comportementale et par neuroimagerie fonctionnelle des patients en état végétatif.

Currently, there remains a high rate of misdiagnosis of the vegetative state. This should incite clinicians to use the most sensitive "coma scales" to detect signs of consciousness in these patients. The gold standard remains the Glasgow Coma Scale (GCS, Teasdale and Jennet, 1974), with the Glasgow Liège Scale (GLS, Born, 1988) adding standardized assessment of brainstem reflexes. New sensible behavioral assessment tools for use in the acute neurocritical care setting include the Full Outline of UnResponsiveness (FOUR, Wijdicks et al., 2005). The Coma Recovery Scale-Revised (CRS-R, Giacino and Kalmar, 2004) specifically tests the diagnostic criteria differentiating vegetative from minimally conscious patients. Detecting signs of consciousness also depends on the employed methodology. We showed that for the assesment of the presence of visual pursuit, using a moving mirror is better suited than using a moving object or person. The clinical diagnosis can be confirmed by cerebral positron emission tomography studies objectively quantifying residual metabolic activity in vegetative and minimally conscious patients. Ongoing studies evaluate the prognostic value of functional magnetic resonance imaging studies in these challenging patient populations.