Pupil dilation response elicited by violations of auditory regularities is a promising but challenging approach to probe consciousness at the bedside

Pupil dilation response (PDR) has been proposed as a physiological marker of conscious access to a stimulus or its attributes, such as novelty. In a previous study on healthy volunteers, we adapted the auditory "local global" paradigm and showed that violations of global regularity elicited a PDR. Notably without instructions, this global effect was present only in participants who could consciously report violations of global regularities. In the present study, we used a similar approach in 24 non-communicating patients affected with a Disorder of Consciousness (DoC) and compared PDR to ERPs regarding diagnostic and prognostic performance. At the group level, global effect could not be detected in DoC patients. At the individual level, the only patient with a PDR global effect was in a MCS and recovered consciousness at 6 months. Contrasting the most regular trials to the most irregular ones improved PDR's diagnostic and prognostic power in DoC patients. Pupillometry is a promising tool but requires several methodological improvements to enhance the signal-to-noise ratio and make it more robust for probing consciousness and cognition in DoC patients.

Systematic prolonged video-electroencephalograms identify electrographic seizures in 5% of acute stroke patients with aphasia

In stroke units, diagnosing seizures may be difficult, especially in aphasic patients. We discuss herein our systematic 4-hour video EEG monitoring of 61 patients with aphasia within the first 72hours after the onset of ischaemic stroke. Five electrographic seizures were identified in 3 patients, with no clinical signs apparent on the video and no symptoms reported by patients. We did not record status epilepticus nor generalized seizure. Comparative analyses disclosed a higher risk of early seizures in patients with haemorrhagic transformation. Video EEG monitoring detected electrographic seizures in 5% of stroke patients with aphasia. This monitoring could be useful for selected patients, especially those with haemorrhagic transformation.

[Metabolic encephalopathies]

Metabolic encephalopathies (ME) are a common cause of admission to emergency rooms, to hospitalization wards or to intensive care units. They could account for 10 to 20% of causes of comatose states in ICU and could be associated to a poor outcome especially in older patients. Nevertheless, they are often reversible and are associated with a favorable outcome when diagnosed and rapidly treated. They correspond to an altered brain functioning secondary to the deficiency of a substance that is mandatory for the normal brain functioning or to the accumulation of a substance that can be either endogenous or exogenous. It preferably occurs in co-morbid patients, complicating its diagnosis and its management. Altered brain functioning, going from mild neuropsychological impairment to coma, movement disorders especially myoclonus and the absence of any obvious differential diagnosis are highly suggestive of the diagnosis. Whereas some biological samplings and brain MRI are essential to rule out differential diagnosis, some others, such as electroencephalogram, may be able to propose important clues in favor of the diagnosis. Once simple symptomatic measures are introduced, the treatment consists mainly in the correction of the cause. Specific treatment options are only seldom available for ME; this is the case for hepatic encephalopathy and some drug-induced encephalopathies. We will successively describe in this review the main pathophysiological mechanisms, the main causes, favoring circumstances of ME, the differential diagnosis to rule out and the etiological work-up for the diagnosis. Finally, a diagnostic and therapeutic strategy for the care of patients with ME will be proposed.

Epilepsy after stroke: Definitions, problems and a practical approach for clinicians

Stroke, whether ischemic or hemorrhagic, is the main etiology of epilepsy in the elderly. However, incidences and outcomes differ according to stroke subtype and delay of onset following the stroke. While the medical literature is extensive, it is not always consistent, and many questions still remain regarding risk factors and management of vascular epilepsy. Thus, the present report here is an overview of the clinical aspects of vascular epilepsy using a practical approach that integrates data from meta-analyses and the more recently published expert recommendations.

Conscious processing of auditory regularities induces a pupil dilation

Pupil dilation has been reliably identified as a physiological marker of consciously reportable mental effort. This classical finding raises the question of whether or not pupil dilation could be a specific somatic signature of conscious processing. In order to explore this possibility, we engaged healthy volunteers in the 'local global' auditory paradigm we previously designed to disentangle conscious from non-conscious processing of novelty. We discovered that consciously reported violations of global (inter-trials) regularity were associated with a pupil dilation effect both in an active counting task and in a passive attentive task. This pupil dilation effect was detectable both at the group-level and at the individual level. In contrast, unreported violations of this global regularity, as well as unreported violations of local (intra-trial) regularity that do not require conscious access, were not associated with a pupil dilation effect. We replicated these findings in a phonemic version of the 'local global'. Taken together these results strongly suggest that pupil dilation is a somatic marker of conscious access in the auditory modality, and that it could therefore be used to easily probe conscious processing at the individual level without interfering with participant's stream of consciousness by questioning him/her.

Survival and consciousness recovery are better in the minimally conscious state than in the vegetative state

BACKGROUND

The prognosis value of early clinical diagnosis of consciousness impairment is documented by an extremely limited number of studies, whereas it may convey important information to guide medical decisions.

OBJECTIVE

We aimed at determining if patients diagnosed at an early stage (<90 days after brain injury) as being in the minimally conscious state (MCS) have a better prognosis than patients in the vegetative state/Unresponsive Wakefulness syndrome (VS/UWS), independent of care limitations or withdrawal decisions.

METHODS

Patients hospitalized in ICUs of the Pitié-Salpêtrière Hospital (Paris, France) from November 2008 to January 2011 were included and evaluated behaviourally with standardized assessment and with the Coma Recovery Scale-Revised as being either in the VS/UWS or in the MCS. They were then prospectively followed until 1July 2011 to evaluate their outcome with the GOSE. We compared survival function and outcomes of these two groups.

RESULTS

Both survival function and outcomes, including consciousness recovery, were significantly better in the MCS group. This difference of outcome still holds when considering only patients still alive at the end of the study.

CONCLUSIONS

Early accurate clinical diagnosis of VS/UWS or MCS conveys a strong prognostic value of survival and of consciousness recovery.