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

in Archives Italiennes de Biologie (2009), 147(1-2), 51-7

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 ... [more ▼]

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. [less ▲]

Perception of pain in the minimally conscious state with PET activation: an observational study.

in Lancet Neurology (2008), 7(11), 1013-20

BACKGROUND: Patients in a minimally conscious state (MCS) show restricted self or environment awareness but are unable to communicate consistently and reliably. Therefore, better understanding of cerebral ... [more ▼]

BACKGROUND: Patients in a minimally conscious state (MCS) show restricted self or environment awareness but are unable to communicate consistently and reliably. Therefore, better understanding of cerebral noxious processing in these patients is of clinical, therapeutic, and ethical relevance. METHODS: We studied brain activation induced by bilateral electrical stimulation of the median nerve in five patients in MCS (aged 18-74 years) compared with 15 controls (19-64 years) and 15 patients (19-75 years) in a persistent vegetative state (PVS) with (15)O-radiolabelled water PET. By way of psychophysiological interaction analysis, we also investigated the functional connectivity of the primary somatosensory cortex (S1) in patients and controls. Patients in MCS were scanned 57 (SD 33) days after admission, and patients in PVS 36 (9) days after admission. Stimulation intensities were 8.6 (SD 6.7) mA in patients in MCS, 7.4 (5.9) mA in controls, and 14.2 (8.7) mA in patients in PVS. Significant results were thresholded at p values of less than 0.05 and corrected for multiple comparisons. FINDINGS: In patients in MCS and in controls, noxious stimulation activated the thalamus, S1, and the secondary somatosensory or insular, frontoparietal, and anterior cingulate cortices (known as the pain matrix). No area was less activated in the patients in MCS than in the controls. All areas of the cortical pain matrix showed greater activation in patients in MCS than in those in PVS. Finally, in contrast with patients in PVS, those in MCS had preserved functional connectivity between S1 and a widespread cortical network that includes the frontoparietal associative cortices. INTERPRETATION: Cerebral correlates of pain processing are found in a similar network in controls and patients in MCS but are much more widespread than in patients in PVS. These findings might be objective evidence of a potential pain perception capacity in patients in MCS, which supports the idea that these patients need analgesic treatment. [less ▲]

The boundaries of consciousness: lessons from coma and related states

in Advances in Clinical Neuroscience and Rehabilitation [=ACNR] (2008), 8(2),

Le Locked-In Syndrome : la conscience emmurée

in Revue Neurologique (2008), 164

The Locked-In syndrome(LIS) is defined by: (i) the presence of sustained eye opening (bilateral ptosis should be ruled out as a complicating factor);(ii) preserved awareness; (iii) aphonia or hypophonia ... [more ▼]

The Locked-In syndrome(LIS) is defined by: (i) the presence of sustained eye opening (bilateral ptosis should be ruled out as a complicating factor);(ii) preserved awareness; (iii) aphonia or hypophonia; (iv) quadriplegia or quadriparesis; and (v) a primary mode of communication that uses vertical or lateral eye movement or blinking. Acute ventral pontine lesions are its most common cause. Following such brainstem lesions patients may remain comatose for sometime and then gradually awaken, remaining paralyzed and voiceless, superficially resembling the vegetative state. Background. – It has been shown that more than half of the time physicians fail to recognize early signs of awareness in LIS. Given appropriate medical care,life expectancy may be several decades but the chances of good motor recovery remain small. Eye-controlled computer technology now allows LIS patients to communicate and control their environment. Recent studies show that most LIS patients self-report meaningful quality of life and the demand for euthanasia is infrequent. Conclusion. – Patients suffering from LIS should not be denied the right to die – and to die with dignity –but also they should not be denied the right to live–and to live with dignity and the best possible pain and symptom management and revalidation. [less ▲]

Consciousness and cerebral baseline activity fluctuations

in Human Brain Mapping (2008), 29

The origin of within-subject variability in perceptual experiments is poorly understood. We here review evidence that baseline brain activity in the areas involved in sensory perception predict subsequent ... [more ▼]

The origin of within-subject variability in perceptual experiments is poorly understood. We here review evidence that baseline brain activity in the areas involved in sensory perception predict subsequent variations in sensory awareness. We place these findings in light of recent findings on the architecture of spontaneous BOLD fluctuations in the awake human brain, and discuss the possible origins of the observed baseline brain activity fluctuations. [less ▲]

Voluntary brain processing in disorders of consciousness

in Neurology (2008), 71(20), 1614-1620

Background: Disentangling the vegetative state from the minimally conscious state is often difficult when relying only on behavioral observation. In this study, we explored a new active evoked related ... [more ▼]

Background: Disentangling the vegetative state from the minimally conscious state is often difficult when relying only on behavioral observation. In this study, we explored a new active evoked related potentials paradigm as an alternative method for the detection of voluntary brain activity. Methods: The participants were 22 right-handed patients (10 traumatic) diagnosed as being in a vegetative state (VS) (n 8) or in a minimally conscious state (MCS) (n 14). They were presented sequences of names containing the patient’s own name or other names, in both passive and active conditions. In the active condition, the patients were instructed to count her or his own name or to count another target name. Results: Like controls, MCS patients presented a larger P3 to the patient’s own name, in the passive and in the active conditions. Moreover, the P3 to target stimuli was higher in the active than in the passive condition, suggesting voluntary compliance to task instructions like controls. These responses were even observed in patients with low behavioral responses (e.g., visual fixationand pursuit). In contrast, no P3 differences between passive and active conditions were observed for VS patients. Conclusions: The present results suggest that active evoked-related potentials paradigms may permit detection of voluntary brain function in patients with severe brain damage who present with a disorder of consciousness, even when the patient may present with very limited to questionablyany signs of awareness. [less ▲]

Comment prédire l'évolution du coma post-anoxique?

in Revue Médicale de Liège (2008), 63(5-6), 263-268

Editorial. Le cerveau dans tous ses états.

in Revue Médicale de Liège (2008), 63

Mesurer la douleur chez le patient non communicant.

in Revue Médicale de Liège (2008), 63(5-6), 429-37

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 ... [more ▼]

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. [less ▲]

Measuring the effect of amantadine in chronic anoxic minimally conscious state.

in Journal of Neurology, Neurosurgery & Psychiatry (2008), 79(2), 225-7